Volume 2, Issue 1 March 2017

Current Practice

Feasibility study on using sheet pile as mitigation measure
for road failure alongside of canal in Thailand
Dr. Ittichai Boonsiri*, Dr. Pastsakorn Kittiyodom***Geotechnical Engineer, Construction Design & Planning Group.
**Executive Director, Geotechnical & Foundation Engineering Co., Ltd.
Central part of Thailand is located in a river deposit soil which consists of a thick soft to very soft clay layer on the top
deposit, namely Bangkok clay, underlain by stiff clay and sand layer. These types of soft soils are very sensitive todeformations and have low shear strength. Many parts of the central part area are utilized as agricultural zone. A road
alongside of irrigation canal has been used for transportation of agricultural products from plantation to a market.
However, some of irrigation canals are exploited as flood drainage. These misuse and low bearing capacity of soil werecaused many failure of the road as shown in Photo 1. In addition, one of the main reason for road failure comes fromwater level inside a canal. During drought season, soil under canals show large settlement due to lowering of groundwaterlevels. In addition, slope of canal tends to increase due to water erosion. As a result, canal is vulnerable to collapse whenwater level is decreasing.
At present, mitigation measure thatis employed to prevent the problems
is construction of retaining wall
between road pavement and canal as
displayed in Figure 1. Combination ofconcrete pile with concrete sheet
wall has been chosen for protectingof road slope failure (Figure 2). The
length of concrete retaining wall isapproximately
16kmandspecification is shown in Table 1.
However, some retaining walls werecollapse during drought season due
to slope failure of soil under canal. It
can be said that an interlock force
between concrete pile and concrete
sheet pile is not enough to prevent aslope failure.
Steel sheet pile wall could be one ofpossible solution for permanently
solving the problems. Use of steel
sheet pile become popular because itis reusable. Furthermore, price ofsteel material tends to reduce inThailand because there is more
import from China and increasing
number of manufacturers. The majoradvantage of this type of wall is itprovidesresistanceduringinstallation stresses. The sheets must
be driven into the ground and they
contain high resistance to the force ofbeing driven down. The pile length iseasily adaptable and can be weldedor connected for suitable work.

Photo 1 Road settlement alongside of irrigation area canal
Before failure

After rehabilitation
Road pavement

Road pavement
Concrete pile

Max. water level

Min. water level
Canal level

Slopefailure line
Canal level

Figure 1 Typical section of roadway along a canal15

Volume 2, Issue 1 March 2017

Pile cap(S)(T)

0.5 m(W)

(W)

0.5 m

Concrete pile

(H)

(H)

(A)

Concretepile

Figure 2 Detail of concrete retaining wall

Conventional methods for installation ofsteel sheet pile are percussion andvibratory. These methods produce noiseand vibration to nearby existing structuresor roadways. The vibration can cause fatigue
or resonant frequency to structures anddisturbance to the soil slope. As a result, it
leads cracks to those structures or it will
trigger a reduction of soil stability.
Inaddition, these conventional methods
require large working area for a machine
and temporary platform. Occasionally, anearby transportation system need to be
shut down or rerouted for installation ofretaining wall. Non-staging method or GRB
system (Giken Reaction Base) proposed by
Giken may be used to tackle theseproblems. This technique could constructretaining wall directly without any
temporary platform.
Therefore, feasibility study has beenperformed. U steel sheet pile with 400mm
width (typical size in Thailand) is selected todesign for proposed retaining wall. Typicaldrawing of U sheet pile retaining wall isdescribed in Figure 3. Long U sheet pile(L=15m) and short U sheet pile (L=6m) areconnected alternatively. Long sheet pile isdesigned as structural element for resisting
main lateral load and short sheet pile isdesigned as non-structural element for
preventing water penetration.

Unit (m)Specification
Type I

Type II

Type III

Size of concrete pile

40 x 40 cm

30 x 30 cm

40 x 40 cm

Length of concrete pile

9-15

99-15

Spacing of concrete pile (S)

1.00

1.00

1.00

Spacing for concrete (A)

5.30

5.30

5.30

Width of concrete sheet (W)

0.75

0.85

0.75

Height of concrete sheet (H)

5.00

5.00

5.00

Thickness of concrete sheet (T)

0.10

0.10

0.10

Table 1 Specification of typical concrete retaining wall

Figure 3 Drawing of U steel sheet pile wall (SP-III A)
16

Volume 2, Issue 1 March 2017

Description

Spacing

SectionSectionMoment of inertia

Elastic

EI(m)

Modulus

ModulusI

Modulus(kNm2/m)

Z (cm3)Z (cm3/m)(cm4)(cm4/m)E x 108(kN/m2)Concrete
Retaining

0.40x0.40m

1,000

11,447

4,579

228,933

91,5730.25

22,893

SP-III A

400-760-

11,4002.10

23,940wall
Steelsheetpile wallTable 2 A comparison between concrete retaining wall and steel sheet pile wall
From Table 2, it could be seen that steel
sheet pile wall can be used as substitutefor concrete retaining wall because EI
value of proposed steel sheet pile wall ishigher than existing concrete retaining
wall. Typical price of concrete retaining
wall and steel sheet pile wall including
material, workforce and instruments are
summarized in Figure 4. Type of concrete
pile retaining structure are divided by sizeof the pile, length of pile and quantity ofreinforcement of pile cap. A pricedifference between SP-III1 and SP-III2 comefrom an approximately range ofinstallation price by Silent Piler in Thailand.
A comparison price shows that price ofSteel sheet pile wall is between the highest
and the lowest price of concrete retaining
wall. Therefore, steel sheet pile wall could
be considered as alternative solution tosolve a collapse of concrete retaining wall
during drought season. In addition, arestoration process of road failure due towall collapse need to clear a slide
pavement as shown in Photo 2. As the lessrequirement of temporary platform areafor the Press-in Method, the installation of
new retaining wall and remove of debris
pavement during the restoration process
can be conducted simultaneously which is
the great benefit to the rehabilitation
time. Finally, It is inevitable that anadverse effects caused by vibration andnoise become more and more serious due
to limited space, sloped working area andenvironmental concern. Silent technology
is a promising solution that can handle
these difficulties. As a result, there is an
opportunity for Silent technology in theThailand market.

Price (Baht)/ 1km

Retaining wall depth: 15 m46,000,000
44,000,000
42,000,000
40,000,000
38,000,000
36,000,000

10.4x0.4
12A

2SP-III1

30.4x0.4
15A

4SP-III2

50.4x0.4
14C

Type of concrete pile and U sheet pile
Note: SP-III1 for installation price = 400 baht/m2
SP-III2 for installation price = 600 baht/m2

Figure 4 Comparison price between concrete retaining walland steel sheet pile all

Photo 2 Restoration process of road settlement

17