Mechanical properties in relation to vehicle mobility of Sepang peat terrain in Malaysia

Journalof

www.elsevier.com/locate/jterra

TerramechanicsJournal of Terramechanics 41 (2004) 25–40

Mechanical properties in relationto vehicle mobility of Sepang peat

terrain in Malaysia

Ataur Rahman *, Azmi Yahya, Mohd. Zodaidie, Desa Ahmad,Wan Ishak, A.F. Kheiralla

Faculty of Engineering, University Putra Malaysia, 43400 UPM Serdang Selangor DE, Malaysia

Abstract

An analytical framework for determining the mechanical properties of peat and predicting

the tractive performance of tracked vehicle is presented. It takes into account the load-sinkage

and shearing characteristics of peat as well as all major design parameters of tracked vehicle.

An experimental study on the mechanical properties of peat soil was conducted at Sepang

area, Selangor, Malaysia. The stiffness values of surface mat and underlying weak peat deposit

from load-sinkage test were determined by specially made bearing capacity apparatus. The

mean values of surface mat stiffness before and after drainage were found to be 31 and 45.62

kN/m3, respectively and the mean values of underlying peat stiffness before and after drainage

were found to be 252 and 380.20 kN/m3, respectively. The mean value of the internal frictional

angle, cohesiveness and shear deformation modulus of the peat soil sample were determined

using a direct shear box apparatus in the laboratory. The mean values of internal friction

angle, cohesiveness and shear deformation modulus before and after drainage were found to

be 22.80� and 24.31�, 2.63 and 2.89 kN/m2, and 1.21 and 1.37 cm, respectively.

� 2004 ISTVS. Published by Elsevier Ltd. All rights reserved.

Keywords: Peat; Bearing capacity; Shear deformation modulus; Shearing stress; Internal frictional angle

and cohesiveness

*Corresponding author.

E-mail address: [email protected] (A. Rahman).

0022-4898/$20.00 � 2004 ISTVS. Published by Elsevier Ltd. All rights reserved.

doi:10.1016/j.jterra.2004.01.002

mail to: [email protected]

26 A. Rahman et al. / Journal of Terramechanics 41 (2004) 25–40

1. Introduction

The key to off-road vehicle performance prediction lies in the proper evaluation of

the mechanical properties of the terrain. Peat terrain deformation due to track

motion is dependent upon the applied forces as discussed by Chang and Bekker [1].

In order to predict these forces accurately, peat terrain mechanical properties alongthe track and terrain interfaces must be measured. Peat covers a significant portion

of the plantation land of Malaysia. There are about 2.8 million ha of peat in Ma-

laysia accounting for about 8% of the total land area of the country. Sarawak has the

largest area of peat in the country. This is followed by Peninsular Malaysia which

has about 984,500 ha, comprising 7% of its total area, while Sabah 86,000 ha, rep-

resent 1% of the state [2]. Large tracks of peat lands are being converted for oil palm

plantations as a result of global increase of oil palm demand. At the moment, there is

no appropriate vehicle on the mechanization of oil palm in peat land of Malaysia. Toevaluate the vehicle mobility over this type of terrain, it is important to develop

appropriate methods for identifying and measuring those mechanical properties of

peat that are considered to be relevant to vehicle mobility. To properly identify the

mechanical properties of peat terrain from an off-road vehicle mobility viewpoint,

measurement need to be taken under loading conditions similar to those exerted by a

vehicle. The vertical load that an off-road tracked vehicle exerts on the peat terrain

results in sinkage. A special plate sinkage apparatus has been designed and devel-

oped to evaluate the load-sinkage parameter. Furthermore, an off-road tracked ve-hicle applies horizontal load to the peat terrain surface through its running gear and

this results in the development of shearing strength and associated slip. The digital

shear vane was used in situ to evaluate the shearing strength of the peat terrain. The

digital direct shear box apparatus was used to evaluate the shearing parameters of

peat terrain such as peat cohesiveness, internal frictional angle, shear displacement

and shear deformation modulus.

