Void Ratio and Void Ratio and Shear StrengthShear Strength of Two Compacted Crushed Stones-1966

8/10/2019 Void Ratio and Void Ratio and Shear StrengthShear Strength of Two Compacted Crushed Stones-1966

1/25

Engineering

Experiinent

Station

TO

IOWA

STATE

HIGHWAY COMMISSION

V061f}

RAYHO

ANID

S H I E ~

S1 RIENG1M OIF

TWO

by

Fernando H. Tinoco Graduate

Assistant

Richard L. Handy Professor of Civil

Engineering

James M Hoover

Assistant Professor

of Civil Engineering

Contribution

No.

66-6

from the Soil

Research

Laboratory Project 516-S

Iowa Highway Research Board Project HR-99

Iowa

State

University

Ames

Iowa


2/25

1

VOID RATIO

ND

SHEAR STRENGTH OF

TWO COMPACTED

CRUSHED

STONESl

by

2

Fernando

H.

Tinoco Richard

L. Handy and James

M.

Hoover

ABSTRACT

Triaxial

compression

tests of two crushed

limestones

of

differ ing

highway

service records

indicate a

fundamental

difference

in their shear

strength

--

void

rat io

relat ionship.

Analyses

were

based

on

stress

C

.

C

:

J

C

C

.

C

I

-

>

.

C

l

>

:

J

.

.

I

>

0

I

>

C

C

c

.

c

.

0

I

I

)

Q

.

E

C

t

J

:

J

>

0

E

:

0

I

>

I

I

(

C

c

0

-

0

-

u

~

U

0

CJ

CJ

UJ

a::

a

UJ

>

I -

u

UJ

u..

u..

UJ

\

300

200

100

0

0.15

\

0.16 0.17

17

GARNER SAMPLES

Standard compaction

a Consolidation pressure

o Effective

pressure

0.18 0.19 0 20 0 21

0 22

VOID R TIO

Fig

6

Garner stone: effective

pressure

and consolida-

t ion

pressure

as

related

to

void

ra t io

0 23


19/25

- -

2

/)

0 750

18

GARNER SAMPLES

Standard compaction

w

w

a

49 C

w

0

a

47

45

0 700

____ ____ ..i........ J _ _ _ _ _ _ __ ___

0.15 0.16 0.17

0.18 0.19 0 20 0.21

MINIMUM VOID RATIO

Fig

7 Garner stone:

values

of s i n ~ ,

and

as

re la ted

to

minimum

void

r a t io

0 22

0 23


20/25

19

A similar extrapolation can be made for the Bedford

crushed

stone,

as

shown

in Table 3.

Table 3. Shear strength components of the Bedford

crushed

stone calculated

at e . = 0.

min

Degree of Compaction Cohesion, psi

Angle of

Frict ion,

deg.

Standard

Proctor

1171

36.5

Modified Proctor

1116

39.9

Calcite i s

also

the

predominant mineral of the

Bedford crushed

stone.

Von Karman

(1911)

performed t r iaxia l tes ts

on marbl.e at

very

high

cel l pressure,

up to 36,000 ps i and Bridgman (1936) and

Griggs

(1942)

performed high pressure

tes ts

on

calcite .

The envelopes

ob-

tained are

sl ight ly curved

and

the

mean

resul ts are

sunnnarized

in

Table 4.

Table

4 also shows the resul ts obtained

for

the

Bedford

material on

the

assumption that

the

fr ict ion angle

was

34.0, in

order

that

a

comparison could

be

drawn

with

the

above

quoted

authors

resul ts .

Table

4.

Shear strength

components of

calci te

for

a 80,000 psi .

Author

Von Karman

Bridgman

Griggs

Tinoco, e t . a l .

Tinoco,

e t . al .

Rock

Marble

Calcite

Bedford

(Std.

Comp.)

Bedford

Mod

.

Comp

. )

Cohesion, psi .

Angle

of

Frict ion,

deg.

