Influence of Different Stress Conditions on Behaviour of Rockfill Materials

7/31/2019 Influence of Different Stress Conditions on Behaviour of Rockfill Materials

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O R I G I N A L P A P E R

Influence of Different Stress Conditions on Behavior

of Rockfill Materials

Pankaj Sharma N. V. Mahure Murari Ratnam

Received: 20 July 2010 / Accepted: 20 July 2011 Springer Science+Business Media B.V. 2011

Abstract Rockfill material is the most readily

available and the most flexible material for the

construction of dams especially in the seismic prone

regions. The material is obtained either by blasting

available rock or is collected from the alluvial

deposits of the river. During construction of the

dam, the available rockfill material is compacted to

required density layer by layer using various sophis-

ticated compactors to achieve the required density

and slope. Gradually the vertical load on the lower

layers goes on increasing due to placement ofsubsequent layers of the materials to achieve the

desired height. This may result in variation of grain

size distribution of the lower layers due to the

breakage of particles. This will certainly influence the

shear parameters. Present studies have been carried

out to find the influence of loading the rockfill

materials under two different stress conditions i.e.

multistage loading and single stage loading on the

grain size distribution and its subsequent effect on its

shear parameters. Consolidated drained triaxial shear

tests have been conducted on the materials obtainedby blasting available rock as well as on the materials

collected from the alluvial deposits of the river which

are generally used for construction of rockfill dams.

Test data have been analyzed to study the breakage

factor and corresponding shear parameters under both

conditions.

Keywords Rockfill materials Consolidateddrained triaxial shear tests Multistage loading Single stage loading Particle size

Strength parameters and breakage factor

1 Introduction

Construction of dams using rockfill (RF) is becoming

increasingly more common because of self realigning

capacity of the materials. This makes RF dams more

stable even in the seismic zones. The abundant

availability of such materials in the vicinity of

proposed dam construction sites makes dams con-

struction more economical. The materials consist

primarily of angular to sub-angular particles obtained

by blasting parent rock (QRF) or rounded/sub-

rounded particles obtained from terrace alluvialdeposits of the river (RBRF).

During construction of the dam the available RF

material is compacted to required density layer by

layer using various sophisticated compactors to

achieve the required density and slope. Gradually

the vertical load on the lower layers goes on

increasing due to placement of subsequent layers of

the materials to achieve the desired height. This may

result in variation of grain distribution of the lower

P. Sharma (&) N. V. Mahure M. RatnamCentral Soil and Materials Research Station, Hauz Khas,New Delhi, Indiae-mail: [email protected]

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DOI 10.1007/s10706-011-9435-8


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layers due to the breakage of particles. The behavior

of RF material is significantly affected by the grain

size distribution of the used materials.

This paper deals with the effect of different stress

conditions encountered during construction stage on

the Breakage of particles and its corresponding effect

on the shear parameters for the QRF and RBRFmaterials. Consolidated drained tests (CD) have been

conducted on both type of materials generally being

used for construction of rockfill dams i.e. QRF and

RBRF materials under multistage loading condition

(MS) and single stage loading condition (SS). The

test data has been analyzed to study the breakage of

particles as percent cumulative particle breakage

factor Bg(cum) (%) in MS) and percent particle

breakage factor Bg (%) in SS and shear parameters

under both conditions.

2 Review

Investigations conducted on rockfill materials indi-

cate that the magnitude of the particle breakage

during loading has a direct impact on the shear

parameters. The amount of particle breakage is

affected by the stress level, stress magnitude and

stress path. Large amount of particles breakage is

generated when stress levels are higher and when

large amounts of strains occur in regions of highstress magnitudes. These empirical factors either

cause the variation of grain diameter (Lee and

Farhoomand 1967; Lade and Yamamuro 1996) or

the shift of the whole grain size distribution curve

(Marsal 1967; Hardin 1985). The results of tests

conducted by Marachi et al. (1972) show a variation

of the angle of internal friction with the grain size

distribution. High pressure causes considerable par-

ticle breakage (Becker 1972; Hardin 1985; Murphy

1987; Colliat-Dangus et al. 1988; Fukumoto 1990;

Hagerty et al. 1993; Lade et al. 1996; Daouadji andHeicher 1997). There are several factors that affect

the amount of particle breakage in a geological

material (Lee and Farhoomand 1967; Ramamurthy

1969; Murphy 1971; Billam 1971; Lo and Roy 1973;

Ramamurthy et al. 1974; Gupta 1980; Hardin 1985;

Kjaernsli et al. 1992; Venkatachalam 1993; Lade

et al. 1996). Marsal (1965), Vesic and Clough (1968),

Marachi et al. (1969), Ramamurthy et al. (1974) and

Venkatachalam (1993) have quantified the particle

breakage by defining it based on the modification of

the grain size distribution curves before and after the

tests and have presented it as breakage factor Bg (%).

