abstract of my thesis

vi

3.2.4 Anchorage Elements ................................................................................ 25

3.2.5 Welding Work .......................................................................................... 25

3.3 Soil .................................................................................................................. 26

3.4 Experimental Programs ................................................................................... 27

3.4.1 Compaction Test ...................................................................................... 27

3.4.2 Tensile Tests ............................................................................................ 28

3.4.3 Pull-out Tests ........................................................................................... 30

3.5 Finite Element Analysis .................................................................................. 36

3.6 Conclusion ....................................................................................................... 38

CHAPTER 4 RESULTS AND DISCUSSION ...................................................... 40

4.1 Introduction ..................................................................................................... 40

4.2 Results of Pull-out Test ................................................................................... 42

4.2.1 Pull-out Tests on Plain Strip .................................................................... 43

4.2.2 Pull-out Tests on Strip with 1 cm Anchorage Elements .......................... 46

4.2.3 Summary of Pull-out Tests ...................................................................... 49

4.3 Results of Finite Element Modelling .............................................................. 52

4.3.1 Deformed Mesh ....................................................................................... 55

4.3.2 Axial Force............................................................................................... 57

4.3.3 Zones of Horizontal Displacements ......................................................... 59

4.3.4 Zones of Shear Stresses ........................................................................... 61

4.3.5 Total Principal Stresses ............................................................................ 63

4.3.6 Summary of Finite Element Modelling ................................................... 64

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS ........................ 66

5.1 Conclusions ..................................................................................................... 66

5.2 Recommendations for Future Works .............................................................. 68

REFERENCES ............................................................................................................. 69

APPENDIX A

APPENDIX B

3

1.2 Applications in Malaysia and Abroad

The application method of reinforced soil has been reinvented for design of reinforced

retaining wall (Shukla et al., 2009). In the international arena, the use of reinforced

retaining wall intensified in the 1980s and 1990s (Walls, 2009). In Malaysia, where soil

reinforcement methods have been widely used in geotechnical projects, the use of

reinforced earth for various geotechnical structures has become very popular in recent

years. From the front, view as shown in Figure 1.2 has become common sights in the

country.

Figure 1.2: A View of MRE Showing Decorative Facing

8

gave higher increment of stress because sand used in the study consists of poorly

graded and particle size is smaller than red soil and black silty soil.

Figure 2.2: Result of Pull-out Test for Soil-Geotextile Interaction by Awdhesh and

Murali, (2011)

2.4 Boundary Conditions

Sugimoto et al., (2001) concluded that pressure applied on front wall during pull-out

decrease as the position moved from top to bottom with the maximum pressure

occurred near the reinforcement. Farrag et al., (1993) found that the flexible

reinforcement member has better uniform load distribution on interface area. The effect

of the boundary conditions at the front wall has been studied by many researchers using

pressure cells which placed at different position of front wall. Generally these

researchers have found that pressure applied on the front wall increases continuously at

the test progresses (Johnston and Romstad, 1989; Chang et al., 2000).

Palmeira and Milligan (1989a) studied the effect of boundary condition by first

carrying out tests using two types of top boundary rigid and flexible and followed by

different wall roughness coefficient. The results as shown in Figure 2.3(a), the rigid top

Black silty soil-geotextile

Red soil-geotextile

Sand-geotextile

Displacement, mm

Pu

llou

t, k

N/m

14

sand thickness encapsulating the geogrid enhanced the reading in pull-out capacity.

Thus, the optimum thickness of sand containing the geogrid was 10mm. Furthermore,

the result showed that increasing the normal stresses will result in the highest reading in

pull-out capacities. Also, the given thickness of sand has provided useful drainage and

prevented pore pressure build up during pull-out.

Figure 2.5: Arrangement of Pull-out Tests by Abdi and Arjomand, 2011

Figure 2.6: Pull-out Appratus as Used by Abdi and Arjomand, 2011

15

2.6 Finite Element Modelling (FEM)

Khedkar and Mandal, 2009 studied the interaction of pull-out test with different height

of cellular reinforcement along with planar sheet reinforcement which carried out under

two different normal pressure of 75 kPa and 100 kPa. In their studies, the interactions

of cellular reinforcements in pull-out test was compared with the results obtained from

finite element method application using PLAXIS software as shown in Figure 2.7 and

Figure 2.8. The analysis of dimension optimization for cellular reinforcement is done

and found that the optimum longitudinal spacing to height ratio is to be 3.3. Also, pull-

out capacity was found to have increased with increasing height of cellular element.

Figure 2.7: Finite Element Modelling (FEM) of a Pull-out Test by Khedkar and

Mandal, 2009

20

Figure 3.1: Location of Pull-out Test Site

Figure 3.2: Pull-out Test Concrete Box

21

3.2 Materials for Pull-out Tests

3.2.1 Strips

The strips used in this research are shown in laboratory photos of Figure 3.3 and 3.4.

The strips were all fabricated in-house in the laboratories of the School of Civil

Engineering and the School of Mechanical Engineering. Geometric specifications of

strips designed for pull out tests are given in Table 3.1 while properties of strip and

anchorage elements are given in Table 3.2. Each strip may consist of longitudinal

member, such as anchorage elements, stiffeners, and welding, which will be described

next.

