低品質条件で作製された繊維材混合流動化処理土の強度・変形特性に関する研究
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公開日: 2020-12-15
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https://doi.org/10.15118/00010335

Study on Strength and Deformation Property ofLiquefied Stabilized Soil Mixed with Fibered Material
Prepared under Poor Quality Condition

By
Cui Yujie
A DISSERTATION SUBMITTED TO THE FACULTY OF THE
MURORAN INSTITUTE OF TECHNOLOGYIN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF
DOCTOR OF ENGINEERING

Division of Civil and Environmental Engineering
MURORAN INSTITUTE OF TECHNOLOGY
September 2020

Acknowledgments
I would like to express my gratitude to all those who helped me during the writingof this thesis.
First and foremost, I want to thank my supervisor Professor Yukihiro Kohata, whoprovided me many precious opportunities and constant support during my PhD andacted as a role model to me not only academically but also in life. There are many things
his taught me, but nothing was more precious than his enthusiasm to push theboundaries of human knowledge. If not for his dedication, motivation and energy, thisstudy and many others not covered in this thesis would undoubtedly never haveachieved fruition.
A similar gratitude belongs to Professor Shima Kawamura and Associate Professor
Noriyuki Sugata, for their insightful comments and encouragement, but also for the
hard question which incented me to widen my research from various perspectives.
I also want to thank them for looking after me with such kindness and patience all
the staffs of at the Centre for International Relations, Muroran IT, Mr. Jinro Endo, Ms.
Hatsuki Noda, and Ms. Kozue Takekawa for making my life in Hokkaido really
comfortable and enjoyable. They always extended instant help whenever I needed.
Especially thanks to Associate Professor Naoko Yamaji’ s teaching, my Japanese has
been improved much.
Of course, thanks must go to my parents. they tried their best to support andencourage me to do what I want. Without their constant support, I would never have
had a chance to start and finish a PhD or even to come to study in Japan. Thanks to mybrother Cui Jiahui for his help in life.
Finally, I want to thank my husband, Liu Weichen. There is so much I want to say
but so little than can be expressed. His created a comfortable environment allowing me
to focus on my work.
Regarding research, he brought me a lot of helpDiscussions and Research assistanceWithout his help and encouragement, it would have been impossible for me to go
through the last three years without any regrets.
ii

These were the happiest three years I have had While challenging, it was undoubtedly
exciting. Thank you to everyone I have met along the way.

iii

Abstract
Nowadays, Environment degradation is growing into a grave concern in various
parts of the world. Countries especially in developing regions are suffering fromenvironmental problems emanating from the rapid urban constructions anddevelopment. During urban constructions, tremendous amount of construction waste
soils is generated which might not be suitable for reuse in constructions but on the other
hand may be harmful to the environment if not treated appropriately. In order to solve
this problem, some countries like Vietnam and Japan are making attempts to recycle
this kind of waste soil by mixing it with solidification agent like cement or gypsum.
This kind of recycling alleviated the pressure on the environment to some extent but
there still has a lot of uncertain part of the mechanical property of the recycled soil.
As one of the recycled materials, the Liquefied Stabilized Soil is widely used inJapan currently. However, as a cement solidified material, the adding of cement content
will surely increase the stiffness and strength while the problem of brittleness must be
considered in terms of its seismic behavior. On the other hand, in order to reduce theoverburden pressure when the LSS is used as a backfill soil for cut and cover tunnel
etc., there is a concern about the use of the LSS prepared with a relatively lower slurry
density with considering the strength reduction. However, it is considered that someproblem might arise for the quality of LSS on the strength, stiffness, durability and soon. In the past, in order to improve the brittle property of the LSS, a series of studies
on the Liquefied Stabilized Soil mixed with newspaper prepared like cotton wool as thefiber material was carried out, and it was reported that the brittle property after the peakis improved due to the reinforcing effect of the fiber. However, as for decreasing theoverburden pressure by preparing the LSS in lower slurry density, it is still not clear
about the influence of reduction of slurry density.
The purpose of this study is to investigate the influence of reduction of slurry density
while preparing the Liquefied Stabilized Soil specimens with different cement content
that mixed with fibers. Therefore in this study, a series of triaxial compression tests andunconfined compression tests were conducted on LSS specimens prepared in differentiv

slurry densities of 1.216, 1.280 g/cm3, cement contents of 80, 100 kg/m3 and the fiber
contents of 0, 10 kg/m3 with different curing time of 28 and 56 days respectively. The
results of undrained triaxial tests showed that slight decrease of slurry density candecrease the peak stress of LSS remarkably. Meanwhile, the changing in cement content
can affect peak strength as well as the decreasing rate of Etan/E0 in the early loading
stage. In addition, by adding fiber material, the local damage caused by shearing andthe brittleness were improved. Based on these results of the triaxial tests and unconfinedcompression tests, the influences of changing in slurry density, as well as added amountof fiber on the triaxial shear properties of the LSS with different cement contents, arediscussed in detail.

v

Table of Contents
CHAPTER 1
INTRODUCTION ......................................................................................................... 1
1.1 General Background ........................................................................................ 1
1.2 Current Research of the Liquefied Stabilized Soil .......................................... 6
1.3 Objective of This Study ................................................................................. 10
1.4 Organization of the thesis .............................................................................. 13
REFERENCES .................................................................................................... 15
CHAPTER 2OVERVIEW OF LIQUEFIED STABILIZED SOIL ................................................... 16
2.1 Introduction .................................................................................................... 16
2.2 Component of Liquefied Stabilized Soil........................................................ 17
2.2.1 Base Materials ......................................................................................... 17
2.2.2 Cementitious materials ............................................................................ 18
2.2.3 Fiber Material .......................................................................................... 20
2.3 Historical development .................................................................................. 22
2.4 Applications of the LSS ................................................................................. 27
2.4.1 Problem of backfilling method in China ................................................. 30
2.4.2 Disposal of waste soil in China ............................................................... 31
2.4.3 China extracts new materials from natural resources .............................. 32
2.4.4. Utilization of LSS ................................................................................... 32
REFERENCES .................................................................................................... 34
CHAPTER 3
MATERIALS AND PREPARATION METHOD OF SPECIMEN ............................. 37
3.1 Introduction .................................................................................................... 37
3.2 Test material ................................................................................................... 39
3.3 Mixing method ............................................................................................... 40
3.4 Specimen preparation..................................................................................... 42
3.5 Detailed preparation steps .............................................................................. 43vi

REFERENCES .................................................................................................... 48
CHPATER 4
APPARATUS AND TESTING PROCEDURES ......................................................... 49
4.1 Introduction .................................................................................................... 49
4.2 Triaxial apparatus and monitoring instrument ............................................... 50
4.3 Test procedures of triaxial compression test .................................................. 54
4.3.1 Calibration experiment ............................................................................ 54
4.3.2 Preparation of test equipment .................................................................. 57
4.3.3 Saturation of specimen using double vacuum method ............................ 59
4.3.4 Isotropic consolidation............................................................................. 65
4.3.5Triaxial compression test .......................................................................... 65
4.4 Procedures of Unconfined compression test .................................................. 67
4.4.1 Setting of the specimen ............................................................................ 67
4.4.2 Unconfined compression test ................................................................... 69
REFERENCES .................................................................................................... 70
CHAPTER 5
TEST RESULTS OF UNDRAINED TRIAXIAL COMPRESSION TEST ANDDISCUSSIONS ............................................................................................................ 71
5.1 Introduction .................................................................................................... 71
5.2 Stress-strain Relationship............................................................................... 73
5.3 Pre-failure Deformation Property .................................................................. 77
5.4 Summaries...................................................................................................... 82
REFERENCE....................................................................................................... 83
CHAPTER 6
TEST RESULTS OF UNCONFINED COMPRESSION TEST AND DISCUSSIONS...................................................................................................................................... 85
6.1 Introduction .................................................................................................... 85
6.2 Stress-strain Relationship............................................................................... 86
6.3 Comparison of Failure Pattern ....................................................................... 89
6.4 Summaries...................................................................................................... 91
vii

REFERENCE....................................................................................................... 92
CHAPTER 7
CONCLUSIONS AND SUGGESTIONS ON FUTURE WORK ............................... 93
7.1 Conclusions .................................................................................................... 93
7.2 Suggestions on Future Work .......................................................................... 95

viii

List of Tables
Table 2.1 Physical parameter of NSF-CLAY…………………………………….….17
Table 3.1 Physical parameters of NSF-CLAY……………………….………………39
Table 4.1 Progress of double vacuum………………………………………………..63
Table 5.1 Details of testing cases in undrained triaxial compression test……………72
Table 6.1 Details of testing cases in unconfined compression test………………..…85ix

List of Figures
Figure 1.1 Urban transport…………………………………………………………….2
Figure 1.2 Metro rout map of Shanghai city ………………………………………….3
Figure 1.3 China-Vietnam International Road Freight Trial Launch…………………4
Figure 2.1 The components of liquefied stabilized soil……………………………...17
Figure 2.2 Fiber material made by newspaper……………………………………….21
Figure 2.3 Flow of Liquefied soil stabilized method (Tomoharu et al., 2005)………25
Figure 2.4 Cement treated soil using as slope protection (Tang et al., 2001)………..25
Figure 2.5 Production system for foam mixed lightweight soil……………………...26
Figure 2.6 Placement of cement treated soil along slope (Tang et al., 2001)……..…26
Figure 2.7 Placement of cement treated soil along slope (Tang et al., 2001)………..26
Figure 2.8 Use of LSS for filling cavity under road surface…………………………27
Figure 2.9 LSS used for backfill at upper part of cut and cover tunnel……………...28
Figure 2.10 LSS used for invert material of shield tunnel…………………………...28
Figure 2.11 Using LSS for various backfilling works in Japan……………………...30
Figure 3.1 Pulverized newspaper (left) and slurry (right)……………………………40
Figure 3.2 Available range of slurry density…………………………………………41
Figure 3.3 Bucket…………………………………………………………………….43
Figure 3.4 Electronic scale…………………………………………………………...43
Figure 3.5 metal container……………………………………………………………44
Figure 3.6 Container for removing air bubbles………………………………………45
Figure 3.7 Negative pressure generator………………………………………………45
Figure 3.8 Plastic mold……………………………………………………………….46
Figure 3.9 Curing sample…………………………………………………………….47
Figure 4.1 Schematic figure of test apparatus………………………………………..49
Figure 4.2 Axial load cell…………………………………………………………….50
Figure 4.3 Dial gauge………………………………………………………………...51
Figure 4.4 Gap sensor………………………………………………………………...51
Figure 4.5 Local displacement transducer……………………………………………52
Figure 4.6 Pore water pressure transducer and cell pressure transducer……………..52xFigure 4.7 Gap sensor………………………………………………………………..54
Figure 4.8 Local Deformation Transducer…………………………………………...55
Figure 4.9 Dial Gauge………………………………………………………………..55
Figure 4.10 Load cell………………………………………………………………...56
Figure 4.11 Driver box of mega torque motor……………………………………….58
Figure 4.12 ATT amplifier…………………………………………………………...58
Figure 4.13 Schematic figure of connections………………………………………..64
Figure 4.14 Progress during isotropic consolidation…………………………………64
Figure 4.15 Connection and screw of gap sensor…………………………………….68
Figure 4.16 Locker of the loading rod………………………………………………..69
Figure 5.1 Stress-strain relationship up to 5% axial strain (28 days curing, C = 80kg/m3)……………………………………………………………………………...…73
Figure 5.2 Stress-strain relationship up to 5% axial strain (56 days curing, C = 80kg/m3)……………………………………………………………………………...…73
Figure 5.3 Stress-strain relationship up to 5% axial strain (28 days curing, C = 100kg/m3)……………………………………………………………………………...…74
Figure 5.4 Stress-strain relationship up to 5% axial strain (56 days curing, C = 100kg/m3)……………………………………………………………………………...…74
Figure 5.5 Stress-strain relationship up to 5% axial strain (C = 80 kg/m3)………….75
Figure 5.6 Stress-strain relationship up to 5% axial strain (C = 100 kg/m3)………...75
Figure 5.7 Relationship between maximum deviator stress and changing rate of slurry
density (28 days)……………………………………………………………………..76
Figure 5.8 Definition of various Young’s moduli……………………………………77
Figure 5.9 Relationship between initial Young’s modulus and cement contents…….78
Figure 5.10 Relationship between initial Young’s modulus and curing times……….78
Figure 5.11 Relationship between Etan/E0~q/qmax (cement content = 80 kg/m3, 28 days
curing)………………………………………………………………………………..79
Figure 5.12 Relationship between Etan/E0~q/qmax (cement content = 80 kg/m3, 56 days
curing)………………………………………………………………………………..79xi

Figure 5.13 Relationship between Etan/E0~q/qmax (cement content = 100 kg/m3, 28
days curing) ………………………………………………………………………….80
Figure 5.14 Relationship between Eeq/E0~q/qmax (cement content = 80 kg/m3, 28 days
curing)………………………………………………………………………………..80
Figure 5.15 Relationship between Eeq/E0~q/qmax (cement content = 80 kg/m3, 56 days
curing)…………………………………………………………………………...…...81
Figure 5.16 Relationship between Eeq/E0~q/qmax (cement content = 100 kg/m3, 28
days curing)………………………………………………………………………….81
Figure 6.1 Stress-strain relationship up to 5% axial strain (28 days curing, C = 100kg/m3)………………………………………………………………………………..86
Figure 6.2 Stress-strain relationship up to 5% axial strain (56 days curing, C = 100kg/m3)………………………………………………………………………………..87
Figure 6.3 Stress-strain relationship up to 5% axial strain in different loading
conditions (left: unconfined compression test, right: undrained triaxial compressiontest)…………………………………………………………………………………..87
Figure 6.4 Stress-strain relationship up to 5% axial strain in different loading
conditions (left: unconfined compression test, right: undrained triaxial compressiontest)…………………………………………………………………………………..88
Figure 6.5 Specimens with 28 days curing after unconfined compression test……...89
Figure 6.6 Specimens with 56 days curing after unconfined compression test……...89
Figure 6.7 Specimens with 28 days curing after undrained triaxial compression
test……………………………………………………………………………………89




xii

CHAPTER 1
INTRODUCTION

1.1 General Background
Environmental degradation is growing into a grave concern in various parts of theworld today. Countries especially in developing regions are suffering from problems
emanating from a combination of factors including population growth, concentrationof population in cities, industrialization, and poverty, resulting in urban air pollution,water contamination, decline in sanitation, degradation of forests and soil, loss of
biodiversity, marine pollution, etc. Moreover, pollutants released in countries aroundthe world are spreading across boundaries and transcending generations to cause
problems of a wide range, such as climate change and acid deposition.
These problems are not only threatening human health and living but also
undermining the foundation of development for future generations with thediminishment of environmental resources.
"Global Environment Outlook" pointed out the issue of urbanization. The Outlook
report pointed out that urbanization can improve the well-being of residents while
reducing the environmental impact by improving the effectiveness of governance, landplanning and increasing green infrastructure.
When the PRC was founded in 1949, transport was underdeveloped. Total railway
length was only 21,800 km, half of which was paralyzed. Highway traffic length was
only 80,800 km, and civil automobiles numbered only 51,000. Inland waterways were
undeveloped, and only 12 civil air routes were operative. Postal outlets were limited.
The major means of transport were animal-drawn vehicles and primitive boats..
Following the founding of the PRC, the Chinese government decided to create thebasic conditions to restore transport. During the economic recovery period (1949-1952)
damaged transport facilities were repaired, and water, land and air transport were1resumed. In 1953 China began to develop transport in a planned way. During the First(1953-1957) and Second (1958-1962) Five-Year Plan periods and the economic
adjustment period (1961-1965) China tilted state investment in support of transport. It
renovated and built a number of railways, highways, ports and piers, and civil airports;
expanded the transport infrastructure coverage in the western and remote regions;dredged major navigation channels; opened new international and domestic sea and airroutes; expanded the postal network; and increased the amount of transport equipment.
In recent years it has been called one of the most polluted cities in Asia shown in
Figure1.1.
It has enhanced the supply and management of basic public services for transport,
supporting the development of transport infrastructure in contiguous impoverishedareas, urban and rural passenger transport and urban public transport. China has also
promoted balanced development of transport in its eastern, central, western andnortheastern regions. In this regard, western China has quickened its pace in developing
high-speed railways, and overall central and western China’s transport conditions havebeen greatly improved. In 2013, the Motuo Highway in Tibet was opened to traffic,
indicating that every county in China now had access to highways.


