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A soil frost-susceptibility test and a basis for interpreting heaving rates
td
2 \ 6
National
Research
Conseil national
b
o . Q \ 4
I$
Council Canada
de
recherches Canada
a.
A SOIL FROST-SUSCEPTIBILITY TEST
A N D A BASIS FOR INTERPRETING
HEAVING
RATES
by
E.
p n n e r and
T.
Ueda
Reprinted, with permission, from
Vol. 1, Proceedings 3rd International Conference
on
Permafrost
held in Edmonton, Alberta,
10
13 July
1978
p.
721
-
727
DBR Paper No. 814
Division of Building Research
A SOIL FROST-SUSCEPTIBILITY TEST AND A BASIS FOR INTERPRETING HEAVING RATES Edward Penner, D i v i s i o n o f B u i l d i n g Research, N a t i o n a l Research Council o f Canada,. Ottawa, O n t a r i o . Takao Ueda, Takenaka Technical Research Laboratory, Tokyo, Japan.
A s o i l f r o s t s u s c e p t i b i l i t y t e s t i s proposed. The method i n v o l v e s t h e u n i d i r e c t i o n a l f r e e z i n g o f a s a t u r a t e d sample by imposing a s t e p f r e e z i n g temperature a t one end o f t h e specimen and, measuring t h e heave r a t e . The two most important c o n d i t i o n s t h a t i n f l u e n c e heave r a t e d u r i n g the t e s t a r e t h e overburden pressure and t h e f r e e z i n g temperature. Results show t h a t t h e heave r a t e can be expressed as an e x p o n e n t i a l f u n c t i o n o f t h e a p p l i e d overburden/freezing temperature r a t i o . The d e s i r a b l e f e a t u r e s o f t h e proposed. f r e e z i n g technique and t h e method o f i n t e r p r e t i n g t h e r e s u l t s a r e o u t 1 ined.
ESSAl DE G ~ L I V I T ~ DtUN SOL, ET BASE D'UNE M ~ T H O D E D 1 INTERPR~TATION DES TAUX DE SOULEVEMENT D I F F ~ R E N T I EL
DO
AU GELEdward Penner* and Takao Ueda*"
*
Chef, s e c t i o n de geotechnique, D i v i s i o n des recherches en bstirnent, Conseil n a t i o n a l de recherches du Canada, Ottawa, O n t a r i o , Canada.**
A s s i s t a n t 3 l a D i v i s i o n des recherches en bztirnent, employe p a r l e l a b o r a t o i r e de recherches techniques de Takenaka, Tokyo, Japon.Dan$ l e present a r t i . c l e , on d e c r i t un e s s a i de mesure de l a g e l i v i t d d t u n s o l . C e t t e methode, basde s u r l e g e l u n i d i r e c t i o n n e l d ' u n e c h a n t i l l o n s a t u r d , c o n s i s t a B sournettre une e x t r e m i t e de l ' e c h a n t i l l o n 3 d i v e r s e s dtapes de c o n g e l a t i o n , e t 3 mesurer l e t a u x de soulZvement d i f f e r e n t i e l p a r l e g e l . Les deux elements p r i n c i p a u x q u i i n f l u e n t s u r l e t a u x de,soulZvement d i f f e r e n t i e l pendant l t e s s a i s o n t l a p r e s s i o n de.surcharge e t l a temperature de c o n g e l a t i o n . Les r 6 s u l t a t s i n d i q u e n t que l e t a u x de soulZvement peut s t e x p r i m e r p a r une f o n c t i o n e x p o n e n t i e l l e du
q u o t i e n t p r e s s i o n de surcharge appliquee/tempCrature de c o n g e l a t i o n . On d e c r i t aussi l e s avantages de l a technique de c o n g e l a t i o n proposee, e t ceux de l a M t h o d e d ' i n t e r p r e t a t i o n des r e s u l t a t s .