Figure 3.3: Strips in Lateral View

22

Figure 3.4: Strips in Longitudinal View

Table 3.1: Geometric Specifications of Strips Designed for Pull-out Tests

No

Geometric specifications

(subscripts showing dimensions length, width, and thickness in cm)

Height

of

element

s

(cm)

No. of

eleme

nts

(n)

1 PL60050.5cm 0 0

2 PL60050.5cm + 6PL510.5cm[element] + 6PL410.5cm[stiffener] 1 6

Table 3.2: Properties of Strips and Anchorage Elements

Property Value

Density, 7850 kg/m3

Elasticity modulus, E 200 GPa

Poisson ratio, v 0.3

27

3.4 Experimental Programs

3.4.1 Compaction Test

The compaction tests were carried out in accordance with ASTM D1557 (ASTM,

2007b). This laboratory test is called Modified Proctor Test and the equipment used is

shown in Figure 3.8. This test was conducted to obtain the maximum dry unit weight of

compaction and the optimum moisture content. The sand was sieved by No. 4 sieve

(4.75 mm) and placed in the mould having a volume of 944 cm3. The sand was then

compacted in five layers by a hammer that has a mass of 4.54 kg. The drop of hammer

was 457 mm and the numbers of hammer blows were 25 per layer, evenly over the area

in the mould.

Figure 3.8: Compaction Test Equipment

29

Figure 3.10: Tensile Test Equipment

Two tensile tests were carried out on the strips used in this research, which were plain

strip and strip with 1 cm anchorage elements. Each strip used in the test was 100 cm

length, 5 cm width, 0.5 cm thickness. The rate of tension was 18 mm/min. The strips

were expected to yield the same tensile strength as their dimensions were same.

However, there was a possibility that the work of attaching anchorage elements and

stiffeners could affect the tensile strength due to disturbance that might have been

inflicted upon the otherwise plain and perfect strips. Figure 3.11 shows the condition of

the strip after the tensile test.

30

Figure 3.11: Strip Broken after Tensile Test

3.4.3 Pull-out Tests

The set-up of the pull-out test is shown in Figure 3.12. The components seen were

concrete test box, bricks, hydraulic jack, displacement transducers, load cell, data

logger, and laptop computer.

Figure 3.12: The Overview of the Pull-out Test

31

The dimensions of the concrete test box was 10 m 1 m 0.75 m. The soil was first

placed inside the concrete box until 0.8 m high where compactions were done for each

0.2 m of soil layers. The compaction process was done uniformly by using the plate

compactor as shown in Figure 3.13.

Figure 3.13: Compaction Process by Using Plate Compactor

After the strip was placed, the soil was filled until the top of concrete box, levelled and

compacted again before bricks were laid on top of it. The rear hole of strip was

connected to the SDP-C displacement transducer by using stainless steel wire rope, as

shown in Figure 3.14, whereas the front hole was connected to the pulling rod that

pulled by hydraulic jack.

32

Figure 3.14: Rear Displacement Transducer

The pulling rod and the hydraulic jack were assembled into a steel frame in the front

face of the box as shown in Figure 3.15 where the displacement of the pulling rod was

monitored using CDP displacement transducer. The pull-out force was created by

hydraulic jack and was monitored by using a load cell. The load cell which calibrated

properly was used to measure the pull-out force of the reinforcement strip. The

maximum pull-out force which could be measured by the load cell was 44.48 kN. The

CDP displacement transducer is shown in Figure 3.16 and the load cell is shown in

Figure 3.17.

33

Figure 3.15: Steel Frame Consisting of Pulling Rod, Load Cell, Hydraulic Jack, and

Front Displacement Transducer

Figure 3.16: Front Displacement Transducer

34

Figure 3.17: Load Cell Used to Monitor Pull-out Capacity

The data from the load cell, front and rear displacement transducers were transmitted to

a fully configurable data logger which interfaced with the laptop computer and utilized

software WINHOST to view and analyse the collected data. For the pull-out tests, it

was programmed to record data for every 0.25 second. The data logger used in the test

is shown in Figure 3.18.

Figure 3.18: Data Logger Used for the Pull-out Tests

36

Figure 3.19 shows an example of 6 layers of bricks. Approximately 1218 bricks were

used for 6 layers of bricks to simulate normal stress of 8.25 kPa.

Figure 3.19: Example of 6 Layers of Bricks

3.5 Finite Element Analysis

The pull-out capacity of the reinforcement strip was simulated and assessed by the

finite element model. The obtained results were then compared with the results of field

pull-out tests.

The numerical analysis of the pull-out tests was prepared using the software package

PLAXIS 2D AE, as shown in Figure 3.20. This software employs a commonly-used

finite element code for geotechnical engineering problems. The pull-out tests were

simulated as a 2D problem having 15 nodes (i.e. 2D elements). In general, about 5000

elements and 40000 nodes were generated for every pull-out analysis in the PLAXIS

software.

