Publisher’s version / Version de l'éditeur:
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la
première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.
Questions? Contact the NRC Publications Archive team at
PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
Report (National Research Council of Canada. Division of Building Research), 1954-12-01
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.
https://nrc-publications.canada.ca/eng/copyright
NRC Publications Archive Record / Notice des Archives des publications du CNRC : https://nrc-publications.canada.ca/eng/view/object/?id=a130df9a-00da-4a14-954e-94231afd8923 https://publications-cnrc.canada.ca/fra/voir/objet/?id=a130df9a-00da-4a14-954e-94231afd8923
NRC Publications Archive
Archives des publications du CNRC
For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.
https://doi.org/10.4224/20331506
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
Laboratory Study of Varved Clay from Steep Rock Lake, Ontario Eden, W. J.
NATIONAL RESEARCH COUNCIL CANADA
D I V I S I O N OF BUILDING RESEARCH
A LABORATORY STUDY OF VARVED CLAY FROM S T E E P ROCK LAKE, ONTARIO
by W . J. E d e n
(Assistant Heaearch O f f i c e r , D . B . R . , N . R . C . )
Ottawa
A
LABORATORY STUDYOF
VARVED CLAY FROM STEEP ROCK LAKE, ONTARIOby
W.
J. EdenThroughout Canada, but especially in the northern areas, deposits of fine-grained glacial soils are found. These soils have frequently been the cause of a good deal of trouble to the construction and mining industries. When found in a saturated condition these
soils often have the ability to liquefy whenever they are disturbed. The Division of Building Research of the National Research Council has undertaken a study of such northern soils. When high-grade iron ore was discovered beneath the waters of Steep Rock Lake and mining operations led to the dewatering of the Lake and subsequent dredging of the Lake bottom deposits, a good opportunity for study arose.
The deposits of soil in Steep Rock Lake were for the most part varved clays, one of the more treacherous of the glacial soils. With the co-operation of Steep Rock Iron Mines Company Limited, the Division of Building Research undertook a detailed study of the Steep Rock varved clays with emphasis on the engineering standpoint.
At the outset of the study, varved clays were treated
by the usual practice of soil mechanics, as a uniform soil. Testing was conducted irrespective of the laminations which make up the
varved clay. The results of this study have been previously presented by Legget and Bartley (1). It was soon recognized that the separate laminations which make up a varve had remarkably different physical properties. Part of the detailed study was therefore directed toward finding the properties of the individual laminae and the variations in properties within the laminae.
T h i s p a p e r d e a l s w i t h some r e s u l t s of t h i s d e t a i l e d s t u d y . Although n o t t h e o b j e c t i v e of t h e s t u d y , a good d e a l of i n f o r m a t i o n h a s been assembled which may be v a l u a b l e t o g e o l o g i s t s , T h i s p a p e r p r e s e n t s t h e g e o l o g i c a l a s p e c t s of t h i s s t u d y . The test r e s u l t s a r e d i s c u s s e d i n t h e l i g h t of c u r r e n t t h e o r i e s concerning t h e f o r m a t i a n of varved c l a y s .
LABORATORY W QRK
To c a r r y out t h i s l a b o r a t o r y i n v e s t i g a t i o n , b l o c k samples sf
z
s i z e which could be c o n v e n i e n t l y handled were c o l l e c t e d by t h e a u t h o r a t S t e e p Rock Lake, s e a l e d bn p a r a f f i n o r petrowax, packed i n damp sawdust, and shipped t o O t t a w a f o r t e s t i n g . Samples were t a k e n from f r e s h exposures i n o r d e r t o p r e s e r v e t h e n a t u r a l w a t e r c o n t e n t of t h e varved c l a y s . The samples were chosen from w i d e l y s e p a r a t e d l o c a t i o n s , and w i t h t h e o b j e c t of r e p r e s e n t i n g t y p i c a l specimens of t h e varved c l a y which o c c u r s i n t h e Lake b o t t ~ m . OnceIn t h e l a b o r a t o r y t h e samples were s p l i t i n t o f r a c t i o n s of l i g h t (summer) and d a r k ( w i n t e r ) l a y e r s f o r t h e v a r i o u s p h y s i c a l t e s t s .
( a ) N a t u r a l Water Content
The n a t u r a l w a t e r c o n t e n t i s determined by comparing t h e wet and oven d r y w e i g h t s of t h e m a t e r i a l . Qven d r y i n g was c a r r i e d
out a t a t e m p e r a t u r e of 1 0 5 ~ ~ . S i n c e t h e s e s o i l s were s a t u r a t e d , t h e m o u n t of w a t e r p r e s e n t r e p r e s e n t s t h e volume of v o i d s of t h e c l a y . The void r a t i o was determined s e p a r a t e l y , by c a r e f u l l y %rimming a sample, t h e n weighing and measuring. I n a l l c a s e s i t was found t h a t t h e varved c l a y s were a t l e a s t 99 p e r c e n t s a t u r a t e d . S i n c e t h e w a t e r c o n t e n t al3o r e p r e s e n t s t h e void r a t i o of t h e c l a y s , It 1s a measure of t h e s t r u c t u r e of t h e s o i l . Water c o n t e n t t e s t s
were conducted with the objective of determining the variations in structure between the dark and light layers, and also the variations within any one layer.