4980 34

2990 34

1315

34

3868

34

The

implication

of

the

above

comparisons is

that

the

behavior

of

the

Bedford and Garner

stones

belongs in two

different

systems; the


21/25

2

Garner

extrapolates

to

pure sl iding f r ic t ion whereas the Bedford

extrapolates to

s l id ing

fr ict ion

plus

a cohesion comparable to values

found

in solid

rock.

he exponential shear stress-void ra t io

function

for the Bedford

would appear

to indicate

increased

cohesion

caused by increased

grain

contact

areas under

higher

pressures.

This

implies a compressibil i ty

of the

Bedford

stone par t ic les . Under repeated

loading,

sl ight in ter-

granular

shear

movements could perhaps cause

the

loss in cohesion,

since grains

would

rio

longer

be properly arranged

or

interlocked to

cause an

increase

in

contact areas

with

loading.

That

i s

repeated

compressions resu l t in densif icat ion

and

a

mass

action ra ther

than

a

point-contact building-block action of individual grains .

In

the case

of the Garner mater ia l ,

the shear stress-void rat io

function is l inear and

therefore

ref lec ts the state

of

packing

within

the granular system. he

fr ict ion

parameter i s therefore a measure of

the

in terpart icle

in teract ion ra ther than

the f r ic t iona l characteris t ics

of

the par t ic les . Thus most crushed stones,

unlike

the Bedford, tend

to maintain strength under repeated

loading.

ON LUSIONS

he

shear-stress-void

ra t io

function

is

an

index

to

the

behavior

of compacted

crushed stone

materials under shear. Two different

types

of

behavior

are

inferred: a) compression of par t ic le contacts under

loading,

increasing

cohesion

and

giving an exponential

re la t ionship

between

shear

strength and

void r a t io

and

b)

sl iding a t point

contacts


22/25

2

between

par t ic les

giving a

l inear

re la t ionship between

shear

strength

and void r a t io .

Behavior

(a)

apparently

is

not

stable

under

repeated loading,

since

shear

strength

is

gradually

los t . This

suggests a s tructura l

rearrangement of the

grains which

reduces grain- to-grain

contact

under

pressure,

and

therefore cohesion.

That is

the benefic ia l effect of

consolidating pressures

is

gradually

los t .

Thus

under repeated loading

the behavior

i s similar to that of a clay.

In

contras t ,

behavior

(b)

should

be

stable

under

repeated loading.

The difference in behavior

of

the two stones thus may re la te

to

the compression

and shear

character

of

the individual grain- to-grain

surface

contacts,

which

in

turn

should re la te

to

some

petrographic

characteris t ics of the rock.

ACKNOWLEDGEMENTS

The research reported herein

is

a portion

of

a project on ' 'Factors

Influencing

Stabi l i ty

of Granular Base

Course

Mixes under contract

with

the Iowa Highway Research Board, Iowa State Highway Commission and

Bureau of Public Roads, U.S . Department of Commerce

Appreciation i s extended

to the

following

organizations and per

sonnel:

to the

Iowa

Highway Research Board

and

Bureau of Public

Roads

for the i r

continuing support of th i s project; to

Mr.

Steve

Roberts,

Director

of Research, Mr.

Tom McElherne, Materials Engineer, and Mr. Ted

Welp, Geologist ,

Iowa

State

Highway

Commission, for their

valuable as

sistance and counseling;

and

to Dr. Turgut Demirel, Iowa State Universi ty,

for

his

advice,

in teres t and cri t ic isms.


23/25

22

REFERENCES

1.

Anderson,

A. A.

and Welp,

T. L. (1960).

An

engineering

report

on the

soi ls ,

geology, terrain

and

climate of Iowa.

Iowa

State

Highway Connnission. Ames, Iowa pp. 3-12.

2. Best , T. (1966). Private communication. Ames, Iowa.

3. Bishop,

A.

W. and

Henkel, D.

J .

0957,) . The measurement of soil

properties in

the

t r iaxia l tes t . 190 pages. Edward Arnold

Ltd,

London.

4. Bridgman, P. W.

(1936). Shearing

phenomena

a t

high pressures.

Proc.

Amer.

Acad.

Arts. Sci . , 71, pp.

387-469. In

Skempton,

A.

W.

(1960). Effective Stress in soils., concrete

and

rocks. Proc. of

Cpnference on Pore

Pressure

and

Suction:in Soi ls . Butterworths,

London, pp.

4-16.

5.

