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Unconfined compression tests on anisotropic frozen soils from
Thompson, Manitoba
.
.. .j
Ref
Ser
I
National Research
Conseil national
I
no.
1168
Council Canada
de recherches Canada
UNCONFINED COMPRESSICN TESTS ON ANISOTROPIC FROZEN
SOILS FROM THOMPSON, MANITOBA
by T.H.W. Baker and G.H. Johnston
Reprinted from
Permafrost: Fourth International Conference
Fairbanks. Alaska, July
17
-
22, 1983
Proceedings, p. 40
-
45
DBR Paper No. 1168
Division of Building Research
On t r o u v e dans l a p a r t l e nord d e l ' a n c l e n l a c g l a c l a i r e Agasslz d e s s o l s g e l & l a m l n k , constitu'es de couches a l t e r n k s h o r i z o n t a l e s d ' a r g l l e brun sombre e t d e limon brun c l a l r , e n t r e l e s q u e l l e s s o n t i o t e r c a l & s d e s l e n t l l l e s d e glace. Des essaLs c o n d u l t s e n l a b o r a t o l r e o n t conflrm'e l e s r 6 s u l t a t s d e s e s s a l s I n s l t u a v e c ancrages au s o l , p&'etrom>tres e t c a p s u l e s manonfatrlques ?Thompson, au Manltoba. i Ces e s s a l s a v a l e n t d&nontr€ que l e s s o l s p r h e n t a i e n t une m e l l l e u r e r h i s t a n c e m'ecanlque dans l e s e n s h o r i z o n t a l , p a r a l l e l e m e n t aux couches, que dans l e s e n s v e r t i c a l . On a 6chantlllonn'e d e s b l o c s oon ~ e r t u r b ' e s de c e s s o l s sel'es lamin'es
-
(3
varves). e t or'eoar'e d e s. .
S p r o u v e t t e s , orlent'ees de €&oms d l v e r s e s p a r r a p p o r t A l a d l r e c t l a n de l a s t r a t l f i c n t i o n . Des e s v a l s de r E s l s l a n c a 3 l a c o m p r e s n l o n s a n s B t r e l n t e l a t ' e r a l e , e f f e c t u ' e s s u r d e s 6 c h a n t i l l o n s n a t u r e l l e m e n t gel'es, e t s u r d ' a u t r e s remanl'es e t a r : l f l c I e l l e m e n t nel'es. o n t d6montr'e I ' l m o o r t a n t e a n l s o t r o n l e-
de l a r ' e s i s t a n c e mecanique due B l ' a n l s o t r o p i e n a t u r e l l e d e l a s t r u c t u r e du s o l .Reprinted from: Permafrort: Fourth laternotional
Conference, Proceedings
ISBN 0-309-03435.3
National Academy Press
Washington, D.C. 1983 UNCONFINED COMPRESSION TESTS ON ANISOTROPIC FROZEN SOILS FROM THOMPSON, MANITOBA
T. H. W. Baker and G. H. Johnston
Division of Building Research, National Research Council of Canada, Ottawa, Ontario, KIA OR6
Laminated frozen soils, consisting of alternate horizontal layers of dark brown clay and light brown silt, with ice lenses between the layers, are found in the northern area of ancient glacial Lake Agassiz. Laboratory tests confirmed the results of in situ ground anchor, penetrometer, and pressuremeter tests performed at Thompson, Manitoba, which showed these soils to be stronger in the horizontal direction, parallel to the layers, than in the vertical direction. Undisturbed block samples of these laminated (varved) frozen soils were obtained and test specimens were prepared at various orientations to the direction of layering. Unconfined compression tests, using both naturally frozen and remolded frozen specimens, have shown the extent of strength anisotropy due to the natural anisotropic soil structure.
INTRODUCTION
A series of in situ creep loading tests was undertaken in the frozen varved clay soils at Thompson, Manitoba, between 1967 and 1974. These
field tests included circular plate anchors (Ladanyi
and Johnston 1974), power-installed screw anchors
(Johnstan and Ladanyi 1974), pressuremeter (Ladanyi and Johnston 1973) and electric penetrometer tests
(Ladanyi 1976, 1982). Creep equations were developed
using the theory of an expanding spherical cavity.