MCllblTAHME I'PYHTOB HA MOP030YCTOnYMBOCTb M P A C Y E T CKOPOCTM IlYqEHMR
~ p € ? ~ n a I ' a e ~ ~ R M e T O A H C n b l T a H H R T P Y H T O B H a M O P O ~ O Y C T O R V W B O C T ~ ~ COCTORUlHft B C T y n e H v a T O M H a n p a B J l e H H O M 3 a M O p a X H B a H H H . O A H O r O K O H I J a H a C b l - U e H H O r O o6pasqa H M 3 M e p e H H H C K O P O C T H n y s e H H R . n B Y M H ~ a ~ 6 o n e e B a X H W H Y C n O B H R M H , o n p e n e n R m u u M t i C K O ~ O C T ~ n y s e e s R B npoqecce H c n u T a H H R , R B n R - IOTCR B H e U I H e e A a B n e H M e M T e M n e p a T y p a n p O M e p 3 a H H ~ . P e 3 y n b T a T b l H C ~ X J T ~ H H R n O K a 3 b l B a I 0 T P Y T O C K O p O C T b I l y s e H H R M O X e T 6 b I T b B H p a X e H a K a K 3 K C n O H e H U U - a n b H a R Q Y H K U H R O T H o w e H m B H e w H e r o x a B n e H H f f K T e M n e p a T y p e ~ P O M ~ P ~ ~ H H R . O n i i c a ~ b l n p e H M y u e c T s a n p e w a r a e M o r o M e T o x a s a M o p a X a s a H u R 0 6 p a 3 ~ 0 ~ H 0 6 p a 6 0 T K H p e 3 y n b T a T O B M C n b l T a H k I R .
A SOIL FROST-SUSCEPTIBILITY TEST AND A BASIS FOR INTERPRETING HEAVING RATES
Edward Penner and Takao Ueda
Division of Building Research, National Research Council of Canada, Ottawa, Ontario;
Guest worker with DBR from Takenaka Technical Research Laboratory, Tokyo
Frost action is a prime consideration in the
design of stable foundations for cold regions. It
is well known that the major destructive factors
caused by frost action are the heaving forces
developed and the associated volume increase of the
soil due to the water/ice phase change. Frost
heaving is particularly serious when the uplift is
uneven as this induces racking and distortion in
the structure usually not allowed for in the design.
In roads, streets and airport runways thaw soften-
ing follows heaving. This can be equally serious
i
as such thoroughfares deteriorate rapidly and may
become completely impassable unless load and travel
restrictions are imposed.
The frost action problem in engineering is
usually dealt with at the design stage. Removal
of or avoiding the use of frost-susceptible soils
that will undergo freezing while the structure is
in service is usually recommended unless water can
be effectively excluded. If high costs rule out
either of these recommendations or if neither is
possible, soil freezing is sometimes prevented by
installing insulation or by supplying heat.
The key to the frost action problem in
engineering is to be able to establish the frost
susceptibility of soils or prefera6ly the degree of
frost susceptibility. This is often done from the
grain-size distribution of the soil (Beskow 1935,
Casagrande 1938, Riis 1948, U.S. Corps of Engineers
1953). The frost susceptibility of the soil is
then predicted on the basis of "frost action
criteria" of which there are many available. These
criteria are used to compare the soils under consi-
deration with soils with similar grain-size curves
and whose heaving performance is known. Difficul-
ties are encountered with this approach however,
because grain size, as a criterion of frost action,
is not completely reliable although it is one of
the best methods available at present.
For structures where frost action is likely to
be an extremely critical factor in stability, the
approach has been to saturate samples of the soils
involved and subject them to freezing tests,
usually to determine heave rates although heaving
pressures are sometimes more relevant. The problem
is to establish a laboratory test procedure,
including sample preparation, moisture control,
load application, freezing technique and test dura-
tion, and from it determine the behavior of the
soil during freezing that can be expected for a
@
particular field condition. Laboratories that
have a large demand for frost-susceptibility tests
often develop their own methods but these usually
have as their basis the technique described by
Line11 and Kaplar (1959) which was developed by
ACFEL (the predecessor to CRREL)
,
U.S. Army Corps
of Engineers. Designers are frequently dissatis-
fied with the results obtained, however, and the
search continues for more meaningful and less time
consuming freezing tests.
A frost-susceptibility test method is proposed
in this paper using a frost cell developed by
Northern Engineering Services Company Limited,
Calgary, Alberta. to which the authors have made
minor modifications (Penner and Ueda 1977).
