creep of sand

8/18/2019 creep of sand

1/63

T R

190

o

00

'

t

. . -

fachntcd

Report

190

C R E E P

O F F R O Z E N

S A N D S

by

Francis

H .

Sayles

September

1968

CONDUCTED

ro*

CORPS

OF ENGINEERS,

U.S.

A R MY

v

U.S.

A R M Y

M A T E R I E L

C O M M A N D

TERRESTRIAL

S C I E N C E S

C E N T E R

C O L O

R E G I O N S

R E S E A R C H

iE N G I N E E R I N G L A B O R A T O R Y

H A N O V E R , N E W

H A M P S H I R E

THIS DOCUMENT

HA«

SEEN PPROVCO

C OW

PUBLIC

NLf4M

«NO

SALE;

irs

DiJTHIOUTIOM »

UNLIMI

TED.

C

.

A

N

H

O

,

~ ®mmmm®

0


2/63

CRREL,

Technical R e p o r t

1 9 0

C R E E P

O F

F R O Z E N

S A ND S

by

Francis H . Scyles

September

1 9 68

CONDUCTCD

FOP

CORPS

OF FMGINEfcRS,

U.S.

ARMY

BY

U.S.

ARMY

MATERIEL

COMMAND

TERRESTRIAL

SCIENCES

CENTER

C O L O R E G I O N S

R E S E A R C H

i

E N G I N E E R I N G

L AB O R AT O R Y

HANOVER, N E W

HAMPSHIRE

THIS

DOCUMfcNT

HAS

»EEK

APPROVED

FOR PUBLIC ELEASE

AND

SMLKJ

T« DISTRIBUTION S UNLIMITED.

.-K**,~r—i /..-*....* .«^iifci

e**-viifM

:-*A;J>


3/63

PREFACE

Authority or

he

nvestigation reported

herein

s contained n

FY

961

Instructions

and

Outline, Military

Construction nvestigations,

Engineering

Criteria and

nvestigations

and Studies,

Investigation

of

Arctic Construction,

Creep of

Frozen

Soils.

This tudy

was onducted

or

he

Engineering Division, Directorate

of

Military Construction,

Office,

Chief

of Engineers, The program was ad-

ministered

by

he

Civil

Engineering

Branch,

Mr.

T.B.

Pringle,

Chief.

Mr. Francis

H.

Sayles,

Research Civil Engineer, Applied Research

Branch

carried

out he tudy

and

prepared

his

eport.

The

nvestigation

was

nder

he

general

direction

of Mr. K.A. Linell, Chief, Experimental

Engineering

Division,

and he mmediate direction of

Mr.

Albert

F. Wuori,

Chief, Applied

Research

Branch, Cold

Regions

Research and

Engineering

Laboratory

CRREL),

U.S.

Army

Terrestrial

Sciences

Center USA

TSC).

Personnel assisting

n

he

nvestigation

were SP Richard

Putnam and

SP

Richard O. Lunde.

Mr.

Robert

Bonnett assisted n he

esting.

This

eport

has

been

critically

eviewed

by

Professor

Clyde E.

Kesler

of

he University

of Illinois

and y

Mr. Frederick

. Sänger

of

USA TSC.

The author wishes o hank he eviewers

and

Dr. A. Assur,

Chief

Scientist,

USA

TSC,

for heir

constructive

uggestions.

Lieutenant

Colonel

ohn

E. Wagner

was

Commanding

Officer

/Director of

the

U.S. Army Terrestrial Sciences Center uring

he

publication of his e-

port and Mr.

W. K, Boyd

was

Chief Engineer.

USA

TSC s

esearch

activity of

he Army

Materiel

Command.

CITATION

OF

COMMERCIAL

PRODUCTS

S FOR

NFORMATION

ONLY

AND DOES NOT

CONSTITUTE

OFFICIAL ENDORSEMENT OR

APPROVAL.


4/63

Ill

CONTENTS

Page

Preface

Conversion

able

-

Summary i

Introduction

Definition of

erms

Review

x heory-

Testing

Apparatus

Materials 1

Preparation

and

reezing

of est pecimens 2

Creep

and trength

esting

procedure

4

Test

esults

4

Discussion--

3

Conclusions

6

Literature cited

7

Appendix

A. 9

ILLUSTRATIONS

Figure

1.

echanical

heological

models

2.

iew

of

four

reezing

binets

nside

40F

cold

oom

3.

ront of reezing cabinet

4. reezing

mold

5.

reezing

mold

charged

with

pecimens

eing

de-aired and

saturated -*

6.

neumatically

actuated hydraulic press

7.

onstant

tress

apparatus

8. ever-type

press

with

motorized moving ulcrum

0

9.

nconfined

compression

chamber

0

10. radation

curve,

Manchester

ine

and 2

11.

ypical Ottawa and

pecimens fter

esting

5

12. ypical Manchester ine and

pecimens

after

esting

6

13. ypical ce pecimens fter esting

7

14.

reep

ests,

Ottawa and

20-30),

1

5F

8

15.

reep ests, Manchester ine and, 15F 8

16.

reep est

on

ce

n

unconfined

ompression 9

17.

ime

vs

train,

Ottawa

and

20-30),

1 5F 9

18.

ime

s

train, Ottawa and 20-30),

25F-

0

19.

ime

s

train,

Ottawa and

20-30),

29F

0

20. ime

s

train,

Ottawa

and

20-30), 31F

1

21.

ime

s

train,

Manchester

ine

and,

15F 1

22.

ime

s

train,

Manchester ine

and, 25F 2

23.

ime

s

train,

Manchester

ine and,

29F

2

24. ime

s train, Manchester ine

and,

">1F

3

25. ebound and

classical

creep

curves,

Ottawa

and

4

26.

ercent of

strain

at start

of

ertiary

creep,

Manchester

ine

sand 8

27.

reep

ate

and ime, Ottawa

and 20-30), 31F-- 8

28.

reep ate and eciprocal

of

ime,

Ottawa

and,

31F

9

29.

