Conference Paper, Published Version

Punrattanasin, P.; Subjarassang, A.; Kusakabe, O.; Nishimura, T.Collapse and Erosion of Khon Kaen Loess with TreatmentOption

Verfügbar unter/Available at: https://hdl.handle.net/20.500.11970/100405

Vorgeschlagene Zitierweise/Suggested citation:Punrattanasin, P.; Subjarassang, A.; Kusakabe, O.; Nishimura, T. (2002): Collapse andErosion of Khon Kaen Loess with Treatment Option. In: Chen, Hamn-Ching; Briaud, Jean-Louis (Hg.): First International Conference on Scour of Foundations. November 17-20, 2002,College Station, USA. College Station, Texas: Texas Transportation Inst., Publications Dept..S. 1081-1095.

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C O L L A P S E A N D E R O SI O N O F K H O N K A E N L O E S S WI T H T R E A T M E N T O P TI O N

B y

P. P u nr att a n asi n1, A. S u bj ar ass a n g

2, O. K us a k a b e

3, T. Nis hi m ur a

4

A B S T R A C T

K h o n K a e n l o ess is o n e of t h e pr o bl e m ati c s oils i n t h e N ort h e ast er n r e gi o n of T h ail a n d. T h e s oil h as a p ot e nti al t o c oll a ps e, w hi c h h as b e e n c a us e d b y w etti n g. T his st u d y r e p orts t h e c h ar a ct eristi cs of K h o n K a e n l o ess u n d er s at ur at e d a n d u ns at ur at e d c o n diti o ns. Fr o m l a b or at or y t esti n g r es ults, s h e ar str e n gt h of K h o n K a e n l o ess i n cr e as es li n e arl y wit h m atri c s u cti o n at l o w s u cti o n pr ess ur e a n d r e m ai ns c o nst a nt b e y o n d t h e r esi d u al s u cti o n. Its r el ati o ns hi p gi v es b p ar a m et er of 3 2 d e gr e es. Si n c e K h o n K a e n l o ess e xists i n a b u n d a n c e a n d c o v ers a v er y l ar g e ar e a of t h e r e gi o n, t his st u d y ai ms t o i n v esti g at e t h e s uit a bilit y of t his s oil as a m at eri al f or r o a d c o nstr u cti o n. A s eri es of tri al sl o p e e m b a n k m e nts w er e c o nstr u ct e d i n or d er t o e v al u at e t h e b e h a vi or of t h e l o ess. T h e fi el d o bs er v ati o ns s h o w e d t h at t h e t esti n g e m b a n k m e nt w as st a bl e u n d er tr affi c l o a di n g a n d er osi o n of s oil o c c urr e d b y w at er i nfiltr ati o n fr o m gr o u n d s urf a c e. T h e tri al e m b a n k m e nt r ei nf or c e d wit h g e os y nt h eti c m at eri als w as als o t est e d. T h e r es ults s h o w e d t h e eff e cti v e n ess of g e os y nt h eti c m at eri al as o n e of t h e r e m e di al m e as ur es.

1. I N T R O D U TI O N

L o ess is k n o w n i n ci vil e n gi n e eri n g as o n e of t h e m aj or pr o bl e m s oils b e c a us e of its c oll a ps e a n d s u d d e n d e cr e as e i n v ol u m e of v oi ds w hi c h h as c a us e d s e v er e s ettl e m e nt pr o bl e ms f or m a n y str u ct ur es f o u n d e d o n it. T h e l o ess t err ai n e xists i n a b u n d a n c e i n t h e N ort h e ast er n r e gi o n of T h ail a n d. T h e l o ess d e p osits c a n b e cl assifi e d i nt o t w o, R e d L o ess a n d Y ell o w L o ess ( P hi e n- w ej et al., 1 9 9 2). Lit h ol o gi c all y a n d mi n er al o gi c all y, t h e t w o u nits ar e si mil ar b ut diff er e nt i n o xi d ati o n st at es c a usi n g c ol or diff er e n c e. T h e t hi c k n ess r a n g es fr o m a f e w m et ers t o m or e t h a n 6 m. T hi c k l o ess d e p osits ar e f o u n d i n hi g h el e v ati o n ar e as of t h e r e gi o n i n cl u di n g K h o n K a e n, w hi c h is t h e e c o n o mi c c e nt er of t h e u p p er r e gi o n ( Fi g. 1). Firstl y, t h e s oil w as c o nsi d er e d as a g o o d b e ari n g l a y er. S ar uji k u mj o n w att a n a et al. ( 1 9 8 7) f o u n d t h at w etti n g of t h e s oil b y l e a ki n g w at er fr o m dr ai ns a n d s e w ers c a us e d t h e s e v er e s ettl e m e nt a n d d a m a g e of t h e irri g ati o n str u ct ur es a n d l o w-ris e b uil di n gs.