This paper represents the experimental results on the determination of cohesive-

ness, internal friction angle, shear deformation modulus, vane shearing strength,surface mat stiffness and underlying stiffness of peat and track vehicle tractive per-

formance on peat terrain. Shear deformation model equation by Wong et al. [3] was

used to compute the shear deformation modulus of peat while the pressure-sinkage

model equation by Wong et al. [4] was used to compute the surface mat stiffness and

underlying stiffness of peat.

2. Materials and methods

2.1. Test site

Field tests were carried out at Sepang peat area, located about 45 km from Kuala

Lumpur, Malaysia. The area was heavily infested with palm roots, low shrubs,

grasses, and sedges as shown in Figs. 1 and 2. The field conditions were wet and the

water table was found to be 0–12 cm below the surface level. The surface mat and the

Fig. 1. Tested site before drainage.

Fig. 2. Tested site after drainage.

A. Rahman et al. / Journal of Terramechanics 41 (2004) 25–40 27

peat deposit thickness were not distinct by visual observation. The surface mat

thickness was about 5 to 25 cm at the center location between adjacent palm rowsand 10–35 cm at the palm tree location. The underlying peat deposit thickness for the

whole area was about 50 to 100 cm. The water field capacity was almost at saturation

level and walking on such a terrain condition was only possible with the use of a

Fig. 3. Bearing capacity measuring scenario.


special made wooden clog as shown in Fig. 3. The dominant features of this site may

be described as high water content and weak underlying peat that could easily bedisturbed by vehicle movements. The overall area was divided into three equal area

blocks and each block was again divided into three equal sub-blocks. Peat moisture

content, bulk density, cohesiveness, internal friction angle, shear deformation

modulus, vane shearing strength, surface mat stiffness, and underlying stiffness of

peat were determined. In situ determinations for vane shearing strength, surface mat

stiffness, and underlying stiffness were carried out at 10, 25 and 40 cm depth in triplet

replications at the center location between adjacent palm rows within each sub-block

in the field during un-drained and drained conditions. Similarly, undisturbed sampleof 216 cm3 volume were taken at the mentioned depths and points in the fields in

triplet replications for the determinations of moisture content, bulk density, cohe-

siveness, internal friction angle, shear deformation modulus of peat. The samples

were wrapped with aluminum foil and sealed in a plastic container before they were

immediately taken to the laboratory for the relevant analysis.

2.2. Cohesiveness, internal friction angle, and shear deformation modulus

A Wykeham Farrance 25402 shear box apparatus as shown in Fig. 4 was used to

determine cohesiveness, internal friction angle, and bulk deformation modulus of

peat. The apparatus was setup to run at a shear rate of 0.25 mm/s and a maximum

shear displacement of 12 mm. Prior to the actual shear test, the prepared test sample

in the rectangular box was subjected to a consolidation load of 1 kg for 24 h.

Readings on the shear displacement in cm and shearing stress in kN/m2 were

Fig. 4. Wykeham Farrance 25402 shear box apparatus.


recorded every minute until failure on the sample. The same test procedure was

repeated for the consolidation load of 1.5 and 2 kg, and again repeated on samples

taken from different depths, different sampling points, and different drainage

conditions.

The shear deformation modulus of peat was determined by using the equation

proposed by Wong et al. [3]:

K ¼ �P

1� ssmax

� �2

j2

P1� s

smax

� �2

j ln 1� ssmax

� �h i ; ð1Þ

where, K is shear deformation modulus in cm, smax is maximum shearing stress inkg/cm2, s measured shear strength in kg/cm2 and j is corresponding shear strength

in cm.

The relationship between normal stress and shearing stress of peat for different

samples is shown in Fig. 5. From the interpretation of normal strength and shearing

strength, the cohesiveness and the internal frictional angle of peat were computed.

Information of shear deformation modulus, cohesion, and internal frictional angle

could be used in the computation of traction, engine power, drawbar power and

tractive efficiency of a vehicle.

2.3. In situ shearing strength

A RMU I012 digital vane test apparatus shown in Fig. 6 was used to determine

the in situ shearing stress of peat. The apparatus comprises a set of hollow rods for

Fig. 5. (a) Typical trend of shearing stress versus shear displacement (b) typical trend of strength stress

versus normal stress.