reep ate and eciprocal

of

ime,

Manchester

ine

and,

15F

9

*£i


5/63

CONTENTS Cont'd)

Figure age

30.

reep

ate

nri

eciprocal

of

ime,

Manchester

ine and

at

various

emperatures 0

31.

tress, strain

and

ime,

31F 2

32.

ime,

factor

A, and

emperature

2

33.

actor and

emperature 3

34.

train

and

ime

comparative

curves, 15F 4

35. actor M nd tress 4

36.

train

and

ime,

15F

5

37.

train ate

at

ime

r,

and

tress 6

38.

emperature nd stress

or

unit

train

ate at

r

6

39.

ltimate

trength

and

ime

o

ailure,

Ottawa and

9

40. ltimate

trength

and ime o ailu/e, Manchester fine sand

- 9

41. ime

and

eciprocal of ultimate tress,

Manchester fine sand

1

42.

ime

and

eciprocal

of ultimate tress,

Ottawa

and

1

43. trength or

various conditions,

Ottawa

and

3

44.

trength or various conditions, Manchester

ine

and

3

45.

emperature, ß and

parameters

4

TABLES

Table

I.

Types

of deformations rom

ebounded

creep

ests,

frozen

Ottawa and 5

II. Strain components nd strain

at

critical points under nter-

mediate

tresses

26

III.

alue of

m

n

Vialov's

train

quation 31

IV. onstants or Vialov's train

quation

31

V.

Constants or train quation

37

VI. Long-term

unconfined

compressive trength 40

VII.

Constants

or q as determined rom Figures 1

and 2 40

VIII.

Percent of

nstantaneous

trength

oss

fter

application

of *

stress

2


6/63

I

ONVERSION

TABLE

9

in. 5.4

ft

0.48

Multiply y o obtain

°F

/9(°F-32)

C

r

K

mm

cm

sq

n.

.

4

5

16

q

cm

Ib/sq

n.

.070307

g/sq

cm

cu t

.0283168 u m

lb .45359237 g

qt

.94633

iter

,


7/63

SUMMARY

Unconf

ned

compressive

cieep trengths

na

strains

were

measured

for

rozen aturated Ottawa

and

20-30)

and

Manchester ine

and.

The

creep

ests were conducted

at

approximate

stress evels f

0,

35,

20

and

5%

of he conventional

ur.confined

compressive trength.

Testing empera-

tures

were 5 , 25, 29

and 1F.

It

was

ound

hat

he

unconfined

compres-

sive

creep

trength

of

he

rozen

and

an

e

predicted

using

Vialov's

strength ormula;

hat creep

strain

can

e

predicted

using wo

hort-term,

t 4 »

high-stress-level creep ests using «

=

ij

1/K ̂

predicted

using

. < * «

£[e/öo>+

if

+

€

that

oca."

train

can e

and

hat

or tresses

below he ong-term

trength,

the

strain ate

s

directly

proportional o

the

eciprocal

of ime during tress

action

until

complete tabilization

occurs,

(t = train ate

nour

after tress

s

pplied;

ime;

4 /

M-l)/M,

where M r

'

w

und

w

s a constant

or

ach

material

0;

emperature

n

degrees below reezing

point of

01

= tress at

water;

9

0

=

a

constant eference

alue

of ; a and Kare onstants;

* initial

nstantaneous

train.)


8/63

• CREEP

OF FROZEN SANDS

by

Francis H. Sayles

INTRODUCTION

The

design

of

table

tructures

n

permafrost equires knowledge of

the trength

and deformation

characteristics

of

rozen

oil.

Published mat-

erial

on he trength and deformation properties of

rozen

oil prior o 952

was f Russian

origin

and was generally

ncomplete

as

o

description of oils

and esting

procedures.

In 952 he ormer Arctic Construction and

Frost

Effects

Laboratory

ACFEL)*

of

he

.

S.

Army Engineer

Division,

New

Eng-

land,

published

eport

ummarizing

xperimental data

obtained

p

o

hat

time, including he

esults of

heir

nvestigations

ACFEL, 1952).

Since 952

the Russians,

notably

Tsytovich

and

Vialov,

have

published ather omplete

experimental

data

on

he

trength

and

deformation

properties

f

ome naturally

frozen

ilts

nd clays Tsytovich, 1954, 1958; Vialov,

1959;

Vialov

^

al.,

1962; Vialov

and Tsytovich,

1955).

In addition,

they

ummarized nd

ormu-

lated

heories nd

empirical

eqjations

elating trength and deformation of

frozen

oils

o

he

oil

emperature and duration

of he applied oad. Sänger

and Kaplar

1963)

published

deformation data and mpirical quations elat-

ing unconfined ompressive deformation nd ate f

deformation

o

applied

stress

nd emperature. This

nvestigation

ncluded

variety

of

oils,

tested

at

various

emperatures rom

about

8F

to

2F. Each

creep

est

was

imited

to

0

hours duration.

The

purpose

of

his

nvestigation

s

o

valuate

he

nfluence

of

empera-

ture

and tress on creep

and ong-term trength of aturated

rozen

ands,

and o provide

data

or

design

n

rozen soils.

This eport

with

ts

ppendix

presents

the completed

results

of the un-

confined

compression

ests

performed on

saturated Ottawa and

20-30) and

Manchester ine

and.

This

s

only he irst

phase

of he urrent nvestiga-

tion

which ncludes: (1) unconfined ompression creep ests

n

Ottawa and,

Manchester

ine

and, New

Hampshire

ilt and clay

and

2)

riaxial

creep

testing of

Ottawa

and.

DEFINITION OF

TERMS

Instantaneous

trength

s

he

maximum

tress determined y oading he

test

pecimen

at

constant

train

ate

of

0.

033/min.

Long-term tren

gth

s

he

maximum

tress

hat

he rozen

oil

can

with-

stand ndefinitely and xhibit

ither

a

zero or

continuously

decreasing

strain

ate with irne.

*

ACFEL was merged with he ormer U.S. Army

Snow,

Ice and Permafrost

P.esearch Establishment SIPRE)

n

961 o orm he U.S.