3 Material Used for Testing

3.1 Quarried Material from Kol Dam Project,

H.P., (QRF)

The rockfill material was collected by blasting the

parent rock. The rockfill material consists of angular

to sub-angular particles in shape and size up to

500 mm. The parent rock at this project site is either

dolomite or limestone. The QRF materials possess

the following mechanical properties;

Uniaxial compressive strength: 37.1 MPa to 40.4MPa

Los Angeles abrasion value: 48.1%

Aggregate impact value: 42.3%

Aggregate crushing value: 41.2%.

3.2 River Bed Material from Kol Dam Project,

H.P., (RBRF)

The material was collected from the alluvial deposit

of the river near the proposed dam axis. It consists of

well graded rounded/sub rounded grayish coloredparticles up to 500 mm size, mainly composed of

quartzite and dolomite/lime stone. The RBRF mate-

rials possess the following mechanical properties;

Uniaxial compressive strength: 42.7 MPa to 50.1

MPa

Los Angeles abrasion value: 44.2%

Aggregate impact value: 39.8%

Aggregate crushing value: 37.9%.

4 Gradation of Materials

4.1 Gradation of Prototype Materials

Representative rockfill materials are collected from

different locations and are subjected to grain size

analysis. The grain size distribution results are plotted

and an average curve is drawn. This curve has been

designated as the average prototype curve of the

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representative rockfill materials. Prototype gradation

curves for both quarried and river bed rockfill

materials from Kol H.E. Project, H. P. are shown in

Figs. 1 and 2, respectively.

4.2 Gradation of Modeled Materials

The maximum particle sizes available in the proto-

type material is of the order of 500 mm. Testing of

such a material having this big size particles in the

laboratory is not possible so the actual prototype

material are scaled down to some degree to keep

maximum particle size of the particles as 80 mm. The

material so obtained is designated as modeled

material is used for the testing.

Three modeled gradation curves are derived usingJohn Lowes Parallel Gradation modeling technique

(Lowe 1964) having a maximum particle size of 80,

50 and 25 mm, respectively. Modeled gradation

curves in respect of QRF and RBRF material are

presented in Figs. 1 and 2, respectively. Using these

model grain size distribution curves, the required

quantities of various fractions of rock fill materials

have been calculated. The total quantities of materials

thus required for carrying out laboratory tests are

sieved from the materials collected from two

potential locations of Kol dam.

5 Laboratory Investigations

Laboratory tests were conducted on both type of

materials collected from the project site for evaluat-

ing Relative Density, Specific Gravity, Shear param-

eters under MS loading and SS loading and their

corresponding breakage factor.

5.1 Relative Density

The values of the maximum dry density, minimum

dry density and relative density have been determined

as per IS 2720 (Part 14):1983 Method test for soils

Determination of density index (relative density) of

cohesion less soils. The values of the maximum dry

density, minimum dry density and required dry

density corresponding to 87% of relative density

(ID) are given in Table 1.

0

20

40

60

80

100

0.01 0.1 1 10 100 1000

Grain size (mm)

Percentfiner(%)

Prototype Model (80mm)

Model (50mm) Model (25mm)

Fig. 1 Prototype and modeled grain size distribution curves(QRF)

0

20

40

60

80

100

0.01 0.1 1 10 100 1000

Grain size (mm)

Percentfiner(%)

Prototype Model (80mm)

Model (50mm) Model (25mm)

Fig. 2 Prototype and modeled grain size distribution curves(RBRF)

Table 1 Results of relativedensity test

Type of material Max. particlesize (mm)

cmin. (gm/cc) cmax. (gm/cc) Test density (ID, gm/cc),(87% relative density)