Fig. 6. RMU I012 digital vane shear test apparatus.


holding the vane blade, a twisting instrument on the upper end for twisting the rod

set, and a digital measuring gearbox for measuring the twisting torque. The digital

measuring gearbox is powered by 12 V DC battery Three vane blades having a di-

ameter of 4.4, 5.4 and 6.4 cm were used to shear the peat. This apparatus was setupto run at a twisting torque ranging from 500 to 600 kg cm at an accuracy of 1 kg cm


resolution. Prior to the actual test, the digital measuring gearbox was calibrated.

During the operation of the apparatus for the shear test, the twisting instrument was

rotated at a speed of 12 �/s to shear the peat. Reading on the twisting torque was

recorded for every 7.5 s until a complete 360� rotation. The maximum twisting

torque of a complete 360� rotation was recorded. The measured value was later used

to compute the shearing stress of the peat. The same test procedure was repeated fordifferent depths, different blades with diameter of 5.4 and 6.4 cm for different sam-

pling points, and different drainage conditions.

The shearing strength of the peat in situ can be calculated using the following

equation:

sf ¼3T

2pr2ð2r þ 3HÞ ; ð2Þ

where, sf is shearing stress in kN/m2, T is torque in kg cm, r is radius of the shear

vane in cm, and H is height of the shear vane in cm.

2.4. Surface mat stiffness and underlying stiffness of peat

A special developed apparatus as shown in Fig. 7 was used to determine the

surface mat stiffness and underlying stiffness of peat. The apparatus comprises of aproof ring with a dial gauge for measuring the force, a shaft with diameter of 1.59 cm

Fig. 7. Bearing capacity measuring apparatus.


and with length of 45 cm for transferring load to sinkage plate and a rectangular

plate with size of 15� 5� 0.5 cm for measuring the sinkage. Three sinkage plates

having a diameter of 10 and 15 cm and a size of 15� 5 cm were used to determine

the stiffness of peat. This apparatus was setup to run at a proving ring constant of

0.2 kg/division. It was operated manually to determine the stiffness of peat.

Prior to the actual stiffness test, the proof ring dial gauge was calibrated. Duringthe operation of the apparatus for the stiffness test, the long shaft with sinkage plate

diameter of 10 cm was manually pushed down at a approximately speed of 2.5 cm/s

to sink the plate. Reading on the pushing load in kg and sinkage in cm was recorded

for every 2 cm plate sinkage. The measured value was later used to plot a graph as

shown in Fig. 8. The parameter characterizing the behavior of the surface mat that is

represented by ‘m’ was determined from the slope of the Fig. 8 regression line. The

same test procedure was repeated for sinkage plates with diameter of 5.4 and 6.4 cm,

for different sampling points, and different drainage conditions.Surface mat stiffness and underlying stiffness of peat was determined from the

following equation of Wong [5]:

p ¼ 1

100½kpzþ mkpz2ðL=AÞ�; ð3Þ

with

mm ¼ mkp;

where, p is load applied on the handle of the apparatus in kN/m2, A is area of the

plate in m2, L is perimeter of the plate in m, z is sinkage in m, kp is stiffness of the peatin kN/m3, m is a parameter characterizing the behavior of the mat, and mm is surface

mat stiffness in kN/m3.

A split-plot completely randomized block design was adopted in statistical

analysis to reveal the effect of field drainage conditions, on depths, normal loads,vane blade size, and plate sinkage, on cohesiveness, internal friction angle and shear

deformation modulus, and on surface mat stiffness and underlying stiffness of peat.

The effect of field drainage conditions, depths, normal loads, vane blade size, and

plate sinkage at significant (Pr < 0:01) level is considered to be highly significance.

Fig. 8. Typical load-sinkage trend of peat for (a) un-drained and (b) drained.


3. Results and discussion

3.1. Cohesiveness, internal friction angle, and shear deformation modulus

Shearing stress of peat for un-drained and drained conditions at depths of 10, 25

and 40 and at normal load of 1, 1.5, and 2 kg are shown in Table 1. Typical graph ofconsolidation and shearing stress versus shear displacement is shown in Figs. 9 and

10. Mean shearing stress of peat increased from 14.03 to 16.22 kN/m2 when the field

condition was changed from un-drained to drained.