Handy, R. L. (1965). Quanti tat ive X-ray dif f rac t ion measure

ments

by fast scanning. Analytical

Techniques for

Hydraulic

Cements and Concrete, ASTM STP

395,

Am.

Soc. Testing

Matl ' s . ,

pp.

30-44.

6. Henkel, D. J . (1959) , The relat ionships between shear

s t rength ,

pore water

pressure and volume-change character is t ics of saturated

clays . Geotechhique, Vol. 9, pp. 119-135.

7.

(1960).

The

relat ionship

between

the

effect ive

stresses and water

content in

saturated

clays. Geotechnique,

Vol. 10, pp. 41-54.

8. Horn, H. M.

(1961)

. An investigation

of

the fr ict ional character is t ics

of minerals. Ph.D. Thesis. Department of Civil Engineering,

Universi ty

of I l l ino i s ,

Urbana.

9. Hvorslev,

M. J .

(1937). ueber

die

Fest igkei t

seigenschaften

gest8rter

bindiger B8den . (On the

strength

properties of

re-

molded cohesive soi ls) .

Ingeniorvidenskabelige

Skrif ter A. No.

45, 159 pages. Reviewed in Hvorslev, M. J . (1960) .

Physical

components of the shear strength of saturated clays. Research

conference on Shear

Strength

of Cohesive Soi ls .

Am.

Soc. Civ.

Engr. Boulder, Colorado,

pp.

169-273.

10. (1960) .

Physical

components of the shear strength

of

saturated

clays . Research Conference

on Shear Strength of

Cohesive Soils . Am. Soc. Civ. Engr.

Boulder, Colorado,

pp. 169-273.

11. Griggs, D.

T. (1942).

Strength

and plas t ic i ty .

Handbook

of

Physical Constants ,

Geol.

Soc.

America.

Special Paper,

No.

36,


24/25

23

pp. 107-130. In

Skempton,

A.

W.

(1960).

Effective Stress in

Soils , Concrete and Rocks. Proc.

of Conference

on Pore Pressure

and

Suction in Soi ls . Butterworths,-London, pp.

4-16.

12.

Karman,

Th.

Von

(1911). Festigkeitsversuche unter

allseit igen

Druck .

Ziet. Vereines Deutsch.

Ing. ,

55,

pp.

1749-57.

In

Skempton, A.

W.

(1960). Effective stress

in

soi l s concrete

and rocks.

Proc.

of

Conference

on Pore

Pressure

and

Suction

in

Soils. Butterworths, London, pp. 4-16.

13. Lambe, T.

W.

( 1958) . The

structure

of compacted clay .

Proc.

Am.

Soc. Civ. Engr. SMF

Div., Vol.

84, No.

SM2 Paper

No. 1654,

34 pages.

14.

Rutledge, P.

C.

(1947).

Review

of cooperative t r iax ial

research

program of the Corps

of

Engineers . Progress

Report

on

Soil

Mechanics Fact Finding

Survey. Waterways Experiment

Station,

Vicksburg,

Mississippi,

pp. 1-178.


25/25

a

3c

al

a l

I

a

I

2

I

+

a

I

1

2

I

e

c

I

r

cp I

r

c

1

Cz

s1

Sz

24

PPENDIX A

Symbols used

in th is paper

Effective consolidation

pressure;

i . e .

applied consolida-

t ion pressure less pore pressure.

Effective

major principal st ress

Maximum shear st ress

Effective

mean pressure or effect ive pressure

Equivalent consolidation

pressure

which gives void ra t io

e under conditions of normal consolidation.

Effective cohesion

Effective

angle of internal

f r ic t ion

Q I

3

Intercept

of

fa i lure l ine

for

CJ

e

0

a +a

1 3

Intercept

of

fa i lure l ine for ~ a _ . . . ~

e

0

I

3

Angle that the fa i lure l ine makes with

hor izontal

axis 0: V

Angle that the fa i lure

l ine

makes

with

horizontal

axis

+a

1 3

2

I

e

e

Void Ratio and Void Ratio and Shear StrengthShear Strength of Two Compacted Crushed Stones-1966

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Transcript of Void Ratio and Void Ratio and Shear StrengthShear Strength of Two Compacted Crushed Stones-1966