Presentation of Soil Hydraulics

8/9/2019 Presentation of Soil Hydraulics

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INTRODUCTION

BACKGROUND

METHODOLOGY

RESULTS AND DICUSSION

CONCLUSION AND RECOMMENDATIONS

ACKNOWLEDGEMENT

PRESENTATION OUTLINE

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INTRODUCTION

Recent trends are very much focusedon fibre reinforcement, where use ofthe artificial fibre is very common.

The use of natural fibres such aswheat straw, rice husk is very littleaddressed in the literature to be used

as reinforcing materials.

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INTRODUCTION

Therefore, this study was focused toinvestigate effectiveness of wheatstraw as soil stabilizing agent.

The analysis was carried out throughexperimentation.

Mechanical behaviour of soil such as

its consistency, shrinkage,consolidation, density andcompressive strength, etc. wereinvestigated.

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BACKGROUND

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BACKGROUND

It has been long recognized that natural

fibre is abundance as a raw material and

there has been little utilization of it as anengineering material to be used as

reinforcing materials.

the production of wheat straw or ricehusk in Pakistan has a continuous rising

trend through decades. Pakistan wheat

production by year is shown in Figure.6


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BACKGROUND

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BACKGROUND

World wheat production by year is

shown in Figure

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MECHANICAL PROPERTIES OF CLAY

Consistency

Shrinkage

Density Consolidation

Compressive strength, etc.

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EFFECT OF CLAY CONSISTENCY

10

The stability of adobe (mud) houses mainlydepends on clay consistency and compressive

strength


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EFFECT OF SHRINKAGE

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EFFECT OF CONSOLIDATION

12

Effect of consolidation and soil saturation isobvious on buildings and subgrades


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EFFECT OF DENSITY/STABILITY

13

The performance of highways significantly depends

on the stability/compressive strength of subgrades


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METHODOLOGY

Clay

Wheat StrawMaterials

Consistency Limit Test Shrinkage Limit Test

Compaction TestCompressive strength Test

Consolidation Test

ExperimentalSetups

Detail is on next SlideTesting

Procedure

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CLAY STOCK

15

Clay stock

Fine clay of breaking the lump


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COMPOSITE MATERIALS

17

Clay mixed with fibre (dry mixing)Threshed wheat straw

Clay mixed with fibre and water at OMC Clay mixed with fibre and water at WP


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EXPERIMENTAL SETUPS

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TESTING PROCEDURE

Unit weight

Average specific gravity

Volume of solids

Void ratio

Constant compaction efforts

Targeted unit weight

Targeted relative density

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UNIT WEIGHT

=

= 100100 + +

Mcement=C

100+C+F

Mtotal

=

100 + +

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AVERAGE SPECIFIC GRAVITY

=100

100 +

100 +

100

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VOLUME OF SOLIDS

=

=

22

=


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VOID RATIO

=

42

23

=

=


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TARGETED RELATIVE DENSITY

=

24

=

1 +

=

=

=


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DIFFICULTIES IN SAMPLE PREPARATION

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DIFFICULTIES IN SAMPLE PREPARATION

26

Provision of collar

Controlled compaction efforts


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SAMPLE PREPARATION

27

(a) Sample prepared mould without collar (b)Sample prepared mould with collar.

(a) (b) (a) (b)


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SAMPLE TRIMMING

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SAMPLE TRIMMING

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SAMPLE TRIMMING

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RESULTS AND DISCUSSION

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RESULTS AND DISCUSSION

Average Specific Gravity

32

% WS Gsoil Gws Gav

0 2.6 0.36 2.6

2 2.6 0.36 2.548

4 2.6 0.36 2.496

6 2.6 0.36 2.444

8 2.6 0.36 2.392

10 2.6 0.36 2.34


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EFFECT OF %AGE OF WS ON THE Gav

33

2.00

2.20

2.40

2.60

2.80

3.00

0 5 10

Avg.Sp.Gr.(Gav

)(%)

Fibre Content (%)


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CONSISTENCY LIMITS

Fibrecontent

(%)

LiquidLimit(%)

PlasticLimit(%)

PlasticityIndex(%)

0 21.8 13.87 7.93

0.5 29.3 18.52 10.78

1 36.1 22.98 13.12

2 41.1 24.4 16.7

4 42.79 25.87 16.92

6 45.1 27.81 17.29

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CONSISTENCY CHARACTERISTICS

35

0

10

20

30

40

50

0 2 4 6 8 10

Consistencylim

its(%)

Fibre content (%)

Liquit limit

Plastic Limit

Plasticity Index


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SHRINKAGE LIMIT

Fibre Content

(%)

Shrinkage Limit

(%)