It was found that the creep exponent deduced from the static penetration tests was much higher than that found in the pressuremeter tests. Still higher values were obtained from creep tests on the ground anchors, performed earlier at the same site. Since the anchar and penetrometer tests loaded the soil in a Vertical direction and the pressuremeter loaded the soil in a horizontal direction, this indicated that
the frozen varved clay was more resistant to
deformation (i.e., stronger) in the horizontal direction than in the vertical direction. This was attributed to the natural anisotropic structure of
the frozen varved soils (Ladanyi 1976). A systematic
study was undertaken to determine the influence of the anisotropic structure of these soils on the response to the various loading conditions described
above. This paper describes a series of unconfined
compression laboratory tests an field samples of
frozen varved clay from the Thompson area.
INVESTIGATING STRENGTH ANISOTROPY The term strength anisotropy is used
exclusively in this paper to describe the variation of stress-strain behavior in the soil with direction
of loading. Most soils exhibit stress-strain
anisotropy, due mainly to the nature of the depositional process. This anisotropy becomes marked in layered or laminated (varved) soils formed by cyclic sedimentation and subsequent one-
dimensional consolidation. The testing of unfrozen varved soils to determine their strength and deformation properties has been reported by several
authors, including Tschebotarioff and Bayliss (1948).
Eden (1955), and Metcalf and Townsend (1960). These
investigators performed unconfined compression tests
at various orientations to the varves and found a
distinct anisatropy in shear strength. In testing Lake Agassiz varved clays from Steep Rock, Ontario, Eden (1955) found that when clay layers
predominated, the shear strength was higher when the direction of loading was parallel to the layers. When silt layers predominated, the shear strength was higher when the direction of loading was perpendicular to the lavers.
~.
Frozen fine-grained soils often have an anisotropic structure, due to the existence of ice lenses formed perpendicular to the direction of freezing. Livingston (1956) studied the strength anisotropy by performing unconfined compression tests on frozen Keweenaw silt at various
orientations to the ice lenses. There was a large scatter among the observed stress and strain values, due to specimen variability and to the extreme sensitivity of the soil-ice mixture to slight variations in temperature at the time of the test, particularly in the temperature range (-1 to -2*C) at which the tests were conducted. These tests indicated that the shear strength was generally
higher for specimens with ice lenses parallel to the
direction of loading.
The strength anisotropy of sails is usually expressed as the ratio of the shear strength with the major principal stress oriented at various angles to the vertical (So) to the shear strength in the vertical direction ( S O ) The obvious angles of significance for horizontally layered soils are
0 = 4 5 ' . where the maximum shear stress is parallel to the layers, and 8 = 90", where the major stress is parallel to the layers.
The shear strength ratios for the Steep Rock varved clay and frozen Keweenaw silt are shown in
Table
I.
These ratios indicate a definite strengthanisotropy which is dependent upon the properties of the individual layers. It was thought that the frozen varved clay from the Thompson area would show an even greater strength anisotropy than the soils mentioned above, due to the combined presence of horizontal Tarvea and ice lenses.
'TABLE 1 S t r e n g t h Anisotropy of Some S o i l s From t h e L i t e r a t u r e
S o i l
-
'90 Referenceso
SoLake Agassiz varved c l a y ( S t e e p Rock, Ontario)
predominantly c l a y 1.18 0.51 l a y e r s
Eden (1955)
Ground Temperatures
Ground temperatures were measured weekly by NRC s t a f f an t h e t h e r m i s t o r c a b l e i n s t a l l e d a t t h e s i t e by t h e Geological Survey of Canada. F i g u r e 3 shows ground temperatures o b t a i n e d i n e a r l y March 1978 and t h e maximum, minimum, and mean temperatures f o r t h a t year. The maximum and minimum temperatures f o r 1978 were near t h e extreme values observed f o r t h e years
1975-1978. The mean annual ground temperature, a t t h e depth a t which t h e block samples were obtained, was between -1 and -2'C. A t t h e time of sampling, t h e ground temperature, i n t h e sampling zone, was between -2 and -3'C.