Quarried material 25 1.81 2.04 2.01

50 1.77 2.01 1.98

80 1.71 1.99 1.95

River bed material 25 1.55 2.22 2.10

50 1.55 2.22 2.10

80 1.60 2.28 2.16

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Table 2 Details of triaxial shear tests conducted on QRF and RBRF materials

Max particlesize (mm)

Test procedure: 1 (multistage loading) Test procedure: 2(single step loading)

Step 1 Step 2 Step 3 Step 4

80 Sample 1 r3

Kg/cm23 6 9 12 12

Sample 2 3 6 9 9

Sample 3 3 6 6

50 Sample 1 r3

Kg/cm23 6 9 12 12

Sample 2 3 6 9 9

Sample 3 3 6 6

25 Sample 1 r3

Kg/cm23 6 9 12 12

Sample 2 3 6 9 9

Sample 3 3 6 6

0

10

20

30

40

50

60

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/sqcm

0

10

20

30

40

50

60

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/sqcm

0

10

20

30

40

50

60

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/sqcm

CBA

0

10

20

30

40

50

60

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/sqcm

0

10

20

30

40

50

60

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/sqcm

0

10

20

30

40

50

60

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/sqcm

FED

0

10

20

30

40

50

60

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/sqcm

0

10

20

30

40

50

60

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/sqcm

0

10

20

30

40

50

60

0 4 8 12 16 20

Strain (%)

DirectStress,

kg/sqcm

IHG

Legends for A, D & G Legends for B, E & H Legends for C, F &I

Fig. 3Stressstrainbehavior of QRF material

for samples with 25 (ac),50 (df) and 80 (gi) mmmaximum particle size

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In accordance with the model gradation curves, the

total dry weight required for achieving 87% of

relative density is computed for each of the speci-

mens to be tested.

5.2 Triaxial Shear Tests

Consolidated drained (CD) triaxial tests have been

conducted on the modeled rockfill materials. A

specimen size of 381 mm diameter by 813 mm long

was used for testing. For testing, a dry density

corresponding to 87% of relative density was

adopted. Samples were isotropically consolidated

under four different confining pressures (r3), kg/

cm2 in the range between 3 and 12 kg/cm2 for each

modeled rockfill material. In accordance with the

modeled gradation curves the total quantity of

various fractions of rockfill materials required to

achieve the specified density was determined byweight. The computed quantity of fractions was

thoroughly mixed and moistened with 34% water by

weight for maintaining reasonably uniform composi-

tion as per physical observations based on pilot test.

The mixed sample was compacted in a split mould in

0

10

20

30

40

50

60

70

80

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/s

qcm

0

10

20

30

40

50

60

70

80

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/s

qcm

0

10

20

30

40

50

60

70

80

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/s

qcm

A B C

0

10

20

30

40

5060

70

80

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/sqcm

0

10

20

30

40

5060

70

80

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/sqcm

0

10

20

30

40

5060

70

80

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg/

sqcm

FED

0

10

20

30

40

5060

70

80

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg

/sqcm

0

10

20

30

40

5060

70

80

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg

/sqcm

0

10

20

30

40

5060

70

80

0 4 8 12 16 20

Strain (%)

DeviatorStress,

kg

/sqcm

IHG

Legends for A, D & G Legends for B, E & H Legends for C, F & I

Fig. 4 Stressstrainbehavior of RBRF materialfor samples with 25 (ac),

50 (df) and 80 (gi) mmmaximum particle size

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six equal layers by vibratory compaction. The sample

was saturated by allowing water to pass through thebase of the triaxial cell and using a top drainage

system for removing air from the voids. CD tests

were conducted adopting Multistage Loading (MS)

and Single Stage Loading (SS).

In the MS loading, the sample was consolidated at

the lowest pre decided r3 and then sheared at 1 mm/

min rate of loading under drained conditions to near

failure stage.1 The specimen was reconsolidated at

next higher pre decided r3 keeping the attained load

constant and then it was again sheared to near failure

stage (if it was intermittent step) or to achieve thefailure stage (if it was final step).

In SS loading, specimen is consolidated at the pre

decided r3 and then sheared at 1 mm/min. rate of

loading under drained conditions to achieve the

failure stage.The details of the various tests conducted on QRF

and TRF under the two procedures is presented in

Table 2.

5.2.1 StressStrain Behavior

Care was taken to avoid attaining of failure stage at

each intermittent step during shearing under MS

loading by plotting stressstrain curve for each test

simultaneously during shearing of the specimen.