Figure 1.1 Urban transport
The solution is to expand the transportation capacity of the existing public
transportation and road networks as well as establish a new urban rapid transportation
system as soon as possible.
A full-coverage highway network has been set up. By the end of 2015, China’s total
highway traffic length was 4.58 million km. Expressway length was 123,500 km,
ranking first in the world. The national and provincial trunk highway network has been2

improved, connecting administrative regions at and above the county level nationwide.
Rural highway length was 3.98 million km, connecting 99.9 percent of towns andtownships and 99.8 percent of administrative villages. The technology structure of the
highway network has been improved, with graded highway length accounting for 88.4
percent of total highway length. shown in Figure 1.2
Figure 1.2 Metro rout map of Shanghai city
However, experts predict that a large amount of excavated soil will be discharged
from the city underground construction projects in the next ten years. Protecting theecological environment. China is promoting ecological conservation in the planning,
designing, construction, and operation of transport projects, and has built a number ofrailways, highways, ports and sea routes for demonstration purposes. It is also3experimenting with ecological restoration technologies in transport infrastructure indeserts, alpine regions, and reclamation areas. During the 12th Five-Year Plan period,
China restored the ecology along 1,300 km of transport lines, with a total area of 50
million sq m. The recycling rate of road-surface materials reached 40 percent. In
addition, many backfill materials used in construction projects are extracted fromnatural resources, such as sand mining in rivers and gravel in the mountains. These havecaused serious negative effects on the environment.


Figure 1.3 China-Vietnam International Road Freight Trial Launch
Since 1994, China and Vietnam have been cooperating with each other since the1994 National Highway Exhibition and have been cooperating with each other on theroads of the two countries shown in Figure 1.3.
In Japan, the muck produced from urban buildings is often discarded as an industrial
waste to the dump. According to the research report: The average lifespan of landfills
in Japan is estimated to be 13.6 years, 14 years in the Kinki region and only 4.3 years
in the Tokyo metropolitan area. Furthermore, it can be seen that for a long period, themuck has not been widely and effectively used. Therefore, how to use the muckproduced by construction has become an urgent problem to be solved.
To solve this problem, Japan launched a construction waste promotion plan in May
2000. The plan makes clear that it will focus on recycling three types of industrial wastefrom construction: concrete blocks that have been added, asphalt concrete blocks,
building debris and wood waste. The program paid off in 2002, and according to the
May 2002 construction waste recovery report, the three priority recovery projects4

(mixed construction waste, construction silt and construction muck) have beensignificantly reduced. The Liquefied Stabilized Soil is one of the materials that makes
the use of recycled construction waste.

5

1.2 Current Research of the Liquefied Stabilized Soil
Liquefied Stabilized Soil materials can be divided into two types: traditional
solidified materials and new solidified materials. Initially, the research object oftraditional solidified materials was limited to cement and quicklime.
Yuji Maeno (1996) considered that the slag passed the compaction test, unconfinedcompression test, CBR value test, consolidation compression test under the conditionsof different, single solidified materials (such as cement, quick lime) and their dosage.
He Comparatively systematically analyzed and studied the reasons that influenced theunconfined compressive strength, optimal water content, CBR value, and change trendof the treated soil, which provided a basis for future research and engineering practice.
Researchers have developed different slag solidification materials for different soil
qualities, such as Medina reinforced red clay with phosphoric acid. Tomohisa (1997)
believes that the use of fine recycled powder, pulp slag, fly ash, and volcanic ash soil
for high moisture content and high organic matter content Slag soil. Bobrowski (1997)
developed an ionic curing agent to strengthen soft foundation soil. Zalihe (1998) used
fly ash and lime to solidify expansive calcareous clay.
When scholars study the slag solidifying agent, the research objects and ideas arebroader, including not only the research on the various additives of cement and lime,
and the recycling of waste, but also the in-depth study of fungus reinforcement andinsect reinforcement technology.
Shirazi (1998) believes that the mixture of lime and fly ash can avoid cracking
caused by the shrinkage of cement soil. Bell (1999) added PFA (an additive) to cement
and lime to strengthen the effect of clay reinforcement Research. Miller (2000) studied
the performance of cement pit dust (CKD) reinforcement treatment of slag. Kohata(2001) had considered a method of adding crushed old newspapers as a fibrous material
to add Liquefied Stabilized Soil Reinforcement methods.

Robert (2001) studied ahighly concentrated liquid slag solidification material (CLS). Saboundjian (2002)
reported on the application of an organic slag solidification material (EMC2) in roadbed
reinforcement. Attom ( 2002) It has been reported that burned olive waste can be used
as a new material for the solidification of dregs. Thecan (2003) studied basidiomycetes
in the decomposition of lignin by saprophytic organisms. He believed that it has an
essential role in the solidification of dregs Function.
6Nene (2004) studied the method

of natural termites using clay to solidify and build nests and proposed the concept ofgeotechnical entomology.
Now muck-solidified materials have been widely used in water conservancy
projects, high-speed railways, highways, airport runways, the benefits are very obvious.
It was named as one of the great inventions of the 20th century by the United States"engineering news." In Japan, it was also called the new materials of the 21st century.
In many countries, slag solidified specialized companies produce materials as abranded product, such as Parma curing enzymes, Soilrock, EN-1 slag solid materials
produced in the United States. Roadbond Roadpacker was developed in Australia.
Moreover, the UKC company in Japan Produced various brands of slag solidificationmaterials.
Mechanism of solidified soil
The research on the solidification mechanism of treated soil is mainly carried out
from theory and experiment, and its research methods are various. In the experiments,
chemical analysis, scanning electron microscope (SEM), differential thermal analysis,or X-diffraction (XIM) methods are generally used to study the solidified matter
generated in the solidified soil. The mechanism is to perform ion adsorption andexchange of the curing agent and the components of the slag. It is to reduce the surface
electricity of the slag micelle and the thickness of the electric double layer of the slag
micelle. It can make the slag particles tend to agglomerate. The chemical reaction
generates new substances to strengthen the links between the muck particles. The
volume expansion of the product improves and fills the pores between the muckparticles. The distance between the muck particles is shortened under the action of
external squeezing force, and the muck structure is compact, making the solidified soil
easy to compact Become one, to obtain excellent macro mechanical properties.
Supabj Nontananalldhn (1996) used X-rays to irradiate the treated soil, studied thereasons that affected the strength change of the reinforced soil at different ages, andobserved the changes in the microstructure and morphology of the reinforced soil
through an electron microscope. From a micro perspective, they are more scientific andreasonable.
Linda Hills and Vagn C. Johansen (1996) proposed the formation model of thestructure of solidified soil according to the actual solidification process of solidified7soil.

The structure of solidified soil is composed of the solidification agent hydrates

fully surrounding the soil particles and filling the pores between the soil particles.
Experiments and theoretical calculations with cement-solidified soil show that theamount of cementing agent corresponding to the cemented soil particles and the porefilling is quite consistent. The model reflects the relationship between the structure of
the compacted soil filled with the cement-filled pores and the strength growth of thesolidified soil.
Masashi Kaman (1996) studied the role of liquid curing agent in cement-based
composite consolidated soil. He determined that the consolidation of cement-based
composite consolidated soil is the interaction of curing agent, cement, and clay, which
promote each other to form dense, stable, Higher strength structure. The chemicalbonding of the hydration of the curing agent and the cementation of the cementing
material can form the early strength of the solidified soil. In contrast, the performanceof the solidified soil of the slag curing agent continues to improve for a long time. It
depends on the interaction of the composite slag cement and the slag.
Mechanical properties of solidified soil
At present, the commonly used curing agents are cement and quicklime, which areevenly distributed in the sludge by manual or mechanical stirring. Therefore, themechanical properties of the solidified soil of the sludge are similar to the cement soil.
Many scholars have used the method of the indoor geotechnical experiment to study
the characteristics and influencing factors of reinforced soil more systematically.
MA Khan, A. Usmani, SS Shah, and H. Abbas et al. (1996) conducted indoor
geotechnical tests on solidified soil and found that the unconfined compressive strength
increases with the increase of cement content. The dry density increases with thecement content Under the same conditions, the compressive strength of the mixed
curing agent is increased by a maximum of 10 to 138% compared with the non-mixed,
and the dry density is increased by 0.01 to 0.07g / cm3. Good anti-seepage performance.
Permeability coefficient can reach the order of 10-8cm / s. The slow freezing method
was used to conduct the anti-freeze test. After 50 freeze-thaw cycles, the strength loss
was 13.5-21.07%. For the slag soil, the curing effect is remarkable; first, the curing
agent and the soil are mixed and placed, and then the cement or lime is added to obtaina better curing effect. First, after mixing the curing agent with the soil for a while, theoptimal moisture content of the soil will decrease, and the soil will feel wet and viscous,8and the cohesion of the soil will increase. At this time, adding cement or lime can obtaina higher degree of compaction and dry density.
KOHATA (2000) conducted a series of unconfined and triaxial compression tests
after it was discovered that crushed old newspapers were incorporated as a fibrousmaterial. The results show that the peak value of the brittle characteristic curve of theslag is higher than that of the ordinary curing agent after the fiber material is mixed bythis method.
Environmental impact of solidified soil
Scholars have also done much research on the environmental impact of fluidized
soil treatment. Mitchell emphasized the problem of pollution caused by seepage causedby fluidized soil. Shackelford, Daniel, Yong (1996) outlined the treatment of soil
seepage mechanical properties, as well as methods for controlling and mitigating soil
seepage pollution. Meta J and Sano (1996) proposed to cover the surface of thereinforced soil with a layer of clay to alleviate the alkaline penetration pollution
problem of the reinforced soil. Masashi (1996) discussed the method of controlling theenvironmental pollution caused by cement solidified soil through experiments. Basedon the test results, some quantitative parameters, such as the thickness value of the antifiltration layer, were suggested to solve the problem of seepage pollution caused by thefluidity treated soil used in water conservancy construction.

91.3 Objective of This Study
Due to the great utility of LSS in the recovery of excavated soil, LSS has brittle
characteristics similar to cement stabilized soil, as the brittleness increases, the strength
will increase, and the seismic performance will decrease. Therefore, improving thischaracteristic of LSS is a critical task. In order to improve the performance of LSS,
Professor Kohata of Muroran Institute of Technology carried out the method of mixing
with shredded newspaper fiber materials, from the test results, after the mixing of thefiber materials, the brittleness after the peak is improved.
Before 2010, LSS used NSF clay sold in the Japanese market, and Vinh Phuc clay
sold in the Vietnamese market as the original materials. It was concluded that thestrength and deformation characteristics of the two LSSs are similar. (Giang, 2010). In
2015, LSS used fiber material 0, 20kg / m3 clay and the density of slurry was 1.280g /cm3. Under four different axial strain rates, a series of undrained triaxial compression
tests (Hung, 2015) under a confining pressure of σ_c^'= 98 kPa were conducted.
Moreover, the conclusion was that the fiber material added by LSS qmax of the
maximum partial stress q~ε_a curve has no relationship with the number ofmaintenance days. However, without the LSS of the fiber material, as the number ofcuring days increases, the initial strength tends to increase. Since the fiber material in
the LSS has a reinforcing effect, in the LSS of the blended fiber material, the indication
range of the Etan / E0 value tends to 1.0.
The 2019 study is to use LSS as backfill material in the construction project in Hanoi.
The central part of this study carried out experiments and analytical work to study themore advantages of LSS and LSS mixed with fiber materials. (Anh, 2019) Research is
divided into experimental research and simulation research. Experimental research is
divided into indoor research and outdoor research. In the part of the experimental study,
two kinds of mud are used, which are 1.280g / cm3 (Drf = 100%) and 1.216g / cm3 (Drf
= 95%), and the LSS and 0,10kg / m3 ( Pc-0, 10) fiber materials are mixed and cured
simultaneously indoors and outdoors (28 days, 56 days). At a constant strain rate of100.054% / min and effective confining pressure of 98 kph, the CUB test was performed.
1. By adding fiber materials, the brittleness of the LSS outside the peak is increased.
The density of the mud has a great influence on the degree of shear damage. The
damage degree tends to decrease after the fiber material is added. However, more
research is needed, but the LSS mixed with fiber material is used as a backfill materialon the construction site. It can be less ductile.
The cone penetration test (CPT) is used in Vietnam to estimate soil dynamics
parameters. Because LSS has productive potential as a countermeasure against
vibrations caused by vehicles on the road, this attribute is a new advantage of LSS.
In this study in order to investigate influence of slurry density on strength anddeformation properties of LSS reinforced with fiber material, NSF-clay was used as apresentative of LSS using excavated soil. With the increase of added amount ofstabilizer, an increase in strength of Liquefied Stabilized Soil (LSS) is observed while
the seismic resistance might decrease due to its brittleness. On the other hand, when the
LSS is used as a backfill soil for cut and cover tunnel etc. with the aim of reducing theoverburden pressure, there is a concern about the use of the LSS prepared with arelatively lower slurry density instead of the normal slurry density with considering thestrength reduction. In the past, a series of studies on the Liquefied Stabilized Soil mixed
with newspaper prepared like cotton wool as the fiber material was carried out in orderto improve the brittle property of the LSS, and it was indicated that the brittle property
after the peak is improved due to the reinforcing effect of the fiber. However, there arefew study cases and still many unexplained parts about the LSS with reduced slurry
density. In this study, a series of triaxial tests were conducted on LSS with different
added amount of fiber as well as slurry density and the results showed that the strengthand initial stiffness were influenced by the slurry density while the degree of damage
was reduced by the addition of fibers.
The first of all, The Liquefied Stabilized Soil (LSS) is easy to occur brittle failure
with the increase of cement content and it was found that the addition of fiber content
might improve the brittle property of the LSS. Meanwhile, the LSS produced with11

lower slurry density than standard slurry density is often used to reduce the overburdenpressure during the in-situ constructions which may cause several problems. The resultsof undrained triaxial tests showed that slight decrease of slurry density can decrease thepeak stress of LSS remarkably. Meanwhile, the changing in cement content can affectpeak strength as well as the decreasing rate of Etan/E0 in the early loading stage. In
addition, by adding fiber material, the local damage caused by shearing and thebrittleness were improved. In this study, a series of triaxial compression tests andunconfined compression tests were conducted with LSS specimens prepared indifferent slurry densities of 1.216, 1.280 g/cm3, cement content of 80, 100 kg/m3 andthe fiber content of 0, 10 kg/m3. Based on these results of the triaxial tests andunconfined compression tests, the influences of changing in slurry density, as well as
added amount of fiber on the triaxial shear properties of the LSS with different cement
contents, will be discussed in detail.