predominantly s i l t 0.57 0.92
l a y e r s LABORATORY TESTING
Frozen Keweenaw s i l t 1.23 0.63 L i v i n g s t o n (1956)
SITE LOCATION AND DESCRIPTION The c i t y of Thompson (55'45'N, 97'50'W) i s l o c a t e d i n n o r t h e r n Manitoba about 640 km n o r t h of Winnipeg, w i t h i n t h e discontinuous ~ e r m a f r o s t zone. P e r e n n i a l l y f r o z e n ground occurs i n s c a t t e r e d s m a l l patches o r i s l a n d s varying i n s i z e from a few square metres t o s e v e r a l h e c t a r e s (Johnston e t a 1 1963).
Thompson i s a l s o l o c a t e d w i t h i n t h e n o r t h e r n e x t r e m i t y of a n c i e n t Lake Agassiz, which e x i s t e d during t h e Wisconsin period of g l a c i a t i o n ( F i g u r e 1 ) . C h a r a c t e r i s t i c of t h e d e p o s i t i o n a l processes a s s o c i a t e d with g l a c i a l Lake Agassiz was t h e formation of e x t e n s i v e d e p o s i t s of laminated (varved) s i l t and c l a y . The varved e o i l s are f u l l y s a t u r a t e d and o f t e n c o n t a i n i c e l e n e e s from h a i r l i n e t o 5-10 cm i n t h i c k n e s s , normally o r i e n t e d p a r a l l e l t o t h e predominantly h o r i z o n t a l laminations. The a l t e r n a t i n g h o r i z o n t a l l a y e r s of l i g h t brown s i l t and dark brown c l a y combine w i t h t h e h o r i z o n t a l i c e l e n s e s t o produce an a n i s o t r o p i c s o i l s t r u c t u r e .
FIELD PROGRAM Sampling
A backhoe was used t o excavate a t e s t p i t t o a depth of about 3 m a t a s i t e approximately 5.5 !a
n o r t h of t h e c i t y of Thompson, near t h e southwest c o r n e r of t h e Thompson a i r s t r i p , i n March 1978. The p i t was l o c a t e d i n a l a r g e spruce i s l a n d c l o s e t o a ground temperature c a b l e i n s t a l l e d by t h e Geological Survey of Canada (GSC) i n 1973. The a i t e (GSC 2A) i s d e s c r i b e d i n d e t a i l by Klassen (1976). The w a l l s of t h e p i t were v i s u a l l y logged, and samples were obtained f o r w a t e r c o n t e n t , o r g a n i c c o n t e n t and g r a i n s i z e a n a l y s e s . A l o g of t h e t e s t p i t i s shown i n F i g u r e 2.
A l a y e r of d i s t i n c t l y laminated (varved) f r o z e n c l a y occurred between t h e depths of 1.25 and 2.25 m.
Small (0.3 m3) blocks of t h e f r o z e n varved m a t e r i a l were wrapped i n polyethylene s h e e t i n g ,
m laced
i n i n s u l a t e d boxes packed w i t h i c e , and shipped t o Ottawa by a i r . These samples were maintained a t -6'C i n a c o l d room u n t i l specimens were preparedf o r t e s t i n g .
T e s t Specimen P r e p a r a t i o n and D e s c r i p t i o n
C y l i n d r i c a l t e s t specimens 76 mm i n diameter and 152 mm i n h e i g h t were machined from t h e block samples using a band saw and l a t h e i n a c o l d room. The procedures f o r sawing, machining and p r e p a r i n g t h e specimens a r e described by Baker (1976). Specimens were machined a t v a r i o u s a n g l e s t o t h e plane of t h e h o r i z o n t a l varves. " V e r t i c a l "
specimens contained varves o r i e n t e d p e r p e n d i c u l a r t o t h e v e r t i c a l a x i s of t h e specimen. "Horizontal" specimens contained varves o r i e n t e d p a r a l l e l t o t h e v e r t i c a l a x i s of t h e specimen. Another s e t of apecimena was machined w i t h v a r v e s o r i e n t e d a t 45' t o t h e v e r t i c a l a x i s of t h e specimen. Each specimen contained from 15 t o 20 v a r v e s , c o n s i s t i n g of dark brown clay l a y e r s from 8 t o 12 mm i n t h i c k n e s s and l i g h t brown s i l t l a y e r s from 2 t o 5 mm i n t h i c k n e s s . Ice l e n s e s v i s i b l e on t h e s i d e s of t h e specimens ranged i n t h i c k n e s s from h a i r l i n e t o a few m i l l i m e t r e s .