Army

Cold Regions

Research

nd Engineering

Laboratory.


9/63

L

REEP

OF

FROZEN

SANDS

Coti

v

e.itional

tra

i

n s he

xiai deformation

divided y

he

original

ength

of

he pecimen

e

c

AL/L

0

)

True train is

he

xial

deformation

t given

nstant of

ime

divided y he

actual

pecimen ength t ha' ime ir erms of

conventional

train,

e

t

ln(l/(l-e

c

)].

Incipient ailure

of a

est

pecimen occurs when he train ate tarts o n-

crease

with

ime start

f ertiary creep),

after period of

minimum

strain ate point

, Fig.

Z5).

Failure

of compression est

pecimen

of

rozen and means continuous

loss

f esistance o oading,

after

eaching

peak.

It occurs

y

either

an

abrupt

brittle-type

racture

or

plastic

low

accompanied

by

issur-

ing nd often nding

n

upture of

he

pecimen.

Elastic

def

ormation

disappears ntirely

upon elease

of

he

tress

which

caused t.

Delayed

lastic

deformation

is

lastic

deformation

hat equires

noticeable

period

of

ime

o occur

r

ecover.

Theoretically,

elastic

deformation

velocities

lower

han

he

peed

of

pund

are

delayed.

In

his

eport

delayed

lastic

ecovery

s lower

han

he

peed

f

ound periods y

hours

nd days.

Viscous

deformation

s

n

rreversible

deformation

n

which

he ate

of de-

formation

depends

pon he

pplied tress.

Plastic

deformation

s

n

rreversible

deformation

which

s

ndependent

of

time.

Stress atio,

Applied

constant

tress

'"instantaneous"

trength

REVIEW OF THEORY

Deformation

Vialov and

Tsytovich 1955)

xplain

he

physical

process f creep

n

rozen

soil

y

considering he

ondition

of

applying

constant

ead

o

a

rozen

oil

mass. This oad

oncentrates

he tress

between

he oil particles t heir

points

f contact

with

he

ce,

causing

pressure-melting

of

he

ce.

Differences

in water urface

tensions

re

produced

and he

unfrozen water moves o e-

gions

f ower tress

where t

efreezes.

The

process

f ce

melting and water

movement

s

ccompanied

y

a

breakdown

f

he

ce

and

structural

onds

f

he

soil

grains,

the plastic

deformation

of

he

pore

ce and eadjustment

n he

particle

rrangement, the esult

f which s

he

ime-dependent

deformation

phenomenon of creep. This

tructural

deformation

eads o a

denser

packing

of he oil particles, which

n

urn causes trengthening of he material due

to he

ncreased number

f irm

ontacts between

oil

grains

nd

ence

an

n-

crease

n

nternal

riction

etween grains ACFEL, 195.2) .

During

his

process

there s

lso

weakening

f

he

tructural

cohesion

and

possibly

n

n-

crease

n

he

mount

f unfrozen

water

n he

rozen oil particularly

n

ine-

grained

oils). All

of

his

ction

s ime-dependent.

If

he

applied

oad

does

not

xceed

he

ong-teim

trength f

he

rozen

oil, then he weakening

process s ompensated

y

he

trengthening; the

deformation

s

amped,

i.e.,

the

ate

of deformation

decreases with

im

. However,

if

he

applied oad

x-

ceeds he

rozen oil

ong-term

trength,

the breakdown of

nternal

bonds s

not

completely compensated

y

he

trengthening

process

nd

hen

he

ate

f


10/63

CREEP

OF

FROZEN SANDS

deformation ncreases with

ime,

resulting

n

undamped

deformation which

eventually

develops

nto

plastic low

nd

nds

n

breakdown f

he

rozen

soil

tructure.

Experiments* how

that

he deformation characteristics

f

frozen

oil

are imilar o hose depicted

y

he classical

creep

curve or metals Fig.

1). As . n id

n

tudying hese

deformation

characteristics, Vialov nd

others .

ve proposed mechanical heological models.

In

Figure , Vialov's

model 1959) with the various omponents labeled, depicts he irst nd

second tages

of creep,

but

does

not

nclude

he nitial plasfic deforma-

tion or hird tage f creep, i. e. the visco-plastic low

preceding

complete

collapse

f

he

material

tructure.

RUPTURE

DEFORMATION

PLASTIC

D

ELASTIC®

TIME

CLASSICAL

CREEP C U R V E

If

' S P R I N G

Elastic d*f

;

I I

l i . i l

lill I

IIOH

< * >

km

(£) VISCOUS, Dojhpot

^BLOCKING

, /

DEVICE*

I

*

Newtonian iquid

® Spnng-dasnpot Voiot-K«lvin ltmtnl)

Visco«loitic

ef

*

Blo^hmq ' ;« lid» whyn ore«

icesds

a

imit

L

'4)

V I S C O US ,

Daihpot

®VISCOPLAST

iZA

M E C H

/UX

L

M O D E L

Vltlf

Viulov

A

MODIFIED

VIALOV

MECHANICAL MODEL

Figure . Mechanical

heological

models.

*

Vialov,

1962, Fig. 27, Translation page Oi)

for ilt nd clay nd

Figures

14

and

5

f

this

eport

for

aturated

Ottawa.

*nd

and Manchester

fine and.

*W»»JM

m*mwMwao


11/63

4 REEP OF FROZEN SANDS

In

Figure

1

Vialov's model s modified o

nclude

plastic

characteristics.

The arious lements n he

model re abeled o

correspond

o

he ppro-

priate

ection

f he lassical reep curve.

In he

modified

model, the nitial

plastic

deformation s

represented y

rictional

lide.

An

ir

ap

this ap

may ave inite

alue

r e ero) between he

slide nd he Voigt lement per-

mits displacement

o ake

place

efore viscoelastic movement

begins. If

he

load

xceeds he

yield

point

f

he

material,

the

lide will mo'e

o educe

r

close he

gep, thus producing

nstantaneous plastic eformation. When

he

load s

emoved,

this part f

he deformation s ot ecovered. In

ome

n-

stances

elastic

deformation may

ccur without

eaching he

plastic

imit

upon

loading,

thus

producing

purely elastic

ei

or

mation.