121.4 Organization of the thesis

Study on Strength and Deformation Property of Liquefied

Stabilized Soil Mixed with Fibered Material Prepared by
Poor Quality Condition







Chapter 1
Introduction

Chapter 2
Overview of Liquefied Stabilized Soil

Chapter 3
Materials and Preparation Method of Specimen

Chapter 4
Apparatus and Testing Procedures

Chapter 5
Test Results of Triaxial Compression Test







Chapter 6
Test Results of Unconfined Compression Test

Chapter 7
Conclusions and Future Plan
Figure 1.4 Flow chart of this dissertation
As seen in Figure 1.4, this dissertation contains seven chapters. Chapter 1 described
the general background, objectives and scopes of research and organization of the13dissertation.
Chapter 2 presented an overview of LSS as an effective method for utilization of
excavated soil. The problems regarding excavating works in China and Japan werepointed out and then feasibility for utilization of LSS in China has been highlighted inthis chapter.
Chapter 3 introduced the materials and test apparatus applied in this study.
Chapter 4 introduced the detailed test procedures in undrained triaxial compression
test and unconfine compression test.
Chapter 5 presented the result of undrained triaxial compression test on LSS
specimens prepared in different condition. Influence of different parameters is
discussed in detail from different division based on the test results.
Chapter 6 introduced the result of unconfined compression test and its results.
Difference between unconfined test and triaxial test were discussed. Failure pattern on
the surface of the specimen after test were also discussed.
Finally, the conclusions drawn from this study and recommendations for future
works were given in chapter 7.

14REFERENCES
Kuno, G., eds (1997): Liquefied stabilized soil method-Recycling technology ofconstruction-generated soil and mud, Gihodo publication (in Japanese).
Japanese Geotechnical Society (2005): Committee Report Chapter 2, 2.1, 2.2 on test
methods and physical properties of cement-modified soil, Proc. of symposium, pp.222, on survey, design, construction and properties evaluation methods of solidifying
stabilized soil using cement and cement-treated soil (in Japanese).
Kohata, Y. (2006): Mechanical property of liquefied stabilized soil and future issues,
Doboku Gakkai Ronbunshuu, F, Vol.62, No.4, 618-627 (in Japanese).
Kohata, Y., Fujikawa, T., Ichihara, D., Kanda, M., and Murata, O. (2002): Strengthand deformation properties of fibered material mixed in liquefied stabilized soil
obtained from uniaxial compression test, Proc. of the 36th Japan National Conf. on
Geotech. Eng., pp.635-636 (in Japanese).
Kohata, Y., and Tsushima, H. (2004): Effect of fibered material mixing in liquefied
stabilized soil on the triaxial shear characteristics, Proc. of the 39th Japan National Conf.
on Geotech. Eng., 721-722 (in Japanese).
Kohata, Y., Ichikawa, M., Nguyen, C. Giang., and Kato, Y. (2007): Study of damage
characteristics of liquefied stabilized soil mixed with fibered material due to triaxial
shearing, Geosynthetics Engineering Journal, Vol.22, 55-62 (in Japanese).
Ito, K., Kohata, Y., and Koyama, Y. (2011): Influence of additive amount of cement
solidification agent on mechanical characteristics of Liquefied Stabilized Soil mixed
with fibered material, Japanese Geotechnical Society Hokkaido Branch Technical
Report Papers, Vol.51, 131-136 (in Japanese).

15CHAPTER 2OVERVIEW OF LIQUEFIED STABILIZED SOIL

2.1 Introduction
The soil stabilization is process improving if geotechnical properties to stratify
engineering requirements. Until now, numerous kinds of stabilizers including cement,
lime and fly ash etc. were used as soil additives to improve its properties. The LSS
manufacturing process utilizes soil which has been excavated in construction projects
and which would otherwise be discharged to natural environment as soil waste. LSS
can be used for confined spaces or excavation areas and it can be easily placed without
vibration and compaction. The characteristics, benefits, advantages and applications of
LSS has been shown such as:Characteristics:-

Impermeability

Benefit:-

Reduce cost of construction projects-

Reduce manpower-Protect environment

Advantage:-

Excavated out easily-

Quick setting time-

Convenient compared to normal backfilling-

Faster than normal backfilling-

No soil stockpile needed

Application:-

Backfill sing concrete pump-

Cavities and excavated trenches can be backfilled easily

16

2.2 Component of Liquefied Stabilized Soil
Liquefied stabilized soil involves the use of binder materials in soils to improve its
geotechnical properties such as compressibility, strength, permeability, flexibility anddurability. The components of liquefied stabilized soil include soils, binders(cementitious materials). (Figure 2.1)

Soil

Water

Binders

Figure 2.1 The components of liquefied stabilized soil
2.2.1 Base Materials
Most soils in liquefied stabilized soil method are soft soils. The stabilization has
been performed to achieve desirable engineering properties. The main purpose ofliquefied stabilized method is to recycle excavated soil for backfilling processes forconstruction projects. Therefore, almost types of excavated soils can be used for thismethod. However, fine-grained granular materials are the easiest to stabilize due to alarge surface area in their contact diameter. The excavated soils can be modified toperform mainly with the purpose of improving their usability in construction. At present,
excavated soils are stabilized by binders which are selected in relation to the type ofsoil. The stabilization has improved the strength of the soils and their resistance tosoftening.
In this study, NSF-CLAY was used as a homogenous base material, which was acommercially available cohesive soil with very clearly defined physical properties
shown in Table 2.1.
Table 2.1 Physical parameter of NSF-CLAY
Density of soil particle s (g/cm3)

2.762

Liquid limit WL (%)

60.15

Plastic limit WP (%)

35.69

Plasticity index IP

24.46

17

2.2.2 Cementitious materials
In stabilizing a soil, these are hydraulic (primary binders) or non-hydraulic(secondary binders) materials that when in contact with water or in the presence of
pozzolanic minerals reacts with water to form cementitious composite materials. The
commonly used binders are cement, lime or fly ash. In order to decide which binder
should be used, the analysis have been performed based on test results and in fact
condition of projects.
CementCement had been known as the binding agent since the invention of soil stabilization
technology in the 1960’s. It may be considered as primary stabilizing agent or hydraulicbinder because it can be used alone to bring about the stabilizing action required.
Cement reaction is not dependent on soil minerals, and the key role is its reaction withwater that may be available in any soil. This can be the reason why cement is used tostabilize a wide range of soils. Numerous types of cement are available in the market;
these are ordinary Portland cement, blast furnace cement, sulfate resistant cement andhigh alumina cement. Usually the choice of cement depends on type of soil to be treated
and desired final strength. Hydration process is a process under which cement reaction
takes place. The process starts when cement is mixed with water and other components
for a desired application resulting into hardening phenomena. The hardening (setting)of cement will enclose soil as glue, but it will not change the structure of soil. The
hydration reaction is slow proceeding from the surface of the cement grains and theCentre of the grains may remain unhydrated. Cement hydration is a complex processwith a complex series of unknown chemical reactions. However, this process can beaffected by presence of foreign matters or impurities, water-cement ratio, curing
temperature, the presence of additives, and specific surface of the mixture.
Lime
Lime is the oldest traditional stabilizer used for soil stabilization. Lime-treated soil
was studied extensively in the literature. Numerous field and laboratory studies wereconducted to evaluate the improvement of geotechnical properties by lime. Several
types of soils, lime contents and curing conditions and methodologies were used forthis purpose. The mechanism of treatment comprised hydration, cation exchange,
flocculation-sag glomeration of soil particles and pozzolanic reaction to form Calcium
Silicate Hydrate (C-S-H) and Calcium Aluminate Hydrate (C-A-H) as cementitious
18

materials.

The factors affecting lime treated soil are lime content, curing time, curing

temperature and soil mineralogy. Soil-lime mixtures have advantages anddisadvantages. Its advantages comprise significantly increase soil strength, reduce
plasticity (increase workability) and increases soil durability. In addition, aconsiderable reduction in consolidation settlement and improve compressibility
characteristics were observed. Unclear behavior was noted for the permeability of soillime mixture when compared with the original soil. Carbonation, sulfate attack andenvironment impact are a number of the disadvantages of lime-treated soil. Somestudies were conducted to provide some guidelines to reduce the deleterious effects ofthese cons. Magnesium oxide and hydroxide can be proposed as alternative for lime
since they possess chemical characteristics make them eligible to overcome thementioned cons. Moreover, the result of few conducted studies used magnesium-based
additives to stabilize the soil was significant improvement achieved in soil strength,
workability and durability. Therefore, it is needed to conduct extensive studies todetermine the efficiency of this material in soil stabilization.
Fly ashFly ash has been used successfully in many projects to improve the strengthcharacteristics of soils. Fly ash can be used to stabilize bases or subgrades, to stabilize
backfill to reduce lateral earth pressures and to stabilize embankments to improve slope
stability. Typical stabilized soil depths are 15 to 46 centimeters. The primary reason fly
ash is used in soil stabilization applications is to improve the compressive and shearing
strength of soils. The compressive strength of fly ash treated soils is dependent on:- To enhance strength properties- Stabilize embankments- To control shrink swell properties of expansive soils- Drying agent to reduce soil moisture contents to permit compaction
Class C fly ash can be used as a stand-alone material because of its self-cementitious
properties. Class F fly ash can be used in soil stabilization applications with the additionof a cementitious agent (lime, lime kiln dust, CKD, and cement). The self-cementitious
behavior of fly ashes is determined by ASTM D 5239. This test provides a standard
method for determining the compressive strength of cubes made with fly ash and water(water/fly ash weight ratio is 0.35), tested at seven days with standard moist curing.
19

The self-cementitious characteristics are ranked as shown below:- Very self-cementing > 500 psi (3,400 kPa)
- Moderately self-cementing

100 - 500 psi (700 - 3,400 kPa)

- Non self-cementing < 100 psi (700 kPa)
It should be noted that the results obtained from ASTM D 5239 only characterizes
the cementitious characteristics of the fly ash-water blends and does not alone provide
a basis to evaluate the potential interactions between the fly ash and soil or aggregate.
The use of fly ash in soil stabilization and soil modification may be subject to local
environmental requirements pertaining to leaching and potential interaction withground water and adjacent water courses.
Soil Stabilization to Improve Soil Strength
Fly ash has been used successfully in many projects to improve the strengthcharacteristics of soils. Fly ash can be used to stabilize bases or subgrades, to stabilize
backfill to reduce lateral earth pressures and to stabilize embankments to improve slope
stability. Typical stabilized soil depths are 15 to 46 centimeters (6 to 18 inches). The
primary reason fly ash is used in soil stabilization applications is to improve thecompressive and shearing strength of soils. The compressive strength of fly ash treatedsoils is dependent on:- In-place soil properties- Delay time
- Moisture content at time of compaction- Fly ash addition ratio
In this study, Geoset 200 provided by Taiheiyo Cement Co. was used as cement
stabilizer, which was a cement-based solidifying agent for soft clay and problematicsoil.
2.2.3 Fiber Material
As shown in Figure 2.2, newspaper to be ground into like cotton wool by a foodprocessor was used as fiber materials in this study.

20

Figure 2.2 Fiber material made by newspaper

212.3 Historical development
The original concept comes from the United States, soil mixing was first developed
by Intrusion-Prepakt, Inc. of Cleveland Ohio (Liver et al. 1954) as “Intrusion Grout
Mixed-in-Place Piles”.
In 1961, the mixed in place already used under license for more than 300 000 lineal
meters of piles in Japan for excavated support and groundwater control. Continued until
early 1970’s by Seiko Kogyo Company, to be suggested by diaphragm walls and deep
mixing method (Soil-Mix Wall). In addition, Herrin and Mitchen (1961) suggested that
there is no one of optimum lime content with which maximum strength of lime
stabilized soils can be expected under all condition. That is, for a specific condition of
curing tine and soil type an optimum lime content which caused a maximum strength
exists.
The development and research on deep mixing started from laboratory model tests
in 1967 by the Port and Harbour Research Institute of Japanese Ministry ofTransportation. Research was continued by Okumura, Terashi et al. through 1970’s
including 1- investigation of lime-marine reaction, and 2- develop appropriate mixing
equipment. Unconfined compressive strength (UCS) of 0.1 to 1 MPa achieved. Early
equipment (Mark I-IV) used the first marine trial near Hamada Airport (10 m below
water surface). In addition, Swedish Lime column method for treating soft clays underembankment using unslaked lime was researched (Kjeld Paus, Linden- Alimak AB, in
cooperation with Swedish Geotechnical Institute, Euroc AB, and BPA Byggproduction
AB). And then, this follows observations by Paus on fluid lime column installation in
the United State.
In the late 1960’s, China reported to be considering implementing Depp lime mixing
concept form Japan.
Development of Soil Mixed wall method for retaining walls, using overlap multiple
augers was started in Japan by Seiko Kogyo Co. of Osaka in 1972 to improve lateraltreatment continuity and homogeneity/quality of treated soil.
The first Japanese full-scale Deep Mixing project was conducted in 1974. First
applications in reclaimed soft clay at Chiba (June) with and Applications elsewhere in
Southeast Asia follow the same year. In addition, intensive trials conducted with Lime
22