Bulk d e n s i t i e s were determined p r i o r t o t e s t i n g by measuring t h e volume and weight of t h e t e s t specimens. A f t e r t e s t i n g they were weighed, oven d r i e d , and weighed again t o determine t h e i r t o t a l water contents. The d e n s i t i e s and w a t e r c o n t e n t s
are
c resented
i n Table 2.Hydrometer t e s t s on "combined" samples ( c o n t a i n i n g both l i g h t and dark l a y e r s ) i n d i c a t e d t h a t t h e varved s o i l c o n s i s t e d of 80-90% c l a y s i z e (<0.002 m) m a t e r i a l . I g n i t i o n - l o s s t e s t s (ASTM
D 2974) i n d i c a t e d a n average o r g a n i c c o n t e n t of 122. Eight Atterberg Limits t e s t s showed a l i q u i d l i m i t of 52.04, a p l a s t i c l i m i t of 32.7%, and a p l a s t i c i t y index of 19.3%. The average water c o n t e n t was 35.02, about 2-32 lower t h a n t h a t determined a t t h e f i e l d s i t e (Figure 2 ) .
S e v e r a l remolded specimens were s p e c i a l l y prepared i n t h e l a b o r a t o r y t o t r y and remove t h e a n i s o t r o p i c s t r u c t u r e formed by t h e varves and i c e l e n s e s . Some specimens were completely thawed, and t h e s o i l was mixed and remolded t o d e n s i t i e s and water c o n t e n t s s i m i l a r t o t h e n a t u r a l samples. These remolded c y l i n d r i c a l specimens were placed i n t h e cold roam a t -6'C and allowed t o f r e e z e from a l l s i d e s . They were removed from t h e molds, and t h e i r ends were machined p r i o r t o t e s t i n g . Small h a i r l i n e r a d i a l i c e l e n s e s could be seen a t t h e ends of t h e f r o z e n remolded specimens. These remolded specimens were t e s t e d f o r comparison w i t h r e s u l t s obtained on the n a t u r a l (undisturbed) f r o z e n s o i l * . Frozen hulk
TABLE 2 Properties of Test Specimens
Bulk Dry Water Loading
Specimen density density content direction
(kg/m3) (kg/m3) (% dry to plane wt.) of varves Undisturbed CS-1 1,799 1,332 35.1 Parallel CS-2 1,791 1,353 32.4 Parallel CS-3 1,780 1,334 33.5 90" CS-4 1,766 1,316 34.2 90' CS-5 1,761 1,284 37.2 90' CS-6 1,751 1,298 34.9 Parallel CS-7 1,769 1,288 37.3 45' CS-8 1.772 1.318 34.4 45" CS-9 1;759 1;303 35.0 45' CS-10 1,828 1,374 33.1 Parallel Mean 1,778 1,320 34.7 Stand. Dev. 23 29 1.6 Remolded RS-1 1,776 1,340 32.6 RS-2 1,852 1,440 28.6 RS-3 1,761 1,303 35.1 RS-5 1,768 1,303 35.7 Mean 1,789 1,347 33.0 Stand. Dev. 42 65 3.2
densities and total water contents were determined before and after testing; these are presented in Table 2.
Unconfined Compression Tests
Unconfined compression tests were performed at
a cold room temperature of -6'C, using a 250 kN
capacity screw-driven universal testing machine. These tests were carried out at nominal strain rates of 0.01 and 1.OXlmin. Some tests were performed at
an intermediate strain rate of O.l%/min, but were
incomplete due to the limited amount of sample material available. Data from this incomplete test series will not be presented. An extensometer consisting of three displacement transducers located
on the specimen, measured axial deformation and
tilting (Baker et a1 1982). Compliant platens
(Baker 1978) were used to reduce end effects and to ensure a uniform normal application of pressure to the specimen ends.
