May 2024 No.101
Japanese Infrastructure Newsletter

IDI

QUARTERLY
InfrastructureDevelopment Institute—JAPAN

Conical ShapeCONTENTS
D･Box Method: Soft ground improvement, Vibration Reduction Measures, Liquefaction Mitigation Measures,
Mud Pumping Measures, Anti-Erosion Measures for Forest Roads, Improvement of the very soft ground1

Introduction of the Brochure and Videos introducing the winners of the Minister’s Award and the Minister’s
Encouragement Award for Outstanding International Infrastructure Engineers

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Infrastructure Development Institute – Japan (IDI)
Plaza Edogawa-bashi 3F. 1-23-6, Sekiguchi, Bunkyo-ku, Tokyo, 112-0014, JAPAN
Tel: +81-3-5227-4107 Fax: +81-3-5227-4109 E-Mail: idi17@idi.or.jp Website: http://www.idi.or.jp/en/Infrastructure Development Institute - Japan

D・Box Method
D・Box Construction Method
1. Introduction
D･Box construction method (invented byMetry Technical Institute Co., Ltd.) is a very soft
ground reinforcement technique that offers a
combination of benefits such as vibration
reduction and mitigation of liquefaction damage,while also having excellent environmental
characteristics.
D ･ Box is a flat rectangular bag-shaped
product (LS100: 1.0m × 1.0m × 0.25m, LS150:1.5m×1.5m×0.45m), which is filled with crushed
rock※1 or similar materials. D・Box can be liftedwith a single lift band while maintaining its
square shape, and even when installed on softground, its shape remains unchanged.

(2) Comparison of other types of foundations
Figure-1 shows three types of foundations
on a very soft ground: ①Concrete plate, ②Soilbag, and③ D･Box. When loaded, Concrete plates
tend to sink unevenly due to eccentricity, while
Soil bags deform into an arch shape with lateralflow and reduced support.
In contrast, D ･ Box maintains its shapethrough internal restraining bands, dissipatingexcess pore water pressure directly below thefoundation, gradually increasing the groundstrength. Soil particles that enter the depression
create a resistance surface on the bottom of D･Box,
providing a bearing capacity more than threetimes stronger than that of the original ground.

( ※ 1 Recommended filling materials are C40-0 andRC40-0)① Concrete plateLoad

2. Outline(1) Internal structure of D･Box
By incorporating internal restraining
bands within D ･ Box (Photo-1), D ･ Box itself
gains its own strength regardless of groundconditions. This allows for shape retention andenables easy transportation and installation
using a single lift band (Photo-2), while
minimizing deformation when placed on a very
soft ground.

Pore water pressure

The load incurs theeccentric subsidence

Shearing deformation② Soil bag
Load

Load deforms Soil bad

Dissipation of porewater pressure

Elevation led bya shearing deformation

Internal restraining band

③ D・Box
Photo -1

Internal structure of D･Box

LoadNo deformation

Internal restraining band

Crushed rock filling into D･Box

Dissipation of porewater pressureLifting situation of D･Box

Increase shearingresistance(Load on D･Box entirely effects the bottom surface ofD･Box )Photo -2: Filling of the intermediate material
and a lifting status of D･Box

Figure -1: Comparison of 3 types offoundations on Soft ground1

Infrastructure Development Institute - Japan
3. Detailed Description(1) Description of D･Box
D ･ Box-LS series are products that
effectively bring about Soil reinforcement,Vibration
reduction measures, Liquefaction mitigation
measures, Mud pumping measures, Anti-Erosion
measures for forest roads, High water permeability
enabling various structures, and Reduction in CO2emissions.
The shape and material characteristics of D･
Box are shown in Tables 1 and 2.
Table-1

D･BoxLS100

1,000

1,000

250

D･BoxLS150

1,500

1,500

450

Lift bandRemarks

Width Depth Height

Table-2(d) The fillings can be effectively bound andsolidified by the internal binding effect of
the truss bands.

Size of D･BoxSize(mm)Type(c) As the upper side opens thoroughly,
filling works can be done effectively.
Opening and closing works of the bag arealso easy to handle with Velcro tapes.