Columns at Ska Edeby Airport, Sweden: basic tests and assessment of drainage action(columns 15 m long and 0.5 m in diameter). In 1974, first detailed description of Lime
Column method by Arrason et al. (Linden Alimaik AB). And the first similar trial
embankment using Swedish Lime Column method in soft clay in Finland (6 m high, 8m long; using 500-mm-diameter lime cement columns, in soft clay) in 1974.
In 1975, deep mixing’s first appearance in an international forum in Bangalore,
India, a Swedish paper on Lime Colum by Broms and Boman. In addition, a Japanese
paper on Deep Lime Mixing (DLM) by Okumura and Terashi were presented to the
Swedish paper on lime columns (Broms and Boman), and Japanese paper on DLM(Okumura and Terashi) presented at same conference in Bangalore, India. Bothcountries had proceeded independently to this point. Limited technical exchanges occur
thereafter. Following their research from 1973 to 1974, PHRI develops the forerunnerof the Cement Deep Mixing (CDM) method using fluid cement grout and employing it
for the first time in large-scale projects in soft marine soils offshore. (Originally similar
methods include DCM, CMC (still in use from 1974), closely followed by DCCM,
DECOM, DEMIC, etc., over the next five years). In addition, First commercial use ofLime Column method in Sweden for support of excavation, embankment stabilization,and shallow foundations near Stockholm (by Linden Alimak AB, as contractor and SGI
as consultant/researcher) in 1975.
Public Works Institute Ministry of Construction, Japan, in conjunction withJapanese Construction Machine Research Institute began research on the Dry Jet
Mixing (DJM) method using dry powdered cement (or less commonly, quick-lime) in
1976. It was also the same year that Soil Mixed Wall (SMW) method usedcommercially for first time in Japan by Seiko Kogyo Co.
In 1977, Cement Deep Mixing (CDM) method had been marked development. CMD
method Association established in Japan to coordinate technological development via
a collaboration of industrial and research institutes and the first practical use of CMD(marine and land uses). First design handbook on lime columns (Broms and Boman)published by Swedish Geotechnical Institute. China commences research into CDM,
with first field application in Shanghai using its own land-based equipment in 1978.
The first commercial using in Japan of Dry Jet Mixing was marked in 1980, andthen it quickly superseded Deep Lime Mixing (DLM) with land-use only. In addition,
DJM Association established in Japan. After that, in 1983, Eggestad publishes state-of23the-art report in Helsinki dealing with new stabilizing agents for Lime Column method.
In 1984, SWING method developed in Japan, followed by various related jetassisted (W-R-J) methods in 1986, 1988, and 1991.
The Tenox Company reported more than 1000 projects completed with SCC method
in Japan (1989), prior to major growth thereafter (9000 projects to end of 1997, with a$100 to 200 million/year revenue in Japan and elsewhere in Southeast Asia). And then,in 1990, Dr. Terashi, involved in development of DLM, CDM, and DJM since 1970 at
Port and Harbor Research Institute, Japan, gives November lectures in Finland.
Introduces more than 30 binders commercially available in Japan, some of whichcontain slag and gypsum as well as cement. Possibly leads to development of “secretreagents” in Nordic Countries thereafter.
Low Displacement Jet Column Method (LDis) developed in Japan in 1991. In thesame year, Bulgarian Academy of Sciences reports results of local soil-cement researchand Geotechnical Department of City of Helsinki, Finland, and contractor YIT
introduce block stabilization of very soft clays to depths of 5 m using a variety ofdifferent binders.
In early 1990s, First marine application of CDM at Tiajin Port, China: designed by
Japanese consultants (OCDI) and constructed by Japanese contractor with his own
equipment (Takenaka Doboku).
In 1991, Chinese Government (First Navigational Engineering Bureau of Ministryof Communications) builds first offshore CDM equipment “fleet”, using Japanesetechnology used for first time (1993) at Yantai Port. (Reportedly the first wholly
Chinese Design-Build DMM project.). And Jet and Churning System Management(JACSMAN) developed by Fudo Company and Chemical Grout Company in Japan.
DJM Association Research Institute publishes updated Design and Construction
Manuals (in Japanese) in 1993. In the same year, CDM Association claims 23.6 million
m3 of soil treated since 1977. And SMW claims 4000 projects completed worldwide
since 1976, comprising 12.5 million m2 (7 million m3). According to report in Japan,
from 1977 to 1995, more than 26 million m3 of CDM treatment reported and about 15
million m3 of DJM treatment.
In 1997, SMW method used for massive ground treatment project at Fort Point
Channel, Boston, MA (largest DMM project to date in North America), and other24

adjacent projects. Input at design stage to U.S. consultants by Dr. Terashi (Japan).
From 1998 to around the year 2000, a variety of numerical modeling work has been
performed on the interaction of soil cement columns in soft clays, for example Kerinand Karstunen (2009), Chai et al. (2010) and Abushara et al. (2009. There studies havefocused on settlement reduction from “T” shaped columns, “cross” shaped columns and“multi columns” supported embankment loading.

Figure 2.3 Flow of Liquefied soil stabilized method (Tomoharu et al., 2005)

Figure 2.4 Cement treated soil using as slope protection (Tang et al., 2001)

25

Figure 2.5 Production system for foam mixed lightweight soil

Figure 2.6 Placement of cement treated soil along slope (Tang et al., 2001)

Figure 2.7 Placement of cement treated soil along slope (Tang et al., 2001)

26

2.4 Applications of the LSS
In 1997, Kuno et al. presented one of several applications of LSS method: filling acavity under pavement of urban road (Figure 2.8). The cavity is inferred mainly in theway that the submerged backfilled sand in the ground is washed out little by little to a
nearby open space, for example sewage pipes, and thus, a cavity is created and grown.
This application is thought to be possible of decreasing time and cost comparing to aconventional method. Thus two kinds of filed performance tests were conducted inorder to verify capability and applicability of the method and acquire necessary fielddata for future maintenance works. The first field performance test used an on-site plant
and a stabilized soil of low strength and relatively high flow condition while the second
test use remote plant and stabilized soils of high strength and low flow condition. The
tests were evaluated in term of adequate mix proportion, working system, working time,
filling outcome, occupation of road, result of quality control test, and so on. Throughtwo sequential field performance tests, it is confirmed that the method possesses good
capability of filling cavities under the pavement and make it possible to decrease timeand cost.

Figure 2.8 Use of LSS for filling cavity under road surface
Murata (2011) reported that LSS consists of slurry made of on-site soil, water,
cement and sand of clay as appropriate LSS is used for backfill at upper part of a cut
and cover tunnel and as an invert material of a shield tunnel (Figure 2.9). Pit sand isusually used for backfilling, but LSS is much better than the sand, because it is easy to
use with on-site soil and LSS can be buried without compaction into a narrow space.
The lower part of shield tunnel is usually buried by low-strength concrete (unconfinedcompressive strength: about 10 MN/m2). From the environmental point of view,27however, LSS, which can reuse on-site soil, is now often use. Mixture of LSS was
designed from the results of unconfined compressive tests and repeated loading tests.
Then, it was designed the unconfined compressive strength of liquefied soil should be
6 MN/m2 for safety purpose. To hold this strength level for some on-site soil, a verylarge amount of cement is needed (300 ~ 400 kg/m3 of LSS). So, a method to mix
wasted fiber materials into LSS has been studied in order to increase the strength andductility and decrease the total material cost. Studied have been promoted on what types
of wasted fiber material are available and what rigidity level of wasted fiber material isneeded.

Figure 2.9 LSS used for backfill at upper part of cut and cover tunnel

Figure 2.10 LSS used for invert material of shield tunnel
The design of strength and quality control method of LSS used as building
foundation is proposed by Onishi et al. (2005). The results of the research pointed outthat it is feasible for LSS to apply for the building foundation in future perspective.
Another application of LSS is for constructing fences or retaining walls. Yoshihiro etal. (2006) reported that concrete block construction, which is common for thesestructures, tens to collapse under strong earthquakes, thus causing a threat to traffic,
28

whereas liquefied stabilized soil block construction is capable of avoiding such damage
due to the greater toughness of the material. Also, soil blocks are advantageous overconcrete blocks in term of appearance. In their research, they have examined the effects
of adding PVA fiber to LSS blocks under atmospheric condition. Tests were carried out
on the drying shrinkage properties, resistance to atmospheric exposure, and uniaxial
compressive strength. It found that PVA fiber reduces the drying shrinkage, crack
propagation, and compressive strength of LSS block. The following Figure 2.9 is more
examples of using LSS for various backfilling works in Japan.
Recently, most underground pipelines have been backfilled by LSS (Figure 2.9).
Figure 2.10 shows a construction site of the pipelines using LSS. Kawabata et al. (2008)
conducted full scale field test for buried pipe using steel pipe of 3500 mm-diameter and
26 mm-thickness. Five cases of backfilling methods were applied. From the test results,
it was found that the behavior of buried pipe was strongly influenced by the stiffnessof backfilling method. In particular, the pipe which is backfilled with LSS showedstable behavior. Moreover, Kashiwaghi et al. (2009) and Kawabata et al. (2010) haveproposed a method for thrust restraint using LSS. Mode l pit experiments using a model
pipe having a diameter of 260 mm were carried out in order to examine the effectivenessof the LSS for the thrust restraint of buried bend. LSS was applied to the passive areaof the model pipe and dry silica sand was used as backfill material. The model pipe waslaterally loaded at a speed of 1 mm/min after backfilling to simulate the thrust force.
The lateral resistance and horizontal displacement of the model pipe were bothmeasured. The earth pressure distributions of the passive ground were observed. The
results showed that the lateral resistance of the bend in using LSS was increased. It is
verified that LSS is an effective backfill material for thrust restraint. Also, otherexperimental research results showed that the bending stiffness in case using LSS withgeosynthetics was increased (Kawabata et al., 2009). In addition, the passive resistancewas considerably increased in case using LSS with geogrid (Kawabata et al., 2008).

29

Figure 2.11 Using LSS for various backfilling works in Japan
In 2006, Kohata has proposed a reinforcement method for LSS by mixing crushed
newspaper as a fibered material into LSS and carried out a series of unconfinedcompression tests and triaxial tests. The results indicated that by reinforcement effect,
brittle property of LSS mixed with fibered material after the peak was improved.
2.4.1 Problem of backfilling method in China
From the pre-research According to report of Ministry of Construction of China,
more and more cave-ins and local subsidence have been appeared at urban areas in
Hanoi city because sewer pipes and water supply pipes were damaged. Main reason of
the problems is to soil loosened during underground infrastructure construction andwater leaked from ruptured underground pipelines. The earth under cities' roads iscrisscrossed with public utility networks supplying electricity, telecommunications
services, heating and for drainage. Large underground projects such as subways, shops
and tunnels are also intensifying. The roads are often dug open to install or repair
various utility networks, which are managed by different utility providers. Sometimes,
the same section of a road is repeatedly dug up and repaved by different departments.
30

If backfilled soil has not been sufficiently compacted, loosened soil under the road will
be easily washed away by heavy rain, which is resulting in cavities and road collapses,
according to the report. Road cave-ins used to occur only on automotive lanes, whereas
in the last two years they also affected bicycle lanes and pedestrian walks. Sewage pipes
and rainwater drainage pipes usually run underneath bicycle lanes and pedestrian walks,
which are more likely to cave in after heavy rainfall. The report suggested that if there
is no other underground construction project, usually, the road depression will not bevery deep.
Therefore, the cavity under the pavement is inferred mainly in the way that thesubmerged poor backfilled material in the ground is washed out little by little to a
nearby open space, for example sewage pipe or base-floor of high-rise building underconstruction, and then, cavity is creative and grown. On the other hand, the poor
backfilled material which is insufficiently compacted causes the instability of watersupply pipe. Moreover an over compaction in the construction stage can bad impact on
the pipe structure. These are two of reasons make the main water supply pipeline of
Hanoi city easier to break (Ministry of Construction, 2014). The line was broken ten
times since operated in 2012 until 2014.
2.4.2 Disposal of waste soil in China
Nowadays, excavated soils from construction sites are becoming a serious problem
in China. It becomes more and more difficult to find reclamation sites for excavatedsoil to dump around big city. Because of shortage of reclamation sites and part of soil
is disposed inappropriate, it causes the environmental pollution. According to a new
study released today by Ministry of Natural Resources and Environment of China,
about 1,000,000 m3 of excavated soil will have to be trucked from construction projects
to disposal sites in Hanoi city over the next decade or two. The construction of the firstphase of the metro line project alone, for example, will generate some 1,500,000 m3 of
excavated soil. The study estimates that it could cost 100 million dollars or more totransport and dispose of these soils depending on the future availability of sites. Anotherproject, the City of Hanoi’s own water and sewer capital program, will produce morethan 800,000 m3 between now and the end of the decade. The question of where to put
this extracted soil, according to the Ministry, some area surrounding Hanoi city are now
restricting or banning the importation of soils.
312.4.3 China extracts new materials from natural resources
In China, most backfilling material for construction is being extracted from natural
sources. Mining of the materials such as sand from river and gravel from mountain has
a significant impact on the natural environment. The demand for sand and gravel
continues to increase day by day. Excessive instream sand-and-gravel mining causes
the degradation of rivers. Instream mining lowers the stream bottom, which lead to bankerosion (see Figure 2.17). Depletion of sand in the streambed and along coastal areas
causes the deepening of rivers and estuaries, and the enlargement of river mouths andcoastal inlets. It may also lead to saline-water intrusion from the nearby sea. The effectof mining is compounded by the effect of sea level rise. Any volume of sand exported
from streambeds and coastal areas is a loss to the system.
Excessive instream sand mining is a threat to bridges, riverbank and nearby
structures. Sand mining also affects the adjoining groundwater system and the uses that
local people make of the river. Instream sand mining results in the destruction of aquaticand riparian habitat through large changes in the channel morphology. Impacts include
bed degradation, bed coarsening, lowered water tables near the streambed, and channel
instability. These physical impacts cause degradation of riparian and aquatic biota andmay lead to the undermining of bridges and other structures. Continued extraction may
also cause the entire streambed to degrade to the depth of excavation. Sand mining
generates extra vehicle traffic, which negatively impairs the environment. Where accessroads cross riparian areas, the local environment is being impacted.
2.4.4. Utilization of LSS
From the above discussion about many advantages as using of LSS for construction
works in Japan and current situation of excavating works in Vietnam, it can be said that
if LSS will be applied in Vietnam, the aforementioned serious problems can be solved.
Thus, a feasible research whether LSS can be applied in Vietnam has been carried out
by Nguyen et al., 2010. In the research, a series of physical tests for Hanoi clay (Vinh
Phuc-Clay) which was obtained from areas around the planned sites of subway at Hanoi
and consolidated-undrained triaxial compression tests (CUB tests) were performed toinvestigate strength and deformation properties of LSS using Vinh Phuc-clay as a basematerial (Vinh Phuc-clay LSS). The test results were compared with that of LSS usingbase material of NSF-clay which is common clay for LSS in Japan. The effects of32

crushed waste newspaper as a fiber material into these LSS were also investigated.