The

iscoelastic lement

is he Voigt or

Kelvin lement which contributes delayed elastic ffect. The

dashpot

f element epresents he

iscous portion

f

he

curve.

The fric-

tion lement blocking device)

equires he ctivating orce o each

certain

magnitude

before

plastic

nd

iscous

deformation

an

ccur. To epresent

viscoplastic

low

a

pecially

haped dashpot s hown

o

permit

n ncreasing

rate f

low

as he material pproaches ailure. The

modified

model

s

oo

complicated

or practical numerical nalysis

nd

s merely hown o llus-

trate

he

eformation

omponents.

Streng'

Strength

of

rozen

oils,

as with nfrozen

ohesive oils, depends

pon

both

he ohesion

and

he

nternal

riction

f he omponent

materials. In ro-

zen oils he ohesion

component

according

o Vialov and Tsytovich l°55)

can e

attributed

o:

(1)

he molecular

orces

f

attraction

between

olid

particles;

(2)

physical

r

chemical

cementing

f

particles

together;

ard

(3)

cementing

he oil particle

by ce ormation n he oil

voids.

Cementing

by

ce

s he result f

he onds

between

he

c?

crystals nd he

oil

particles

even hough

he

oil particles

aie

urrounded y ilm f unfrozen vater.

This nfrozen water s nder

he

nfluence f

molecular orces f

he oil

particles

nd

t

eems

possible

hat

he trongly attached

water

molecules re

capable

f

ransmitting normal

nd

hear orces

between

olid

ce

and olid

grains. The ce

cohesion

depends pon

he mount

f

ce,

the

trength

of he

ice, and he rea of

ce

n ontact with he

oil

particles,

each f

which de-

pends upon

he

oil

emperature.

The nternal riction

depends

n he

oil

grain

arrangement,

sizes,

distribution,

shape, and

n

he

number

f grain-to-

grain

contacts.

It

s

mphasized hat

ce

cohesion

s

he dominant trength

factor in

frozen

oil

even

though

internal f riet i o n

becomes

ignificant

in

dense

sands.

TESTING

1121

The

unconfined

compression

test

was chosen

as

the primary

test for

this inves-

tigation

because

o f

its simpli-.ity

and

its

suitability

for

adoption as ield

aboratory

test.

In ddition

o he

compression est, sonic ests

nd

ball penetration ests

were

performed.

The onic

ests

were

xploratory

n

nature with he primary

purpose

f esting

quipment and

developing

echniques.

Both

ests

howed

some

promise

but he

allotted

ime did

not permit

continuance until echniques

could e

perfected.


12/63

CREEP OF

FROZEN

SANDS

APPARATUS

Freezing

aci

l

ities

Soil

nd

ce

pecimens

were

rozen n

reezing

cabine'.s

mounted n

USA CRREL walk-in ype cold nnm maintained t 40F+1F. The rees

ing

cabinets used in

this project

(Fig.

2, 3)

were

quipped with

hinged

covers

o n

op and

hermal-pane window

n he

ront.

Insulation vas provided

n

the ides nd over. The

bottom

f he abinet consisted f r. xpanded

metal grill

allowing he

bottom

f

he

pecimens

o

be

xposed

o he

ÜF

"oom

emperature

during reezing

while he ops

f

he

pecimens

were

subjected

o

he

desired

reezing

emperature.

The

reezing

cabinet

was

cooled

y coils mounted n ts ides nd

back

wall,

from

3

n. above

he

bottom o

he

op

of

he cabinets.

The abinet emperature could be controlled o wituin

0.

5F y means

of

heating

coils

ocated

n

he air tream f

he

air circulation an. The

heat upplied

was egulated

y

a

Bayley emperature controller

Model

22.

De-aired

water was upplied

o he

bottom

of he

pecimens

uring

reezing

by

means

of

an

external

eservoir.

Figure . View of our

reezing

cabinets

nside

40F

cold

oom.

••-';■ -•< }«j£.


13/63

REEP OF ROZEN ANDS

Figure . Front

of

reezing

cabinet showing

reezing

mold

in position

with

hermocouple eads o

he

center pecimen.

The

bimetallic hermal-regulator s hown

o

ight

of view-

ing

window.

Freezing m

old

The reezing mold Fig. 4,

5 )

consisted of Plexiglas block 7 /4 n.

square

and

n.

thick,

through

which

5

3-in.

diam holes

were

bored.

Each

hole

was itted with

plit

leeve

aving

wall hickness of

about

/8 n.

to

permit pecimen jection rom he mold without ubjecting he pecimen

to he jection orce. The

op

and bottom of he

mold

were

overed

by /2-in.

thick

aluminum

plates ealed o he

mold

block

with /2-in. soft ubber gas-

kets.

When he

reezing mold

was

ssembled,

an

xpanded metal creen with

1/2x1

4-in.

openings,

a

200-mesh

bronze creen

and

muslin

mat

were

placed

t he

op

and

ottom f

he

mold

block o

etain

he unfrozen

oil

peci-

mens

n he

cylinders

nd

o act

as

ilter.

Loading quipment

Three ypes of oading devices were used n he esting program o accom-

modate

he

different

trength nd

eformation

haracteristics of

he

rozen

sands.

Tests o determine

he

nstantaneous ompressive trength and hort-term

creep trength

of

rozen

oils with

elatively

high esistance

were performed

in

20,

00U-lb

apacity air-actua^d

ydraulic

press

Fig.

6).

Loads

were

applied

o he est pecimen y means

f

an

unconfined est chamber placed n

the

press.

The

press s apable of head movement ates up

o

8 n.

/min.

For

reep

ests,

vibration-free

constant

oads an

be

maintained

y

he

hy-

draulic press or

xtended

periods i ime within of

he applied oad

or

loads

greater

han 000 b.