Filling
Material:
0.25 m3FillingMaterial: 1.0m3

Truss band
Internal perspective view

Photo-3: D･Box lifted by a lift bandSpecification of D･Box
LS100/LS150
VerticalHorizontal

1850 or more

16,000o r more

Elongation (%)

18 or le ss

25 or le ss

Vertical

30 strands/5cm

Horizontal

30 strands/5cm

4. Scope of application
D･Box has the capabilities as shown below.

Inte rnal Band
StrapsTensile Strength (N)(a) Reinforcement of Soft Ground
D ･ Box serves as a foundation for
temporary road construction on very soft
ground (N value <1), distributing the load ofsuperstructures evenly and providing stableground reinforcement.
D･Box can increase the ground bearing
capacity to more than three times that of theoriginal ground.

FiberDensity

Material

Lifting D･Box by a lift band

Polypropylene(with UV inhibitor)(2) Main Characteristics of D･Box(a) When D･Box is lifted up, the truss bands
connected with the lift band at the center
will give strong compression stress to thefilling material, in addition to thetension force of the bag.
This mechanism leads to solidification of
the filling material and enables lifting
without deformation (Photo-3).

D･Box Ls150Temporary road

Clay N value < 1

Photo-4: Temporary bridge foundation inRamsar Convention wetlands(b) Working productivity is remarkably
improved as one sling operation work
can be done in a tidy shape.

2Infrastructure Development Institute - Japan(e) Anti-Erosion Measures for Forest Roads
Usage of highly permeable D･Box allows
for repair of security forest roads that become
impassable due to waterfall erosion from themountain side during heavy rains.

(b) Vibration Reduction Measures
By installing D･Box in the lower layersof roads (subgrade or sub-base course),
vibrations such as traffic-induced vibrations
are reduced (vibration energy is reduced by
6-7 dB, or 1/4 to 1/5 of its original amount).
Resident complaining
traffic vibrations

Very soft clay under thepavement after removal

Photo-8: Erosion measures for forest road

Measurement position of vibration

Installation of D･Box(f) Improvement of on the very soft ground
Even in viscous ground conditions such as
marshes, the high permeability of D ･ Box
allows it to absorb excess pore water generated
during loading or rolling, increasing theadhesive strength of the cohesive soil at thebottom.
Furthermore, the concave shape of thelower surface of D･Box restrains the weak clay,
resulting in an increase in shear resistance.

Re-pavement after
installation of D･Box

Photo-5: Reduction of traffic vibration(c) Liquefaction Mitigation Measures
D･Box helps mitigate liquefaction damage
in roads and other structures during
earthquakes.

Installed 2 layers on the pond.

Photo-6: Liquefaction Mitigation Measures
Photo-9: Construction road on the pond ofdesignated National Park Area(d) Mud Pumping Measures
The high permeability and increased
ground bearing capacity (more than threetimes that of other foundations) of D ･ Box
allow for mud pumping countermeasures inrailways, roads, etc.

Photo-7: Mud pumping measuresat Railway subgrade3

Infrastructure Development Institute - Japan(b) The countermeasure against the mud
pumping in 2017 (Photo-6).
D･Box was used in Myanmar Railway(360m) in the JICA project to improve thesoft ground of rail tracks, to prevent mud
pumping and improve the bearing capacityof the soft ground.

5. Anticipated Results
Main effects (merits) of D ･ Box are shownbelow.
(a) Environmentally friendly as cementbased solidification materials are notused.
(b) Permeability similar to that of coarse
sand will not bring negative effect to theoriginal ground.
(c) D･Box can alleviate CO2 emissions as its
filling material consists only of soil
particles (our company’s comparison).
(d) Cost effective as ground reinforcement
and vibration reduction can be attainedat the same time.
(e) D ･ Box can be easily and accurately
installed, as each box can be lifted by only
one lift band retaining its cuboid shape.

Ballast:0.15m

Before installation of D･Box

Photo-10: Improvement of the railway
subgrade using D･Box(c) The countermeasure against the liquefaction
in 2012 (Photo-6&11).
D･Box were installed under the lower
road base (thickness: 25cm).