Vertically oriented specimens had the maximum normal stress direction perpendicular to the plane of the varves to simulate the anchor and
penetrometer tests performed in the field.
Horiz~ntally oriented specimens had the maximum
normal stress direction parallel to the plane of the varves, in a manner similar to the field
pressuremeter tests. Specimens oriented at 45' had the maximum shearing stress directed parallel to the plane of the varves.
Stress-strain curves for the two nominal strain rates are shown in Figures 4 and 5. The loading
direction relative to the plane of the varves for each specimen is indicated. Some tests were duplicated to show the variation in stress-strain behavior between specimens. The maximum axial strain imposed on specimens was between 10 and 15%.
due to the limitations imposed by the 83 mm diameter
extensometer ring. As a result, none of the tests reached peak stress.
DISCUSSION AND CONCLUSION
All of the specimens exhibited an initial yield at about 0.15% axial strain; the stress then
continued to increase until the test was stopped. Although none of the specimens reached failure (peak stress), the value of the stresses at and beyond yield is an indicator of the relative strength of specimens and can be used to determine strength anisotropy. All specimens deformed as right cylinders without central bulging or expansion of individual layers. This indicated that the strains within the specimen were uniformly distributed.
In both ranges of strain rate the horizontally oriented specimens were consistently the strongest,
followed by the specimens oriented at 45'. The
vertically oriented specimens were the weakest. This relationship was also observed in the limited tests performed at the intermediate strain rate. Strength increase with strain rate seemed to be similar far all specimen orientations. Teets that
were duplicated showed v e r y similar stress-strain
behavior. This probably reflects the narrow range in the natural physical properties (densities and
total water content). The similarities in physical
properties between specimens enhanced the reliability of comparing the test results. The
remolded laboratory-frozen specimens were as m c h as
80% stronger than the naturally-frozen undisturbed specimens. Although there was some anisotropy in the structure of the remolded specimens, these results indicated that the natural anisotropic structure acts to reduce the shear strength.
The strength anisotropy is s h w n in Table 3 for the two strain rates and for axial strain8
corresponding to yield (0.15%) and 10%. The amount of anisotropy is not pronounced at yield or at small strain rates, but it becomes quite significant at 10% strain. High horizontal strengths are similar
TABLE 3 Strength Anisotropy
Axial strain Nominal $90
-
$45So
strain rate
-
( % ) (%/min) 0
so
SR0.15 0.01 0.93 0.99 0.55
(yield)
to those observed by Eden (1955) in unfrozen varved clays from Steep Rack when the clay layers
predominated. Specimens in this study had a high
clay content (80-90%). High shear strengths at 45'
orientations have not been seen in any of the data on varved soi'ls in the literature. Ice cementation may resist the shearing Stresses acting between the layers. The higher strain rates used in this study
are comparable to those used by Eden (1955) and
Livingston (1956) in their test programs. Frozen Thompson varved clays appear to exhibit a greater strength anisotropy than either the unfrozen varved clay from Steep Rock (Eden 1955) or the frozen Keweenaw silt (Livingston 1956).
An estimate of the average unfrozen water
content of the combined soil at the in situ
temperature of -lDC, based on the liquid limits, is
15% (Tice et al. 1976). The unfrozen water content
would probably be different in the individual clay and silt layers, due to the surface area of the soil grains, and would influence the relative stress- strain behavior of these layers. It is recognized that the change from the in situ temperature to the laboratory temperature of -6OC, coupled with sublimation of the samples during 2 years of cold storage, would lower the unfrozen water content. The strength anisotropy in these specimens is probably due to the combined effect of the varves and their different unfrozen water contents, and other physical properties, as well as to the ice lenses. No attempt was made to estimate the relative contribution of these various components.