Stress strain curves for samples with 25 mm,50 mm and 80 mm maximum particle size for QRF

material and RBRF material are presented in

Figs. 3ai and 4ai.

It can be seen from the stress strain curves that

during the MS loading conditions the axial strain at

failure ef, (%) is comparatively more than that during

the SS loading condition. The same trend is observed

even for each intermittent relative loading step during

MS loading condition.

Table 3 Results of the triaxial shear tests for QRF material under both MS and SS conditions for sample with 25 mm maximumparticle size

Test type r3 (kg/cm2) Density (gm/cc) ef (%) () degrees Breakage factor (%)

cp cc cnf cf Bg(cum) Bg

MS 3 2.01 2.059 2.080 7.6

6 2.091 2.100

9 2.107 2.114

12 2.119 2.125 18.5 42.51

MS 6 2.01 2.063 2.103 7.1

9 2.104 2.106

12 2.107 2.111 17.5 43.03

MS 9 2.01 2.073 2.086 6.6

12 2.087 2.091 15.5 43.81

SS 12 2.01 2.070 2.109 14.5 44.50 6.2

MS 3 2.01 2.063 2.101 5.7

6 2.108 2.115

9 2.123 2.124 16.5 43.41

MS 6 2.01 2.063 2.103 5.2

9 2.110 2.126 14.0 44.21

SS 9 2.01 2.073 2.091 12.5 45.2 4.8

MS 3 2.01 2.063 2.102 4.8

6 2.110 2.113 14.0 44.8

SS 6 2.01 2.063 2.101 11.0 45.45 4.0

1 Stress strain curves for each test were simultaneously plottedduring the shearing of the specimen (Figs. 3ai, 4ai) to takethe decision for the application of next r3 before achievingmaximum deviator stress (a near failure stage).

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ef % 3;6;9;12[ef % 6;9;12[ef % 9;12[ef % 12

ef % 3;6;9[ef % 6;9[ef % 9

ef % 3;6[ef % 6

Contrary to this, the maximum deviator stress (rd,

kg/cm2) achieved at failure is more for SS loading

condition than MS loading condition. The same trend

is observed even for each intermittent relative loading

step during MS loading condition.

rd12[rd9; 12[rd6;9;12[rd3;6;9;12

rd9[rd6; 9[rd3;6;9

rd6[r

d3;

6

The maximum deviator stress (rd, kg/cm2)

achieved at the near failure stage of each step of

loading, their corresponding percent axial strain ef(%), initial placement density of each sample (cp),

density at the end of consolidation at each step (cc),

density at the transition stage i.e. near failure stage

(cnf), the density at the final failure stage (cf), angle of

internal friction () in degrees for each step and

cumulative breakage factor Bg(cum) (%) in percent

occurred during MS and breakage factor Bg (%) in

percent occurred during SS represented against

maximum r3 of that particular test are presented forboth materials QRF and RBRF in Tables 3, 4, 5, 6, 7,

8, respectively.

5.2.2 Angle of Internal Friction ()

The values of the angle of internal friction (), in

degrees are presented in Tables 3, 4, 5, 6, 7, 8 for

QRF and RBRF materials, respectively. The pq

plots for QRF and RBRF materials with 25 mm,

50 mm and 80 mm maximum particle size under MS

as well as SS conditions are presented in Figs. 5 and6. For finding average angle of internal friction for

MS loading condition the p and q values correspond-

ing to maximum deviator stress achieved on the

ultimate r3 during MS loading [rd(3, 6, 9, 12), rd(3, 6, 9),

rd(3, 6)] are taken.

The value of the angle of internal friction () for

various samples with different maximum particle size

for both the materials are presented in Table 9. Angle

of internal friction (), is found to be slightly lesser




MS 3 1.98 2.010 2.022 9.8

6 2.027 2.032

9 2.036 2.041

12 2.045 2.051 19 42.21

MS 6 1.98 2.032 2.071 9.1

9 2.072 2.074

12 2.075 2.080 16.5 43.01

MS 9 1.98 2.041 2.054 8.7

12 2.055 2.056 15 43.62

SS 12 1.98 2.016 2.062 12.5 44.11 8.4

MS 3 1.98 2.009 2.028 8.4

6 2.028 2.027

9 2.039 2.048 16 43.56

MS 6 1.98 2.032 2.069 7.9

9 2.077 2.086 15.5 44.07

SS 9 1.98 2.041 2.058 13.5 44.81 7.5

MS 3 1.98 2.012 2.028 5.9

6 2.035 2.046 11.5 44.74

SS 6 1.98 2.032 2.070 10.5 45.43 5.0

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for MS loading irrespective of type of material or

maximum particle size.

