September 2016 No.73
Japanese Infrastructure Newsletter

IDI QUARTERLYInfrastructure

Development

Institute—JAPANRAKUNA-IV✓ High stability✓ Excellent durability✓ Big porosity (56.5%)✓ Low life cycle cost

TNF Method for Soft GroundC O N T E N T S
New Raft Foundation Method (TNF Method) for Soft Ground2

Conservation and maintenance technologies offered by Kawasaki Geological Engineering

4

Infrastructure Development Institute – Japan (IDI)
Suido-cho Bldg, 3-1, Suido-cho, Shinjuku-ku, Tokyo, 162-0811, JAPAN
Tel: +81-3-5227-4107 Fax: +81-3-5227-4109 E-Mail: idi17@idi.or.jp Website: http://www.idi.or.jp/english/00index.htm

Infrastructure Development Institute - Japan

New Raft Foundation Method (TNF Method) for Soft Groundfoundation steel frame, slab concrete, and finally１．Background of Technical Development
In Japan or Asian countries, first-story or
second-story

buildings

are

being

built

floor slab concrete is constructed.

onfarmlands. Especially, several areas of river deltaregions are located in Southeast Asian countries.
There are soft ground and structurally weak, asthese are typically unsuitable for buildings on soft
ground. In these cases, raft foundation isconsidered to be effective, but uneven settlement

6and other damages become a problem. Therefore,
we

proposeTNF(Tender

Net

Foundation)

construction method. The proposed method is a
simplified ground improvement of raft foundation

5

with curb pattern structure of a combined unit oftheimproved

groundandfoundation.

The

combined unit is stable and can support tobuilding’s load. After that, it can restrain to4

3

uneven settlement and lifting of the building.

２．Technical Characteristics of TNF Method
The TNF method is different from pilefoundation method or raft foundation method. As
1mentioned above, it is a foundation system to2

support the low structure on soft ground using
Fig. 1-1 Image of TNF Method

both the raft foundation and shallow soil
improvement mass constructed directly under the

1: First Improvement

raft foundation. The image of this method is

2: Enclosure Soil Improved Groundshown in Fig.1-1 and Fig.1-2. According to the Fig.

3: Second Improvement

1-1, first improvement means improved ground as

4: Excavation of Foundation

curb pattern at the deep position. It includes

5: Steel Frame Foundation and Slab Concrete

enclosure soil unimproved ground parts. The

6: Floor Steel Frame and Slab Concrete

second improvement layer is constructed as entire
surface improvement as a cover layer. And then,
excavation for foundation with preparation mold

A complete image of first improvement is shownin Fig. 1-2.

of soil layer is included. The next step is

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Infrastructure Development Institute - Japan

underground buried objects.
(2) This method can reduce CO2 emissions
because less running machine and using
small amount of materials.
The most effectiveness of this method is
low-cost as described in the following.
(1) This method is raft foundation and the shallow
soil improvement mass constructed directly
under the raft foundation. According to thisFig. 1-2 Image of Shallow Improved Section

foundation with unifying of foundation slab

３．Benefits of TNF Method
The benefit points of TNF method are safety,
relief, environmental friendly and low-cost. Safety
is extremely important for a building, and safetybuildings can secure in relief for people.
The advantages in safety and relief of thismethod are described as follows.
(1) TNF method is possible to prevent subsidence
damage of the building.
(2) Unequal settlement of the building can be
restrained.
(3) Lifting of foundation will be eliminated byusing the TNF method.
(4) It is possible to prevent in liquefaction
occurrence during an earthquake, because
buildings are integrally responded due toentireimproved

ground.

structure, foundation beams exist in the raftEven

throughand improvement layer.
(2) It is constructed in improvement of current
situation of ground.
(3) It is short construction period.
According to above, this method is named as
Tender Net Foundation.
４．Achievements of TNF Method in JapanTNF method has already certified a patented
technical system in Japan. It has been alreadyapplied to supermarkets, factories, warehouses
and etc., all over the Japan and it is gradually
increasing every year in history until now. Total
applied buildings of this method are 664 buildings(1,664,339 m2) at the end of June 2016 as
illustrated in Fig. 2-1 and Fig. 2-2.
700

entire improved ground.