14/63

CREEP

OF FROZEN

SANDS

Figure

a. Empty

reezing

mold howing

projecting

plit

i

eeves.

Figure

4b. Fr

_.?zing mold illed

with dry and howing

plit

sleeves. Mold

s

upported

n

jection

rame.


15/63

CREEP OF

FROZEN

SANDS

Figure

. Freezing

mold

charged

with

pecimens being de-

aired

and

aturated.

Figure

. Pneumatically actuated ydraulic press.


16/63

CREEP

OF

FROZEN

SANDS

Creep

ests n

which arge

deforma-

tion

ccurs were

performed

on

a

con-

stant

tress

press

capacity

4000

b)(Fig.

7).

This

press eatures

programming

cam hat

maintains onstant axial stress

to

within % of

applied

tress

n the est

specimen

during

deformation.

The

oad-

programming

s

based

on

he

assump-

tions

hat

he

cross-sectional

area

of

he

specimen

emains

niform

hroughout

ts

length

during

deformation,

and

hat he

volume

emains onstant

hroughout

he

test.

Long-term

reep ests esulting

n

small

deformation

were

performed n

a

lever-type press capacity 2000 b) Fig.

8). As he ample deforms,

the

eight

of

he ulcrum is djusted

to

maintain

he

loading

level

approximately

horizontal.

Test

chamber

The unconfined compression chamber

in

he

hydraulic press Fig.

9)

s basically

a

rame

with

a

eveling

base

pon

which

the est

pecimen ests. The oading

pis-

ton mounted n ecirculating ball

bushings

provides base plate or he oad measur-

ing

ransducer.

This

ransducer

s

n

direct

contact

with

he

op

spherical sur-

face

of he est

pecimen

nd

cap.

This

arrangement permits

measurement

of

he

load applied

o he

est pecimen

at

ny

time.

Average

deformations

re

meas-

ured

by

wo

inear

motion

potentiometers

mounted

diametrically

opposite

ach

other n

he

Circumference f

he oad ransducer.

Load

and

deformation

measurements

All oads

pplied

o

est pecimens

n

he

hydraulic nd

onstant

tress

presses were

measured

with

Baldwin-Lima-Hamilton

oad

cells aving

appro-

priate

oad

anges.

Hydraulic

press

oads

were

measured

using

he

oad

ells

with

eadout

o n

one channel

of

Leeds

nd

Northrup

Azar

G-type

X-X

ecorder.

After

calibration,

loads

were

measured

continuously

o

within

. 0% of

he

applied

load.

Average axial deformations

of

est

pecimens n

he

hydraulic

press were

measured using wo carbon-strip, infinite-resolution, resistance-type inear-

motion

potentiometi

rs

mounted diametrically

opposite ach

other

on he oad

cell see Fig.

9), and

movements were

ecorded

on

one

channel

of

he

and

recorder. Using

calibration

charts, deformations were

measured

o

within

0.0025 n. for movements ess han 0. 25 n. and .005 n.

for

movements

greater

han

0.25

n.

Figure

.

Constant

stress ppa-

ratus howing programming cam

and

oad measuring ystem.

fc&Sä***^


17/63

CREEP

OF

FROZEN

SANDS

a

c

o

d£

E

o

u

-

o

u

c

-a

ID

i

o

El

c

3 o

E X

_e

C

>

O

£

-a

o

N

0

0

£

*

m

in

a;

-,

I- ,

a

a

>

a -

3

M


18/63

CREEP

OF

ROZEN

SANDS

i

Cons

tant-

str

e

ss-a

p

paratus oads

were

measured

with

he oad

ell

nd

read manually using B-L-H ype

N

portable train ndicator.

Loads

were

determined ccurately

o

within

.3% f he

pplied

oad.

Deformations were

measured sing

dial

ndicators

with

1/10,000

n. gradations

nd

ensitivity

of 2/100,000

n.

(See Figure or

arrangement

o f oad ell nd dial

indica-

tors.

)

Constant

oad

ever-type-press oads were determined y omputing

he

hanger weights sing he

ever

arm

ratio. The

oad

pplied o

ach

pecimen

was

hecked y placing

a

oad cell

n

he pecimen est space nd

reading

the

oad

with

he

anger

weights n

place.

Deformations were measured

using

he

ame

ype

o f

extensometer

s

was

sed

in

he

onstant

tress

appa-

ratus

see

Fig.

7).

Temperature

control

Test emperatures

f

25F and

ower

n

he walk-in

old

room

were

on-

trolled

o within ±1F. To damp emperature luctuations o

ess han ±0. ÜF ,

tests

were conducted

n

nclosures

onstructed

f

n.

thick

igid ype n-

sulation

Sty

rofoam).

Test

emperatures

bove

25F

were

controlled y heating and irculating

air within he

nsulated

est nclosures. Each est

pecimen

was oused n

split Lucite ylinder

o

reduce

temperature

lue

tu

a

t'ons f

he air surrounding

it.

Heat

was

upplied

y

ight ulbs

mounted n

he

an

air-stream.

The em-

perature

was

egulated

y

mercury-column-type hermoregulator which

activated

elay

o upply

heat upon

demand.

Air emperatures

within

he

Lucite

nclosures

urrounding

he est peci-

men

were held constant

well

within

±0.

IF

of

he desired

emperature.

Tempera

t

u

r

e

measurem

ent

s

Temperatures

5F

nd ower were

measured

o he nearest

. SF

with

mercury hermometer placed within

he

nsulated nclosures.

Inside he

Lucite

nclosure hermistor ensed

he emperature f

he air urrounding

the

est

pecimen

and

the

readings

v.ere

recorded

very

1.2S

min

on

I

l~

point nd

ype ecorder,

to he

nearest

0.

IF Test

emperatures

bove

25F

were

measured o

within I). F

sing

he

ame

ensing and recording

y.

tern

ut

with

ncreased

ensitivity.

Thermistor

eadings were hecked aily

using manually operated

Wheatstor.e

bridge. Cold-room

emperatures

out-

side

f

nclosures)

were

recorded

ontinuously.