1 L e ct ur er, D e pt. of Ci vil E n gi n e eri n g, F a ct. of E n gi n e eri n g, K h o n K a e n U ni v ersit y, T h ail a n d

2 F or m er Gr a d u at e St u d e nt, D e pt. of Ci vil E n gi n e eri n g, T o k y o I n stit ut e of T e c h n ol o g y, T o k y o, J a p a n

3 Pr of ess or, D e pt. of Ci vil E n gi n e eri n g, T o k y o I nstit ut e of T e c h n ol o g y, T o k y o, J a p a n

4

Ass o ci at e Pr of ess or, D e pt. of Ci vil E n gi n e eri n g, As hi k a g a I nstit ut e of T e c h n o l o g y, T o c hi gi, J a p a n

C oll a ps e a n d E r osi o n of K h o n K a e n L o ess wit h T r e at m e nt O pti o n

First I nt er n ati o n al C o nf er e n c e o n S c o ur of F o u n d ati o ns, I C S F- 1T e x as A & M U ni v ersit y, C oll e g e St ati o n, T e x as, U S A N o v e m b er 1 7- 2 0, 2 0 0 2

1 0 8 1

Collapse and Erosion of Khon Kaen Loess with Treatment Option

First International Conference on Scour of Foundations, ICSF-1

Texas A&M University, College Station, Texas, USA November 17-20, 2002

1081

In this study, the properties of Khon Kaen loess are presented under saturated and

unsaturated conditions. Trial embankments are also tested. The objectives of this test

were to provide a case record and to evaluate the potential of the soil as a material for

road construction.

2. SOIL PROPERTIES

A series of laboratory tests were carried out on red loess unit. The samples were from

outcrop found in Khon Kaen University, where several foundation problems associated

with this soil had occurred. Undisturbed samples of the soil were taken by means of

block sampling. The samples were carefully trimmed and waxed from the bottom of

excavated pits (Fig.2). The tests were initially conducted on the soil under in situ water

content, after which the soil was wetted by water infiltration from the ground surface. In

the laboratory tests, engineering properties of the loess were investigated through index

tests, the direct shear test, the oedometer test and the saturated and unsaturated triaxial

compression test.

2.1 Index properties

Index properties of Khon Kaen loess are summarized in Table 1. The soil is silty fine

sand (SM). The loess consists of 65% sand, 30% silt and 5% clay (Fig.3). Udomchoke

(1991) studied the microstructure of this soil and found that Khon Kaen loess consists

of well-sorted fine sand grains but poorly sorted silt and clay particles. Sand grains have

smooth, sub-rounded surfaces indicating eolian origin. The skeleton grains are held

together by means of cementation of clay matrice in the form of clay bridge bonds.

Most of the clay content, which is predominantly kaolinite, is present in the form of a

surface coating on coarse grains.

2.2 Direct shear test

The direct shear test is the simplest, the oldest and the most straightforward procedure

to measure the short term shear strength of soil in terms of total stresses. To obtain the

strength parameters c and of the soil, the direct shear tests were performed with

natural undisturbed samples and pre-wetted samples with various depths of soil layers.

In the experiment, the direct shear tests were performed under unconsolidated undrained

condition. Figure 4 shows the strength parameters c and with depth.

2.3 Compressibility of soil

The oedometer test is used for the determination of the consolidation characteristics of

soils of low permeability. Analysis of data from tests is presented as a standard

conventional procedure to explain the compressibility of soils. However, the loess is

naturally unsaturated. In the test, the unsaturated undisturbed and remolded samples

were subjected to the axial load in the oedometer box without the swelling process.