600

method can support to durable and safetybuilding.
TNF method is also an environmental friendly
method including the following advantages.
(1) TNF method is a shallow improvement
ground method; therefore it does not disturb
both original underground condition and

500
400
300
200
100
0
1993
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016

By the above mentioned advantages, TNF

No. of Buildingsliquefaction occurs, integrally resistance ofFig. 2-1 Total number of TNF-based buildings(At the end of June 2016)

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Infrastructure Development Institute - Japan

Built-up Areas [m2]2.0E+06
1.5E+06
1.0E+06
5.0E+05

1993
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016

0.0E+00

Fig. 2-2 Build-up areas of TNF-based Buildings(At the end of June 2016)

Fig. 3-1 TNF-based Hardware Store(Recorded Date: 17th March 2011)

The TNF method is widely applied after
happening of the great east Japan earthquake in2011 because almost TNF based buildings could
not be affected by the earthquake. TNF- based
building

andconventional-based

building

conditions are compared in the following figures.
According to our records, TNF-based building
didn’t occurred in unequally subsidence as
described in Fig. 3-1. On the other hand,conventional-based building had wavy asphalt
according to Fig. 3-2.

Fig. 3-2 Conventional-based building(Recorded Date: 17th March 2011)

Contact:
E-mail : mail@takeuchi-const.co.jp

Technical Developer Information

TEL : +81-848-60-1331

Takeuchi Construction Inc.

FAX : +81-848-62-6973

President Kinji Takeuchi

Conservation and maintenance technologies offered by Kawasaki Geological Engineering(Exploration, diagnosis and survey technologies for maintenance and management of roads, rivers,
harbors and other social infrastructure)
１．Conservation and maintenance technologies ofKawasaki Geological Engineering
For more than 70 years since its inception in 1943,

of social infrastructure to be built as a group of

KawasakiLtd

specialists in the field of geological survey,(“KGE”) has provided information on the groundbuilding on their expertise in boring survey,

necessary for the construction and improvement

geophysical exploration, and field measurement.

GeologicalEngineering

Co.,

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Infrastructure Development Institute - Japan

Meanwhile, facing the rapid aging of thewhich are laid at various depths going down to 4

infrastructure constructed for the high economic

to 5m. Therefore, to explore aging deterioration of

growth period in JAPAN, KGE found a field in

the cavities, it has been necessary to carry out

which

exploration periodically and repeatedly.

it

could

contributeasageologicalconsultant, created a conservation division, andhas provided various technical services for
exploration, diagnosis, and survey required forthe maintenance of various infrastructure. This
introduction presents a look at the specialized
technologies in the field of conservation andmaintenance KGE has to offer.

This problem has led to an increase in survey costand collapses immediately after exploration,affecting both investigation cost and users’ safety.
As one of the solutions, we have developed avehicle-towed

multi

chirp

radar,

agroundpenetrating radar for the exploration of deep
cavities, capable of surveying down to the depths
lifelines are buried.

２．Vehicle towed multi-chirp radar exploration
Recently, there has been increasing demand forunderground cavity investigation in order toprevent accidents caused by depression in roads,
portfacilities,

river

embankment,

etc.

In

particular, some of the lifelines beneath the roadsurface are more than 40 years old since being
laid, present advanced deterioration, and are oneof the factors causing cavities. Since cavities are
an invisible problem in the soil, geophysicalexploration technologies capable of covering theunderground linearly and in broad areas are
required.
Among others, the ground penetrating radar
exploration technology with excellent cavity
detection ability and workability is applied inmany cases. However, the ground beneath roads
in Japan is mostly comprised of sand rich infine-grained fractions, contains a high ratio ofwater,

andhence

attenuates

radio

wave

significantly.
This limits the maximum detection depth ofcurrently available ground penetrating radars to
only 1.5 m under the ground and makes it
impossible to detect all deteriorated life lines,[Characteristic of a Chirp-Radar]
A chirp

radar

is

a

radar

that transmits

electromagnetic sine waves into underground andcompresses reflected signals into pulse waveforms.
The

radar

transmits

signalschangingthefrequency of sine waves according to desired
bandwidth(frequency

range

of

signalstransmitted). In this case, the transmission
output depends on the transmission time. Further,since the limit of resolution depends on the widthof transmission frequencies, the radar canincrease

its

transmission

power

without

impairing its resolution ability, which has beendifficult for conventional underground radars
using conventional pulse waves.
Fig-1 shows the results of the comparison
between a conventional radar and a chirp radar of
exploration

targeting

iron

pipes

buriedatdifferent depths down to 3 m underground at 0.5mintervals.

detected

the

While

the

conventional

iron

pipes

down

to

radar
2.0

m

underground with semicircular waves, the chirpradar clearly detected all of the iron pipes down to

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Infrastructure Development Institute - Japan

3 m underground.