The relationship between the angle of internalfriction and the maximum particle size for both the

materials is presented in Figs. 7 and 8. It is observed

that the QRF material shows decrease in the angle of

internal friction with the increase in size of particles.

Marachi et al. (1969) has reported a similar trend for

blasted angular materials. The RBRF materials show

an increase in the value of the angle of internal friction

with the size of the particle. Venkatachalam (1993)

has reported similar trend for river bed materials.

5.2.3 Breakage Factor

The breakage is quantitatively expressed as breakage

factor, Bg (%) or Bg(cum) (%) as proposed by Marsal

(1965). It is taken as percent variation in the pre and

post shear grain size distribution of the rockfill

material used. Bg (%) and Bg(cum) (%) has been

determined using following equation for each test

conducted under MS as well as SS for both QRF and

RBRF materials.

Bg % RPD RPI

where PD, percent decrease in particle distribution incertain sizes; PI, percent increase in particle distri-

bution in certain sizes.

The Bg(cum) (%) for MS tests could be determined

only after completion of the shearing of that sample at

maximum r3. The values of Bg(cum) (%) for different

loadsteps inMS and Bg (%) in SS are presented against

highestr3 forthattest.ThevaluesofBg (%)andBg(cum)(%) are presented in Tables 3, 4, 5, 6, 7, 8 for QRF and

RBRF materials, respectively. For the samples with

same particle size the breakage factor shows variation

in the following order

Bg cum 3;6;9;12 f g % [Bg cum 6;9;12 f g %

[Bg cum 9;12 f g % [Bg 12 %

Bg cum 3;6;9 f g % [Bg cum 6;9 f g % [Bg 9 %

Bg cum 3;6 f g % [Bg 6 %

Breakage factors also increases in magnitude with

the increase in the maximum particle size for both the

materials. Similar trends have been reported by




MS 3 1.95 1.998 2.019 13.2

6 2.025 2.030

9 2.038 2.044

12 2.054 2.057 16.0 41.62

MS 6 1.95 2.016 2.021 12.6

9 2.025 2.030

12 2.034 2.043 15.0 42.06

MS 9 1.95 2.051 2.061 12.0

12 2.065 2.069 13.5 42.82

SS 12 1.95 2.060 2.075 12.0 43.16 11.7

MS 3 1.95 1.998 2.022 10.5

6 2.027 2.041

9 2.048 2.050 13.5 42.99

MS 6 1.95 2.014 2.027 9.9

9 2.032 2.038 14.5 43.42

SS 9 1.95 2.051 2.061 11.5 44.02 9.3

MS 3 1.95 2.011 2.037 7.6

6 2.038 2.047 12.5 43.93

SS 6 1.95 2.011 2.039 9.5 44.42 6.7

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Marsal (1965), Vesic and Clough (1968), Marachi

et al. (1969), Ramamurthy et al. (1974) and Venk-

atachalam (1993).

Usually, the alluvial materials suffer less breakage

and have high angle of shearing resistance. But the

project being located in the upper reaches of the river,

the fluvial transport distance for the RBRF is less

which might not have allowed sufficient wearing of

the particles, therefore particles in the size range of

40 mm to 80 mm show higher breakage which

contribute to high value of Bg (%) and Bg(cum) (%).

5.2.4 Effect of Breakage Factor on Angle of Internal

Friction

The value of angle of internal friction () as observed

for max. confining pressure r3 during each MS

loading condition {r3(3, 6, 9, 12), r3(6, 9, 12), r3(9, 12)},

{r3(3, 6, 9), r3(6, 9)}, {r3 3, 6)} and for SS loading

condition r3(6), r3(9) & r3(12) for samples with

25 mm, 50 mm and 80 mm max particle size are

plotted against the Breakage Factor, Bg(cum) (%) for

MS and Bg (%) for SS loading condition for QRF

(Fig. 9) and RBRF materials (Fig. 10). It is observed

that the angle of internal friction () decreases as the

particle breakage increases. As discussed in 5.2.3, the

cumulative breakage factor Bg(cum) (%) increased as

the number of intermittent steps increased during MS,

accordingly the angle of internal resistance ()

decreased.