The results of the water content determinations revealed a remarkable difference betweez t 5 e dark and light layers which aake up
a
varve. Figure 1, which illustrates the variation foundin one ample, is typical of the moisture content variations found fc all the
teat
w c ~ k . T h e wa'er content of the dark layers ranged from 60 to 100 per cent, and of the light layers from 20 to40
per cent. This range in water content corresponds to a range from1 - 6 9
to 2.83 in void ratio for the dark layers, and from0.56
to1-11
far
the light layers. Thus the dark layera have a void ratio approximately 2 1/2 to3
times that of the light layers, Thespecific gravity of the soil particles was 2.80 and 2.76 for the dark and light materials respectively.
(b) Plasticity
The plasticity in clays is due to the molecular forces acting between small particles. These forces vary acc~rding to the structure of the clay particless i,e., the type of clay mineral present, the aize and aurface development of the particles, and
according to the concentration and type of electrolyte in the water.
A ka~linite clay and a montmorillonite clay having the aame grain size would have entirely different plasticity characteristics, In a ayatem of pure kaolinite clay and pure water, Hauser and Le Beau
( 2 ) attribute plasticity to molecular attraction forces between uncharged particles (van der Waala forces). Recent inveatfgations show that plasticity is greatly influenced by the cation complex of the clay. Ahlberg
(3)
found that the a m e clay treated with hydrogen,sodium, and o t h e r c a t i o n s underwent g r e a t changes in p l a s t i c i t y depending on t h e c a t i o n .
The p l a s t i c i t y of t h e varved c l a y s from S t e e p Rock was i n v e s t i g a t e d by means of t h e A t t e r b e r g l i m i t s t e s t s . T h i s method h a s been s t a n d a r d i n s o i l mechanics p r a c t i c e ; a d e t a i l e d procedure f c r t h e t e s t may be found i n A.S .T.M. "Procedures f o r T e s t i n g S o i l s "
( 4 )
o r i n many of t h e r e f e r e n c e books on S o i l Mechanics. The A t t e r b e r g limits a r e made up of t h e l i q u i d l i m i t and p l a s t i c l i m i t . The l i q u i d i i m i t i s d e f i n e d a s t h e water c o n t e n t r e q u i r e d t o r e n d e r t h e s o i l j u s t f l u i d as d i s t i n c t from p l a s t i c . The p l a s t i c l i m i t i~ d e f i n e d as t h e water c o n t e n t r e q u i r e d t o r e n d e r t h e s o i l p l a s t i c a s d i s t i n c t from f r i a b l e o r crumbly. The d i f f e r e n c e i n w a t e r c o n t e n t s between t h el i q u i d and p l a s t i c l i m i t s i s t h e range i n which t h e s o i l i s p l a s t i c , and h a s been d e f i n e d as t h e p l a s t i c i t y index. Highly p l a s t i c s o i l s have a high numerical v a l u e f o r t h e p l a s t i c i t y index and c o n v e r s e l y n o n - p l a s t i c s o i l s have a v a l u e of z e r o f o r t h e p l a s t i c i t y index.
It should be noted t h a t t h e procedure followed f o r
d e t e r m i n a t i o n of t h e l i q u i d l i m i t v a r i e d s l i g h t l y from t h e s t a n d a r d procedure l i s t e d i n
( 4 )
whereas i t i s u s u a l t o conduct t h e l i q u i dl i m i t on s o i l which h a s been a i r d r i e d , t h e v a l u s s of l i q u i d l i m i t l i s t e d were determined on s o i l i n i t s n a t u r a l s t a t e . It was found t h a t l i q u i d
l i m i t d e t e r m i n a t i o n s conducted on S t e e p Rock varved c l a y a i n t h e i r n a t u r a l s t a t e y i e l d e d g e n e r a l l y h i g h e r r e s u l t s t h a n d e t e r m i n a t i o n s
conducted on a i r - d r i e d samples.