Fig. 1 Comparison of exploration ability between theconventional radar and a chirp radar[Vehicle-towed Multi-Chirp Radar]
A vehicle-towed multi-chirp radar is an
exploration device equipped with seven small

Fig. 2 Overview of the vehicle-towed multi-chirp radar

antennas using chirp signals and a large antenna

Towing the radar of a vehicle makes it possible to(Fig. 2). With transmission frequencies of 50 toscan underground at a speed of 40 to 50km/h. In

800 MHz, the seven small antennas are capable ofaddition, the width of the radar being 2.5m (withexploring down to about 3 m underground while

the antennas stretched out), the whole single lane

keeping high resolution equal to conventionalof the road can be scanned at a time.

radars. On the other hand, though using

Further, the radar features a drive camera thattransmission frequencies of 50 to 300MHz andfilms front and side outside scenes in sync withhence with resolution inferior to the small

the radar data and a VRS-GPS system capable ofantennas, the large antenna is capable ofhigh-accuracy position management of abnormal

exploring the underground even deeper, down to 4

points.

to 5m.

[Applications of vehicle-towed multi-chirp radars]
As shown in Fig. 3, vehicle-towed multi-chirpradars made it possible to explore undergroundcavities deeper than 1.5 m that has been difficult
for conventional radars. Hence, we think it ispossible to use these radars not only for the
exploration of shallow hollow cavities underpublic roads, service roads along river

September 2016 No.73
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Infrastructure Development Institute - Japanembankments, or under harbor quay aprons, but

degradation depths. There has not been any

also for the exploration of cavities or groundmethod for surveying and diagnosing concrete

structures at a variety of underground depths.

structures capable of checking their physicality atHence, they will be very useful in detecting

desired depths of structures and identify thecavities in their early development, estimating

depth of deterioration.

their causes, and developing effective

That is an exact reason why we have developed

maintenance plans.

GoTEN (partial loading test in boreholes), a new
test method aimed at evaluating and diagnosing
the deterioration depth of concrete structures.

[Overview of GoTEN]
The test apparatus of GoTEN is comprised of acylindrical "body" of 40 mm in diameter and about
270 mm in length with a built-in displacement
meter and hydraulic piston, a hemispherical“loading tip” of 6 mm in diameter to be inserted
into a core hole drilled in the structure, and a“CCD camera" used to visually check the loading
point (attached as necessary) (Photo 1).
Data collection device
Fig. 3 Examples of cavities detected by chirp radars

Hydraulic pump

3. Concrete diagnostic technology
The measurement of ultrasonic propagation
velocity on core holes, on obtained cores, or on
concrete surfaces, the measurement of intensityof obtained core samples, including

直径 40mmsmall-diameter cores, and/or the improved on site

長さ 270mm
Test device

pull-off method are typical survey or diagnosing
methods to identify the depth of deterioration of
concrete structures. However, in addition tohaving difficulty in quantitative evaluation, all of

Test device
CCD camera
attached as necessary

Semispherical loading tip
of 6 mm in diameter

the above methods still have limitations (such as
evaluation in the direction of depth in the
structure being only the average over several
centimeters) and have not yet been established asa research and diagnostic techniques of

Photo-1 GoTEN

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Infrastructure Development Institute - Japan

The procedure of measurement is as follows:(i) Drill a core hole of 42 mm or more in diameter;(ii) Insert the test device into the core hole;(iii) Fix the test device at the measurement depth;(iv) Pressurize the test device with a hydraulicpump and penetrate the loading tip into the holewall;(v) Collect data on the load and amount ofpenetration during the penetration into the holewall; and(vi) Turn the test device to change directions ofmeasurement, and collect data on six or morepoints at the same depth.