Figure 5 shows the comparison of the compressibility characteristic between

undisturbed and remolded sample. From the curve of undisturbed sample, the

compression index is 0.0135 with maximum past pressure of 1334 kPa. The

compression index of remolded sample is only half of the undisturbed sample. In the

section of unsaturated soil, the results from modified oedometer test with soil suction

control will be shown.

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2.4 Triaxial compression test

Series of triaxial compression tests were carried out to obtain strength parameters of the

loess under various consolidation pressures. Specimens prepared from cylindrical

samples 50 mm in diameter were used. The tests conducted in this study were the

consolidated-undrained test. Figure 6 shows the triaxial test setup and the strength

envelop of the three tests. From the experimental results, the Mohr-Culomb shear

failure envelope gives a 'c value of approximately zero and ' of 38 degrees.

2.5 Unsaturated soils

A theoretical framework for unsaturated soil mechanics widely accepted in geotechnical

engineering is the concept of stress state variables introduced by Fredlund and

Morgenstern (1977). Unsaturated soil behaviors could be explained in terms of two

independent stress state variables (i.e., net normal stress, au and matric

suction, wa uu ). The shear strength equation for unsaturated soils proposed by

Fredlund et al. (1978) has been accepted widely in geotechnical engineering and is

given as,

b

waa uuuc tan'tan' (1)

where, = shear strength, 'c = effective cohesion intercept, = total normal vertical

stress, ' = effective angle of internal friction with respect to net normal stress, au =

pore-air pressure, wu = pore-water pressure, b = angle of internal friction with respect

soil suction.

2.6 Soil-Water Characteristic Curve

The SWCC can be described as a measure of the water –holding capacity (i.e. storage

capacity) of the soil, when subjected to various values of suction. Changes in soil, water

and air phases take on different forms and influence the engineering behavior of

unsaturated soils. The relationship between amount of soil water and soil suction was

evaluated using a pressure plate apparatus and vapor equilibrium technique (Fig.7). The

soil-water characteristic curve for Khon Kean loess was tested from a saturated

condition to a totally dry condition (i.e. for soil suctions ranging from 0 to 1,000,000

kPa) and was shown in Fig.8. The air-entry value can be obtained by extending the

constant slope portion of the soil-water characteristic curve to intersect the suction axis

at saturated condition. Evaluated air-entry value for the soil is 27 kPa. When matric

suction exceeds the air-entry value, desaturation starts in the liquid phase. The soil dries

rapidly with increasing suction.

2.7 Triaxial for unsaturated soil

Figure 9 shows the schematic diagram of modified triaxial apparatus for unsaturated

soil. A series of unconsolidated-undrained triaxial tests were carried out in order to find

the b value. The shear strength under constant net normal stress and varying matric

suction are summarized in Table 2. Figure 10 (a) shows the relationship between shear

strength and matric suction up to 100 kPa. An extended Mohr-Colomb equation (Eq.1)

is used to interpret the test results. When matric suction is zero (saturated condition), the

1083

shear strength is calculated as 820 kPa with 'c equal to zero, b equals to 32 degrees

under a constant net normal stress of 200 kPa. The shear strength data of Khon Kaen

loess subjected to high suctions are presented in Fig.10 (b). A constant net normal stress

of 200 kPa was applied with various total suctions. The suctions applied were always

larger than the residual suction of 500 kPa. Figure 10 (b) shows that shear strength of

Khon Kaen loess remains constant beyond residual soil suction.

2.8 Modified oedometer test

The relationship between the volume change and loading conditions of unsaturated soil

can be illustrated by the modified oedometer test result. The test aims to obtain the

volume change characteristic of the soil with different matric suctions compared to the

saturated condition. The modified oedometer apparatus is schematically shown in Fig.

11. The specimen is subjected to air pressure through a top cap. The burette connected

with high air entry ceramic disk at the bottom base can measure the drained water. The

pe log curve is shown in Fig. 12. The curves show that the deformation characteristic

of the unsaturated soil is flatter than that of the saturated soil. Under the same pressure,

the settlement of saturated soil is larger than the unsaturated one.

3. TRIAL TEST EMBANKMENT

Evaluation of slope instability is an inter-disciplinary effort requiring contributions from

engineering geology and soil mechanics. The main objectives of the slope analysis of

Khon Kaen loess embankment are to assess the stability of slope under given conditions

and to assess the potential of the soil as a material for road construction. Natural slopes

in soil are of interest to geotechnical engineers. The soil composing any slope has a

natural tendency to collapse under the influence of gravitational and other forces. Figure

13 shows agricultural pond in Khon Kean University before and after raining. The

collapse and erosion phenomenon of the loess are evident in Fig 13 (b).

