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

Investigation of Efficiency and Labor Saving by Utilizing ICT in Ground
Improvement WorkYoichi TANAKA
National Research and Development Agency, Public Works Research Institute, Tsujuba-shi, Japan
Email: yo-tanaka@pwri.go.jp

Yasushi NITTA
National Research and Development Agency, Public Works Research Institute, Tsujuba-shi, Japan
Email: nitta-y573bs@pwri.go.jp

ABSTRACTIn Japan, i-Construction using ICT has been executed since April 2016 as a way to increase efficiency and save labor.
ICT has been introduced as construction control by earthmoving and paving work, quality as-build management, volumemanagement, compaction management and construction support by machine control and guidance in backhoe, bulldozer
and motor grader. In the future ICT must be introduced and applied to the construction of foundation work strongly linked
to the ground and of ground improvement work etc. in order to perform civil engineering works more efficiently withless labor. In this thesis, we introduce the construction management method in ground improvement work as acountermeasure against soft ground with many applications in Japan, and examples of construction support by ICT, andICT in the future ground improvement work.
Key words: Soft ground, Soil improvement, Management method, ICT

1. Introduction
Embankments, which are one kind of earthwork

reduces the quantity of unequal settlement. The Public

structure, are constructed on soft ground, and theimprovement technology that combines the surface

countermeasures are necessary. The present soft-groundmixing method which is used to ensure trafficability withcountermeasuresthe deep mixing method as a way to control unequal

oftenuseground

improvement

technologies that apply hardening agents such as cement

Works Research Institute has proposed compound groundsettlement.

in order to cut costs and shorten work periods. The deepThis paper reports on a survey of documents

mixing method, a ground improvement method which

conducted

uses hardening agents, achieves high strength byconstruction methods which would benefit from thestrengthening improved bodies and lowers cost ofcompound ground improvement technology, in order toconstruction by lowering the improvement ratio. Butclarify measurement items and control methods needed

lowering the improvement ratio in order to further cut

when executing the shallow and deep mixing methods

costs and shorten the work period of ground improvement

already being executed in Japan. The paper also introduces

increases unequal settlement of embankments, resulting inexamples of construction management methods based on

it becoming more difficult to ensure stability of earth-work

mixing in hardening agents and ICT based construction

structures. Therefore, at work sites where soft groundsupport found in the results of the survey, and describes

countermeasures are needed, combining the deep mixing

methods of using ICT to further improve efficiency andmethod with the sand mat method or the geotextile method

save labor in future ground improvement works.

under embankments and other earth-work structures often- 635 -toclarify construction

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

2. Ground improvement technology
Many methods of executing ground improvement
technology have been developed to achieve various
required effects. In recent years, many consolidation
methods using hardening agents to cut costs and shorten
work periods in addition to achieving total settlement
reduction effects have been adopted. The deep mixing
method, which is one consolidation method, is often
adopted as a soft ground countermeasure in anticipation of
it providing secondary effects in addition to the total
settlement

reductioneffect.

CompoundgroundFig. 1

Differences between various mixing methods based on

improvement technologies presumably reduce unequal

construction depth

settlement of embankment structures by combining thesurface mixing method with the deep mixing method.

Table 1.

Number of technologies surveyed

Present technologies related to the deep mixing
method and the surface mixing method which are now inuse, and to the medium mixing method which is executedat depths between the depths where these 2 methods areexecuted were surveyed. Fig. 1 is a schematic diagram
showing differences between the construction depths ofthese three mixing methods.
The deep mixing method is a technology used tobuild improved bodies by stirring a hardening agent withor spraying a hardening agent onto in-situ ground. Mixing
Table 2.

methods are categorized as mechanical mixing using

Construction machines and improvement depths

mixing blades, as spray mixing which sprays a hardening
agent, and the mechanical mixing plus spray mixing
method which combines the former two methods. Thespray mixing method basically uses a slurry type
hardening agent, but mechanical mixing can also use
powder type hardening agents. The improved body shapeis columnar, but is also executed as pile improvement or
block improvement. So mechanical mixing or spray pipes

means mixing by a rotary or trencher installed mainly on

are often executed as double or triple methods in order forbackhoes.

the improved columns to overlap, and the construction
depth is generally down to about 50 m.