0 24.15

0.1 23.715

0.4 21.21

0.6 20.135

0.8 24.03

1.0 25.6936


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SHRINKAGE TEST

37

15

20

25

30

0.0 0.5 1.0 1.5S

hrinkagelim

it(%)

Fibre Content (%)


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OPTIMUM MOISTURE CONTENT

WaterContent

(%)

Dry UnitWeight

(kN/m3)

10 19.42

12 19.62

14 20.11

16 20.5

18 20.4

20 20.1

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OPTIMUM MOISTURE CONTENT

39

19

19.5

20

20.5

21

8 10 12 14 16 18 20 22

DryDensity(kN/m3)

Moisture Content (%)


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OPTIMUM FIBRE CONTENT

FibreContent

(%)

Dry UnitWeight

(kN/m3)

0 18.65

2 17.57

4 15.87

6 15.04

8 12.98

10 12.40

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EFFECT OF WHEAT STRAW ON MDD

41

10

12

14

16

18

20

0 5 10 15

S

hrinkageLim

it(%)

Fiber Content(%)


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1-D CONSOLIDATION

Fibercontent

(%)

t90(minutes)

Cv(mm2/min)

0 11.088 20.30

2 18.5 14.301

4 29.16 12.63

6 11.90 14.248 29.37 15.96

10 23.42 17.72

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1-D CONSOLIDATION

43

0.00.51.0

1.52.02.53.03.54.0

4.55.05.56.0

0 1 2 3 4 5 6 7 8 9

Settlement(mm

)

t90(min)

0% WS

2% WS

4% WS

6% WS

8% WS10% WS


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1-D CONSOLIDATION

44

10

15

20

25

0 2 4 6 8 10 12

Cv(mm2/min

)

Fibre Content (%)


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UNIAXIAL COMPRESSIVE STRENGTH

45Sample prepared at OMC Sample prepared at WP


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46

0

200400

600

800

10001200

1400

1600

1800

0 5 10 15 20

UCS(kPa)

Axial strain (%)

0% WS-OMC

2%WC-OMC

6%WS-OMC

8%WS-OMC

Effect of fibre content on UCS at OMC


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47

0

200

400

600

800

1000

1200

0 2 4 6 8 10

UCS(kPa)

Axial strain (%)

0% WS-WP2%WS-WP6%WS-WP

8%WS-WP

Effect of fibre content on UCS at WP


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EFFECT OF FIBRE CONTENT ON UCS AT

OMC AND WP

Fibre content

(%)

UCS (kPa)

at (OMC)

UCS (kPa)

at (WP)

0 920 802

2 1244 1042

4 1390 1300

6 1530 1128

8 1173 719

10 628 411

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EFFECT OF FIBRE CONTENT ON UCS AT

OMC AND WP

49

0

200

400

600

800

10001200

1400

1600

1800

0 2 4 6 8 10 12

UCS(kPa)

Fibre content (%)

OMC WP


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SUMMARIZED RESULTS

50

Type

of soil LL

%

PL

%

PI

%

SL

%Gs

OMC

%

OFC

%

MDD

(kN/m3

)

UCS

(kPa)

Cv

(mm2

/min)

CL 21.8 13.87 7.93 24.15 2.60 16 0 20.5 920 20.3

Properties of clay


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SUMMARIZED RESULTS

51

Type of

fibre

Average

diameter

Average

Length Gs WAR

Tensile

force

Tensile

strength

Wheat

straw3.1 mm

18.4

mm0.34-0.38 300% (24 h)

7.805 kg

(76.48 N)

10.133

MPa

(1470 psi)

Properties of Wheat straw


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52

SUMMARIZED RESULTS

Type

of

soil

LL

%PL

%PI

%SL

%Gs

OMC

%OFC

%MDD

(kN/m3)

UCS

(kPa)

OMC

UCS

(kPa)

WP

Cv

(mm2/min)

CL 21.8 13.87 7.93 24.15 2.60 16 0 20.5 920 802 20.3

CL+

WS

45.1

(6%

WS)

27.81

(6%

WS)

17.29

(6%

WS)

20.14

(0.6%

WS)

2.44

(6%

WS)

--- ---

15.04

(6%

WS)

1530

(6%

WS)

1300

(4%

WS)

12.63

(4% WS)

CL= low plasticity clay, LL = liquid limit, PL= plastic limit, PI= plasticity

index, SL= shrinkage limit, Gs= Specific gravity, OMC= optimum moisture

content, OFC =optimum fibre content, UCS=Uniaxial compressive strength,

MSL = maximum shrinkage limit, Cv= coefficient of consolidation.


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CONCLUSIONS

1. The addition of wheat straw into the clay as

reinforcement there were little or no improvement

noticed in the maximum dry unit weight of clay.