6 Conclusions

During construction, lateral confinement and increase

of vertical load on the lower layers due to placement

of additional layers of the material cause change in

the grain size distribution of the lower layers due to

breakage of the particles. This change of the grain

size distribution certainly has an effect on the shear

parameters of the materials.

Table 6 Results of the triaxial shear tests for RBRF material under both MS and SS conditions for sample with 25 mm maximumparticle size



MS 3 2.10 2.154 2.173 6.3

6 2.183 2.191

9 2.197 2.210

12 2.215 2.224 18.5 44.53

MS 6 2.10 2.180 2.203 5.4

9 2.210 2.226

12 2.235 2.238 17.5 45.67

MS 9 2.10 2.201 2.215 5.0

12 2.225 2.240 15.5 46.44

SS 12 2.10 2.207 2.233 14.5 47.28 4.4

MS 3 2.10 2.156 2.176 5.3

6 2.185 2.205

9 2.207 2.229 17 45.80

MS 6 2.10 2.187 2.219 4.5

9 2.220 2.220 13 46.40

SS 9 2.10 2.203 2.229 13.5 47.61 3.9

MS 3 2.10 2.165 2.181 3.9

6 2.194 2.209 13 46.83

SS 6 2.10 2.170 2.200 13 48.44 3.1

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Stress strain curves indicate that during the

multistage loading conditions the axial strain at

failure ef, (%) is comparatively more than that during

the single stage loading condition. The same trend is

observed even for each intermittent relative loading

step during multistage loading condition.

The deviator stress (rd, kg/cm2) achieved at failure

is higher for single stage loading condition than for

multistage loading condition. The same trend is

observed even for each intermittent relative loading

step during multistage loading condition.

It is observed that the quarried rockfill material

shows decrease in the angle of internal friction with

the increase in particle size. The river bed rockfill

materials show an increase in the value of the angle

of internal friction with particle size.

The breakage factor Bg(cum) (%) increases as the

number of intermittent steps increases during multi-

stage loading. Accordingly the angle of internal

resistance () decreases. The angle of internal

friction () is found to be slightly lower for

multistage loading than that observed in the single

stage loading, irrespective of type of material or

maximum particle size.

For arriving at the design parameters, laboratory

testing of the materials should simulate the field

conditions as much as possible. During construction

stage, the stress level on the lower layer increases

with placement of each layer. Also, during filling of

the dam the stress levels continuously increases more

on the lower layers. The design parameters should be

arrived at by simulating these field conditions.

Overall, in order to properly design a rockfill struc-

ture, it is of critical importance to think over the type

of the laboratory tests which can closely simulate the

stress conditions developing at different stages and to

study their effects on the mechanical behavior of

rockfill materials. CD-MS simulates the effect of step

wise loading which may change the grain size

distribution of RF material during construction stage.