The medium mixing method is a technology thatdeepens the construction depth of the surface mixing

The surface mixing method is executed in order tomethod by extending the component that supports theimprove trafficability. Mixing methods are categorized as

trencher or rotor. There is also a technology that combines

the in-situ mixing method which is mixing in in-situ

a spray mixing technology that is executed by the deepground, and the removal mixing method, which ismixing method and which is a hybrid of the shallow

transporting materials from in-situ ground, mixing it, thenmixing method and deep mixing method.

returning it to the site. Hardening agents are slurry andThree methods now used as mixing method

powder, similarly to the deep mixing method. The powder

technologies were abstracted as 120 technologies andmethod is executed by mixing in the powder with asurveyed and categorized based on the surveyedstabilizer or back-hoe bucket mixer. The slurry method

documents. Table 1 shows the surveyed technologies by- 636 -Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

method. Table 2 shows the principal construction
Table 3.

machines and improvement depths used for each work

Standard values of work progress control criteria

method. Backhoes have often been used for the surface
mixing method and the medium mixing method. The
maximum construction depths of construction machines
are 22 to 55 m for pile-drivers and 20 to 80 m for boringmachines. And the maximum construction depths forsurface mixing backhoes are from 1.8 to 15 m, and for
medium mixing backhoes are 4 to 13 m. The applicablesoils for mixing technologies are sandy soil, gravel,w

cohesive soil, humous, and sludge. Sandy soil (N<20) andC.L.

cohesive soil (N<4) which have low N values can be

G.L.
ℓ2

executed by all the technologies. Humous and sludge canw

be executed by 60 technologies, which are about half ofwℓ1

L

all technologies, and gravel can be executed by 20 of thetechnologies.
w

3. Construction management methods
Construction management in ground improvement

Fig. 2

Measurement locations of work progress control itemswork is executed in conformity with work progress control
standards and quality control standards for the ground

Table 4.

improvement – consolidation method as powder sprayStandard values of quality control criteria

mixing works, high pressure spray mixing works, slurry
mixing works, slaked lime pile works in Civil EngineeringWork

Construction

ManagementStandards

Draft

announced by the Ministry of Land, Infrastructure,Transport, and Tourism.
Work progress control standards are set with theirmeasurement

items

as

“standardheight”,“position/interval”, “pile diameter”, and “depth”. Underand work progress control item measurement locations are

quality control standards, “strength” of the improved bodyshown in Fig. 2. And the standard values of quality control

is set as the result of an unconfined compression test.

standards are shown in Table 4.

“Strength” is an item needed to perform particularly strict
control to improve soft ground. Quality control standards
specify that, “testing is done a total of 3 times—once each

4. Construction management items
Construction management items apply to 80

at the top, middle, and bottom—of each improved body”,technologies—the 120 technologies surveyed as ground

requiring that strength be ensured uniformly in eachimprovement

improved body. So construction management is necessary

technologies—and items which workers actually control

along with elements needed to ensure not only theusing Construction management devices installed on“strength”, but also uniformity of an improved body.

construction machines were surveyed. Construction

Construction

formanagement items are categorized as material quantities

construction quality are presumed to be the six items:

including speed (m/s), pressure (Pa), time (s), quantity“standard height”, “position/interval”, “pile diameter”,

injected (m3) angle (º), and length (m) which are measured“depth”, “strength, and uniformity”. The standard values

values, as confirmation of construction location andof work progress control standards are shown in Table 3

grounding as primarily measurement of change of current

management

items

necessary- 637 -technologies

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

Table 5.

Cause-and-effect relationships of construction quality with each of the construction management

value of rotating parts and others (rotation rate, mixing

and “depth” are few.

frequency, air flow rate). Many ground improvement
technologies measure the quantity of hardening agent thatis injected or added, the penetration speed, and the rotation

5. ICT based Construction management method
Construction management devices that are installed

speed of mixing blades. And three construction

on construction machines can use measured construction

management items are not only used for confirmation

management items to confirm “depth”, “strength” andduring construction, but also saved as construction records.

“uniformity” which are present work progress control andConstruction management items are also organized

quality control items.

according to the cause-and-effect relationships with 6“Standard height”, “position/interval”, and “pileitems necessary in Construction management standards.

diameter” other than depth have not been confirmed under

Table 5 shows the cause-and-effect relationships ofconstruction management items that can be measured byconstruction quality with each of the construction

construction management devices that are installed onmanagementorganized.

construction machines. So under present circumstances,

Measurement data items related to the qualities ofthese must be confirmed by repeated measurements. And

improved bodies, “strength” and “uniformity” aredepth can also be measured and verified by controlling therelatively numerous, while those related to work progress,rod penetration status using construction management“standard height”, “position/interval”, “pile diameter”,

devices, photographs and so on. In the future, it will

items

which

have

been

- 638 -

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

presumably be possible to perform construction location
and a work progress control by installing measurement
devices on construction machines. As this method, it ispossible to propose the use of computerized construction
devices which are used for machine control or machine
guidance. The surface and medium mixing methods
mainly use backhoes as the base machine, so it is thought
to be possible to achieve work progress control using
computerized construction devices.
Under quality control standards, it is necessary toconfirm by again performing unconfirmed compression