The series of in situ tests perforwed by Johnston and Ladanyi in an attempt to determine the bearing capacity of the frozen varved soils at Thompson were analyzed using cavity expansion theory to estimate the stress-strain behavior of the soil. Cavity expansion theory assumes that the soil
behaves aa a homogeneous, isotropic, ideally plastic
material (Ladan~i 1963). Horizontal varves and ice
lenses make these soile heterogeneous. This laboratory study has shown that these soils are not isotropic but anisotropic in their stress-strain behavior. The stress-strain curves indicate that these soils do not deform in an ideally plastic manner. A modification could be made to the cavity expansion theory to take into consideration strength anisotropy. Davis and Christian (1971) have
proposed a modification, taking into consideration
strength anisotropy, to the yield criterion which Scott (1963) recommended for predicting the bearing capacity of undrained soils. They show strength anisotropy to be present in most cohesive soils.
A more detailed laboratory study similar to the one presented in this paper would he needed to determine the complete range and magnitude of strength anisotropy associated with a particular soil deposit. One would have to consider the influences of various components of the soil deposit (number and physical properties of the varves, ice lenses, etc.) that could contribute to the
anisotropy. The results of field testing using the pressuremeter and penetrometer would provide a useful check on the strength relationships obtained and a qualitative appraisal of the influences of sampling and testing procedures.
ACKNOWLEDGMENTS
The authors wish to thank A. Chevrier and C. Hubbs for their help in preparing the specimens and carrying out the tests. This paper is a contribution from the Division of Building
Research, National Research Council of Canada, and is published with the approval of the Director af the Division.
REFERENCES
Baker, T. H. W., 1976, Transportation, preparation
and storage of frozen soil samples for
laboratory testing, Soil specimen
preparation for laboratory testing: ASTM Special Technical Publication 599, p. 88-112. Baker, T. H. W., 1978, Effect of end conditions on
the uniaxial compressive strength of frozen
sand, &Proceedings of the Third International
Permafrost Conference, Edmonton: Ottawa,
National Research Council of Canada, p. 608-
614.
Baker, T. H.
W.,
Jones, S. J. and Parameswaran,V. R., 1982, Confined and unconfined
compression tests on frozen soils, &Roger J. E. Brown Memorial Volume, Proceedings of the Fourth Canadian Permafrost Conference, Calgary: Ottawa, National Research Council of Canada, p. 387-393.
Davis, E. H. and Christian, J. T., 1971, Bearing capacity of anisotropic cohesive soil: American Society of Civil Engineering
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Eden, W. J., 1955, A laboratory study of varved clay
from Steep Rack Lake, Ontario: American
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Johnston, G. H., Brawn, R. J. E. and Pickersgill, D. N., 1963, Permafrost investigations at Thompson, Manitoba: Terrain studies: Division of Building Research, National Research Council of Canada, Technical Paper No. 158, 96 p. Johnston, G. H. and Ladanyi, B., 1974, Field tests
of deep power-installed screw anchors in permafrost: Canadian Geotechnical Journal, v. 11, No. 3, p. 348-358.
Klassen R. W., 1976, Landform and subsurface materials at selected sites in a part of the shield--north-central Manitoba: Geological Survey of Canada, Ottawa, Paper 75-19, 41 p.
Ladanyi, B., 1963, Expansion of a cavity in a
saturated clay medium: American Society of Civil Engineering Proceedings, v. 89, No. SM4, p. 127-161.
Ladanyi, B., 1976, Use of the static penetration test in frozen soils: Canadian Geotechnical Journal, v. 13, No. 2, p. 95-110.
Ladanyi, B., 1982, Determination of geotechnical parameters of frozen soils by means of the cone
penetration test, &Proceedings of the Second
European Symposium on Penetration Testing: Rotterdam, A. A. Balkema, p. 671-678.
Ladanyi, B., and Johnston, G. H., 1973, Evaluation of in sit" creep properties of frozen soils
with the pressuremeter, &The North American
Contribution to the Second International P e m f r o s t Conference, Yakutsk: Washington, D.C., National Academy of Sciences,
Ladanyi, B . , and Johnston, G. H . , 1974, Behaviaur of c i r c u l a r f o o t i n g s and p l a t e anchors i n
permafrost: Canadian Geotechnical J o u r n a l , v. 11, No. 4, p. 531-553.
