Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

Centrifuge Modeling of Circular Sallow Foundation Reinforced with a ThinSleeve
Hercio NOVELA
Graduate Student, Graduate School of Advanced Technology and Science, Tokushima University, Tokushima, Japan

Shohei FUJITAEngineer, Kinki Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism, Osaka, Japan

Suguru FUKUTA
Engineer, Fukuoka Prefectural Government, Fukuoka, Japan

Yuki TAKATSUJI
Engineer, Osaka City Hall, Osaka, Japan

Katsutoshi UENO
Associate Professor, Graduate School of Technology, Industrial and Social Sciences, Tokushima University, Tokushima,Japan
Email: ueno@ce.tokushima-u.ac.jp

ABSTRACT
A reinforcing method for a surface circular foundation with a thin flexible underground structure, called “sleeve”, isproposed in this paper. The sleeve wraps soil cylinder underneath a surface circular foundation to confine lateral
movements of the soil cylinder. This constraint increases lateral confining pressure, which improves shear strength andstiffness of the soil cylinder underneath the circular foundation. Consequently, the bearing capacity of the surface circular
foundation increases and reaches that of massive conventional embedded foundations. In this paper, a series of loading
tests of model footings on model sand was conducted to investigate the effects of reinforcement with a sleeve structure.
The circular model foundation was made of aluminium with a diameter of 30 mm. A sleeve structure with dimensions of40 mm in diameter and 30 mm in height was made from a thin polyethylene terephthalate film with a thickness of 0.1mm. Comparisons of performances of foundations between embedded foundations and surface foundation with sleeve
were made and the advantages of surface foundation with sleeve are discussed. The results showed that the surface
foundation of 1.5 m in diameter with sleeve provided similar values of bearing capacity obtained from a conventional
massive foundation embedded at 1.5 m in prototype scale.
Key words: Shallow foundation, Sleeve foundation, Bearing capacity, Reinforcement, Centrifuge model test

1.

Introduction
For many years, many researches have beenfooting.

Eid et al. (2009) studied the behavior of thesquare foundations resting on confined sand, using the

conducted how to reinforce the foundations or for soil

walls to confine sand laterally. Abu-Farsakh et al. (2013)

reinforcement, using different technics and materials. For

used the geosynthetic to reinforce sand and evaluated theexample, Chen et al. (2016) carried out an experimental

settlement.

study on reinforced foundation using transparent soil

scales of foundations have not been sufficientlytechniques. Sawwaf and Nazer (2005) investigated aninvestigated.

improvement of footing by using Unplasticized Polyvinyl
Chloride Cylinders (UPVC) to confine soil around the- 73 -However, the effectiveness for practical

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

2.

Background and objective of the project
Concrete has been used in the constructions as theLoadLoadLoadessential element, mainly in foundation work, hence themain source of raw material could be scarce, which can
imply an increment cost of acquisition, and consequently

Sleevethe construction work cost becomes high. It is therefore
important to investigate a method of reducing costs for theCase 1
Case 2
Surface Foundation Embedded
without Sleeve
Foundation

foundation construction.
The aim of this research is to develop a low cost

Fig. 1Case 3
Surface Foundation
with SleeveCases in tested in the centrifuge apparatusreinforcement for foundations. To achieve this objective,
Table 1. Model footings and test cases

the authors concentrated into the method to reduce theCase 1

Case 2

Case 3underneath the foundation with a thin circular structure. In

Footing

Surface

Embedded

Surfacethis research sleeve was chosen to wrap and confine soil

Sleevenone

none

t=0.1mmvolume of concrete of foundations by confining soil

PET filmand reinforce the foundation. Tensile strength of thematerial used for sleeve was examined in this study. A
Patternseries of vertical loading tests of model circularfoundations on sand was conducted under bothgravitational and centrifugal force fields to verify thePrelim-effects of sleeve on reinforcement of bearing capacity ininary

prototype scales.
3.

Model description

3.1. Model footings and test cases

Accel.

All

Case 2

Case 3(G)

Df (m)hf(m)Ds (m)

hs(m)

10.03

NA

0.03-

0.01-

0.06

0.06

150

1.50

1.50

2.00

1.50

238

1.14

1.14

1.52

1.14

325

0.75

0.75

1.00

0.75

413

0.39

0.39

0.52

0.39

Three cases of foundations were employed, as shown

Df: diameter of footing,hf: embedment length of footing,in Fig. 1 and Table 1. In all cases, the diameter of models

Ds: diameter of sleeve,

hs: height of sleeveof circular footing was 30 mm.