The A t t e r b e r g t e s t s r e v e a l e d a g r e a t d i f f e r e n c e i n p l a s t i c i t y between t h e d a r k and l i g h t l a y e r s . The change i n p l a s t i c i t y i s of t h e same o r d e r a s t h a t f o r n a t u r a l w a t e r c o n t e n t and void r a t i o . F i n u r e 2
fraction (after Skemptcn
( 5 ) ) ,
Figure3
shows the difference between light and dark layers when plotted on the Casagrande chart of plastici- ty index vs. liquid limit (6).In
Figure 4 the variations in plastici- ty within one varve are shown, This figure shows results which are typical of the variations found in other samples in which the layers aye uf more equal thickness. Figure 4 demonstrates a very rapid changein plasticity from dark to light material, as was the case with water content and grain size. Figures 2 and 3 contain results of tests from all portions of the varves, and indicate no transitional zone of any appreciable thickness between the dark and light layers,
( c ) Grain Size
The investigation of grain size was directed toward determf- ning the difference between the dark and light layers and whether any gradation in grain size existed within the varves, The techniques used for grain-size determinations were hydrometer analysis, pipette analyeis, and measurement of individual grains under the microscope. The procedures used have been thoroughly investigated by various authorities.
In
the hydrometer analysis, the procedure followed was developed by Arthur Casagrande (11) and is described by Lambe (121, In the pipette analysis, the procedure outlined by Krumbein (13) wasfollowed. Microscopic grain-size analysis was conducted by the
technique given by Krumbein (13), The three techniques for grain-size analysis were found necessary because of the difficulty in obtaining a sufficient amount of soil to make any one test standard. Comparative tests were conducted on the same sample by both the hydrometer and
pipette methods; the results were f,ound to compare closely, It is difficult to conduct a comparison between the hy&rometer or pipette methods with the microscopic method because, with the latter, the
g r a i n - s i z e frequency i s based on number r a t h e r t h a n by weight as w i t h t h e o t h e r methods. The hydrometer and p i p e t t e a n a l y s e s were conducted on samples which had been d i s p e r s e d w i t h a s m a l l amount 0%
The r e s u l t s of mechanical a n a l y s i s f o r g r a i n s i z e a r e u s u a l l y p r e s e n t e d g r a p h i c a l l y by means of a g r a i n - s i z e d i s t r i b u t i o n
Pseqaencg curve c r a g r a i n - s i z e d i s t r i b u t i o n a c c w u l a t i o n c u r v e . Because of t h e barge number of tests conducted, i t i s d i f f i c u l t t o compare a l l t h e c u r v e s o n one diagram. The v a l u e s p r e s e n t e d i n F i g u r e s 4 and
5
weye obtained by s t a t i s t i c a l methods ~f d e s c r i b i n g such curves. The s t a t i s t i c a l methods a r e d e s c r i b e d by Ksumbein
(131,
O t t o ( 1 4 ) andIrman ( 1 5 ) . The geometric mean d i a m e t e r i s t h e s i z e which c s r r e a p o n d s t o t h e g r a i n - s i z e diameter a s s o c i a t e d w f t h t h e most abundant g r a i n s i n a n a s m e t r i c a l d i s t r i b u t i o n . Using t h e geometric mean and t h e s t a n d a r d d e v i a t i o n i t f s p o s s i b l e t o d e s c r i b e most of t h e g r a i n - s i z e d i s t r i b u t i o n curve by: two numbers, By c o n v e r t i n g t h e g r a i n s i z e In
m i l l i m e t r e s t o t h e
9
s c a l e ( t h e g s a i n s i z e i n9
u n i t s e q u a l l i n g t h e n e g a t i v e log2 g r a i n s i z e i n m i l l i m e t r e s ) and p l o t t i n g t h e g r a i n - s i z e d i s t r i b u t i o n curve on p r o b a b i l i t y paper, it i s p o s s i b l e t o d e r i v e t h e geometric mean d i a m e t e r and s t a n d a r d d e v i a t i o n bya
simple g r a p h i c a l c o n s t r u c t i o n ( I m a n ( 1 5 ) ).
The g r a i n - s i z e t e s t s were conducted t o determine t h e d i f f e r e n c e i n g s a i n s i z e between t h e d a r k and l i g h t l a y e r s and t o determine whether t h e S t e e p Rock varved c l a y s were d i a t a c t i c " .
% F r a s e r ( 1 8 ) d e i i n e s d i a t a c t f c s t r u c t u r e of a varve a s one i n which t h e m a t e r i a l s of t h e varve a r e s o r t e d a c c o r d i n g t o s i z e and s p e c i f i c
g r a v i t y of p a r t i c l e s , t h e c o a r s e s t a t t h e bottom and t h e f i n e s t a t t h e t o p .