Livingston, C. W., 1956, Excavations i n f r o z e n ground, P a r t I , Explosion t e a t s i n Keweenaw s i l t : Boston, U.S. Army Snow, I c e , Permafrost Research Establishment, Rep. 30, 97 p,
Metcalf, J. 8. and Tawnsend, D. L., 1960, A
preliminary study of t h e g e o t e c h n i c a l p r o p e r t i e s of varved c l a y s a s r e p o r t e d i n Canadian Engineering Case Records,
&
Proceedings of t h e Fourteenth Canadian S o i l Mechanics Conference, Niagara F a l l s , Ontario: N a t i o n a l Research Council Canada. Technical Memo, No. 69, p. 203-225.S c o t t , R. S., 1963, P r i n c i p l e s of s o i l mechanics: Reading, Mass., Addison-Wesley, 440 p. T i c e , A. R., Anderson, D. M., and Banin, A , , 1976,
P r e d i c t i o n of unfrozen water c o n t e n t s i n f r o z e n s o i l s from l i q u i d l i m i t determinations:
Hanover, N. H., Cold Regions Research and Engineering Laboratory, Rep. 76-8, 17 p. T s c h e b o t a r i o f f , 6 . P., and B a y l i s s , J. R., 1948, The
d e t e r m i n a t i o n of t h e s h e a r i n g s t g e n g t h of varved c l a y s and t h e i r s e n s i t i v i t y t o remoulding,
&
Proceedings of t h e Second I n t e r n a t i o n a l Conference on S a i l Mechanics and Foundation Engineering, v. 2: Rotterdam, Haarlem, p. 203-207. 1 9 0 ~ N . W . T . S A S K . i H O M P S O N SOIL ICE SOlL DESCRIPTION PHASE PHASE
I
~ l ~ i n g moss, ?eat(
~t(
None/
Dark brown frozen/
Frozen varved clav1
1
Ilght brown sllt layers
Ill2
-
2 cmldark brown clay layers CL v s
12
-
6
cml, Ice lenses Llght brown frozen clay sllt, plastlc frozen lnot lamlnatedlSOUTHERN LiMlT OF
I
- -
DliCONiiNUOUS PERMAFROSTLAKE A G A I I I Z
U . S . A .
FIGURE 1 Location map.
L
0
100
200
300
400
500
TOTAL WATER CONTENT B Y DRY W E I G H T , 9b
4 5 S A M P L I N G ZONE \ ! M A R C H 1918 - I - 6 - 5 - 4 - 3 - 2 - 1 0 TEMPERATURE, 'C
FIGURE 3 Ground temperatures, from temperature cable. GSC site ZA, Thompson, Manitoba.
FIGURE 4 Stress-strain curves at O.Ol%/min.
3 m & E v; 2 0 0 1" A X I A L S T R A I N . % l " " I ' a " D I R E C T I O N OF L O A D TO P L A N E OF V A R V E S
-
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P E R P E N D I C U L A R...
P A R A L L E L---
45"-
,-.-.
-
D I R E C T I O N OF L O A D TO P L A N E OF V A R V E S-
P E R P E N D I C U L A R m R E M O U L D E D a-
TEMP. -6'C 0 I / I I , I I * L m 0 5 1 0 15 A X I A L S T R A I N . %T h i s p a p e r , w h i l e being d i s t r i b u t e d i n r e p r i n t form by t h e D i v i s i o n of B u i l d i n g Research, remains t h e c o p y r i g h t of t h e o r i g i n a l p u b l i s h e r . It should n o t be r e p r o d u c e d i n whole o r i n p a r t w i t h o u t t h e p e r m i s s i o n of t h e p u b l i s h e r . A l i s t of a l l p u b l i c a t i o n s a v a i l a b l e from t h e D i v i s i o n may be o b t a i n e d by w r i t i n g t o t h e P u b l i c a t i o n s S e c t i o n , D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l R e s e a r c h C o u n c i l of C a n a d a , O t t a w a , O n t a r i o , K1A OR6.