The
method stems from the work of Northern Engineering
Services in connection with the geotechnical
research carried out with respect to the design of
a proposed Mackenzie Valley gas pipeline. Equally
important is the proposed method of interpreting
the heave results. Both the test technique and
the interpretation circumvent difficulties
encountered previously. The two most important
test conditions that have a strong influence on the
results are the thermal conditions and applied
loads and these have been given special considera-
tion. The understanding of these conditions forms
the basis of the evaluation and interpretation of
the results obtained.
METHODS AND MATERIALS
The experimental method has been described in
detail (Penner and Ueda 1977) and is only reviewed
briefly in this paper. The test cell was designed
to hold a sample
4in. long and 4 in. in diameter
(10.2 cm).
The thermocouples and about 12 in.
(0.3 m) of the thermocouple lead were placed in
shallow grooves around the inside wall of the cell
in contact with the outside of the sample in an
isothermal plane.
,These measurements were used to
monitor temperatures, determine thermal gradients
and locate the O"C isotherm in the sample. Loading
of the sample for the consolidation phase and con-
finement of the sample during freezing was done by
pressurizing a loading chamber mounted above the
freezing cell. Water movement in and out of the
sample in response to freezing and the amount of
heave were recorded continuously on a Hewlett-
Packard 2010H data acquisition system.
l i m i t s f o r t h e s o i l s t e s t e d a r e g i v e n i n Table I . Sample p r e p a r a t i o n was t o p l a c e s o i l s , which had been p r e v i o u s l y s a t u r a t e d t o n e a r t h e l i q u i d l i m i t , i n t h e t e s t c e l l f o r c o n s o l i d a t i o n . A f t e r c o n s o l i - d a t i o n was complete, t h e p r e s s u r e was reduced t o a value s e l e c t e d f o r t h e run and t h e c e l l was condi- t i o n e d thermall'y i n s i d e a Tenney c o n s t a n t tempera- t u r e chamber a t some p r e s e l e c t e d temperature c l o s e t o O°C. One end o f t h e sample had f r e e a c c e s s t o b u b b l e - f r e e w a t e r w i t h t h e water t a b l e h e l d a t t h e b a s e o f t h e specimen. Heaving was i n t h e open system mode throughout t h e t e s t . To s t a r t a run, a s t e p f r e e z i n g temperature was imposed a t t h e end o p p o s i t e t h e w a t e r s u p p l y . Freezing took p l a c e u n i d i r e c t i o n a l l y a s t h e c e l l w a l l s were h e a v i l y i n s u l a t e d .
I
RESULTS AND DISCUSSIONF i g u r e 1 shows t y p i c a l heaving curves f o r t h e s o i l s s t u d i e d and responses t o two d i f f e r e n t over- burden p r e s s u r e s , 1 . 0 and 4 . 0 kg/cm2. The r a t e o f heave was e s s e n t i a l l y c o n s t a n t i n b o t h experiments and t h e d i r e c t i o n o f water movement r e v e r s e d from e x p u l s i o n t o i n t a k e a t t h e h i g h e r p r e s s u r e . I n f l u e n c e of Load A p p l i c a t i o n , P
S i n c e t h e sharp r e d u c t i o n i n t h e heave r a t e r e s u l t i n g from s u r c h a r g i n g was r e p o r t e d by Beskow
I has been s t r e s s e d by many r e s e a r c h workers. (1935), t h e s i g n i f i c a n c e o f t h e overburden p r e s s u r e
One school o f thought i s t h a t a t a p a r t i c u l a r s t r e s s l e v e l , which can b e found e x p e r i m e n t a l l y , t h e f r e e z i n g o f i n s i t u w a t e r and i t s a t t e n d a n t expan- s i o n w i l l proceed while t h e heaving a t t r i b u t e d t o t h e f r e e z i n g o f migratory w a t e r from o u t s i d e s o u r c e s , e . g . , t h e w a t e r t a b l e o r unfrozen s o i l ,
w i l l b e s t o p p e d . From t h i s concept t h e term "Shut-
o f f " p r e s s u r e was i n t r o d u c e d i n t o t h e s o i l mechanics 1 i t e r a t u r e by Arvidson and Morgens t e r n
(1974) and d e f i n e d by McRoberts and Nixon (1975) a s
t h e " e f f e c t i v e s t r e s s a t t h e f r o s t l i n e which w i l l
cause n e i t h e r flow o f w a t e r i n t o o r away from t h e f r e e z i n g f r o n t
."