Note: dimensions in prototype scale except t

A series of preliminary tests was conducted byTakatsuji et al. (2017), under 1 G to determine the100
Toyoura sanddiameter and height of sleeve. According to the results,
80

Percent finer, (%)

Ds=40mm and hs=30mm were employed for centrifuge
tests.
Twelve cases of centrifuge loading test were carriedout to evaluate the performance of reinforcement using
sleeve for practical sizes of footings. Diameters of footing
employed were 0.39 m to 1.50 m in prototype scale,considering the ability of the centrifuge apparatus used.

60
40
2000.013.2. Properties of the sand used
The sand used in this study was Toyoura sand, which

0.1
Grain size, (mm)1Fig. 2 Grain size distribution of the sandis fine sand. The density of soil particles, 𝜌𝑠 =2.628 g/cm3,

corresponding maximum and minimum void ratios

was determined according to the Japanese Industrial

measured wereStandards (JIS) A 1202. The maximum and minimum

respectively. The particle size distribution was obtained bydensities were also measured by JIS A 1224 as 𝜌𝑑𝑚𝑎𝑥 =the sieving analyses method according to JIS A 1204, and1.638g/cm and 𝜌𝑑𝑚𝑖𝑛 = 1.351g/cm , respectively. The

the result is shown in Fig. 2, with the effective particle33- 74 -𝑒𝑚𝑎𝑥 = 0.946 and𝑒𝑚𝑖𝑛 = 0.605,

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

sizes 𝐷10 = 0.121 mm, 𝐷30 =0.141 mm and 𝐷60 =0.187

estimated from the tensile strength of the PET sleeve

mm. Coefficient of uniformity 𝑈𝑐 and coefficient of

σ 𝑡 and the internal friction angle of sand φ as Eq. 1,curvature 𝑈𝑐 ′ are 1.545 and 0.879, respectively.

however, 𝜎𝑢 could not be determined due to the limit of
the loading apparatus used. In Eq. 1, t and Ds are the3.3. Material to simulate sleeve
The material for the sleeve model employed in thisthickness and the diameter of the sleeve, respectively.
𝜎𝑢 = 2study was KOKUYO OA VF-1 transparent polyethylene𝑡 1+sin 𝜑
𝐷𝑠 1−sin 𝜑𝜎𝑡(1)

terephthalate (PET) film with a 0.1 mm thickness
corresponding to 144 g/m2. To measure the mechanicalproperties of PET film, a series of tensile test was carriedout with five samples. A universal testing machine(Instron model 5985) was employed to obtain therelationships between tensile strain and tensile stress, as
shown in Fig. 3. All samples yielded at a tensile stress of
120 MPa.
(a) sleeve(b)compression test

1500

Axial stress , σ , (kPa)Tensile stress, T , (MPa)200

10000Figs.

50Strain, ε, (％)

100Fig. 3

Result of the tensile stress4(a-c)

illustrateaseriesof1000

hs
10mm
20mm
30mm

500002440mm
50mm
60mm
68Axial strain, ε, (％)(c)results

uniaxial
Figs. 4(a-c)

compression test on sand cylinders, with a diameter Ds ofCompression test on sand cylinder

30 mm and various heights, confined laterally with a thin
PET sleeve. Firstly the PET film was cut and connected

4.

Centrifuge tests

both ends each other to make a circular sleeve with 30 mm

4.1. Test setupdiameter and various prescribed heights for hs=10 mm toFig. 5 shows the test setup for centrifuge tests and an

60 mm. Secondly, the sleeve was attached around a

example of footing with sleeve. The embedded model

cylindrical pedestal made of aluminum, then Toyoura sandwas poured into the sleeve by air pluviation method, asFig. 4(a) shows. A cylindrical cap made of aluminum wasplaced on the top of the sand cylinder after sand heap on
the top was scraped to be flat. Axial load was applied
through the cap and the relationships between axial stressand axial strain were obtained. Tangential moduli weregradually increasing with increasing axial strains thatdeveloped lateral hoop reaction in the sleeve (see Fig.
4(c)). The ultimate value of axial stress 𝜎𝑢 can be- 75 -Fig. 5

Test setup

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

footing used was made of aluminum with 30 mm diameter400

and height with 30 mm, to set up the experiment for Case
Load intensity, q, (kPa)

2. The soil container used was a rigid rectangular box ofwhich dimensions were 450 mm in length, 200 mm inwidth and 350 mm in height.
4.2. Preparation of model sand
The model sand was prepared by means of a methodof air pluviation. A spot hopper was used for 1 G
preliminary tests, while a line hopper was used for

1G tests
Df=30mm20030mm

Case 1

60mm

1020Settlement, S, (mm)introduced by Ueno (2000).
The apparatus used for centrifuges tests consists of a

Ds=50mm
40mm

00centrifuge tests. A typical method of air pluviation was

Case 3hs=30mmA part of results of preliminary tests under 1G.