37

Figure 3.20: PLAXIS 2D AE Software

To simulate the field pull-out tests, the geometry of the test box was modelled such that

it was similar to that of the real test box. The bottom boundary was modelled with total

fixity, whereas the side boundaries were fixed horizontally. In this study, in order to

model the sand, it was decided to use the non-linear Mohr-Coulomb criteria due to their

simplicity, practical importance and the availability of parameters needed. The

properties of the sand and the reinforcement strips used in both the field tests and

numerical analysis were exactly identical. Normal pressure was modelled by a vertical,

uniformly-distributed load on top of the sand layer. The displacements obtained from

the field results were then assigned as the prescribed displacements in horizontal

direction.

For this FEM analysis, 6 model were generated for both plain strip and strip with 1 cm

anchorage elements that having normal pressure 4.25 kPa, 8.50 kPa, and 12.75 kPa.

39

Figure 3.21: Methodology Adopted in this Research

Start

Desk study

1. Sieve analysis 2. Compaction tests 3. Tensile tests

Pull-out tests

1. Plain strip

2. Strip with 1 cm anchorage elements

FEM analysis

End

44

Figure 4.4: Pull-out Force versus Front and Back Displacements for Plain Strip under

Normal Stress of 4.25 kPa



0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 60 70 80 90

Pu

llou

t fo

rce

(KN

)

Displacement (mm)

Back Force-Displacement

Front Force-Displacement

0

2

4

6

8

10

12

0 10 20 30 40 50 60 70

Pu

llou

t fo

rce

(KN

)

Displacement (mm)



45



Figure 4.7: Pull-out Stress versus Normal Stress for Plain Strip

0

2

4

6

8

10

12

14

0 10 20 30 40 50 60 70 80

Pu

llou

t fo

rce

(KN

)

Displacement (mm)



47

Figure 4.8: Pull-out Force versus Front and Back Displacements for Strip with 1 cm

Anchorage Elements under Normal Stress of 4.25 kPa



0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30 35 40 45 50

Pu

llou

t fo

rce

(KN

)

Displacement (mm)



0

2

4

6

8

10

12

14

16

0 10 20 30 40 50 60 70 80

Pu

llou

t fo

rce

(KN

)

Displacement (mm)



48



Figure 4.11: Pull-out Stress versus Normal Stress for Strip with 1 cm Anchorage

Elements

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90

Pu

llou

t fo

rce

(KN

)

Displacement (mm)



50

Figure 4.12: Pull-out Force versus Displacement for Plain Strip and Strip with 1 cm


Figure 4.13: Pull-out Force versus Displacement for Plain Strip and Strip with 1 cm


0

1

2

3

4

5

6

7

8

9

10

0 10 20 30 40 50 60 70 80 90

Pu

llou

t fo

rce

(KN

)

Displacement (mm)

Plain Strip

Strip with 1 cm anchorage elements

0

2

4

6

8

10

12

14

16

0 10 20 30 40 50 60 70 80

Pu

llou

t fo

rce

(KN

)

Displacement (mm)

Plain Strip


51

Figure 4.14: Pull-out Force versus Displacement for Plain strip and Strip with 1 cm


Red lines (strip with 1 cm anchorage elements) in all cases were noted to have higher

values than blue lines (plain strip). According to Mosallanezhad (2014), adding anchors

to the conventional strip increases the interaction between the soil and the

reinforcement by about 340%. In this case, the result shows that attachment of

anchorage elements can increase the pull-out capacity by at least 46.43%. This also

proven that attachment of anchorage elements significantly increased the frictional

angle between reinforcement and soil which resulted in higher pull-out capacity which

complied to the statement by Mosallanezhad (2014).

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80

Pu

llou

t fo

rce

(KN

)

Displacement (mm)

Plain Strip


55

4.3.1 Deformed Mesh

Figure 4.17: Deformed Mesh Generated for Plain Strip

Figure 4.18: Deformed Mesh Generated for Strip with 1 cm Anchorage Elements

57

4.3.2 Axial Force

Figure 4.19: Pull-out Force on Plain Strip under the Prescribed Displacement 18.42 mm

Figure 4.20: Pull-out Force on Strip with 1 cm Anchorage Elements under the

Prescribed Displacement 67.22 mm

59

4.3.3 Zones of Horizontal Displacements

Figure 4.21: Zones of Horizontal Displacement, ux Surrounding the Plain Strip

Figure 4.22: Zones of Horizontal Displacement, ux Surrounding the Strip with 1 cm

Anchorage Elements

61

4.3.4 Zones of Shear Stresses

Figure 4.23: Shear Stress Zones Surrounding the Plain Strip

Figure 4.24: Shear Stress Zones Surrounding the Strip with 1 cm Anchorage Elements

63

4.3.5 Total Principal Stresses

Figure 4.25: Stress Points Showing Principal Stresses Surrounding the Plain Strip

Figure 4.26: Stress Points Showing Principal Stresses Surrounding the Strip with 1 cm

Anchorage Elements

abstract of my thesis

Documents

tensile tests

finite element analysis

anchorage elements

soil reinforcement methods

zones of shear stresses

appendix b

s walls

plain strip