An opposing view t o which t h e 'a u t h o r s a s c r i b e i s t h a t i t i s n o t p o s s i b l e t o c o n t r o l independently t h e two s o u r c e s o f heave by l o a d i n g t h e s o i l . This has been shown e x p e r i - mentally by Penner and Ueda (1977). The r a t i o o f i n s i t u t o migratory w a t e r which i s f r o z e n changes
c o n t i n u o u s l y d u r i n g t h e t e s t and h a s no i n f l u e n c e I
on t h e heave r a t e .
The i n f l u e n c e o f overburden on t o t a l heave r a t e f o r t h e s o i l s s t u d i e d i s summarized i n F i g . 2. The l i n e a r r e l a t i o n between t h e l o g a r i t h m of t h e r a t e o f heave and a p p l i e d p r e s s u r e a g r e e s with e a r l i e r r e s u l t s o f Line11 and Kaplar (1959).
Influence o f Cold-side S t e p Temperature, T The f r e e z i n g temperature imposed a t t h e c o l d end o f t h e sample ranged from - 0 . 3 t o -3.9S°C. Figure 3 shows t h e d r a s t i c changes i n t h e tempera- t u r e g r a d i e n t i n t h e f r o z e n p o r t i o n d u r i n g t y p i c a l t e s t runs. I t i s emphasized t h a t , d e s p i t e t h e l a r g e g r a d i e n t changes i n t h e f r o z e n l a y e r and t h e a t t e n d a n t d e c r e a s e s i n t h e f r o s t p e n e t r a t i o n r a t e a s t h e experiment progressed, t h e t o t a l heave r a t e remained e s s e n t i a l l y c o n s t a n t ( F i g . 1 )
.
These r e s u l t s s u g g e s t t h a t t h e r a t e o f f r o s t p e n e t r a t i o n does n o t i n f l u e n c e t h e heave r a t e u s i n g t h i s f r e e z i n g technique. I t would seem t h a t t h e s i g n i - f i c a n t f a c t o r i n determining t h e heaving r a t e i s t h e value o f t h e c o l d - s i d e t e m p e r a t u r e . This temperature i s thought t o determine t h e s u c t i o n p o t e n t i a l a t t h e growing i c e l e n s . I t s e f f e c t can b e s e e n i n t h e r e s u l t s from experiments given i n Fig. 4 , where t h e s t e p temperature was lowered i n s t a g e s during one t e s t . A f t e r each lowering o f t h e temperature o f t h e c o l d s i d e both t h e t o t a l heave r a t e and t h e s e g r e g a t i o n a l heave r a t e by w a t e r inflow i n c r e a s e d .TABLE I SUMMARY OF SOIL PROPERTIES
% Clay S i z e % S i l t % Sand % Gravel S o i l <0.002 mm 0.002-0.06 0.06-2.0 > 2.0 W ~ , % W ~ , % IP, % MVS 4 MVS 5 MVS 6 MVS 9 Calgary S i l t No. 1 17.0 83.0 0 0
-
-
-
Calgary S i l t No. 2 30.0 70.0 0 0-
-
-
Leda c l a y 80.2 19.8 9 0-
-
-
*MVS = Mackenzie Valley S o i l sTable I 1 g i v e s r e s u l t s t h a t show t h e s t r o n g e f f e c t o f t h e value o f t h e c o l d - s i d e temperature, although t h e experiments were c a r r i e d o u t e n t i r e l y
d i f f e r e n t l y than d e s c r i b e d above. In t h e s e e x p e r i -
ments t h e c o l d - s i d e f r e e z i n g temperatures were h e l d c o n s t a n t i n t h e f i r s t two s e t s o f experiments f o r t h r e e s u c c e s s i v e r u n s each, b u t t h e warni-side
temperature was changed. The heave r a t e was t h e
same f o r a l l t h r e e runs. The two s e t s o f e x p e r i -
ments were c a r r i e d o u t w i t h d i f f e r e n t overburden
p r e s s u r e s , 2 and 4 kg/cm2. The d i f f e r e n c e s i n t h e
amount o f f r o s t p e n e t r a t i o n f o r each run were, 3.7, 5 . 2 and 7.1 cm, f o r b o t h s e t s , r e s p e c t i v e l y , f o r
t h e same p e r i o d . I n t h e t h i r d s e t , t h e warm-side
temperature was h e l d c o n s t a n t and i n t h r e e succes- s i v e runs t h e c o l d - s i d e s t e p temperature was
changed. A t h r e e f o l d change i n s t e p temperature
r e s u l t e d i n a f i v e f o l d change i n heave r a t e . Again t h e f r o s t p e n e t r a t i o n depth corresponded wi'th t h e f i r s t two s e t s .