Gradual increase in the wheat straw content resulted togradually decrease the dry unit weight of clay.

2. Two series of samples were prepared one series at

optimum moisture content (16% approx. :) and one

series of samples were prepared in a workable pasteform (40% moisture content).

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CONCLUSIONS

3. Addition of wheat straw resulted to a noticeable

improvement in the uniaxial compressive strength of

clay for both at optimum moisture content and at

workable paste.4. However, the uniaxial compressive strength of

samples prepared at optimum moisture content were

thoroughly higher than those of the samples prepared

at workable paste.

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CONCLUSIONS

5. For the specimens prepared at optimum moisture

content, the maximum uniaxial compressive strength

was achieved at an optimum fibre content of 6%,

6.

For the specimens prepared at workable paste (40%moisture content), the maximum uniaxial

compressive strength was achieved at an optimum

fibre content of 4%.

7. The experimental results suggests that the addition of

wheat straw initially decrease the shrinkage to an

optimum content and thereafter there is increase in

the shrinkage due to the addition of further wheat

straw content.

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CONCLUSIONS

8. The optimum wheat straw content at which

maximum decrease in the shrinkage limit noticed was

0.6%.

9. Generally, using wheat straw as a soil stabilizingagent improvement in the mechanical properties of

the soil was noticed. However, further investigations

are essential to come to a conclusive end for the

advantages and commercial viability of using wheat

straw as soil stabilizing agent.

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RECOMMENDATIONS

1. For the constant compaction efforts a typical design is

shown in Figure, which may be adopted for the

preparation of the samples for unconfined

compression and triaxial testing for samples of sizes34 mm, 50 mm and 70 mm diameter. The tamping rod

may be of 16 mm diameter, and of 450 mm (18 in)

height.

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RECOMMENDATIONS

58

Compaction rammer for compacting 50 mm diameter samples


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RECOMMENDATIONS

2. For the preparation of samples with consistent

density throughout its height, the triaxial split mould

may be provided with collar. A typical mould with

collar is shown in Figure. The mould is providedwith the following specifications.

59

Height of

mould

Diameter of mould Height of

collar

Diameter of collar

Internal External Internal External

100 mm 50 mm 67.5 mm 50 mm 50 mm 67.5 mm


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RECOMMENDATIONS

60

proposed triaxial spilt mould provided with collar


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RECOMMENDATIONS

3. As there is high percentage of water absorption ratio

of wheat straw and secondly the addition of wheat

straw is going to reduce the maximum dry density

(while keeping the optimum moisture content of clayunchanged that is 16%); therefore, the effect of wheat

straw on the optimum moisture content of soil must

be checked.

61

Fibrecontent

(%)

0 2 4 6 8 10

OMC

(%)16 -- -- -- -- --


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RECOMMENDATIONS

4. As in present studies thresher shredded length of the

wheat straw was used. The average length of

threshed wheat straw was measured to be 18.4 mm;

however, it is presumed that the effect of fibre length

on the mechanical properties may be varying.

Therefore, the effect of fibre (wheat straw) length on

the mechanical properties need to be investigated.

Moreover, the direction of the placement of wheat

straw should also be in consideration.

62

Fibre

length

(mm)

10 15 20 25 30 35 40 45 50


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RECOMMENDATIONS

5. Hydraulic conductivity of clay may be checked as a

function of percentage of wheat straw added into it,

at loose, medium dense and dense state of soil.

63

Fibre content (%) 0 2 4 6 8 10

Hydraulic

conductivity,

k (cm/sec)

Loose state

(Dr = 0-33%)-- -- -- -- -- --

Medium Dense state

(Dr = 33%-66%)-- -- -- -- -- --

Dense state

(Dr = 66%-100%)-- -- -- -- -- --


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RECOMMENDATIONS

6. The effect of addition of wheat straw on the

compressibility of clay in saturated and semi saturated

state must be investigated. It is proposed that a series

of CBR tests should be conducted on the fibre

reinforced clay.

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Fibre content (%) 0 2 4 6 8 10

CBR value Un-soaked CBR -- -- -- -- -- --

Soaked CBR -- -- -- -- -- --


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RECOMMENDATIONS

7. In order to check the effect of decomposition of

wheat straw on the stability of soil, soaked clay

samples for varying soaking period ranging from

days to several months may be tested.

8. The rate of decomposition of wheat straw and factors

which can render the decomposition of wheat straw

may be studied. For aforementioned purposes:

(i) how many grams of wheat straw to be added intohow much volume of water must be decided?

(ii) How long the samples be placed for soaking

(iii) how much amount of clay is to be added into the

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Presentation of Soil Hydraulics

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