3.1 Site conditions and design of trial embankment

The test site is located in Khon Kaen University. The construction area chosen was flat

for the most part and near the borrow pits of fill material. The design of the test

embankment configuration was based on the typical section from Department of

Highway, Thailand. The final layout of the fill and the cross section of the embankment

are shown in Figs.14 and 15, respectively. The test area is divided into two parts to

simulate the general traffic load of 2 t/m2 and to simulate the rainy season in the

Northeastern region of Thailand as shown in Fig. 16 and Fig. 17. To facilitate

monitoring of the construction and to observe the performance of the embankment, field

instruments were installed. The instrument layout was selected based on the results of

the limit equilibrium analysis and the total number of instruments. The instrumentation

of unreinforced slope consists of piezometers, total pressure cells and inclinometer

casings. Pneumatic piezometers were installed to monitor the positive and negative pore

pressures. The pneumatic-type total pressure cells were installed to measure the total

pressure imposed by the fill on the bottom of the embankment. The applied total

stresses measured from the monitoring agreed well with those deduced based on the

thickness of fill and the measured unit weight of the fill. Horizontal movement of the

ground was monitored by measuring the displacement from inclinometer.

1084

3.2 Embankment construction

The Khon Kaen loess was used as a fill material. The fill unit weight, as determined by

in situ tests, averaged 20.2 kN/m3. The natural water content of the fill was 6%. A series

of soil layers were constructed with a thickness of 0.5 m. Field density measurements

on the layers indicated an average unit weight of 18.5 kN/m3. After reaching a designed

thickness of 2.5 m, the first half of the trial embankment was statically loaded with dead

weight of 2 t/m2. The staged loading is 0.333 t/m

2 in steps. The second half of the

embankment was soaked with water to simulate flood after a heavy rainfall.

3.3 Performance of trial embankment and results

A number of instruments were installed to provide warning of any potential failure.

These instruments which recorded minute movements were monitored during and post

construction. The variations of horizontal displacement with depths obtained from

inclinometers are shown in Fig. 18 (a) and 18 (b). At the end of simulation processes,

maximum horizontal displacement of about 1 mm and 8 mm were found from loading

area and soaked area, respectively.

The embankment was found to stand free at a slope of about 53 . The

displacement profile at 2.5 m embankment thickness did not indicate any failure zone.

The soils in the soaked area suddenly dropped after being soaked for 20 days as caused

by the water infiltration (Fig.19). The erosion continued to occur as more water was

added. The variations of excess pore water pressure with time for different pneumatic

piezometers placed below the fill were recorded (Fig. 20). The excess pore pressures in

all the piezometers were small up to the end of construction. A small increase in the

excess pore pressure is observed in response to the infiltration of water from the top

surface of the embankment. The excess pore water pressure responses indicated by

piezometer 2 and 3 were very similar even though the piezometers were placed at

different depths.

3.4 Treatment option

To enable the redesign of failed slope, the planning and design of preventive and

remedial measures were necessary. The second phase of trial embankment was

constructed. A single layer of geogrid and bi-dimensional geojute were used for the

reinforcement. The random structures of the geojute hinder particle migration,

interlocks with the grass roots while the geogrid is capable of supporting long term

tensile loads. Figure 21 shows the stable reinforced embankment. Details of the

instrumentation, construction and performance of the reinforced embankment will be

provided in a subsequent paper.

4. CONCLUSIONS

The characteristics of Khon Kaen loess have been investigated by both laboratory and

field testing. The results of the laboratory tests on undisturbed and remolded samples

described in this paper are reported. Strength of the loess decreases as a result of wetting.

The research primarily focused on the strength characteristic of the unsaturated soil over

a wide range of soil suctions. Suctions were applied using pressure plate apparatus and

vapor equilibrium technique. The compacted loess was desaturated to the residual state

of unsaturation through the use of chemical salt solutions. The testing results show that

the air-entry value of the soil is about 27 kPa. The SWCC also gives that the residual

1085

water content and residual suction are 5% and 500 kPa, respectively. The unsaturated

triaxial results showed that shear strength of soil increases with matric suction at low

suction pressure. Its relationship between shear strength and soil suction in the transition

stage gives the b of 32 degrees. After the suction exceeds the residual soil suction, the

shear strength remains constant (i.e., horizontal failure envelope with respect to soil

suction). Using Khon Kaen loess as a material for road construction showed that erosion

by water infiltration will cause the soil failure of fill embankment. Geosynthetics

material used as a reinforcement is one of the alternatives to stabilize the embankment.