Fig. 6line hopper with trapezoidal section with dimensions of0.4 x 0.4 x 0.04 m and an automatic alternative sweeper

sudden drops even the sleeves were not broken.

with constant velocities. The line hopper is placed on andFig. 7 shows the result of the centrifuge test forguided by two longitudinal beams supported by two

Pattern 1. The results show that Case 2 and Case 3, justtransversal beams. The transversal beams are suspended

after the applying load, have the same increment of q-S

from rectangular steel frame by chains through 4 pulleysrelationship until the load reaches q=2,500 kPa at S=200

to move upward or downward.

mm. In Case 2, the curve yields at this point.

For the Case 1, the container was fixed below the line
hopper, and filled with sand into two layers of a 100 mm

While inCase 3, q increased to the peak at 5,500 kPa for settlement
S=620 mm.

height each. The sand was dropped from a 700 mm height

The clear breaking of the sleeve in Case 3 wasthrough the air with a constant sweep rate of the line

detected from the changes in circumferential strain

hopper having an opening of 4 mm. The relative density

induced in the sleeve, as shown in Fig. 8. The clear

measured was Dr=50 % corresponding to dry density ofbreaking in the joint parts of the sleeve was observed after

𝜌𝑑 =1.50 g/cm3.

the tests. While the q for Case 1 and Case 2 at the same

For Case 2 and Case 3, the box was filled with sandinto 3 layers. The first layer was 100 mm thick sand, thesettlement, S=620 mm, were q=1,900 kPa and q=4,600
kPa, respectively.

second layer was 70 mm thick sand. Then the sleeve or6000

model foundation was installed on the center of thePattern 1 50G
Df =1.50m

mm was filled. Care was taken during the installation of
the foundation model into the sand to keep the groundcondition uniform in each case.
Similar pouring procedure was employed forpreliminary 1 G tests by using a spot hopper.

Load intensity, q , (kPa)container just touching the ground, and the last layer of 30
4000

2000

5.

Results and discussions
Fig. 6 shows relationships between load intensity andCase 3
Case 2
Case 1settlement for Case 1 and Case 3 with various sleeve
diameters Ds, obtained from a part of the results ofpreliminary tests examined by Takatsuji et al. (2017).

00The case with Ds=40 mm brought the best performance forthe cases with Df =30 mm. Curves with larger Ds showed- 76 -Fig. 7

500
1000
Settlement , S , (mm)Load-settlement relationships for Pattern 11500

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

Pattern 3 25G50000
Case 3 Pattern 125000
A3A1

A2

A3

A4

Load intensity, q , (kPa)

q4000

2000

4000 Df =0.75m

Strain, ε, (μ)

Load intencity, q, (kPa)6000

strain gauges

A12000Case 3
Case 2
Case 1A4
A200500
1000
Settlement, S, (mm)Fig. 801500

00200

Changes in circumferential strain in a sleeveFig. 10400
600
Settlement , S , (mm)Load-settlement relationships for Pattern 3

Fig. 9 shows the results for Pattern 2. The values
obtained from Case 2 and Case 3 just after the applying

Fig. 11 shows the result for Pattern 4. The curve ofload have the same increment of q-S relationship until

Case 3 shows ascending curve with a peak of q-S

q=1,450 kPa and S=80 mm, while Case 1 has the lowest

relationship at q=3,000 kPa and S=170 mm, while the q

600 kPa. After q for Case 3 increased from 1,450 kPa tofor the Case 1 and Case 2 for the same S=170 mm were q

4,500 kPa at the same settlement of S=370 mm, the sleeve=600 kPa and q=1,400 kPa, respectively.

was broken (this broken was in the joint part). At same

4000

settlement, Case 2 has the load of q=3,500 kPa while Case

Df =0.39m

Load intensity, q , (kPa)

1 again shows the lowest value of q=1,200 kPa.
Fig. 10 shows the result for Pattern 3. Case 3 shows
the highest value comparison with Case 2. The load wasincreased until q=3,750 kPa with S=300 mm.