MATERIALS

Ottawa and

20-30)

and

Manchester

inti

and

were

ested.

Ottawa

sand

represents nearly dealized granular soil.

Manchester ine sand

i. ,

a natu-

ral

sand

with

uite niform

gradation;

it

s

finer han

Ottawa and (see

Fig.

0

for gradation).

A

imited

number

f

ce pecimens rozen

nder

he

ame

onditions

s

those

or

he

oils

were ested s correlation

material nd

o

btain

ce-test

data using

he

ame esting

quipment.

Ice-specimen densities

were

ess

than

hat or

olid

ce

oecause f

air

entrapment

during

reezing. (See Table

AIII,

App.

A,

for

densities.

)


19/63

12

CREEP

OF

FROZEN SANDS

U

STD

SIEVE

SIZE

NO 40

O

200

I

*

> -

m

z

Ui


20/63

CREEP OF FROZEN SANDS

After aturation, the pecimen-charged moid was laced n he reeü-ig

cabinet. Spaces etween he

ides

f he

mold

nd cabinet

were

nsulated with

granular cork. After emoval f he

op

mold cover de-aired water upply

was onnected o

he

bottom

of the

mold

o

permit

pecimen

reezing n n open

system.

In

his

rrangement he bottoms

f

he pecimens were xposed o

40F with

a

ree water upply,

and he ops were xposed

o

cold circulating

freezing

air. The

ate

of

progress f he

2F

sotherm

was determined

y

means

f

hermocouples paced

in.

apart

along

he vertical axis of he en-

ter

pecimen.

Soil

samples were

rozen

within

period

of

days,

i

e. the

average ate

f

rost penetration was

1

IZ

n.

per

day.

In

reezing ce amples he procedure

was

imilar

o

hat outlined or

soils.

owever,

o

educe

ntrapment

of

air

bubbles

n

he

ce

he

ate

of

freezing was educed

o

approximately

/4

n.

per

day.

To

emove

he

rozen

pecimens rom he

reezing

mold,

the

mold

was

clamped n pecially constructed

rame

and

ach

pecimen was jected y

pressing

against

he

plit

leeve

using

hydraulic

ack with

n

ejector

plate.

The

jector plate

diameter matched

he

mold bore

nd

ad

aised

outer im

that permitted ejection of he

pecimen

n

he leeve

without

oading he peci-

men.

The

plit

leeve was

emoved rom he

jected

pecimen

y

xpanding

its diameter with

a

hin blade nserted nto he plit.

Tri

mm

ing

After

emoval

of he split leeve, the pecimen was

nspected

or mper-

fections and

cut

o

approximately

a

6-in.

height.

Rough

cutting was

ccom-

plished

with

a

hacksaw

and

wooden

miter

box.

The

nds

were

quared

using

a

special case-hardened vee-shaped miter box and arious gradations f wood

rasps

nd

teel

iles.

After he

pecimen

nds

were

rimmed

o

inal ength,

the dimensions were determined

by

measuring he ircumference at he

op,

midheight, and bottom) and

ength

at ix ocations round he perimeter) o he

nearest /1000

n.

Variations

n

pecimen

ength

ai

ound

he circumference

were within

0. 005

n. of he verage xcept or bout

J pecimens with varia-

tion

up o 0.

01

n.

of

he

average. The diameter varied ess han 0.

003

n.

along he

pecimen

ength.

The olume of ach pecimen

was

determined y ubmergence n

iquid

isooctane 2,

2 ,

4

rimethylpentane) at

20F.

After

olume determinations

were

made,

Ottawa

and

ample

nds

were

capped

with

a hin ayer

of

ce

o

void ocal

tress

oncentrations

t

he

ela-

tively arge and

grains

n

contact with he

oading

caps. The

capping

was c-

complished

y

pouring

ayer

of

2F

water

on

lat

glass

plate,

then

etting

the pecimen nd

on

he

plate

nd

llowing

he

water o reeze o he

pecimen

in he cold oom. The glass plate was emoved y

gently

warming he outer

surface of

he

plate.

It was ot onsidered necessary o ap Manchester ine and pecimens with

ice

ince

he ine

oil

grains

provided

a

mooth

contact

urface

or

he oading

caps.

All

pecimens

were

ealed

n

circumferential

ubber

membranes

nd

metal

end caps

or

esting.

Storage

nd

empering

Prior

o

preparation or esting, the pecimens

sually

emained

n he

sealed

reezing mold.

Occasionally

t was

necessary o

ject

several

pecimens


21/63

1 -1

CREEP

OF FROZEN SANDS

in

dvance

f

preparation

or

esting. Those

pecimens

were ealed

n

ub-

ber membranes

nd

emporary

nd

aps,

then

ealed n plastic ags

with

crushed

ce o liminate ublimation. No change n

pecimen

weight ould

be detected n

weighings

f

elected

specimens

before nd

fter

storage.

Storage

periods

id

ot

exceed

6

weeks.

Before

esting,

all

specimens

were

stored t

the

est emperature

or

minimum

of 8 ours.

The required

empering

ime

was

hecked

sing

hree

thermocouples

mbedded

t he

midpoint

and

quarter points f

he

xial

eight

of ontrol

pecimen. This heck

howed

hat 4 ours was ufficient

ime

for he

sp-cimen

o

reach

quilibrium t he est temperature.

CREEP AND STRENGTH TESTING PROCEDURE

,eh

est

emperature

eries

f

compression type ests

was

on-

first

determining

he instantaneous"

trength* of

he

rozen

oil

-l

* .u

r

.

.

._„.„

.. .. ~. ->

.

At

acl

ducted y irst oeiermimng ne

instantaneous

sirengin--

i

me

rozen on

or ce

nd

hen performing creep ests t educed tress evels. Each est

series ncluded onstant stress nd onstant oad compression ests per-

formed at stress evels f

approximately 0, 35, 20, 10 and .5'%

stress

ratio, p) of

he

verage nstantaneous

trength.