The following observations were made based on Table 1:

• Before drainage: Shearing stress of the peat soil was increased from 10.68 to 13.63

kN/m2 (decrement of 27.62%) and 10.68–17.79 kN/m2 (decrement of 65.54%)

when the normal stress increased from 2.725 to 4.08 and 2.725 to 5.45 kN/m2,

respectively.• After drainage: Shearing stress of the peat soil was increased from 12.8 to 15.34

kN/m2 (decrement of 19.8%) and 12.8 to 20.48 kN/m2 (decrement of 60.0%) when

the normal stress increased from 2.725 to 4.08 kN/m2 and 2.725 to 5.45 kN/m2,

respectively.

From the analysis of variance it was found that the mean effect of field condition,

depth, normal stress, and the interaction of depth and field condition on shearing

strength of peat are highly significant. The significant (Pr < 0:01) effect of field

condition, depth, and normal stress indicate that the shearing strength of the peatsoil was increased and thus may be due to the draw down of the water table by

drainage. The draw down of the water table resulted in increased consolidation of

the fill and other soft underlying materials. Result from least significance difference

(LSDðPr<0:05Þ) shows that the mean value of the shearing strength increased from

15.15 to 16.13 kN/m2 and decreased from 15.15 to 13.907 kN/m2 when the depth

increased from 10 to 25 and 25 to 40 cm, respectively. Result from LSDðPr<0:05Þ shows

that the mean value of the shear strength increased from 11.14 to 14.34 and 14.34

to 19.14 kN/m2 when the normal load increased from 1 to 1.5 and 1.5 to 2 kg,respectively.

Cohesiveness, internal friction angle, and shear deformation modulus of peat for

un-drained and drained conditions at depths below 10, 25, and 40 cm are shown in

Table 2. Mean cohesiveness increased from 2.65 to 2.89 kN/m2, mean internal

friction angle increased from 22.33� to 23.76�, and mean shear deformation modulus

decreased from 1.16 to 1.14 cm when the field condition was changed from un-

drained to drained.

The following observations were also made based on Table 2:• Before drainage: Mean cohesiveness of peat decreased from 3.37 to 2.75 and 2.75

to 1.77 kN/m2, mean internal friction angle of peat decreased from 26.16� to

23.78� and 23.78 to 18.71�, and mean shear deformation modulus of peat in-

creased from 1.12 to 1.17 and 1.17 to 1.19 cm when the depth increased from

10 to 25 and 25 to 40 cm, respectively.

• After drainage: Mean cohesiveness of peat decreased from 3.59 to 3.13 and 3.23 to

1.95 kN/m2, mean internal friction angle of peat decreased from 28.43� to 25.11�

Table 1

Variation of the shearing strength of peat in laboratory analysis

Depth (cm) Normal

stress

(kN/m2)

Shearing strength (kN/m2)

Block 1 Block 2 Block 3 Mean value Increased (%)

Before

drainage

After

drainage

Before

drainage

After

drainage

Before

drainage

After

drainage

Before

drainage

After

drainage

)10 2.725 10.32 11.41 13.7 15.1 9.66 11.74 11.23 12.75 13.53

4.0875 11.30 13.01 17.7 18.05 12.04 13.23 13.68 14.76 7.89

5.45 15.14 17.27 23.47 25.0 16.17 18.54 18.26 20.27 11.00

)25 2.725 10.89 12.0 13.14 13.75 11.04 14.1 11.69 13.28 13.60

4.0875 17.15 17.68 16.44 16.28 13.2 15.69 15.59 16.55 6.15

5.45 19.01 21.2 20.18 22.85 18.3 20.21 19.16 21.42 11.76

)40 2.725 9.0 12.2 9.39 11.5 9.00 13.4 9.13 12.37 35.48

4.0875 11.79 16.4 11.79 13.0 11.23 14.9 11.62 14.77 27.10

5.45 16.26 21.08 18.63 21.15 13.0 17.10 15.96 19.78 23.93

34

A.Rahmanet

al./JournalofTerra

mech

anics

41(2004)25–40

Fig. 9. Typical consolidation test of peat, (a) un-drained and (b) drained.