Fig. 3Sample screen of the guidance system

testing of the improved body that has been built by theconstruction. As the strength test, only 3 of every 500
improved bodies are tested. It is, therefore, difficult toclarify the state of the entire construction. In the future, itwill be possible to estimate the strength of improved
bodies that were not strength tested by comparing
construction management items which are related tostrength with the results of strength testing. And it is also
thought that it will be possible to also estimate the state ofconstruction management with regards to “uniformity”
which is related to “strength” by comparing data obtainedby measurement of the improved bodies tested by

Fig. 4

Example of three-dimensional visualization

unconfirmed compressive testing with measurement datafor other improved bodies. Construction management

added to it, it could also automate the measurement of

items are the information with an important role inwork progress.

confirming the construction quality of all improved

The second technology is a system that three-ground, so it is believed that it is necessary to collectdimensionally visualizes a series of information frommeasurement data as supervision items.

planning deep and medium mixing to construction results.

Among ICT based

Construction

management

Fig.

4showsanexampleof

three-dimensional

methods for ground improvement, three are registered asvisualization. Using this system, in addition to theNew Technology Information Systems (NETIS).

construction location that was measured, the quantity

The first technology is a system that guides groundadded, the rotation speed, grounding of the bearing

improvement machinery to the center of the improved

stratum (current value) which are measured and collectedbody while executing the deep mixing method. With thisby Construction management devices, and which weretechnology, a GNSS antenna is installed on theformerly transcribed on paper, are displayed on screen in

construction machine and the operator sitting in thethree dimensions. It is, therefore, possible to visualize thedriver’s seat monitors, indicates, and guides the machine

work progress items, or “uniformity” of the state of theto the center of the pile to be executed. Figure 3 shows awork in real time to easily confirm the state of the work.

sample screen of the guidance system. This technology

But, this system can only be applied to specified ground

has only a guidance function, but by measuring theimprovement methods, so it will be necessary toconstruction location and calculating its relationship with

eventually be able to apply the same method with otherthe pile center it can measure the work progress items,

ground improvement works.

“standard height” and “position/interval”. Therefore, if a

The third technology is a system that adds a function

method of measuring “pile diameter” and “depth” werethat visualizes and records construction information to the- 639 -Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

obtained from computerized construction devices on
construction machines to measure the “position/interval”,“standard height”, and “depth” of improved bodies. And
in order to perform supervisory inspections more
efficiently, we want to prepare work process control
instructions using ICT and to perform supervisoryinspections remotely using network functions.
In addition to more efficient work progress control,
we also want to provide an environment in which it ispossible to obtain construction management items that areFig. 5

Example of construction management screen

measured by construction machinery by defining dataexchange standards. Data for construction management

function that guides to the center of the improved body initems which have been obtained can be treated as big data

themanagement

by organizing the relationship of ground data obtained

information permits acquisition of the construction

during planning or before construction boring data withlocation, depth, slurry quantity, and ground shape. Thisdata for “strength” based on unconfined compressive

system also permits the sharing of Construction

testing done after construction. Big data for groundmanagement information outside of construction sites

improvement work can be counted on to be used forthrough a network. Fig. 5 shows an example oftheoretical analysis such as the establishment of a method

construction management screen.

of estimating the N-value of in-situ ground. And thefirsttechnology.

Construction

results of theoretical analysis of big data can realize
6. Conclusion
The ICT Introduction Council that discusses i-automatic operation by optimizing the quantity ofConstruction reports on “the application of construction

in turn,history to the supervisory inspections” as a future

management by fewer workers.

hardening agent injected and the penetration speed, which
will permit

more

efficientconstruction

initiative in March 2018. As object work types, taking
ground improvement work as a representative work type,
it achieves work progress control and quality control

References
Road Earthworks - Guidelines for Soil Ground Control.
2012. (in Japanese)

based on the construction machine history data. And
similarly, it discusses the rationalization of supervisory

Civil engineering management standard. March 2008.

inspections from remote sites using “remote construction

Ministry of Land, Infrastructure and Transport. (insuch as staged confirmation etc. through the use of highJapanese)

speed communications”.

New technology information system.

The Public Works Research Institute surveyed
present ground improvement technologies in order toclarify construction machines or construction methods
that are required by compound ground improvement
technologies. We believe that it will be possible to performground improvement works more efficiently with fewer
workers in the future by using computerized construction
devices installed on backhoes and technologies registeredin NETIS. First, as more efficient work progress control,
it is essential to define demanded functions as a system
which,

insteadofapplying

post-constructionmeasurements as in the past, can use position information- 640 -

“http://www.netis.mlit.go.jp/NetisRev/NewIndex.asp”.