4. Asset management of anchor slope

The amounts of penetration and load obtained bymeasurement are expressed in a load-penetration
curve and the "penetration resistance" isdetermined from the slope of this curve. Fig. 4
shows the method for calculating the value ofpenetration resistance. The penetration
resistance value represents how the penetrationof the loading tip into concrete is easy or difficultand is used as an indicator in estimating thestrength of the concrete. As shown in Fig. 5, fromthe results of measurement of concrete test pieces
in laboratory and actual structures, it has beenfound that we can estimate concrete strength bymultiplying the penetration resistance by about 4.

Load
荷重PP(kN)(kN)

10

Fig. 5 Relationship between the penetration resistance value
and the strength of concrete

Ground anchors to stabilize soil structures havebeen widely used in slope stabilization work fornatural or cut slopes for their workability andeconomic efficiency. To ensure safety of social
activities, it is important that we can continue
using these ground anchors installed everywhere
effectively, safely for a long time.
However, it is said that all of anchors have notbeen adequately maintained up to date. One of
the reason is the high testing cost due to the size
and weight (100 to 200 kg) of the center hole jackfor construction work commonly used. It is
important to monitor the tension load of theanchor in the lift off test. It is we have developed
an SAAM system aiming at mitigating, even

Penetration
resistance value =ΔP/ΔL
貫入抵抗値＝ΔＰ／ΔＬ

slightly, the difficulties of the lift-off test

Measurement
data
測定ﾃﾞｰﾀnecessary for anchor health survey.

Regression
回帰線line

5
ΔＰ
ΔＬ[Characteristic of SAAM system]
SAAM system is a lift-off-only compact jack (Photo-1).

0
0

1
2
Amount of貫入量
penetration
L (mm)L (mm)

3

The lift-off test consists in pulling up the anchor headwith a jack and determining the residual tension load at

Fig. 4 Method for calculating the penetration resistance value

the moment it lifts up. In practice it is possible todetermine the residual tension by lifting the anchor head

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Infrastructure Development Institute - Japana few millimeters. Hence the SAAM system reduces theweight and size of the jack by adopting low-strokes (2 to5 cm).

Photo 2 Lift-off test by rope access[Utilization of SAAM system]
Photo 1 SAAM system

By performing the lift-off test with a small and

The current lineup of SAAM systems is as shown

light-weight SAAM system, it is now possible toin Table-1. The commonly used system, SAAM-J

comprehend the residual tension of existing

II 20-82, is weighs of only 19 kg, and can be

anchors more quickly and efficiently than thetransported by persons, which makes it possible

conventional testing method using large centerfor surveyors carry out measurements by ropehole jacks. This made it possible to provide

access on slope surfaces. In principle, use of roughdistribution of residual tension land on broader

terrain cranes, etc. for carrying in equipment or

areas (Fig. 6), while the number of survey had

temporary scaffolding are not necessary (Photo 2).

been carried out. Utilizing these residual tension

Table 1 SAAM system line-up

force distribution charts on broad areas has mademonitoring locations and range of necessary work

SAAM Jack T ypes

Lengths & weight

Performance

Specifications
Maxim um pullforce (kN)Maxim um stroke(m m)Center holediameter (mm )Maxim um outer
diameter (mm )Jack length (m m )Jack weight (kg)J I-300

J II-600

J II-1000

300

600

1000
50

20

10

50

J II-1500 J II-2000
1500

2000

20

20

20

102

67

75

10

20

62

43

153

155 185 185 195 210 210

230

230

260

151

108 114 144 125 115 155

125

145

175

14

15

30

40

63

20

59

82

19

23

25

82

25

32

Contact:［Vehicle towed multi-chirp radar exploration］： Toshimune Imai
E-mail: imait@kge.co.jp［Concrete diagnostic technology］
GoTEN： Hiroki Sawaguchi,
E-mail: sawaguchih@kge.co.jp
SAAM system： Toshiyuki Takanashi
E-mail: takanashit@kge.co.jp

more practical.

Fig. 6 Example of residual tension load distribution

Maintenance Department
Kawasaki Geological Engineering Co., Ltd
TEL： +81-3-5445-2080
FAX： +81-3-5445-2094

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Infrastructure Development Institute - Japan

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association operating under the guidance of Ministry of Land, Infrastructure,
Transport and Tourism of Japanese Government.
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