Case 2 andCase 3 for the same settlement have q=2,250 kPa and
q=700 kPa, respectively.
6000

Pattern 4 13G

Pattern 2 38G

Case 3
Case 2
Case 1

2000

Load intensity, q , (kPa)

Df =1.14m

4000

00Fig. 11100200Settlement , S , (mm)300

Load-settlement relationships for Pattern 42000

The improvement of bearing capacity was also00Fig. 9300600Settlement , S , (mm)Case 3
Case 2Case 1

investigated by Sawwaf and Nazar (2005), using stiff

900

that, when footing is loaded, such confinement resists theLoad-settlement relationships for Pattern 2small cell with diameters up to 200 mm. They concluded
lateral displacements of the soil particles underneath thefooting and confines the soil. Then the strength and- 77 -

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

stiffness of confined sand are increased enough to replace

A series of vertical loading tests under the centrifugal

massive concrete foundations. This sequence results in aforce fields was conducted to verify the reinforcing effects

significant decrease in the vertical settlement and henceof the sleeve at the scale of the real structures. The

improving the bearing capacity (Eid et al. 2009). Similar

relationships between loading intensity (q) and settlement

results were obtained from the present study for actual size(S) were compared and the ratios of improvement wereof foundations, even reinforcement made of a flexible thindiscussed.

film.

Based on the test results, it can be concluded asfollows.
(1) In the case where the sleeve is broken it was seenthat the load was close to the embedded foundation.
(2) It was verified that the sleeve reinforcement wassufficiently effective against load for the size ofactual structures.
(3) Massive embedded footings, used for conventional
circular shallow foundations, can be replaced by thincircular sleeves.
References
Abu-Farsakh, M., Chen, Q., and Sharma, R. 2013. Anexperimental evaluation of the behavior of footing on
geosynthetic-reinforced sand, Soils and Foundations,
53 (2) , pp. 335-348.
Chen, J., Jiang, S., Xue, J., and Guo, P. 2016. Experimental
Study on Reinforced Foundation using Transparent

Fig. 12 Ratio of Improvement

soil Technique, 1st Int. Conf. on Transportation
Infrastructure and Materials, pp. 782-789.

Based on the data in Figs. 8 to 12, the relationshipbetween the ratios of improvements (𝐾𝑖3 /𝐾𝑖2 , 𝑞𝑢3 /𝑞𝑢2 )Eid, Hisham T., Alasari, Omar A., Odeh, Abdelfattah M.,

and diameter of footing (Df) was obtained, as shown in Fig.

Nasr, Mohannad N., and Sadek, Husam A. 2009.

𝐾𝑖3

𝐾𝑖2

are tangential initial

Comparative Study on the behavior of squarecoefficients of subgrade reaction at the origin, for Case 3

foundatios resting on confined sand, Can. Geotech.

and Case 2 respectively. While 𝑞𝑢3 is the ultimate

Journal vol. 46, pp. 438-453.

12. Where,

andbearing capacity obtained from Case 3 and 𝑞𝑢2 is theSawwaf, M. E. and Nazer, A. 2005. Behavior of Circularload intensity for Case 2 at the same settlement. The figure

Footings Resting on Confined Granular Soil, Journal

shows a clear reducing tendency of ratios 𝐾𝑖3 /𝐾𝑖2 andof Geotechnical and Geoenvironmental Engineering,𝑞𝑢3 /𝑞𝑢2 with increasing diameter of footing. However,131 (3), pp. 359-366.

the results show that massive embedded footings can be

Takatsuji, Y., Fujita, S., Shimamura, T., Ueno, K. andreplaced by a thin flexible sleeve and the reinforcing

Uzuoka, R. 2017. Enhancement of bearing capacity

effects of sleeve are still effective, even the size of footingsof shallow foundation on sand using ﬂexible sleeve,exceeds 1 m.

Proc. of the 52nd Japan National Conf. on Geotech.
Engrg. pp. 1173-1174. (in Japanese)

6.

Conclusion
The objective of this study is to evaluate the effects

Ueno, K. 2000. Chapter 2, Methods for preparation ofof sleeve as the reinforcement for the shallow foundations,and also making comparison among the sleeve reinforced,
the embedded and the simple surface circular foundations.

- 78 -

sand samples in Manual of basic centrifuge tests,
Centrifuge 98, 2, pp. 1047-1055.