One

est

eries was onduc-

ted

t

ach

f

he

ollowing

est

emperatures: 15 ,

25,

29

nd

1F. All

com-

pression ype ests

were

performed on pecimens .8 n.

in

diameter y n.

high.

Whether

onstant-stress

r constant-load ests

were

performed de-

pended pon he

magnitude

f he

pplied

tress nd he xpected deformation.

Constant

oad

ests

were

sed

or

igh

tress

nd

or

mall

xpecied

dafor-

mation at

ow

stresses,

while

onstant

tress

ests

were

performed

at

nter-

mediate tress

evels i.e.,

in

he ange

of

15

o

0%)

where

he

deforma-

tions were

xpected

o e arge.

The

compression

creep

est

n

ach

pecimen was performed y irst

applying eating

oad of

approximately

si

o

he

pecimen

o

nsure

posi-

tive ontact between

he

est

pecimen

nd

omponents

f he

oading ystem,

a

we

ive Luiiidv.i

uciwceu tue i

c

•

i

»(JCLUMCII

anu

components

ui

nit* loauiug

&y

bitin,

nd

hen

pplying

he est

oad

n

ess

han

ec. Instantaneous

trengths

were

determined

y

moving

he

oading press ead

gainst he pecimen t

rate

f 0.2

n. per min strain ate

f

,033 p?r min). After ach

est was

completed,

photographs

were

aken

of

he

est pecimen

see

Fig.

11-13

oi

typical specimens)

and

wate-

ontents

were

determined.

TEST

RESULTS

Figures 14-16

how

ypical time-d

e

formation

urves

(Ottawa

and,

Man-

chester ine and

and polye rystal line

ce)

produced

directly

rom data

or

each

pecimen subjected

o

he nconfined

ompression

creep est. The

ime-

strain urves

n Figures 17

hrough

0

and

Figures through 4

ummarize

the

data or Ottawa sand

nd

Manchester ine sand respectively. (Where

more

than one pecimen umber s shown o n

ingle, curve, the

urve represents

the verage

f

he urves btained

or

pecimens ndicated and

he

vertical

bars ndicate he total ange of

values. )

A

ummary

of

ndividual

pecimen

data

s

hown

n

Appendix A.

*

Instantaneous"

strength used

erein

s

he

maximum

trength determined

by oading he est pecimen t constant train

aif f

0.03

3

per

min.


22/63

CREEP

OF FROZEN

SANDS

15

a.

Brittle

ailure n nstan-

taneous trength est. Temp,

25F,

e-0. 58.

OWS-51

b.

Plastic-shear

failure

at

815

psi (63.5% of instantaneous

strength). Temp,

5F,

e

=

0. 60.

c. Specimen ubjected o

Z O O

psi

13.7%

nstantaneous

trength)

for 501

hr

t

25F;

e

=

0

60.

figure 11 .

Typical

Ottawa

and

pecimens

fter

esting.


25/63

18

CREEP OF ROZEN SANDS

0

00 00 00 OO

000

200

I, IME e

Figure 4. Creep ests in

nconfined

compres-

sion,

Ottawa and ZO-30), 15F.

r

'

'

1

T "

MFS

2 v, 50 p» i

i

003

-

T

O

I 00?-

K

o

li.

Id

o

0 01

_MFS

1,

200 ps i

s-

m

r

MFS

7S,

150

p» ,

1.

1

1

400

600

800

hr

2

0

I

0-

JMFS

92

1

9

75

pn

|

—

T

-|

~-

-

I—

.1

..

/̂MFS 75V

_̂̂ _̂ *-̂ ^

560 pii

11

30

m m

Figure IS.

C

reep tests

in

unconfined

compression,

Manchester ine and, 15F.


26/63

CREEP Or

FROZEN SANDS

1 9

1C £ fcV, 160 PI

(595%)

ICt

5V,93p«./

CE

.34p.t

(35%) 1

20X1/'

IC E 14,5

p»i(>M02\)

__

i

zo'

300

4 00

I,

IME r

b

Figure

16 .

Creep est

on

ce in

unconfined

om-

/ est tress

pression.

p = stress ratio

- .

r-

.

'instantaneous

trength

016

012

0.08

a:

0 04-

~r

~r

RANOE

OF

VALUES

600

00

000

t,

IMC

r

Figure

7 .

Time s train, Ottawa and 20-30), i5F.

1200


27/63

< J0

CREEP

OF

FROZEN

ANDS

0

08-

0 04

-OWS 3

a

56,

90

ps i

(60%)

'-

-SPECIMEN

TWISTED O W S 29V)

INSTANTANEOUS

STRENGTH

1460 ps i

OW S

2J.

1IV8 32V, 200 pn 15%)

OW S 8, 180. 19c,

A

20o, SOpli

(4X)

800

1200

TIME

1600

hr

_1 _

2000

400

Figure

8.

Time

s strain, Ottawa and

20-30),

25F.

OW S

Bl.84,86

100

775

ps i

(̂ «60%)

004-

INSTANTANEOUS

STRENGTH

1320

pn

OW S

4

99, 100

pti

(8 )

JL

800

hr

1000

200

Figure 19 . Time

s

train,

Ottawa

and

20-30),

29F,


28/63

imHMiHnMiMOTwnn

CREEP

OF

FROZEN

ANDS

Zl

U 16

I

1

1

0 1?

OW S 34,139,119 8 15 2

150

n *>

20%}

INSTANTANEOUS

STRENGTH

74« p..

0

08

-

[

/

- O W S 136, 38 .

t

42

26C >

135%)

-

/

- O W S 0IV, 02V

a

16 V

400

ps i

(54%)

■

0 04 -

/

-

Z .

W S 121, 22 8 25

'

80

pjr

11%)

"~

ows

13 2

140

»

4

3

20

pii (2.7%)

.

—

i i

400

600

TIME

BO O

hr

1000

Figure 20.

Time

s

train,

Ottawa

and

20-30),

31F.

1200

~ <

0.8-

.

0

4

-

M ^S

84,89

3

92

57a ti

(?