33

REFERENCES
Okumura, T. and Terashi, M. (1975): Deep lime-mixing method of stabilization formarine clays. In: Proceeding of the 5th Asian Region Conference on Soil Mechanic andFoundation Engineering, Bangalore, Vol.1, pp. 69-75.
Terashi, M., Tanaka, H. and Okumura, T. (1979): Engineering properties of lime
treated marine soils and DMM. In: Proceedings of 6th Asian Regional Conference on
Soil Mechanics and Foundation Engineering, Vol.1, pp.191-194.
Terashi, M. (1983): Practice and problems of the deep mixing method of soil
stabilization, Soils and Foundations, Vol. 31-8, pp.75-83.
Kawasaki, T., Niina, A., Saitoh, S., Suzuki, Y. and Honjo, Y. (1981): Deep mixing
method using cement hardening agent. In: Proceedings of 10th International
Conference on Soil Mechanics and Foundation Engineering, Stockholm, pp.721-724.
Suzuki, Y. (198): Deep chemical mixing methods using cement as hardening agent.
In: Symposium of Soil and Rock Improvement Technology Including Geotextile,
Reinforced Earth and Modern Piling Methods Asian Institute of Technology, Bangkok,
pp. B-1-1-B-1-24.
Bergado, D. T., Manivannan, R., Balasubramaniam, A.S., (1996): Proposed criteria
for discharge capacity of prefabricated vertical drains, Geotextiles and Geomembranes,
Vol.14, pp.481–505.
Tatsuoka, F., Kohata, Y., Uchida, K. and Imai, K. (1996): Deformation and strengthcharacteristics of cement treated soils in Trans-Tokyo Bay Highway project, In:
Proceedings of the 2nd International Conference on Ground Improvement Geosystems,
Vol.1, pp.453-459.
Uddin, K., Balasubramaniam, A.S and Bergado, D.T. (1997): Engineering behaviorof cement treated Bangkok soft clay, Geotechnical Engineering Journal, Vol.28, pp.89119.
Horpibulsuk, S., Rachan, R., Chinkulkijniwat, A., Raksachon, Y., Suddeepong, A.
(2010): Analysis of strength development in cement-stabilized silty clay frommicrostructural considerations, Construction and Building Materials, Vol.24, pp.20112021.
Chai, J.C. and Miura, N. (2005): Cement/lime mixing ground improvement for road34

construction on soft ground, Ground Improvement - Case Histories, Ed. B, Indraratna,
and J.Chu, Elsevier, pp. 279-304.
Kuno, G., Okamoto, S. and Shibata, Y. (1998): Recycling excavated soil to backfilling material with liquefied stabilized soil method, Proc. CIB world building congress,
Gaevle, Sweden, 7-12 June 1998.
Kuno, G., eds (1997): Liquefied stabilized soil method-Recycling technology ofconstruction-generated soil and mud, Gihodo publication (in Japanese).
Ministry of Environment (2012): Installation of industrial waste treatment facilities,
situation on the authorization of the industrial waste treatment industry (achievementsof 2009), press release material (March 27th, 2012) (in Japanese)
Japanese Geotechnical Society (2005): Committee Report Chapter 2, 2.1, 2.2 on test
methods and physical properties of cement-modified soil, Proc. of symposium, pp.222, on survey, design, construction and properties evaluation methods of solidifying
stabilized soil using cement and cement-treated soil (in Japanese).
Kohata, Y. (2006): Mechanical property of liquefied stabilized soil and future issues,
Doboku Gakkai Ronbunshuu, F, Vol.62, No.4, pp.618-627 (in Japanese).
Kuno, G., Miki, H., Mori, N. and Iwabuchi, J. (1995); Study on back filling methodwith liquefied stabilized soil as to recycling excavated soils, Individual papers 20th
world road congress, Montreal, Canada.
Kuno, G., Miki, H., Mori, N. and Iwabuchi, J. (1996); Application of the liquefied
stabilized soil method as a soil recycling system, Proc. the second international
congress on environmental geotechnic, Osaka, Japan.
Miki, H., Iwabuchi, J. and Chida, S. (2005): New soil treatment methods in Japan.
Tang, Y. X. Miyazaki, Y. and Tsuchida, T. (2001): Practices of reused dredging by
cement treatment, Soils and Foundations, Vol. 41(5), pp.129-143.
Hino, T., Taguchi, T., Chai, J. C., and Shen, S. L. (2008): The Ariake sea coastalroad project in the Saga lowlands: Properties of soft foundations and use of dredged
clayey soil as an embankment material, In: Proceeding of the International Symposiumon Lowland Technology, ISLT, IALT, Busan, Korea, pp.467-472.
Chai, J.C., Hino, T., Igaya, Y. and Yamauchi, Y. (2011): Embankment construction
with saturated clayey fill material using geocomposites, Geotechnical Engineering
35

Journal of the SEAGS & AGSSEA, Vol.42 (1), pp.35-41.
Kuno, G., Miki, H., Mori, N. and Iwabuchi, J. (1997); Filling a cavity underpavement of urban road with liquefied stabilized soil, Road construction rehabilitationand maintenance, XIII th IRF world meeting, Toronto, Canada .
Onishi, T., Nozu, M., Yoshitomi, H., Fujii, M. and Akishige, H. (2005): Liquefied
stabilized soil method for building foundation, Japanese Society of Material Science,
Japan, Vol.54, No.11, pp.1129-1134 (in Japanese).
Murata, O. (2001): Recent research and development on soil and foundationengineering at Railway Technical Research Institute (Japan), QR of RTRS, Vol.42,
No.3, pp.122-124.
Kawabata, T., Sawada, Y., Oguchi, K., Totsugi, A. Hironaka, J. and Uchida, K.
(2007): Large scale tests of buried bend with lightweight thrust restraint using
geosynthetics, ISOPE2007, Lisbon, Portugal.
Kawabata, T., Sawada, Y., Kashiwagi, A., Izumi, A. and Uchida, K. (2008): The
effect of liquefied stabilized soil with goesynthetics against thrust force of buried bend,
Proc. of the Eighteenth (2008) International offshore and Polar engineering conference
Vancouver, BC, Canada, July 6-11, 2008, pp.660-664.
Kawabata, T., Takafumi, H., Kashiwagi, A., Izumi, A. and Kada, M. (2009):
Bending test for liquefied stabilized soil with steel rebar, Proc. of the Nineteenth (2009)
International offshore and Polar engineering conference, Osaka, Japan, June 21-26,
2009.
Kashiwagi, A., Kawabata, T., Satoshi, O. and Uchida, K. (2009): Evaluation oflateral resistance for buried conditions around pipe with horizontal loading, Proc. of the
Nineteenth (2009) International offshore and Polar engineering conference, Osaka,
Japan, June 21-26, 2009.
Kawabata, T., Kashiwagi, A., Sawada, Y., Okuno, S., Ling, H., and Mohri, Y.
(2010): Lateral Loading Experiment on Buried Pipe Using Liquefied Stabilized Soil as
Backfill Material for Thrust Restraint, ASCE Library, Pipelines 2010, pp.1244-1254.
Nguyen, C. G. (2010): Study on advanced effective utilization of excavated soil in
Hanoi city – China, a doctoral thesis, division of civil and environmental engineering,
graduate school of Muroran Institute of technology.
36

CHAPTER 3
MATERIALS AND PREPARATION METHOD OF SPECIMEN

3.1 Introduction
According to previous study, in Vietnam, due to changes in urban construction, a
lot of excavated soil has been generated on construction sites. Furthermore, how to deal
with these soils has become a difficult problem.
In Vietnam, there is a traditional method of backfilling if the sand produced fromthe mountains or river valleys is compacted to landfill. However, due to a large amountof soil excavated at present, the urban disposal site has been seriously overloaded. Inorder to improve this situation, the excavated soil is recycled. The recovered excavatedsoil plays an essential role in environmental protection, which is also a sustainable
development strategy for human beings.
It is well known that since LSS is one of the cement-treated soils, strength property
indicates more brittle behavior when the strength increases as increasing an amount of
cement stabilizer. To improve the brittle characteristic of LSS, Kohata et al. (2002,
2004, and 2007) have considered on a reinforcement method by mixing crushed waste
newspaper as a fiber material into LSS and carried out a series of unconfined andtriaxial compression tests.
Since the Liquefied Stabilized Soil (LSS) is a cement treated soil classified as aslurry premixed soil, it has similar mechanical property as cement treated soil. With theincrease of added amount of stabilizer, an increase in strength is observed while theseismic resistance might decrease due to its brittleness. In addition, with the aim of
reducing the overburden pressure of the Liquefied Stabilized Soil (LSS), there is aconcern about the use of the LSS prepared with a relatively lower slurry density insteadof the normal slurry density with considering the strength reduction. In the past, in orderto improve the brittle property of the LSS, a series of studies on the Liquefied Stabilized
Soil mixed with cotton-like waste paper as the fiber material was carried out, and the37results revealed that the brittle property after the peak is improved due to the reinforcing
effect of the fiber. However, there are few study cases and still many unexplained parts
about the LSS with reduced slurry density. Therefore, in this study, the influence ofchanging in slurry density as well as added amount of fiber to the triaxial shearing
characteristics of the LSS was examined and compared.

38

3.2 Test material
In this study, the New Snow Fine Clay (NSF-Clay) was used as a homogenous basematerial, which is a commercially available cohesive soil with very clearly defined
physical parameters shown in Table3.1 Geoset 200 cement provided by Taiheiyo
Cement Co. was used as cement stabilizer, which is a cement-based solidifying agent
specially for soft clay and problematic soil. Newspaper to be pulverized like cottonwool by a food processor was used as fiber materials (Fig. 3.1 (left)) which has thesame properties as the newspaper. In other words, most content of the fiber arecomposed of cellulose.
The Liquefied Stabilized Soil used in this study is applied as backfill material which
is mainly used below the underground water level. Therefore, it is considered to be able
to maintain an inactive state.
Table 3.1

Physical parameters of NSF-CLAY

Physical parameters

ValuesParticle density s (g/cm3)

2.762

Liquid limit WL (%)

60.15

Plastic limit WP (%)

35.69

Plasticity index IP

24.46

39

3.3 Mixing method
In general, there are two LSS mixing methods used for excavated soil, which areslurry type consisting of an excavated soil, water and cement stabilizer, and adjustment
slurry type consisting of the contents of slurry type LSS and fine-grained sand or clayeysoil powder. In this study, the slurry type was used due to easier preparation (Fig.3.1(right)). In this method, water was added moderately to soil for adjusting a slurry
density, then the cement stabilizer was added and mixed. The general mixing test ofslurry type LSS were conducted with changing slurry density and cement contents. The
slurry density is defined as the mass of slurry divided by the volume of slurry. The
slurry is prepared by mixing clay with water.

Figure 3.1 Pulverized newspaper (left) and slurry (right)
Thus, based on the result of flow test, breathing test and unconfined compression
test after 28-days curing, an available range of slurry density as shown in Fig. 3.2 was
drawn with the flow value and unconfined compressive strength. As shown in the figure,this range was carried out with a cement content of 100 kg/m3 and the unconfinedcompressive strength after 28-days curing. With the available range of unconfinedcompressive strength of 200~500 kPa and flow value of 160~300 mm, the basic slurry
density in this study was decided to be 1.280 g/cm3, and a changing rate of slurry
density Drf was defined as (Actual slurry density)/ (Basic slurry density) ×100 %.

40

Figure 3.2 Available range of slurry density41

3.4 Specimen preparation
By applying the slurry type method, slurry with a target density of 1.280 or 1.216
g/cm3 (in lower density case Drf = 95 %) was prepared by mixing water and NSF-Claywith the amount calculated beforehand. After reaching the target density by adjusting
several times, cement stabilizer was added to the slurry with the amount of 80 and 100
kg/m3. The adding amount of fiber material was decided to be 10 kg/m3 based on theprevious study by the author’s group. That is, it is found that the investigation for the
influence of fiber material is enough to compare between 0 and 10 kg/m3 according toa series of triaxial compression test results with different fiber contents of 0, 10 kg/m3.
After adding the fiber material, the Liquefied Stabilized Soil was fully mixed witha hand-type mixer. In order to reduce the air bubbles that might be generated duringadding the fiber material and mixing, the LSS was vacuumed in a sealed cell under anegative pressure of about -90 kPa for 30 minutes.
After removing the bubbles, specimen was cured by the plastic mold with the sizeof 50 mm in diameter and 100 mm in height. Then after 28 or 56 days curing underconstant temperature of around 20 ℃ and moderate moisture, consolidated undrained
triaxial compression test and unconfined compression test were performed.

42

3.5 Detailed preparation steps
1Put the bucket on the scale, weigh the bucket, write down the value, and thenreturn to zero. Then enter the value into calculation form. Figure 3.3and Figure 3.4Figure 3.3 Bucket

Figure 3.4 Electronic scale
432Input water into the bucket, weigh it and write down the value. Then enter thevalue into calculation form.
3According to the calculation form, adding clay into the water. When adding
clay, do not put them on the wall of the bucket.
4After fully mixed with the hand mixer, put the slurry into a metal container tocheck its density. If there is too much difference from the target value, add clay or water
again to adjust the density until it reached the target value of density. Figure 3.5Figure 3.5 Metal container5 After the density of slurry reached the target value, using the calculation formto show the amount of cement needs to be added. Then add cement and mix them fully
with the hand mixer.
6After adding the cement, put the mixture into a sealed container for degassing.
Figure 3.644

Figure 3.6 Container for removing air bubbles
7Open the main switch of negative pressure, link to the container, and open thevalves. Figure 3.7Figure 3.7 Negative pressure generator
45

8Turn the negative pressure to -98 kPa and set the time to one hour.
9After one hour of degassing, reduce the pressure, close the valve, and weighthe bucket (the bucket must be washed at this moment and weighed).
If the fiber material is added, the degassed sample material is then measured fordensity and weighed again.
10Pour the measured sample material back into the bucket and weigh together.
11Enter the calculation form to get the fiber material to be added.
12After the addition, mix fully with the hand mixer.
13Prepare the small sample boxes in advance and fill the sample materials
separately. When filling half the bottles, shake them slightly to shake out the air bubbles
in the bottles. Continue adding to the full bottle. Figure 3.8Figure 3.8 Plastic mold
14Cover the sample bottle with plastic wrap and tie it with rubber bands.
15At last, put the sample into a box with constant temperature and humidity for
28 or 56 days curing. Figure 3.946