'Ihe i n f l u e n c e o f t h e c o l d-side temperature on heave r a t e i s summarized i n F i g . 5 by p l o t t i n g l o g a r i t h m heave r a t e v s 1 / T . R e s u l t s e x t r a c - t e d from s t u d i e s by Kaplar (1968), p l o t t e d i n t h e same way, a r e a l s o i n c l u d e d i n t h i s f i g u r e . The Combined I n f l u e n c e o f Overburden P r e s s u r e ,P,
and Cold-side . .- Temperature, T, on Total Heave Rate
A nunher o f r e s e a r c h workers ( e . g . , Koopmans and
M i l l e r 1966, Radd and O e r t l e 1966, Hoekstra 1969) have shown t h a t f o r s o i l s with an a p p r e c i a b l e c l a y c o n t e n t t h e t h e o r e t i c a l heaving p r e s s u r e / f r e e z i n g p o i n t d e p r e s s i o n r a t i o , given by Eq. ( I ) , can b e v e r i f i e d i n t h e l a b o r a t o r y w i t h i n experimental e r r o r . where AP = heaving p r e s s u r e AT = f r e e z i n g p o i n t d e p r e s s i o n a t t h e i c e l e n s below To, O C AH = s p e c i f i c h e a t o f f u s i o n V . = s p e c i f i c volume o f i c e - T = bulk i c e l w a t e r e q u i l i b r i u m 0 temperature, "C I t i s assumed t h a t t h e temperature a t t h e f a c e o f t h e growing i c e l e n s i s p r o p o r t i o n a l t o t h e c o l d - s i d e s t e p temperature, i . e . , t h e lower t h e c o l d - s i d e temperature t h e lower t h e temperature o f t h e i c e l e n s . Based on t h i s assumption and
Eq. ( I ) , an e v a l u a t i o n can b e made o f t h e P/T r a t i o a t t h e lower l i m i t o f t o t a l heave r a t e and AP/AT, t h a t is, a s P/T r e a c h e s t h e maximum value
o f AP/AT ( 1 1 . 3 kg/cm2 O C ) , t h e t o t a l heave r a t e
approaches t h e lower l i m i t .
The s o i l s f o r which heaving r a t e s were measured e x p e r i m e n t a l l y f o r a number o f c o l d - s i d e tempera-
t u r e s and overburden p r e s s u r e combinations were Leda c l a y , a l o c a l marine c l a y , and MVS 4 ( a s o i l from t h e Mackenzie River Valley, Northwest
T e r r i t o r i e s ) . The p l o t t e d r e s u l t s (Fig. 6)
i n d i c a t e t h a t t h e r e i s a 1 i n e a r r e l a t i o n w i t h i n
t h e observed range between logarithm o f t o t a l heave r a t e and P/T t h e r a t i o o f t h e overburden p r e s s u r e and t h e c o l d s i d e , f r e e z i n g temperature.
Figure 6 i s i n f a c t
A
combination of F i g s . 2 and5; t h e r e s u l t s can b e expressed by t h e e q u a t i o n :
AP
- -
AH
1 1 . 3 k g / ( ~ m ~ - ~ C )d h m ~
A T - m = (1) where
-
-
t o t a l heave r a t e , mm/minTABLE I 1 HEAVING RUNS AT VARIOUS WARM- AND COLD-SIDE TEMPERATURES WITH REMOULDED LEDA CLAY
(80% CLAY SIZE; 20% FINE SILT)
S e t o f P r e c o n s o l i d a t i o n runs p r e s s u r e , kg/cm2 4.0 S e t 1 4 .O 4.0 4 .O S e t 2 4.0 4 . 0 4 . O S e t 3 4 . 0 4.0 P r e s s u r e during Temperature heaving o f r u n , kg/cm2 chamber, O C Temperature o f sample I n i t i a l Void c o l d s i d e Y o C M.C.,% Ratio -0.90 39.3 1.10 -0.95 39.7 1.10 -0.90 40.5 1.10 Depth o f O"C T o t a l heave isotherm a t r a t e , mm/min 2000 min.', cm
a and b a r e c o n s t a n t s ( p o s i t i v e ) depending on s o i l type p = overburden p r e s s u r e , kg/cm2 c o l d - s i d e f r e e z i n g temperature below O°C The f o l l o w i n g a r e t h e d e s i r a b l e f e a t u r e s o f t h e f r e e z i n g technique used and t h e i n t e r p r e t a t i o n suggested w i t h r e g a r d t o t h e l a b o r a t o r y e v a l u a t i o n o f f r o s t s u s c e p t i b i l i t y .