Fig. 10. Example of shearing stress variation with shear displacement (a) un-drained and (b) drained.


and 23.78 to 19.39�, and mean shear deformation modulus of peat increased from

1.1 to 1.14 and 1.14 to 1.18 cm when the depth increased from 10 to 25 and 25 to

40 cm, respectively.

3.2. In situ shearing strength

Shearing stress of peat for un-drained and drained conditions at depths of 10, 25,and 40 cm are shown in Table 3. Typical trend of in situ shearing stress variations

with depth for peat under drained and un-drained field conditions are shown in Fig.

11. Mean shearing stress of peat increased from 1.96 to 2.29 kN/m2 when the field

condition was changed from un-drained to drained. Furthermore, mean shearing

strength of peat decreased from 2.86 to 2.167 kN/m2 (decrement of 24.23%) and

2.167 to 1.78 kN/m2 (decrement of 17.85%) with increasing the vane blade size from

4.4 to 5.4 and 5.4 to 6.4 cm, respectively.

The following observations were also made based on Table 3:

Table 2

Variation of the cohesiveness, internal friction and shear deformation modulus of peat

Depth

(cm)

Block 1 Block 2 Block 3 Shear de-

formation

modulus

(cm)

Cohesiveness

(kN/m2)

Internal

frictional

angle (�)

Cohesive-

ness (kN/

m2)

Internal

frictional

angle (�)

Cohesive-

ness (kN/

m2)

Internal

frictional

angle (�)

)10 5.06 27.22 4.37 23.05 4.68 28.22 1.46

)25 3.33 17.66 2.64 21.5 3.48 24.18 1.31

)40 1.57 18.45 1.36 18.08 2.38 19.6 1.26

Table 3

Variation of the in situ shear shearing stress of peat with depth

Depth

(cm)

Vane

blade size

(cm)

Shearing strength, kN/m2

Block 1 Block 2 Block 3

Before

drainage

After

drainage

Before

drainage

After

drainage

Before

drainage

After

drainage

)10 D ¼ 4:4 1.99 4.08 3.77 2.83 3.77 4.48

D ¼ 5:4 1.53 2.21 2.38 3.23 2.72 3.91

D ¼ 6:4 1.53 1.74 1.94 2.14 2.04 2.24

)25 D ¼ 4:4 1.88 2.38 2.09 2.18 1.86 2.98

D ¼ 5:4 1.98 2.30 1.80 2.12 2.52 2.86

D ¼ 6:4 1.34 1.52 1.49 2.10 1.78 2.186

)40 D ¼ 4:4 1.57 2.59 1.77 1.98 1.57 1.84

D ¼ 5:4 1.41 1.63 1.45 1.51 1.80 2.21

D ¼ 6:4 1.73 1.48 1.61 1.68 1.67 2.14

Fig. 11. Typical trend of shearing stress versus depth, (a) un-drained and (b) drained.



• Before drainage: Shearing stress of the peat soil was deccreased from 2.41 to 1.86

and 1.86 to 1.62 kN/m2 when the depth increased from 10 to 25 and 25 to 40 cm,

respectively.

• After drainage: Shearing stress of the peat soil was decreased from 2.98 to 2.29

and 2.29 to 1.89 kN/m2 when the depth increased from 10 to 25 and 25 to 40

cm, respectively.From the analysis of variance it was found that the mean effects of field condi-

tions, depth, and blade size has high significant effect (Pr < 0:01) on in situ shearing

stress of peat. Result from LSD (Pr < 0:05) shows that mean shearing stress was

increased from 1.96 to 2.58 kN/m2 when the field condition was changed from un-

drained to drained. It may be due to the increase of consolidation rate. Result from

LSD (Pr < 0:05) shows that mean in situ shearing stress of peat decreased from 2.90

to 2.13 and 2.13 to 1.78 kN/m2 when the depth increased from 10 to 25 and 25 to 40

cm, respectively. It may be due to the draw down of the water table.