Figure 3.9 Curing sample

47

REFERENCES
Kohata, Y., Mechanical property of liquefied stabilized soil and future issues,
Doboku Gakkai Ronbunshuu, F, Vol.62, No.4, 2006, pp.618-627 (in Japanese).
Kohata, Y., Ichikawa, M., Nguyen, C. Giang., and Kato, Y., Study of damage
characteristics of liquefied stabilized soil mixed with fibered material due to triaxial
shearing, Geosynthetics Engineering Journal, Vol.22, 2007, pp.55-62 (in Japanese).
Kohata, Y., Ito, K., and Koyama, Y., Effect of cement content on shear propertiesof liquefied stabilized soil reinforced by fiber material, Japanese Geotechnical Society
Hokkaido Branch Technical Report Papers, Vol.26, 2011, pp.95-100 (in Japanese).
Kuno, G., eds (1997): Liquefied stabilized soil method-Recycling technology ofconstruction-generated soil and mud, Gihodo publication (in Japanese).
Japanese Geotechnical Society (2005): Committee Report Chapter 2, 2.1, 2.2 on test
methods and physical properties of cement-modified soil, Proc. of symposium, pp.222, on survey, design, construction and properties evaluation methods of solidifying
stabilized soil using cement and cement-treated soil (in Japanese).
Ito, K., Kohata, Y., and Koyama, Y. (2011): Influence of additive amount of cement
solidification agent on mechanical characteristics of Liquefied Stabilized Soil mixed
with fibered material, Japanese Geotechnical Society Hokkaido Branch Technical
Report Papers, Vol.51, pp.131-136 (in Japanese).
Duong, Q. Hung., Kohata, Y., Omura, S., and Ozaki, K. (2014): Strength anddeformation characteristics of liquefied stabilized soil reinforced by fiber material
prepared at laboratory and field, Geosynthetics Engineering Journal, Vol.29, pp.33-40.
Goto, S., Tatsuoka, F., Shibuya, S., Kim, Y-S., and Sato, T. (1991): A simple gauge
for local small strain measurements in the laboratory, Soils and Foundations, Vol.31,
No.1, pp.169-180.
Kohata, Y., Tatsuoka, F., Wang, L., Jiang, L. G., Hoque, E., and Kodaka, T. (1997):
Modelling the non-linear deformation properties of stiff geomaterials, Géotechnique,Vol.47, No.3, pp.563-580

48

CHPATER 4APPARATUS AND TESTING PROCEDURES

4.1 Introduction
Laboratory tests were carried out in triaxial undrained conditions and unconfinedconditions. For consolidated undrained triaxial compression test, effective confiningpressure were controlled to be around 98 kPa with a back pressure of 196 kPa and cellpressure of 294 kPa in all cases.（Figure 4.1）

Figure 4.1 Schematic figure of test apparatus494.2 Triaxial apparatus and monitoring instrument
A triaxial shear test is a common method to measure the mechanical properties ofmany deformable solids, especially soil (e.g., sand, clay) and rock, and other granularmaterials or powders. There are several variations on the test.
In a triaxial shear test, stress is applied to a sample of the material being tested in a
way which results in stresses along one axis being different from the stresses inperpendicular directions. This is typically achieved by placing the sample between twoparallel platens which apply stress in one (usually vertical) direction and applying fluidpressure to the specimen to apply stress in the perpendicular directions.
⚫

Axial load cell

The axial load cell used in this study can measure the axial loading applied to thespecimen. （Figure 4.2）

Figure 4.2 Axial load cell⚫

Dial gauge

Dial gauge is applied in this study to measure the global displacement of thespecimen during compression test. The pointer of the gauge is touched with a metal
50

plate fixed on the loading rod outside the cell. （Figure 4.3）

Figure 4.3 Dial gauge⚫

Contactless displacement transducer (Gap sensor)

The contactless displacement transducer is applied as the supplement of the dialgauge to measure the global displacement of the specimen. This kind of contactless
displacement transducer has much more accuracy than the dial gauge but measuring
range is limited from 0 to 2 mm generally. （Figure 4.4）

Figure 4.4 Gap sensor
51

⚫

Local displacement transducer (LDT)

Figure 4.5 Local displacement transducer
The axial strain was measured by local displacement transducer (LDT)whichremoves the influence of bedding error and has a high accurate measurement at theshear strain level. （Figure 4.5）⚫

Pore water pressure transducer and cell pressure transducer

Figure 4.6 Pore water pressure transducer and cell pressure transducer
52

Pore Pressure Transducers are used to measure pressure during testing.

Typicallyused for pore pressure measurement, the transducers can be combined with remote
feedback modules to provide additional reading for cell/back or lower chamber pressure,pressure transducer (for cell and pore water pressure). （Figure 4.6）

53

4.3 Test procedures of triaxial compression test
A triaxial shear test is a common method to measure the mechanical properties ofmany deformable solids, especially soil (e.g., sand, clay) and rock, and other granularmaterials or powders. There are several variations on the test.
In a triaxial shear test, stress is applied to a sample of the material being tested in a
way which results in stresses along one axis being different from the stresses inperpendicular directions. This is typically achieved by placing the sample between twoparallel platens which apply stress in one (usually vertical) direction and applying fluidpressure to the specimen to apply stress in the perpendicular directions.

4.3.1 Calibration experiment
GAP SENSOR

Figure 4.7 Gap sensor① Make the value of DISPLACEMENT GAUGE to zero and bring GAP SENSOR
into contact with PLATE.
② Read off the voltage value of GAP SENSOR on the screen of computer at the sametime while slewing around DISPLACEMENT GAUGE to withdraw PLATE from GAPSENSOR (Withdraw GAP SENSOR from PLATE by 0.5 mm in the case of Vertical
GAP SENSOR and by 0.25 mm in the case of Horizontal GAP SENSOR.) anddocument the voltage value of GAP SENSOR.
③ When the voltage value becomes about 4800 mV, move PLATE closer to GAPSENSOR in a same way and document the voltage value of GAP SENSOR.
※②’s recorded date and ③’s recorded date should become about the same. It isnecessary to start it again if different.

LDT (Local Deformation Transducer)
54

Figure 4.8 Local Deformation Transducer① Set LDT to A PIECE OF METAL so that the voltage value of LDT becomes about
zero and make the value of DISPLACEMENT GAUGE to zero.
② Read off the voltage value of LDT on the screen of computer at the same time
while slewing around DISPLACEMENT GAUGE to bend LDT by 0.5 mm anddocument the voltage value of LDT.
③ When the voltage value becomes about 4500 mV, slew around DISPLACEMENTGAUGE in the reverse direction in a same way and document the voltage value of LDT.
※ ②’s recorded date and ③’s recorded date should become about the same. It isnecessary to start it again if different.
※ Because LDT is very sensitive, be careful of the handling.

DIAL

MB‐B

PED
Figure 4.9 Dial Gauge
DIAL GAUGE① Put up PEDESTAL to the limit and read off the voltage value of DIAL GAUGE
after having set DIAL GAUGE like a right figure. (The voltage value of DIAL GAUGE
55

of this time is around 3500 mV for the aim of this value.)② Read off the voltage value of DIAL GAUGE on the screen of computer at the sametime while lowering PEDESTAL by 2 mm and document the voltage value of DIALGAUGE.
③ When the voltage value becomes about -3500 mV, put up PEDESTAL in a same
way and document the voltage value of DIAL GAUGE.
※ When one lap of scale of DIAL GAUGE dose it, a PEDESTAL falls 1 mm.
※ The value of the displacement is subtracted.
※ ②’s recorded date and ③’s recorded date should become about the same. It isnecessary to start it again if different.

LOAD

PEDE
Figure 4.10 Load cell

LOAD CELL① Set LOAD CELL like a right figure so that the voltage value of LOAD CELL
becomes about zero.
② Read off the voltage value of LOAD CELL on the screen of computer at the sametime while putting up PEDESTAL and raising by scale 15 and document the voltage
value of LOAD CELL.
③ When the voltage value becomes about 200 mV, lower PEDESTAL in a same56

way and document the voltage value of LOAD CELL.
※ ②’s recorded date and ③’s recorded date should become about the same. It isnecessary to start it again if different.
※ When scale 15 rises, load 43.75 [N] rises.
The request of the calibration factor
GAP SENSOR, DIAL GAUGE① Make date a graph with software (origin, etc) and take displacement [mm] in a
vertical axis, voltage value [mV] in a horizontal axis.
② Set up the formula of the straight line (y = ax + b), the degree of leaning of theexpression of the straight line is the calibration factor.
LOAD CELL① Make date a graph with software (origin, etc) and take loading [N] in a vertical axis,
voltage value [mV] in a horizontal axis.
② Set up the formula of the straight line (y = ax + b), the degree of leaning of theexpression of the straight line is the calibration factor.
LDT① Make date a graph with software (origin, etc) and take displacement [mm] in a
vertical axis, voltage value [mV] in a horizontal axis.
② Set up the formula of the quadric curve (y = ax2 + bx + c) and a, b, c are thecalibration factors.
4.3.2 Preparation of test equipment
1. Open positive pressure, negative pressure switch (front door, backroom) and magnet.
2. When the positive pressure is turned on, make sure the gas inside is opened a little
bit, the oil is still there, and if there is too much water, pour it out.
Switch: ➖ means open.
Loadcell can only be initialized once when there is no pressure. （Figure 4.11）
Turn on the power of PC, Mega torque motor drive box, amplifier.

57

Figure 4.11 Driver box of mega torque motor
ATT amplifier is from the right 1/50, 1/10, 1/10, 1/10, 1/20, 1/10（Figure 4.12）

Figure 4.12 ATT amplifier
1. Start the test recording program (Be careful as opening program because of thedifferent in the case with and without the creep loading test mode).
2. Install in apparatus the porous stone and pedestal which has been soaked in water.
3. To carry out water supply until no air out from the porous stone (flushing), open thewater supply valve (black valve) while holding finger on the installation part of porewater pressure gauge by mounting water supply coupler (water supply, red valve).
58

4. As being sure that the water comes out from the upper drainage route to connect thebifurcation hose that was opened drain valve, ask someone to lift up the degassed water
making machine by open the degassed water supply valve, fix firmly, such as monkey
nuts and tighten the drain valve.
5. Open the valve without attaching upper pipe and lower valve of drainage layer.
6. After fixed by attached gum (rubber) and cover inside of mold the membrane(divided in half if long), glue to the mold in which is removing air (connect green pipeon left).
7. Drop neatly the membrane attached to hinge(Since deformation and fatigue in the hinges as taking and pulling the membrane at thistime, take to thin down the membrane by cutter).

4.3.3 Saturation of specimen using double vacuum method
Preparation of the specimen
1. Measure the dimensions (height: 3, diameter: 6) and mass of the specimen.
2. Put gypsum mixed with water, sharpen little the place for installing hinge(attachment)(While making a horn so as not to slide off of gypsum when sharpen) (Put a plaster toadapt little by little).
3. Leave gypsum to harden firmly.
Perform 1) and 2) simultaneously.
Setting of the specimen
1. The specimen is placed on wetted filter paper which is on pedestal.
(should tear that part filter paper if incurred as part of the gypsum at this time)
2. Put adhesion to gypsum section.
3. Cover to specimen the mold which was contacted with membrane.
4. Turn off the vacuum of the mold, contact the specimen and membrane.
(pull out the pipe on left) ※Note the position of the membrane!
5. The upper side of the membrane is folded back to the specimen, lower cover thepedestal.
59

(Top to cover the load cell, and the lower end to cover the pedestal)
6. Remove the mold, and fix membrane and pedestal by the O-ring. (Fix with ring of
metal)
7. Pass through specimen the O-ring of the top cap.
8. Install the upper plate, tightening the bolt of three places by power of 150kgf/cm bytorque wrench.
(make sure that the upper plate is attached to the position where the gap sensor is
attached)
9. Connect the wires of LDT, load cell, adjust zero for each (set 0 value in computer in
R-Bal of amplifier.
10. Touch to cap so as not to change the value of load cell, apply a stop. (so as not topinch filter paper)
11. Fold membrane on top to the cap. (Fix with O-ring which had prepare in (7)12. Install the upper drainage root of footwall.
13. Open stopcock of valve ① (pore water pressure valve), open valve of footwall,
operate a negative pressure of -15.2cmHg inside the specimen. (the pore water pressure
valve is located in lower right)
14. Install the attachment with adhesive to gypsum portion in specimen bottom. (restfor about 5 minutes until set)
15．Warp LDT around from -1000 to -2000mV (in the case of confining pressure
98kPa) to install to the upper portion attachment. At this time, always put gut so thatLDT can be taken.
16. Grease silicone to footwall and hanging wall side, after removing hanging wall put
the cell on.
17. Lower the loading rod and place a pachinko ball to joint.
(pachinko ball is not rattled, but keep hard … by finger)※How to move the loading rod: Mega torque motor (displacement input → start)
18. Fix the footwall.
19. After confirming the rod position, then tighten the screw (bolt of gold) of the joint.
20. Set up a dial-cage. (set up a dial gauge perpendicular to the plane)6021. While maintaining the zero value of the load cell, release the stopper rod.
22. Attach a positive pressure coupler. (place in the (hanging wall) upper plate)
23. Attach (smaller) lateral pressure gauge. (back) at this time tap-water water supply
also apply.
24. Put water in the cell so as not to be waved and measurement equipment such as loadcell is not submerged at this time. (Roughly, about O-ring at the top)
25. Fill with water the inside lateral pressure gauge, loosen screws of the lateral pressuregauge. After that make a zero adjustment. (part of cell pressure of program)(water become drip-drop)
26. Install the pore water pressure gauge. (larger, front side), connect the pore waterpressure route
27. Install the water supply coupler that was used in flushing, open the black and red
screw. (water supply screw)
28. Fill with water the water pressure gauge, loosen the screw of pore water pressuregauge until drop of water exits. After that, set zero of pore water pressure gauge.
29. After adjustment, close the pore water pressure gauge screw and red screw.
30. Initialize the relative position of the mega torque motor of the program.
(Press the reset button)
31. Confirm whether the stopper rod is loose, gap sensor dial gauge, LDT, load cell isconnected correctly.
32. Start an isotropic stress control program.
Double vacuum method
1. Close the drain valve.
2. Make sure that valve 2 (lateral pressure) is 0cnHg, valve 1 is -15.2cmhg, read valueof dial gauge.
3. Open the black valve of footwall of pore water pressure gauge.
4. Replace the lateral pressure path to negative pressure route, set valve 2 of -7.6cm Hg.
(don’t open forcefully)
5. Set valve 1 of -22.8cm Hg.
6. Open half the drain valve (air bubbles in the hose moves enough), wait until it is61displayed on monitor as “in control stress isotropic”.
7. Open the valve fully.
8. Wait five minutes.
9. Set the valve ② "-15.2cmHg", close the drain valve.
10. Perform the same manner as in 6 Set valve ① "-30.4cmHg".
11. Close the drain valve, set the valve ② "-22.8cmHg".
12. Perform the same manner as in (6), Set valve ① "-38.0cmHg".
13. Wait five minutes.
14. Repeat (8)-(12) until valve 2 becomes -53.2cmHg, valve 1 becomes -68.4cmHg. It
takes 1 hour.
15. Check the main valve and the pressure gauge to see if the meter is 0.
16. Unplug the negative pressure line into a positive pressure line, and the lower
chamber is closed.
17. Following the progress in Table 4.1

62

Table 4.1 Progress of double vacuum
Water Pressure valve①

Lateral Pressure valve ②
valve

valve

38

close

60.8

half → fully

30.4

close

53.2

half → fully

Wait five minutes

22.8

close

45.6

half → fully

15.2

close

38

half → fully

Wait five minutes
7.6

close

30.4

half → fully

0

close

22.8

half → fully

Wait five minutes

18. Close the negative pressure valve after lowering, wait 3 minutes.
19. Replace the backpressure with positive pressure and cut off all connections to thesample before changing the wire.
20. All switches are closed (No. 3, No. 5) and bulb A.（Figure 4.13）