MS 3 2.10 2.180 2.225 8.4

6 2.228 2.237

9 2.252 2.275

12 2.285 2.305 18.5 45.04

MS 6 2.10 2.205 2.238 7.6

9 2.247 2.281

12 2.289 2.307 18 45.87

MS 9 2.10 2.215 2.272 7.1

12 2.285 2.296 16 46.92

SS 12 2.10 2.200 2.298 11.5 47.84 6.6

MS 3 2.10 2.175 2.222 7.2

6 2.230 2.240

9 2.245 2.252 15.5 45.6

MS 6 2.10 2.195 2.223 6.5

9 2.233 2.258 12 47.4

SS 9 2.10 2.215 2.273 11.5 48.2 5.9

MS 3 2.10 2.187 2.206 4.9

6 2.214 2.220 14 48.08

SS 6 2.10 2.203 2.232 11 49.13 4.0

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MS 3 2.16 2.258 2.299 10.8

6 2.316 2.329

9 2.329 2.368

12 2.375 2.386 19.5 45.52

MS 6 2.16 2.267 2.302 9.7

9 2.313 2.341

12 2.355 2.372 18 46.72

MS 9 2.16 2.281 2.341 9.0

12 2.357 2.366 16 47.33

SS 12 2.16 2.271 2.376 13 48.35 8.3

MS 3 2.16 2.237 2.285 8.9

6 2.293 2.304

9 2.313 2.315 17.5 46.55

MS 6 2.16 2.252 2.281 8.1

9 2.291 2.323 15 48.45

SS 9 2.16 2.262 2.320 13 49.04 7.2

MS 3 2.16 2.260 2.279 6.8

6 2.287 2.293 13 49.26

SS 6 2.16 2.265 2.294 9.5 50.3 5.6

For MS

y = 0.678x + 0.176

= 42.680

For SS

y = 0.702x + 0.086

= 44.580

0

5

10

15

20

25

30

0 10 20 30 40 50

Average Normal Stress,

kg/sqcm

Averag

eShearStress,

kg/sqcm

For MS

y = 0.675x + 0.202

= 42.450

For SS

y = 0.697x + 0.113

= 44.180

0

5

10

15

20

25

30

0 10 20 30 40 50


kg/sqcm

Average

ShearStress,

kg/sqcm

For MS

y = 0.670x - 0.105

= 42.060

For SS

y = 0.686x + 0.108

= 43.310

0

5

10

15

20

25

30

0 10 20 30 40 50


kg/sqcm

AverageShearStress,

kg/sqcm

A B C

Fig. 5 pq plots for samples with 25 (a), 50 (b) and 80 (c) mm maximum particle size QRF material

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For MS

y = 0.705x + 0.195

= 44.830

For SS

y = 0.735x + 0.102

= 47.300

0

5

10

15

20

2530

35

40

0 10 20 30 40 50


kg/sqcm

AverageShearStress,

kg/sqcm

For MS

y = 0.708x + 0.238

= 45.070

For SS

y = 0.742x + 0.116

= 47.900

0

5

10

15

20

2530

35

40

0 10 20 30 40 50


kg/sqcm

AverageShearStress,

kg/sqcm

For MS

y = 0.716x + 0.296

= 45.720

For SS

y = 0.748x + 0.189

= 48.420

0

5

10

15

20

2530

35

40

0 10 20 30 40 50


kg/sqcm

AverageShearStress,

kg/sqcm

A B C

Fig. 6 pq plots for samples with 25 (a), 50 (b) and 80 (c) mm maximum particle size RBRF material

Table 9 Results of angle of internal friction () for QRF and RBRF material under both MS and SS conditions for sample with 25,50 and 80 mm maximum particle size

Material Loadingcondition

Angle of internal friction (), degree

Max. particlesize: 25 mm



QRF MS 42.68 42.45 42.06

SS 44.58 44.18 43.31

RBRF MS 44.83 45.07 45.72

SS 47.3 47.90 48.48

41.50

42.00

42.50

43.00

43.50

44.00

44.50

45.00

0 10 20 30 40 50 60 70 80 90 100

Particle Size (mm)

AngleofInter

nalFriction,

degree SS MS

Fig. 7 Variation in angle of internal friction () withmaximum particle size for QRF

0 10 20 30 40 50 60 70 80 90 100

44.50

45.00

45.50

46.00

46.50

47.00

47.50

48.00

48.50

49.00

Particle Size (mm)

AngleofInternalFriction,

degree

SS MS

Fig. 8 Variation in angle of internal friction () withmaximum particle size for RBRF

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Acknowledgments The authors gratefully acknowledge andthank the Rockfill Division of Central Soil and MaterialsResearch Station, New Delhi and the authorities of Kol DamProject, Himachal Pradesh, India for the support extended bythem. We also extend our sincere gratitude to all the authorswhose publications provided us directional information fromtime to time.

References

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41

42

43

44

45

46

2 4 6 8 10 12 14

Breakage Factor (Bg), (%)

Angle

ofInternalFriction

Degrees

80mm: MS - max. 12 kg/sqcm 80mm: SS - 12 kg/sqcm









Fig. 9 Effect of breakage factor (Bg) on angle of internalfriction () for QRF material

44

45

46

47

48

49

50

51

2 4 6 8 10 12 14

Breakage Factor (Bg), (%)

AngleofInternalFriction

Degrees










Fig. 10 Effect of breakage factor (Bg) on angle of internalfriction () for RBRF material

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Documents

Influence of Different Stress Conditions on Behaviour of Rockfill Materials