ACKNOWLEDGEMENT

The research was developed under the cooperation between Khon Kean University,

Thailand, Tokyo Institute of Technology and Asikaga Institute of Technology, Japan.

The construction and monitoring of the test embankments were funded by the

Department of Civil Engineering, Faculty of Engineering, Khon Kaen University and

the Hitachi Foundation, Japan. The authors wish to acknowledge the assistance of

Dr.Watcharin Gasaluck, Dr.Warakorn Mai-riang, Dr.Noppadol Phien-wej and

Mr.Nattapong Kowittayanant. The geosynthetic materials were supplied by Cofra

(Thailand) Ltd.

REFERENCES

1. Fredlund, D.G. and Morgenstern, N.R., 1977. “Stress state variables for unsaturated

soils”, ASCE Journal of Geotechnical Engineering, Vol.103, pp.447-466.

2. Fredlund, D.G., Morgenstern, N.R., and Widger, R.A., 1978. “The shear strength of

unsaturated soils”, Canadian Geotechnical Journal, Vol.15, pp.313-321.

3. Phien-wej, N., Pientong, T., Balasubramaniam, A.S., 1992. “Collapse and strength

characteristics of loess in Thailand”, Engineering Geology, Vol.32, pp.59-72.

4. Sarujikumjonwattana, P., Malapet, M., and Sertwicha, S., 1987. “Settlement of

spread footings in Khon Kaen University Campus caused by moisture increase at

constant load”, Khon Kean Univ.Publ., Thailand.

5. Udomchoke, V., 1991. “Origin and engineering characteristic of problem soils in

Khorat Basin, Northeastern Thailand”, D.Tech.Diss, Asian Institute of Technology,

Bangkok, Thailand.

Table 1 – Index properties of Khon Kaen loess

Property Khon Kaen Loess

Specific gravity

Natural dry unit weight (kN/m3)

Natural water content during rainy season (%)

Liquid limit (%)

Plastic limit (%)

Plasticity index

Soil classification (USCS)

Optimum moisture content (%)

Maximum dry density (kN/m3)

Permeability coefficient (cm/s)

2.60

15.3

8-12

16.0

13.0

3.0

SM

9.7

21.1

2.80 x 10-6

1086

Table 2 – Summary of stress conditions during unsaturated triaxial tests

Net normal stress Soil suction Shear strength

(kPa) (kPa) (kPa)

200 0 820

200 40 837

200 64 870

200 69 867

200 100 880

200 9,800 1,069

200 83,400 1,349

200 296,000 1,460

Fig.1 – Areas of loess deposits (stippled area) in Thailand (after Phien-wej et al. 1992)

(a) Block sample (b) Excavated pit

Fig. 2 – General view of a test pit at Khon Kaen University

1087

0.0010.010.11100

10

20

30

40

50

60

70

80

90

100

Particle size (mm)

Per

cen

tag

e p

assi

ng

Experimental data Best-fit curve

Fig. 3 – Particle size distribution of Khon Kaen loess

0 10 20 30 40

0

1

2

3

4

5

Dep

th (

m)

Cohesion C (kPa)

Natural soilPre-wetted soil

0 10 20 30 40

0

1

2

3

4

5

Dep

th (

m)

Friction Angle (Degree)

Natural soilPre-wetted soil

Fig. 4 – Summary of direct shear tests of undisturbed sample

10 100 1000 100000.5

0.52

0.54

0.56

0.58

0.6

0.62

Vo

id r

atio

, e

Pressure (kPa)

10 100 1000 100000.27

0.28

0.29

0.3

Vo

id r

atio

, e

Pressure (kPa)