■ 35%)

. M F S

85,87,

94

a

5

1660

si (60%)

INSTANTANEOUS

STRENGTH

2790pn

MFS 72V

1V ,

50

pti 1 2 %)

T

600

00

00

t,

IME

Figure 1. Time s train,

Manchester

ine and,

1

5F

400

hr

te*iÄ l̂äij


29/63

IL

CREEP

OF FROZEN

SANDS

06

. 0.4

-

0

2-

MFS

50,64 R

1199

psi

(P-60V.I

M FS

1,52

3

694 li 35%)

20

1

/MF$ S?V, 5H V

4

67

V

400 pn (20%)

INSTANTANEOUS

STRENGTH

2000

pii

M FS

9 0,

60

li 8%)

40

~r

60

TIME

1^

80

—

1

1 00

1 20

Figure 1. Time s train, Manchester ine and, Z5F.

06-

04

M FS 4,19 8

23

77: »i

P-57%)

MF S

25,35

8

0

470 ps, 35%)

-i

/MFS 29V

a

1 V

265 pn

(20%)

INSTANTANEOUS

STRENGTH

1240 pn

MFS 30,38

,45

8

48,

00

p»i

(74%)

i —i 1

'

r~

an

,n

0

00

?0

O

TIME

«n

hr

Figure 3. Time s train, Manchester

ine

and, Z9F


30/63

U P I I|1WW

CREEP

OF

FROZEN

SANDS

23

0 08

I FS 21V

41 V

/

Ü0 pst ̂ --35%)

M FS

7V

a 42V

160

IP

(20%)

INSTANTANEOUS

STRENGTH

805 PJI

JMFS 4V

6V

150

psi

(18

8%)

ME S

5V

V, C

ps i

(9 9%)

Figure 4. Time s train,

Manchester

ine

and,

3IF.

DISCUSSION

Strain-time data

Creep

data presented

as deformation

s

ime

curves are

he

primary e-

sults of his

nvestigation

and,

with

he

xception

of

he

instantaneous" tress-

strain

curves,

are he

basis

of

all

he

urves

eported

herein.

Typical ime-

deformation curves or

ands re

hown n Figures

4

and

5.

From hese

curves, true "logarithmic"

r

"natural")

strains* were

computed by

subtract-

ing

est-machine

calibration values rom he deformations nd

adjusting

he

constant

oad

est alues o

a

constant

stress

basis.

Typical ime-strain

curves

are

hown n

Figures

17

4.

Deformation

s ime, and

strain

s ime, curves

or

ach

emperature

can

be

grouped

according

o

hape.

The

curves

or ower stress

atios 0% )

approach straight

ine

with elatively

mall

deforma-

tions

prior

o

ailure. Figures 17

o 0 Ottawa and) and 1 to

24

Manchester

fine

and) are

ets

of

average

train

s

ime

urves

howing he

hree

differ-

ently

haped

curves.

The

ow stress

atio group of

curves

onsisting

of

nstantaneous lastic,

time-dependent

elastic, and plastic

omponents epresents trains

or

defor-

mations)

esulting

rom tresses maller han he

ong-term trength f

he

frozen oil. The

various

deformation

components

re abeled

on he

deforma-

tion

ebound

curve

n Figure 25a.

The

otal maximum ong-term train

of

he

*

True

train n

/(1-e

c

where

he

conventional

train c AL/L

0

= xial

deformation/original

ength.

t See

page

or

definition of erms.


31/63

Z4

CREEP

OF

FROZEN

ANDS

specimens

ested

did

not xceed

.

Ü 5

nd

. 0

n.

in,

for Ottawa and

nd

Manchester

ine

and, respectively.

Ten

ebound ests

performed

on

rozen

Ottawa and

ndicate

hat he

otal

lastic omponent s

ess

han

5% of he

total

deformation

and

hat he

amount

of

nstantaneous

lastic

deformation

s

generally ess han ime-dependent lastic deformations see Table ).

The

percentage

anges

of otal deformations hown n Table ndie. e hat r-

reversible

plastic

ype)

deformation s

ominant

ven

at tress evels

below

the

ong-term

trength.

0 06

006

<

2

c c

o

U-

UJ

o

004

0.02

H

eformat ion

of test m ac hint

1

nstantaneous

elastic deformation f specimen

IA niiantaneoui

eloihc

rebound of specimen

2 nstantaneous plastic

dtformation

o f iptci

«e n

3

imt dtptndtnt tlaific

rebound

of

specimen

4

tuduol

eformation

of

pecimen

4—*--

2

=^=W

a

ypical ebound

curve

z

-

005

1

4

Jf̂

OWS 58V

600 ps i

TEMP:

5*F

-

"a"

i

STAGE

STAGE

I,I

1 i

STAGE

m

I

200

400

00

00

t,

T M

E, hr

b

Ciassicol Creep

Curve

Typical

1000

1200

Figure

.5 .

Typical

ebound and

classical

creep

curves,

Ottawa

sand 20-30).


32/63

CREEP

OF

FROZEN SANDS

25

Table .

Types

f deformations

rom

ebounded reep

ests,

frozen Ottawa

and.

Percent

f

Total

Deformation

Temp

Stress

JFJ_

(psQ

1 5

24.5

29

17 0

5 0

100

Instant*

rebound

0 o

2.5

0

o

0 o

Delayed

elastic otal

rebound

ebound

1.0 o .3

o

6

to

10

to

14

1

to

2

to 4

Plastic

r

plasto-viscous

d e f

o

r

m

9' o

9

86 o 92

96 o

u

9

Rebound

time

l

erved

____ÜH)

1/2

38 2

1

*

Deformation

observed

0

ec fter emoval

of

oad.

At

he ntermediate stress

a

tios,

the

strain

s

ime curves

display

he

characteristics of

he

classical

creep

curves or

metals.

These curves

how

instantaneous lastic nd delayed lastic

i.e.,

viscoelastic), viscous, visco-

plastic

nd

plastic

trains

nd

ventual

ailure.

In Figure

5b

hesr

ompo-

nents

nd

he

hree

creep

tages re

creep of sand

Documents

Transcript of creep of sand