1 . The r e l a t i o n between f r o s t heave and time i s l i n e a r f o r t e s t p e r i o d s up t o 3 o r 4 days and i s independent of f r o s t p e n e t r a t i o n r a t e f o r a given s t e p f r e e z i n g temperature (Fig. 1 ) . A
c o n s t a n t heave r a t e i s e a s i l y achieved by t h i s method.
2. Tne f r o s t heave-time r e l a t i o n i s independent o f t h e r a t i o o f i n s i t u w a t e r and migratory water i n i c e formation. A t t h e beginning, heave i s t o t a l l y from i n s i t u w a t e r ; when f r o s t p e n e t r a - t i o n s t o p s , heave i s from migratory w a t e r o n l y .
3 . The f i e l d overburden p r e s s u r e a n t i c i p a t e d need n o t b e known i n advance o r simulated i n t h e f r e e z i n g t e s t ; t h e r a t e s a t o t h e r overburden p r e s s u r e s can b e c a l c u l a t e d o r o b t a i n e d g r a p h i -
c a l l y .
4 . The c o l d - s i d e f r e e z i n g temperature used must b e h e l d c o n s t a n t t o c a l c u l a t e t h e P/T r a t i o
c o r r e c t l y . Any s u i t a b l e f r e e z i n g s t e p tempera- t u r e , however, can b e used which can b e
c o n v e n i e n t l y produced by t h e a v a i l a b l e f r e e z i n g equipment.
5 . There i s no w a l l a d f r e e z e problem, hence t h e r e ' i s no need f o r a t a p e r e d c e l l , o r movable r i n g s , e t c . The design o f t h e c e l l , borrowed from Northern Engineering S e r v i c e s , Calgary, i s g i v e n i n t h e p a p e r by Penner and Ueda (1977).
6 . Only one f r e e z i n g t e s t i s r e q u i r e d s i n c e a second s t e p f r e e z i n g temperature can b e imposed i n t h e same experiment t o e s t a b l i s h t h e r e l a - t i o n between l o g a r i t h m heave r a t e vs PIT (Fig. 4 and 7 ) .
7. As t h e r e l a t i o n between t o t a l heave and time i s l i n e a r , t h e experiment can b e terminated a f t e r a r e l a t i v e l y s h o r t time. The o r i g i n a l ACFEL f r o s t heaving experiments r e q u i r e d 24 days t o complete.
CONCLUDING REMARKS
The heaving response t o a s t e p f r e e z i n g tempera- t u r e has been analyzed elsewhere (Penner and Ueda 1977) and a mechanical model was developed t o h e l p understand t h e heaving p r o c e s s (Ueda and Penner)
.
I t i s e v i d e n t from F i g . 1 t h a t i f any heaving o c c u r s d u r i n g t h e f i r s t s t a g e s o f t h e t e s t , a l t h o u g h w a t e r i s e x p e l l e d i n i t i a l l y , water flow must r e v e r s e i f t h e t o t a l heave l i n e a r l y i n c r e a s e s w i t h time. Expulsion d u r i n g t h e e a r l y s t a g e s i s r e l a t e d t o overburden and f r e e z i n g temperature(Ueda and Penner)
.
The r a t i o o f a p p l i e d overburden p r e i s u r e
t o f r e e z i n g temperature can b e expressed b y an e x p o n e n t i a l f u n c t i o n o f t h e heave r a t e . This grea_tly enhances the. u t i l i t y o f t h e heave t e s t .