63

Figure 4.13 Schematic figure of connections
21. Pressure gauge on (No. 2).
22. Watching the computer screw the cell to 70.
23. Turn on the Lower chamber switches.
24. Turn on the two green buttons above the double tube.
25. Initial value: 20.
26. When the final differential pressure is 30, the (No. 3, No. 5) switch is turned on.
27. Start screwing the pressure gauge according to the table.（Figure 4.14）

Figure 4.14 Progress during isotropic consolidation
28. Turn off the degassing drain switch.
29. Turn on the black switch reduces gap pressure 13.
30. Observe on the computer, CH6: If it is not enough 200, screw it back to 200.
BACK: 200.
6431. After waiting for 2 minutes for stabilization, read the number in the tube.
32. Enter values into experiment form.
33. Off black switch.
34. screw cell pressure to 275kPa.
35. After waiting for 1 minute, take a picture of the computer screen and enter theexperiment form to get the B value.
(Pore water pressure coefficient B = increment amount of pore waterpressure/increment amount of lateral pressure)
36. then reduce the cell pressure to 230 (it can be screwed to 240, it will slowly
decrease)
37. Turn on the black switch.
38. cell pressure: 230 to 300. (5 minutes at constant speed)
39. Wait for 2 minutes to stabilize.
40. The final state is ch6: 200 ch7: 300.
41. Turn off the front and rear negative pressure switches.
4.3.4 Isotropic consolidation
1. Consolidate for 15 hours.
2. Observe whether the value on the computer is 200, 300.
3. Try to keep the pressure difference between 98-102, if you need to adjust, wait 2
minutes after the adjustment.
4. Read the value of the dial gauge and burette.
4.3.5Triaxial compression test
Loading
1. Stop the isotropic stress control program.
2. Initialize the relative position of the mega torque motor of the program.
3. Once, set undrained condition by closing the drain valve (No. 4, No. 5, black switch)
4. Keep the pressure gauge on (No. 2)
5. Axial strain rate ：12%65

6. Minute load removal: select ☑️ --- setting --- don't do it after 5%
7. Axial strain rate ：0.054%
8. Save, fill the loading stage and the specimen name, the name of file by clicking therecording destination.
9. Click on the start button of monotonic loading program.
10. If LDT bend until limit (4500mV) pull the Tegus remove LDT
11. Compressive stress decline 2/3 of max, if axial strain reaches more than 15%, end
the loading
After the completion of loading.
1. Click the stop button of monotonically loading program.
2. Check all whether valve of water supply, drainage, front of burette is closed.
3 Remove the dial gauge by moving the sensor gap.
4. Disconnect the water by installing a drainage coupler in place installed the watersupply coupler. At this time, remains a little lateral pressure, exiting the water purely.
5. Remove lateral pressure meter, the pore water pressure gauge, withdraw theremaining water in measuring apparatus by loosening the screw.
6. Remove the wiring of load cell, LDT, dial gauge, the gap sensor.7.
7. After fixing the rod remove joint, raise the rod.
8. Remove the bolts fixing the lower plate, remove the cell.
9. Spraying a lubricant to the loading frame placed lower plate, blow purely wiper JK,
etc…
10. Return to the original location wiping the feet of lower plate.
11. After removing the sample, dry it, draw the damage line, and take a picture.

66

4.4 Procedures of Unconfined compression test
Preparation of test equipment
1.Open negative pressure switch (front door, backroom) and magnet.
2.Loadcell can only be initialized once when there is no pressure.
3.Turn on the power of PC, Mega torque motor drive box, amplifier.
ATT amplifier is from the right 1/50, 1/10, 1/10, 1/10
4.Start the test recording program（Be careful as opening program because of thedifferent in the case with and without the creep loading test mode）.
5.After fixed by attached gum (rubber) and cover inside of mold the membrane (divided
in half if long), glue to the mold in which is removing air (connect green pipe on left)
6. Drop neatly the membrane attached to hinge.
(Since deformation and fatigue in the hinges as taking and pulling the membrane at thistime, take to thin down the membrane by cutter)
Preparation of the specimen
1. Measure the dimensions (height: 3, diameter: 6) and mass of the specimen.
2.Put gypsum mixed with water, sharpen little the place for installing hinge.
(attachment)(While making a horn so as not to slide off of gypsum when sharpen) (Put a plaster toadapt little by little)
3.Leave gypsum to harden firmly. Perform 1) and 2) simultaneously.
4.4.1 Setting of the specimen
1. The specimen is placed on wetted filter paper which is on pedestal.
(should tear that part filter paper if incurred as part of the gypsum at this time)
2. Put adhesion to gypsum section.
3. Cover to specimen the mold which was contacted with membrane.
4. Turn off the vacuum of the mold, contact the specimen and membrane.
(pull out the pipe on left) ※Note the position of the membrane!!
5. The upper side of the membrane is folded back to the specimen, lower cover the67

pedestal.
(Top to cover the load cell, and the lower end to cover the pedestal)
6. Remove the mold, and fix membrane and pedestal by the O-ring. (Fix with ring of
metal)
7. Pass through specimen the O-ring of the top cap.
8. Install the upper plate, tightening the bolt of three places by power of 150kgf/cm bytorque wrench.
(make sure that the upper plate is attached to the position where the gap sensor is
attached)
9. Connect the wires of LDT, load cell, adjust zero for each (set 0 value in computer in
R-Bal of amplifier.
10. Touch to cap so as not to change the value of load cell, apply a stop. (so as not topinch filter paper)
11. Fold membrane on top to the cap (Fix with O-ring which had prepare in (7))

Figure 4.15 Connection and screw of gap sensor
12. Install the attachment with adhesive to gypsum portion in specimen bottom. (restfor about 5 minutes until set) （Figure 4.15）
13. Warp LDT around from -1000 to -2000mV (in the case of confining pressure
98kPa) to install to the upper portion attachment. At this time, always put gut so thatLDT can be taken. （Figure 4.16）

68

Figure 4.16 Locker of the loading rod
4.4.2 Unconfined compression test
1. Confirm whether the stopper rod is loose, gap sensor dial gauge, LDT, load cell isconnected correctly.
2. Initialize the relative position of the mega torque motor of the program.
3. Axial strain rate ：12%
4. Minute load removal: select ☑️ --- setting --- don't do it after 5%
5. Axial strain rate ：0.054%
6. Save, fill the loading stage and the specimen name, the name of file by clicking therecording destination.
7. Click on the start button of monotonic loading program.
8. If LDT bend until limit (4500mV) pull the Tegus remove LDT.
After the completion of loading
1. Click the stop button of monotonically loading program.
2. Remove the dial gauge by moving the sensor gap.
3. After fixing the rod remove joint, raise the rod.
4. Remove the bolts fixing the lower plate, remove the cell.
5. After removing the sample, dry it, draw the damage line, and take a picture.

69

REFERENCES
Kuno, G., eds (1997): Liquefied stabilized soil method-Recycling technology ofconstruction-generated soil and mud, Gihodo publication (in Japanese).
Japanese Geotechnical Society (2005): Committee Report Chapter 2, 2.1, 2.2 on test
methods and physical properties of cement-modified soil, Proc. of symposium, pp.222, on survey, design, construction and properties evaluation methods of solidifying
stabilized soil using cement and cement-treated soil (in Japanese).
Kohata, Y. (2006): Mechanical property of liquefied stabilized soil and future issues,
Doboku Gakkai Ronbunshuu, F, Vol.62, No.4, pp.618-627 (in Japanese).
Kohata, Y., Ichikawa, M., Nguyen, C. Giang., and Kato, Y. (2007): Study of damage
characteristics of liquefied stabilized soil mixed with fibered material due to triaxial
shearing, Geosynthetics Engineering Journal, Vol.22, pp.55-62 (in Japanese).
Goto, S., Tatsuoka, F., Shibuya, S., Kim, Y. S. and Sato, T. (1991): A simple gauge
for local small strain measurements in the laboratory, Soils and Foundations, Vol.31,
No.1, pp 169-180.
Do, T. Anh, Kohata, Y. and Sasaki, M., Effect of slurry density on triaxial
compressive properties for liquefied stabilized soil reinforced with fiber material,
Geosynthetics Engineering Journal, Vol.33, 2018, pp.15-22.

70

CHAPTER 5TEST RESULTS OF UNDRAINED TRIAXIAL COMPRESSIONTEST AND DISCUSSIONS

5.1 Introduction
In order to investigate the triaxial shear property of the liquefied stabilized soil
prepared in different conditions, a series of undrained triaxial compression tests was
carried out. In this chapter, results of undrained triaxial compression tests will be shownand discussed based on data analysis from different visions.
As shown in Table 5.1, specimens prepared in different slurry density, cement
content, fiber content as well as curing time were tested with triaxial apparatus under
undrained condition.

71

Table 5.1 Details of testing cases in undrained triaxial compression test

Case ID

Testing
condition

Curing time(days)

Cement content(kg/m3)Slurrydensity(g/cm3)

T-28-1Fibercontent(kg/m3)0

1.216
T-28-2

10
80

T-28-30
1.280

T-28-4

10
28

T-28-50
1.216

T-28-6

10
100

T-28-7
T-28-8
T-56-10
1.280

Undrained
triaxial
compression
test

10
0
1.216

T-56-2

10
80

T-56-30
1.280

T-56-4

10
56

T-56-50
1.216

T-56-6

10
100

T-56-70
1.280

T-56-81072

5.2 Stress-strain RelationshipIn this part, discussion will be focused on the stress-strain relationship of theundrained triaxial compression test. Figures 5.1 to 5.4 shows the stress-strain
relationship of all cases of the undrained triaxial compression tests carried out onliquefied stabilized soil specimens. In each figure, cases with different fiber contents
but same curing time, cement content, and slurry density are plotted. Legend in the
figure indicates the test condition of the changing rate of slurry density (%), cement
content (kg/m3) and fiber content (kg/m3), respectively.

Figure 5.1 Stress-strain relationship up to 5% axial strain (28 days curing, C = 80kg/m3)

Figure 5.2 Stress-strain relationship up to 5% axial strain (56 days curing, C = 80kg/m3)

73

Figure 5.3 Stress-strain relationship up to 5% axial strain (28 days curing, C = 100kg/m3)

Figure 5.4 Stress-strain relationship up to 5% axial strain (56 days curing, C = 100kg/m3)In all cases, it can be clearly noticed that the slurry density could significantly
influence the strength of the liquefied stabilized soil. Only 5% decrease in slurry density
induced more than 50% decrease in maximum strength. Meanwhile, in each figure, theeffect of fiber can be seen that in most cases, the addition of fiber material improved
the after peak brittleness to some extent.
For better comparison, cases with same curing time and cement content are plotted
together in Figures 5.5 and 5.6.

74

Figure 5.5 Stress-strain relationship up to 5% axial strain (C = 80 kg/m3)
By comparing these figures horizontally, it can be found that the effect of curing
time exists but not so obvious in all cases. Compared with the effect of changing in
cement content or slurry density, this influence is negligible.
From these figures, it seems that the influence of slurry density in Figure 5.5 issomehow different from that in Figure 5.6. This phenomenon indicates that the effectof slurry density is related with the changing of cement content.

Figure 5.6 Stress-strain relationship up to 5% axial strain (C = 100 kg/m3)

75

Figure 5.7 Relationship between maximum deviator stress and changing rate of slurry
density (28 days)
Figure 5.7 shows the relationship between maximum deviator stress and thechanging rate of slurry density in the case with 28 days curing. This relationshipindicates that influence of changing in slurry density is related to the addition amountof cement. With more cement content (line with black symbol), the influence ofchanging in slurry density was much more significant than that in the cases with lower
cement content (line with white symbol). By defining average decreasing rate of
maximum deviator stress as (Decreasing value in maximum deviator stress)/ (maximum
deviator stress with basic slurry density) ×100 %, it can be calculated that the decreasingrate with 100 kg/m3 cement content was 2 times more than cases with 80 kg/m3 cement.
This result indicates that even if the necessary strength can be satisfied with cement
content of 80 kg/m3 at construction site, it needs to be careful to use liquefied stabilized
soil prepared in lower slurry density to decrease the overburden pressure.
As for the addition of fiber material, it can be noticed that maximum deviator stressincreases slightly by adding fibers into the LSS, and the after-peak behavior is improvedin some characteristics. Specimens with fiber generally showed more stable behavior
after maximum deviator stress was reached. Meanwhile, not only the after-peakbrittleness was improved, but the residual strength of LSS specimens was also increasedin most cases.
76

5.3 Pre-failure Deformation Property
In this part, various Young’s moduli are applied to discuss the pre-failure
deformation properties of the LSS. Different kinds of Young’s moduli are defined asshown in Figure 5.8.

Figure 5.8 Definition of various Young’s moduli
The initial Young’s modulus E0 is defined as initial stiffness at 𝜀a = 0.005 % or less.
The tangent Young’s modulus Etan is defined as a tangential gradient in qa𝜀a curve, it
indicates the non-linearity of deformation property in q~𝜀a relation. The equivalent
Young’s modulus Eeq is obtained from small unloading/reloading loop during
monotonic loading and which can indicate the degree of damage under shearing.
Figures 5.9 and 5.10 show the relationship between the initial Young’s modulus andthe cement contents as well as curing times, respectively. Similar as the maximum
deviator stress, the initial Young’s modulus is also affected by the changing of slurry
density. However, the increases in cement content and curing time did not have suchsignificant influence on the initial Young’s modulus as to be indicated for maximum
deviator stress. In the past study, it is reported that the cement content can affect theinitial Young’s modulus apparently at lower degree while the influence decrease77

gradually along with the increase of cement content.

Figure 5.9 Relationship between initial Young’s modulus and cement contents

Figure 5.10 Relationship between initial Young’s modulus and curing times
Figures 5.11 to 5.13 show the relationship between the tangent Young’s modulus
normalized by the initial Young’s modulus (Etan/E0) and the deviator stress normalized
by the maximum deviator stress (q/qmax) in different cases. These relations indicate thenon-linearity of pre-failure deformation property. The degree of non-linearity can becompared normalizing the tangent Young’s modulus and the deviator stress. It can benoticed that even with the increase of curing time, the decreasing tendency of Etan/E0 is
always large in the cases of lower slurry density as well as an increasing tendency of78

nonlinearity. Meanwhile, by comparing Figs. 12 and 14, it can be found that thedecreasing rate of Etan/E0 at the early loading stage becomes lower with the increase of
cement content.

Figure 5.11 Relationship between Etan/E0~q/qmax (cement content = 80 kg/m3, 28 days
curing)Figure 5.12 Relationship between Etan/E0~q/qmax (cement content = 80 kg/m3, 56 days
curing)79

Figure 5.13 Relationship between Etan/E0~q/qmax (cement content = 100 kg/m3, 28
days curing)
The equivalent Young’s modulus (obtained with small loops of unloading/)
normalized by the initial Young’s modulus (Eeq/E0) are shown in Figures 5.14 to 5.16
with the horizontal axis of q/qmax. With all the cases of different curing time and added
amount of fibers, Eeq/E0 seems to decrease earlier when the slurry densities are
relatively lower. Therefore, the degree of damage with shear seems to be larger in thecase of lower slurry density, and that tendency becomes large to be reduced with theaddition of fiber materials.