3.3. Surface mat and underlying stiffness of peat

Surface mat stiffness of peat for un-drained and drained conditions at depth of 10,

25, and 40 cm are shown in Table 4. Mean surface mat stiffness of peat increased

from 27.07 to 44.51 kN/m3 for plate with diameter of 10 cm, 33.93 to 41.79 kN/m3

for plate with diameter of 15 cm, and 32.54 to 50.57 kN/m3 for plate with size of

15� 5 cm when field condition was changed from un-drained to drained.The following observations were also made based on Table 4:

• Before drainage: Mean surface mat stiffness of peat decreased from 41.35 to 33.87

kN/m3 and 33.87 to 18.31 kN/m3 when the depth increased from 10 to 25 and 25

to 40 cm, respectively.

• After drainage: Mean surface mat stiffness of peat decreased from 61.32 to 50.2

and 50.2 to 25.321 kN/m3 when the depth increased from 10 to 25 and 25 to 40

cm, respectively.

Table 4

Variation of the surface mat stiffness of peat with depth

Sinkage

(cm)

Plate size

(cm)

Surface mat stiffness, mm (kN/m3)


Before

drainage

After

drainage

Before

drainage

After

drainage

Before

drainage

After

drainage

)10 D ¼ 10 31.2 52.46 40.21 59.49 34.01 49.4

D ¼ 12 57 59.77 40.89 54.85 44 43

L�B¼ 15� 5 41.4 66.76 39.54 97.68 43.88 68.5

)25 D ¼ 10 22.5 56.76 50.87 67.68 12.5 46.5

D ¼ 12 37.67 39.21 53.91 54.86 13 33.4

L�B¼ 15� 5 44.01 52.4 50.29 48.73 20.12 52.28

)40 D ¼ 10 15.76 23.8 26.44 30.43 10.12 14

D ¼ 12 15.01 36.68 34.69 37.86 9.2 16.32

L�B¼ 15� 5 15.71 24.85 24.01 27.57 13.90 16.4


From the analysis of variance it was found that the main effect of sinkage, field

condition and the interaction of sinkage, field condition and plate size significantly

effect peat surface mat stiffness. The significant effect of sinkage indicates that surface

mat stiffness decreased with increase of sinkage. Result from LSDðPr<0:05Þ shows that

mean surface mat stiffness decreased from 51.336 to 42.043 and 42.04 to 21.831 kN/

m3 when sinkage increased from 10 to 25 and 25 to 40 cm, respectively. It indicatesthat within the depth from 10 to 25 cm, the peat soil strength is provided mainly by

the surface mat due to tension. Beyond this depth, the strength was provided by the

underlying weak and low bearing capacity peat. Again result from LSDðPr<0:05Þ shows

that mean surface mat stiffness increased from 31.18 to 45.63 kN/m3 when field

condition was changed from un-drained to drained. The significant effect of drainage

indicates that the surface mat stiffness increased with drawdown of water table by

drainage. Due to the drainage of the tested site the effective weight of the soil in-

creased and caused consolidation of the fill and other soft underlying materials.Underlying stiffness of peat for un-drained and drained conditions at depths of 10,

25, and 40 cm are shown in Table 5. Mean underlying stiffness of peat increased from

224.38 to 356.95 kN/m3 for plate with diameter of 10 cm, 274.15 to 378.85 kN/m3 for

plate with diameter of 15 cm, and 257.48 to 404.79 kN/m3 for plate with size of

15� 5 cm when field condition was changed from un-drained to drained.

The following observations were also made based on Table 5:

• Before drainage: Mean underlying stiffness of peat increased from 221.3 to 252.14

and 252.14 to 282.55 kN/m3 when the depth increased from 10 to 25 and 25 to 40cm, respectively.

• After drainage: Mean underlying stiffness of peat increased from 356.76 to 370

and 370 to 413.79 kN/m3 when the depth increased from 10 to 25 and 25 to 40

cm, respectively.