'1t i d b e l i e v e d t h a t although a sound approach t o f r o s t s u s c e p t i b i l i t y e v a l u a t i o n o f s o i l s h a s been p r e s e n t e d t h e r e a r e s t i l l a s p e c t s o f t h e t e s t
t h a t need c l a r i f i c a t i o n t o e s t a b l i s h f u l l y i t s u l t i m a t e u s e f u l n e s s . Hence, t h e t e n t a t i v e n a t u r e o f t h e approach should b e k e p t i n mind. F i n a l 1 y,
no mention, has been made o f t h e c r i t i c a l r a t e o f
i
heave t h a t determines a f r o s t - s u s c e p t i b l e s o i l .A t p r e s e n t , a t l e a s t , t h e s c a l e o f heave r a t e s developed by CRREL a r e thought t o b e a c c e p t a b l e
(Line11 and Kaplar 1959).
ACKNOWLEDGEMENTS
I
Appreciation i s e x p r e s s e d t o Northern Engineer- i n g S e r v i c e s f o r t h e use o f t h e i r f r o s t c e l l and f o r a l l o w i n g m o d i f i c a t i o n s t o be made. This paper i s a c o n t r i b u t i o n from t h e D i v i s i o n o f Building Research, National Research Council o f Canada, and i s p u b l i s h e d w i t h t h e approval of t h e D i r e c t o r o f t h e D i v i s i o n .
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I
I
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UEDA, T. and PENNER, E. Mechanical analogy o f a roads and a i r f i e l d s . U.S. Dept. of Army,
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August 1977 f o r p u b l i c a t i o n . To b e i n Vol. 2 o f Tech. Memo. 3-357.
I n t l . Symposium on F r o s t Action i n S o i l s , Univ. o f L u l e l , L u l e l , Sweden. E L A P S E D TIME, m i n
-
u r - 2 1 I I I II
o 1000 2000 3000 a000 E L A P S E D TIME, m i nFigure 1 F r o s t p e n e t r a t i o n and heave measurements
f o r MVS 2 a t 1 . 0 kg/cm2 (above) and 4 . 0 kg/cm2 (below)
.
-
- I I I 1 I I-
-
-
--
-
-
--
-
--
-
C O l D S l D l W A R M Z l O C M Y 5 5 4 4 - 0 . 8 6-
M V I 1 -0.90 1 . 7 0 M V S 3 - I . A 3 Z . A 0 C A l G h l Y 2 - 0 . 9 7 1 . 3 U C A l G A U Y 1 - 0 . V 7 7.30-
L E D A C L A Y - 0 . P j I . I0 l t c n C L A Y - 1 .8? 2.30 I I I I I I I 0 1 Z 3 4 5 P R E S S U R E , k g l c m 2-
T E M P E R A T U R E , 'C C O L D S l D E W A R M S l D E T O T A L H E A V E R A T E-
( C H A M B E R ) ( C H A M B E R ) ( x 1 0 J mm,min, R U N 4 - 0 . 9 0 1 . 3 0 1 . 8 4 R U N 5 - 0 . 9 0 2 . 2 2 1 . 9 6 R U N 6 - 0 9 5 3 . 8 8 1 . 9 0 0 0 2 4 6 8 1 0 1 2 1 4 1 6 18 20 22 24 2 6 28 3 0 TIME, m i nFigure 3 Typical temperature g r a d i e n t changes i n t h e f r o Zen p o r t i o n d u r i n g f r e e z i n g t e s t s .
f.
WHERE T = THE DEGREES BELOW 0 ° C Figure 5 T o t a l heave r a t e v s temperature.ELAPSED T I M E , m i n
Figure 4 The i n f l u e n c e o f lowering t h e c o l d s i d e temperature on heaving r a t e . C O L D S I D E T i l l = -0 4O.C ( 2 ) - 1 45.C W A R M S I D E 1 * 2 3 0 ' C c O N 5 O L l D a T l O N P = 4 k g / c m 2 OVERBURDEN P = 2 k g / c m 2 MC = 3 9 . 8 ' 0 SOIL TYPE L t D A C L A Y
+,
k g l l c m T I . WHERE T = T H E DEGREES BELOW O°Ct , m i n
Figure 7 The i n f l u e n c e o f lowering t h e c o l d s i d e Figure 6 Heaving r a t e vs t h e overburden temperature on heaving r a t e . p r e s s u r e / s t e p temperature r a t i o .