Figure 5.14 Relationship between Eeq/E0~q/qmax (cement content = 80 kg/m3, 28 days
80

curing)

Figure 5.15 Relationship between Eeq/E0~q/qmax (cement content = 80 kg/m3, 56 days
curing)Figure 5.16 Relationship between Eeq/E0~q/qmax (cement content = 100 kg/m3, 28 days
curing)
As for the result obtained with higher cement content, the change of cement content
from 80 to 100 kg/m3 do not have noticeable influence compared with that of curing
time.

81

5.4 Summaries
With a strain controlled triaxial test apparatus employed, a series of undrained
triaxial compression tests were carried out on the LSS specimens prepared in different
curing times, slurry densities, cement contents and fiber contents. Based on the test
results, following conclusions can be obtained.
1) When the slurry density slightly decreases from the normal slurry density obtained
from the standard mix proportion design figure, it is considered that the qmax decreased
remarkably. In addition, it is found that the local damage caused by shearing even in
the case of lower slurry density is reduced by the fiber material.
2) The test results on specimens with higher cement content indicate that cement
content can affect the qmax as same as the slurry density while the fiber material seemed
to behave well in these cases to improve the brittleness.
3) The Etan/E0 ~ q/qmax relationships show that the decreasing rate of Etan/E0 in theearly loading stage was influenced by the cement content. In addition, it seems that theaddition of fiber materials can also decrease the decreasing rate slightly in all cases.
4) The influence of slurry density on the degree of damage caused by shear is quite
large and the degree of damage tends to be reduced by the addition of fiber material.
5) The effect of cement content on the stiffness is relatively small compared with theeffect of slurry density, whereas the effect of cement content on the strength is larger
than that of slurry density. Therefore, it is considered that even if a cement content
increases, the decrease of slurry density causes the reduction of quality for the Liquefied
Stabilized Soil.

82

REFERENCE
Kuno, G., eds, Liquefied stabilized soil method-Recycling technology ofconstruction-generated soil and mud, Gihodo publication, 1997 (in Japanese).
Japanese Geotechnical Society, Committee Report Chapter 2, 2.1, 2.2 on test
methods and physical properties of cement-modified soil, Proc. of symposium, 2005,
pp.2-22, on survey, design, construction and properties evaluation methods ofsolidifying stabilized soil using cement and cement-treated soil (in Japanese).
Kohata, Y., Mechanical property of liquefied stabilized soil and future issues,
Doboku Gakkai Ronbunshuu, F, Vol.62, No.4, 2006, pp.618-627 (in Japanese).
Kohata, Y., Ichikawa, M., Nguyen, C. Giang., and Kato, Y., Study of damage
characteristics of liquefied stabilized soil mixed with fibered material due to triaxial
shearing, Geosynthetics Engineering Journal, Vol.22, 2007, pp.55-62 (in Japanese).
Kohata, Y., Ito, K., and Koyama, Y., Effect of cement content on shear properties ofliquefied stabilized soil reinforced by fiber material, Japanese Geotechnical Society
Hokkaido Branch Technical Report Papers, Vol.26, 2011, pp.95-100 (in Japanese).
Duong, Q. Hung., Kohata, Y., Omura, S., and Ozaki, K., Strength and deformation
characteristics of liquefied stabilized soil reinforced by fiber material prepared atlaboratory and field, Geosynthetics Engineering Journal, Vol.29, 2014, pp.33-40.
Do, T. Anh, Kohata, Y. and Sasaki, M., Effect of slurry density on triaxial
compressive properties for liquefied stabilized soil reinforced with fiber material,
Geosynthetics Engineering Journal, Vol.33, 2018, pp.15-22.
Goto, S., Tatsuoka, F., Shibuya, S., Kim, Y-S., and Sato, T., A simple gauge for local
small strain measurements in the laboratory, Soils and Foundations, Vol.31, No.1, 1991,
pp.169-180.
Kohata, Y., Tatsuoka, F., Wang, L., Jiang., G-L., Hoque, E. and Kodaka, T.,
Modelling of non-linear deformation properties of stiff geomaterials, Geotechnique,83Vol. 47, No. 3, 1997, pp. 563-580.
Kohata, Y., Jiang, G-L., Murata, O., and Tatsuoka, F., Elastic-properties-basedmodeling of non-linear deformation characteristics of gravels, Proc. Of the second Inter.
Symposium on Pre-Failure Deformation Characteristics of Geomaterials-IS Torino 99,
1999, pp. 533-539.

84

CHAPTER 6TEST RESULTS OF UNCONFINED COMPRESSION TEST ANDDISCUSSIONS

6.1 Introduction
In order to investigate the unconfined compression property of the liquefied
stabilized soil prepared in different conditions, a series of undrained triaxial shear tests
was carried out. In this chapter, results of a series of unconfined compression test will
be shown and discussed based on data analysis from different visions. Meanwhile, thedifference between undrained triaxial compression test and unconfined compression
test will also be discussed.
As shown in Table 6.1, specimens prepared in different slurry density, fiber content
as well as curing time were tested with unconfined condition.

Table 6.1 Details of testing cases in unconfined compression test
U-28-1

100

0
1.216

U-28-2

10
28

U-28-3
U-28-4
U-56-10
1.280

Unconfinedcompression
test

10
0
1.216

U-56-2

1056

U-56-30
1.280

U-56-41085

6.2 Stress-strain RelationshipIn this part, discussion will be focused on the stress-strain relationship of theunconfined compression test. Figures 6.1 and 6.2 shows the stress-strain relationship of
all cases of the undrained triaxial shear tests carried out on liquefied stabilized soil
specimens. In each figure, cases with different fiber contents but same curing time,
cement content, and slurry density are plotted. Legend in the figure indicates the test
condition of the changing rate of slurry density (%), cement content (kg/m3) and fiber
content (kg/m3), respectively.
All the stress-strain relationships are combined by the data from local deformationtransducer in the early loading stage and dial gauge for the latter part. This is to avoid
the influence of bedding error caused by the non-flat surface of the specimens.

Figure 6.1 Stress-strain relationship up to 5% axial strain (28 days curing, C = 100kg/m3)

86

Figure 6.2 Stress-strain relationship up to 5% axial strain (56 days curing, C = 100kg/m3)In all cases, it can be clearly noticed that the slurry density could significantly
influence the strength of the liquefied stabilized soil in unconfined compression test.
For better comparison, cases with same curing time and cement content are plotted
together and compared with the undrained triaxial compression test results. Figures 6.3
and 6.4 show the stress-strain relationships in different loading conditions withspecimens cured for 28 days and 56 days, respectively.

Figure 6.3 Stress-strain relationship up to 5% axial strain in different loading conditions(left: unconfined compression test, right: undrained triaxial compression test)

87Figure 6.4 Stress-strain relationship up to 5% axial strain in different loading conditions(left: unconfined compression test, right: undrained triaxial compression test)
As compared to those of triaxial tests, it can be noticed that the maximum deviator
stress was not significantly affected in such different confining conditions. Thisphenomenon was reported by Horpibulsuk, Miura and Bergado in 2004 that due to thecement solidification, cementation bond dominated the strength characteristics of thecement mixed soil. However, due to different stress conditions and stress paths that the
specimen experienced during tests, large difference in the stress-strain relationships canstill be observed from the results of unconfined compression tests.
Specimens with lower slurry density exhibited similar behavior as in triaxial test,
but those with higher slurry density showed obvious after-peak brittleness during thetest. Meanwhile, effect of fiber reinforcement was not clear, due to the irregulardeformation pattern. In some cases with high slurry density, residual strength was evenlower than that of specimen with lower slurry density.

886.3 Comparison of Failure Pattern
By drawing black dotted line on the membrane after test, the formation of shear
bands and cracks can be observed for different cases. Figures 6.5 and 6.6 show failure
pattern observed after unconfined compression test on specimens with different slurry
densities, fiber contents and curing times. Figure 6.7 shows the failure pattern and shear
bands observed after the undrained triaxial compression test for comparison.

Figure 6.5 Specimens with 28 days curing after unconfined compression test

Figure 6.6 Specimens with 56 days curing after unconfined compression test

Figure 6.7 Specimens with 28 days curing after undrained triaxial compression test89Due to the unconfined condition, specimen showed obvious dilatancy in the earlyloading stage and no clear shear band formed as in triaxial test. But with the increaseof slurry density, specimen became more brittle which progressed the formation ofshear band.
However, it is still difficult to find evidence which can present the reinforcement offiber material in these unconfined compression test.

90

6.4 Summaries
With a strain controlled triaxial test apparatus employed, a series of unconfinedcompression tests were carried out on the LSS specimens prepared in different curing
times, slurry densities, and fiber contents. Based on the test results, following
conclusions can be obtained.
1) During unconfined compression tests, specimens with lower slurry density show
similar behavior as in triaxial tests but with the increase of slurry density, brittleness of
specimens may be an increasing.
2) Test results from unconfined compression test and undrained triaxial compression
test indicate that the influence of confining condition is not obvious due to the effect of
cementation.
3) Since no initial effective confining stress existed during unconfined compression
test, formation of shear bands and cracks are more irregular than in triaxial test.
However, with an increase of slurry density, the failure pattern of unconfinedcompression test become better.
4) There is not enough evidence showing the effect of reinforcement by the fiber
material on the unconfined compression behavior of the liquefied stabilized soil.

91

REFERENCE
Kuno, G., eds, Liquefied stabilized soil method-Recycling technology ofconstruction-generated soil and mud, Gihodo publication, 1997 (in Japanese).
Japanese Geotechnical Society, Committee Report Chapter 2, 2.1, 2.2 on test
methods and physical properties of cement-modified soil, Proc. of symposium, 2005,
pp.2-22, on survey, design, construction and properties evaluation methods ofsolidifying stabilized soil using cement and cement-treated soil (in Japanese).
Kohata, Y., Mechanical property of liquefied stabilized soil and future issues,
Doboku Gakkai Ronbunshuu, F, Vol.62, No.4, 2006, pp.618-627 (in Japanese).
Kohata, Y., Ichikawa, M., Nguyen, C. Giang., and Kato, Y., Study of damage
characteristics of liquefied stabilized soil mixed with fibered material due to triaxial
shearing, Geosynthetics Engineering Journal, Vol.22, 2007, pp.55-62 (in Japanese).
Kohata, Y., Ito, K., and Koyama, Y., Effect of cement content on shear properties ofliquefied stabilized soil reinforced by fiber material, Japanese Geotechnical Society
Hokkaido Branch Technical Report Papers, Vol.26, 2011, pp.95-100 (in Japanese).
Goto, S., Tatsuoka, F., Shibuya, S., Kim, Y-S., and Sato, T., A simple gauge for local
small strain measurements in the laboratory, Soils and Foundations, Vol.31, No.1, 1991,
pp.169-180.
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Engineering, Vol.130, No.10, 2004, pp.1096-1105.

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CHAPTER 7
CONCLUSIONS AND SUGGESTIONS ON FUTURE WORK

7.1 Conclusions
With a strain controlled triaxial test apparatus employed, a series of undrained
triaxial compression tests and unconfined compression tests were carried out on the
LSS specimens prepared in different curing times, slurry densities, cement contents andfiber contents. Based on the test results, following conclusions can be obtained.
1) When the slurry density slightly decreases from the normal slurry density obtained
from the standard mix proportion design figure, it is considered that the qmax decreased
remarkably. In addition, it is found that the local damage caused by shearing even in
the case of lower slurry density is reduced by the fiber material.
2) The test results on specimens with higher cement content indicate that cement
content can affect the qmax as same as the slurry density while the fiber material seemed
to behave well in these cases to improve the brittleness.
3) The Etan/E0 ~ q/qmax relationships show that the decreasing rate of Etan/E0 in theearly loading stage was influenced by the cement content. In addition, it seems that theaddition of fiber materials can also decrease the decreasing rate slightly in all cases.
4) The influence of slurry density on the degree of damage caused by shear is quite
large and the degree of damage tends to be reduced by the addition of fiber material.
5) The effect of cement content on the stiffness is relatively small compared with theeffect of slurry density, whereas the effect of cement content on the strength is larger
than that of slurry density. Therefore, it is considered that even if a cement content
increases, the decrease of slurry density causes the reduction of quality for the Liquefied
Stabilized Soil.
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6) During unconfined compression tests, specimens with lower slurry density show
similar behavior as in triaxial tests but with the increase of slurry density, brittleness of
specimens may be an increasing.
7) Test results from unconfined compression test and undrained triaxial compression
test indicate that the influence of confining condition is not obvious due to the effect of
cementation.
8) Since no initial effective confining stress existed during unconfined compression
test, formation of shear bands and cracks are more irregular than in triaxial test.
However, with an increase of slurry density, the failure pattern of unconfinedcompression test become better.
9) There is not enough evidence showing the effect of reinforcement by the fiber
material on the unconfined compression behavior of the liquefied stabilized soil.
10) The liquefied stabilized soil can be prepared with lower slurry density as long as
it is in the range of the design figure of slurry density obtained by the unconfined test
and flow test.
11) With the application of fiber material to fill in the void, it is possible to prepared
the liquefied stabilized soil in lower slurry density.
In this study, the influence of multiple parameters including slurry density, cement
content, fiber content and curing time was investigated through a series of undrained
triaxial test and unconfined compression test on LSS specimens. It has been first timefound that some parameters have complex influence with each other. With theconclusion of this study, several attempts can be made to promote the utilization of LSS
in real construction site. By adjusting the slurry density and cement content, it ispossible to find a balance point which can meet the requirement of the construction.
Meanwhile, this study also shows a direction of future study on investigate the propertyof liquefied stabilized soil in more details.

947.2 Suggestions on Future Work
With the conclusions and findings of this study, several suggestions on future work
can be given as follows:
1) Undrained triaxial compression test with different confining pressure can be done
to investigate the influence of confining condition furtherly. In real construction site, it
is of great importance to apply the backfilling material properly in different situation,
which asks for more detail of the material property in more different conditions.
2) Different types of loading can be considered to apply in both undrained triaxial
compression test and unconfined compression test. For example, cyclic loadings inundrained triaxial condition or unconfined condition are necessary to investigate thebehavior of LSS which might be used as a backfill material. Once utilized as a
backfilling material under the tunnel railway, the long time response of the material
under huge amount of cyclic loading is very important.
3) Based on laboratory works, the constitutive model of the LSS can be established
to conduct some numerical simulation. By numerical simulation, how LSS can work inreal construction site can be concluded and can give more realistic instructions on
construction utilization.
All in all, there is still a lot of work worthy to be done in the future to investigate theproperty of liquefied stabilized soil in more details. With these efforts, we surely believethat this material could have wide utilization in the future.

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