From the analysis of variance it was found that the mean effect of sinkage and

field conditions is significant (Pr < 0:01) on internal peat stiffness. Result from

LSDðPr<0:05Þ shows that mean underlying stiffness of peat increased from 289.03 to

Table 5

Variation of the underlying stiffness of peat with depth

Sinkage

(cm)

Plate size

(cm)

Peat stiffness, kP (kN/m3)


Before

drainage

After

drainage

Before

drainage

After

drainage

Before

drainage

After

drainage

)10 D ¼ 10 228.58 249.01 196.91 339.8 168.65 473.33

D ¼ 12 216.55 342.36 235.82 222.1 212.96 374.66

L�B¼ 15� 5 283.59 465.18 222.39 288.68 226.24 455.72

)25 D ¼ 10 260.68 186.68 218.04 348.21 176.43 523.16

D ¼ 12 267.85 370.46 265.58 284.4 293.78 437.92

L�B¼ 15� 5 255.94 387.90 277.54 301.82 253.43 489.85

)40 D ¼ 10 333.0 380.00 256.94 380.19 180.21 530.26

D ¼ 12 325.00 407.81 288.50 318.3 361.35 453.62

L�B¼ 15� 5 215.86 451.89 291.94 304.3 290.41 497.77


311.09 and 311.09 to 348.19 kN/m3 when sinkage increased from 10 to 25 and 25 to

40 cm, respectively. Again result from LSDðPr<0:05Þ shows that mean underlying

stiffness of peat increased from 244.59 to 380.2 kN/m3 when field condition was

changed from un-drained to drained.

4. Conclusions

(i) Based on the results of laboratory analysis, it appeared that mean effect of drain-

age conditions of the tested site was highly significant on the physical features of

the peat. The mean moisture content decreased to 5.940% and bulk density was

increased to 22.59% when the field condition was changed from un-drained to

drained.

(ii) Based on the results of direct shear test in laboratory on the peat samples, it ap-peared that the mean effect of normal stress, depth and drainage conditions of

the tested site was significant on shearing stress of the peat samples. The mean

shearing stress increased to 22.34% when the normal stress increased from 2.725

to 4.0875 kN/m2 and the mean shearing stress to 63.38% when the normal stress

increased from 4.0875 to 5.45 kN/m2. The mean shearing stress increased 6.4%

and decreased 13.82% when the depth increased from 10 to 25 and 25 to 40 cm,

respectively. Furthermore, the mean direct shearing stress increased 14.68%

when the field condition was changed from un-drained to drained.(iii) Based on the results of in situ shearing stress test, it was found that vane blade

size, depth, and field drainage conditions had significant effect on in-situ shear-

ing stress. Mean in situ shearing stress increased 37.76% and decreased 38.62%

when the vane blade size increased from 4.4 to 6.4 cm and depth increased from

10 to 40 cm, respectively.

(iv) Based on the load-sinkage test, it was found that the plate sinkage increased

with increasing pushing load up to the surface mat thickness and a further in-

crease in plate sinkage caused decrease in pushing load.(v) Based on the results of stiffness of peat, it was found that mean effect of sinkage

and drainage conditions had significant effect at a 99% level of significance on

the surface mat stiffness and underlying stiffness of peat. The mean surface

mat stiffness of peat increased 57.47% and underlying stiffness of peat increased

18.1% when sinkage increased from 10 to 25 and 25 to 40 cm, respectively. Fur-

thermore, the mean surface mat stiffness and underlying stiffness of peat in-

creased 46.48% and 49.46%, respectively when field condition changed from

un-drained to drained.

Acknowledgements

This research project is classified under RM7 IRPA Project No. 01-02-04-0135.

The authors are very grateful to the Ministry of Science, Technology and The En-

vironment of Malaysia for granting the fund for this research project.


References

[1] Chang BS, Bekker WJ. Soil parameters to predict the performance of off-road vehicle mobility. J

Terramech 1973;9(2):13–22.

[2] Jamaludin BJ. Sarwak peat agricultural use. Available from http://www.Alterra.dlo.nl/. Accessed on

March 2002.

[3] Wong JY, Garber M, Radforth JR, Dowell JT. Characterization of the mechanical properties of

muskeg with special reference to vehicle mobility. J Terramech 1979;16(4):163–80.

[4] Wong JYJ, Radforth R, Preston-Thomas J. Some further studies on the mechanical properties of

muskeg in relation to vehicle mobility. J Terramech 1982;19(2):107–27.

[5] Wong MH. Workshop on tropical peat ecosystem in the costal areas of Peninsular Malaysia and

southern Thailand. Malaysian Agricultural R&D Institute, 10 August 1989.

http://www.Alterra.dlo.nl/

Documents

Mechanical properties in relation to vehicle mobility of Sepang peat terrain in Malaysia