(a) Undisturbed sample (b) Remolded sample

Fig. 5 – Oedometer test results

1088

(a) Test setup

(b) Test result

Fig. 6 – Triaxial compression test results from undisturbed samples

(a) Pressure plate apparatus (b) Vapor equilibrium technnique

Fig. 7 - Apparatus for SWCC test

Burette

Transparent

Air cell

Specimen

Ceramic disk

Porous stone

Volume

transducer

Volume fix pin

Produce air

with RH<100%

Suction

Specimen

Chemical salt solution

RH = Relative Humidity

Absorb moisture

0 500 1000 1500 2000 2500 30000

400

800

1200

1600

2000

Shea

r st

ress

(kP

a)

Effective stress (kPa)

= 38.0 degrees

Air pressure in

Pore water out

1089

Fig. 8 – Soil water characteristic for compacted Khon Kaen loess

Fig. 9 - Schematic of modified triaxial apparatus for unsaturated soil

(a) Relationship between shear strength and matric suction at a constant net normal

stress of 200 kPa

0 20 40 60 80 100 120800

820

840

860

880

900

Matric suction (kPa)

Shea

r st

rength

(kP

a)

b= 32 degrees

Water pump

Bypass

switch

Different pressure

transducer

Cell pressure transducer Pore water pressure transducer

Pore air pressure transducer

Volume

transducer

Burette

Air Regurator Air ReguratorLoading frame

Load cell

Cell pressure in Cell pressure out

Air

cell

Ceramic disk

Porous

stone

Dial gauge

100 101 102 103 104 105 1060

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Suction (kPa)

Volu

met

ric

wat

er c

onte

nt

Experimental data Best-fit curve

1090

(b) Relationship between shear strength and high suction a net normal stress of 200 kPa

Fig. 10 – Shear strength versus metric suction

Fig. 11 – Modified oedometer apparatus for unsaturated soil

10 100 1000 100000.2

0.25

0.3

0.35

0.4

0.45

Pressure (kPa)

Vo

id r

atio

, e

Remold-saturated sampleRemolded sample at suction 40 kPaRemolded sample at suction 70 kPaRemolded sample at suction 100 kPa

Fig.12 – Oedometer test result from remolded samples

Air pressure

Specimen

Ceramic disk

Porous stone

Pore water out

Volume

transducer

Loading frame

Load cell

Dial gauge

0 0.5 1 1.5 2 2.5 3

[ 105]

0

400

800

1200

1600

2000

Sodium choride Magnesium nitrate Lithium choride Best-fit curve

Total suction (kPa)

Shea

r st

rength

(kP

a)

Burette

1091

(a) Before (b) After

Fig. 13 – Collapse and erosion of agricultural pond

Fig. 14 – General view of trial embankment

(a) Plan view

Fig. 15 – Cross section of the embankment

2.0 m 10.0 m 10.0 m

1.875 m

6.50 m

1.875 m

Loading AreaSoaked Area

A

A

B B

1092

(b) Section A-A (c) Section B-B

Fig. 15 – Cross section of the embankment

Fig. 16 – Simulation of load by dead weight

Fig. 17 – Soaking process

2.5m

CL

1.88 m 1.88 m6.50 m

3.0m

0.5m

Inclinometer

Casing

1

0.75

Pneumatic Piezometers

Total Pressure Cells

1.88 m 1.88 m10.0 m2.0 m 10.0 m

Dead Weight

1093

Fig.18 – Horizontal movement of the embankment

Fig. 19 – Erosion failure of trial embankment

12 14 16 18 20 22 24 26 28 30-6

-4

-2

0

2

4

6

8

Pore

wat

er p

ress

ure

(kP

a)

Elapsed time (day)

Piezometer1 (0.5 m below the top of embankment)Piezometer2 (1.5 m below the top of embankment)Piezometer3 (2.5 m below the top of embankment)

Fig. 20 – Pore pressure distribution in the embankment erosion process

-0.4 0 0.4 0.8 1.2 1.6 2-3

-2

-1

0

1

2

3

20/3/0121/3/0123/3/0124/3/0128/3/0129/3/0131/3/013/4/018/4/01

Horizontal movement (mm)

Dep

th (

m)

(a) Loading area

-2 0 2 4 6 8 10 12-3

-2

-1

0

1

2

3

20/3/0121/3/0123/3/0124/3/0128/3/0129/3/0131/3/013/4/018/4/01

Horizontal movement (mm)

Dep

th (

m)

(b) Soaked area

1094

Fig. 21 – Reinforced embankment

1095