6. Record of implementation
From past construction examples using D･Box, three typical works are shown below.
(a) Residents complained about the traffic
vibration in 2016 (Photo-5).
The vibration was occured due to theconstruction of a tempomrary detour roadon the soft ground. D･Box were installed
under the sub-base course of the improved
detour road of about 80m long to reduce thetraffic vibration (Figure-2).
After installation of the D ･ Box, theresidents expressed their gratitude forbeing able to sleep soundly for the first timesince the detour road was constructed.

D･Box for subgrade

7. Conclusion
D ･ Box is useful for the soft groundreinforcement, vibration impact reduction, andcountermeasures against liquefaction.
Especially, the D ･ Box method can be
carried out by hand alone if sand or crushedstones are available, and it is one of the effective
construction methods in developing countries
where countermeasures for soft ground arerequired. We hope to develop dissemination
activities with a view to local production.

Acceleration
vibration level(dB)
振動加速度レベル（dB）

60
50
4030
Pre-installation average energy of D･Box
Post-installation average energy of D･Box
×Reduction value●○

100-10-20
11.25 1.6

2

2.5 3.15

4

56.3

810 12.5 16

20 25 31.5 40

50

63

1/3-octave band center frequency (Hz)Section of Pavement

Photo-11: Liquefaction Mitigation Measures70

20

3 bags of D-BOX per row

80

Figure -2: Vibration Reduction by D･Box

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Infrastructure Development Institute - Japan
8.Conctact Information(1) PACIFIC CONSULTANTS CO., LTD.
Project Management Department
Technical Manager
Naohiro.Togawa
naohiro.togawa@ss.pacific.co.jp+81-3-6777-3595
https://www.pacific.co.jp/(2) Metry Technical Institute Co., Ltd.
① President and invanter
Futoshi NOMOTO
info@metry.jp+81-480-47-0366
https://www.metry.jp② Technical General Manager
Hiroshi SHIMADA
shimada@metry.jp+81-480-47-0366
https://www.metry.jp

5Infrastructure Development Institute - Japan

Introduction of the Brochure and Videos introducing the winners of the Minister’s Award andthe Minister’s Encouragement Award for Outstanding International Infrastructure Engineers
The Ministry of Land, Infrastructure,

This year, the MLIT has certified theTransport and Tourism (MLIT) has been certifying

achievements of 237 engineers in 73 projects. The

Japanese Engineers’ achievements in infrastructure“Minister’s Award for Outstanding International

projects abroad, further awarding those who have

Infrastructure Engineer” was awarded to 13 engineers,exceeded in their technical and management skills

while the “Minister’s Encouragement Award forsince 2020.

Outstanding International Infrastructure Engineer”
was awarded to 4 engineers.

It is part of the “International Infrastructure
Project Engineer Certification and Award System”,The brochure introducing the winners ofwhich aims to promote the participation of Japaneseboth awards is available at the following URL.

infrastructure engineers in both domestic andhttps://www.mlit.go.jp/kokusai/content/001745513.pdf

international projects.
In addition, six award winners presented
TheMLITaimstopromotethetheir award-winning international infrastructureinternational development of Japanese Quality

projects.

Infrastructure Systems through allowing engineers toworkboth

domesticallyandPlease click on the URL below to watch

internationally,

their presentation videos.

contributing to the economic development and thehttps://www.youtube.com/playlist?list=PL2RgY_hji

problem solving of developing countries.

mJR_t_KnHBuf0_3XN5TMeakr

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About IDI and IDI-quarterly
Infrastructure Development Institute-Japan (IDI) is a generalincorporated association operating under the guidance of Ministry of Land,
Infrastructure, Transport and Tourism of Japanese Government.
IDI provides consulting services to facilitate international assistance todeveloping countries, to promote international exchange of information andhuman resources, and to support globalization of project implementation systems
targeting both developed and developing countries in the field of infrastructure.
IDI has been publishing a free quarterly journal called “IDI Quarterly”
since1996 to introduce information related to public works and construction
technologies developed in Japan, to foreign countries. We have distributed thejournal to administration officials in more than 90 countries around the world via
e-mail.
It will be highly appreciated if you could send us your opinions,impressions, etc. regarding the articles. We also welcome your specific requests
regrading technologies you would like to see on following Quarterly issues.

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