Symminct s t r x e t u r e r e f e r s t o c l a y d e p o s i t e d under c o n t r o l
cf a n e l e c t r o l y t e , i n which case p a r t i c l e s l a r g e and small go down
t ~ g e t h e r and form an u n s o r t e d mass due t o f l o c c u l a t i o n of t h e g r a i r L s . F S g u ~ e 2 shows a significant d i f f e r e n c e i n g r a i n s i z e . The d a r k
lagers c o n t a i n from
65
t o95
p e r c e n t c l a y - s i z e d p a r t i c l e s whereast l . ~ ~ ~ l.!gnt, laye:cda co2t,air,, only f r o m 18 t o
35
p e r c e n t c l a y - s i z e dp~tr'vl:?,es. F i g u r e
4
shsws a s i g n i f i c a n t d i f f e r e n c e w i t h i n a vakvz, The r e s u l t s of t e s t s conducted on s u b l z y e r s f a i l e d t o show a s i g r : f f i c a c t g r a d a t i o n i n g r a i c sZze w i t h i n one v a r v e . F i g u r e 4Lnd%zates t h e r e s u l t s a h t a f n e d from varved c l a y w i t h abnormally t h i c k da2k l a y e r s ( b e l i e v e d t o be what Antevs ( 1 7 ) t e r n s a d r a i n a g e v a k v ~ ! . Although t h i s v a r v e i s a d m i t t e d l y n o t t y p i c a l , i t was chosen b e c a m e a l a r g e number of t e s t s were made on i t ; t e s t s conducted on samples w i t h v a r v e s of normal t h i c k n e s s a l s o f a i l e d t o i n d i c a t e any g r a d s t i o n wit.hin a varve. F i g u r e
6
P n d f c a t e s t h e r e s u l t s o b t a i n e d by t h emicroscopic examination of a l i g h t (summer) l a y e r which was d i v i d e d i n t o s i x e q u a l f r a c t i o n s throughout i t s p r o f i l e . No g r a d a t i o n w a s i n d i ~ a t e d by t h e r e s u l t s i n F i g u r e
6 ,
Admittedly t h e number of v a r v e s t e s t e d i n t h i s manner a r e comparatively few i n r e l a t i o n t o t h e t o t a l number of v a r v e s which e x i s t a t S t e e p Rock. The samples were, however, chosen t.0 be t y p i c a l
of t h e v a r i o u s t y p e s of v a r v e s which were uncovered. I n a l l t h e t e s t s conducted on t h e S t e e p Rock vakved c l a y , no g r a d a t i o n of p a r t i c l e s i z e w z t h i n a varve was i n d i c a t e d which i s somewhat p u z z l i n g c o n s i d e r i n g t h e work of Antevs
(17)
on t h e S t e e p Rock c l a y s , I n d i s c u s s i n g t h e f c - m a t i o n of t h e S t e e p Rock varved c l a y s , Antevs s t a t e s t h a t t h elaminations were d i a t a c t i c , n o t s ~ m i n e t and l f t t l e f l o c c u l a t i c n t o ~ k p l a c e .
To compare t h i s r e s u l t w i t h v a r v e s from o t h e r l o c a t i o n s , samples were o b t a i n e d from Amos, Quebec ( t h r o u g h t h e c o u r t e s y of D r , A . MacLaren of t h e G e o l o g i c a l Survey of ~ a n a d a ) arid from t h e Don V a l l e y a t Toronto. The Amos samples appeared v e r y similar t o t h e S t e e p Rock samples and l a c k e d any p a r t i c l e - s i z e g r a d a t i o n . The Toronto sample d i d a p p e a r t o have a p a r t i c l e - s i z e d i s t r i b u t i o n ; t h e r e s u l t s p r e s e n t e d i n F i g u r e
5
s u p p o r t t h i s view. T h i s i s , i n t h e a u t h o r ' s o p i n i o n , a d i a t a c t i c v a r v e , w h i l e t h e S t e e p Rock v a r v e s a r e n o t , Itcan
be s e e n from F i g u r e8
of a sample from Toronto t h a t t h e l i g h t m a t e r i a l grades g r a d u a l l y i n t o t h e d a r k w i t h no c l e a r boundary l i n e . I n F i g u r e s 9and 1 0 , showing v a r v e s from S t e e p Rock, e a c h s i d e . o f t h e l i g h t l a y e s h a s a d e f i n i t e boundary. T h i s i s n o t t h e c a s e w i t h t h e Toronto v a r v e (which i s i n v e r t e d i n t h e p h o t o g r a p h ) .
( d ) Thixotropy
Thixotropy i s d e f i n e d a s a r e v e r s i b l e g e l - s o l - g e l t r a n s f o r m a t i o n i n c e r t a i n m a t e r i a l s brought about by a mechanical d i s t u r b a n c e f o l l o w e d by a p e r i o d of r e s t . The word means "change by t o u c h " and hence, s i n c e s o i l p a r t i c l e s a r e s o l i d m a t e r i a l s , t h i x o t r o p y a p p l i e d t o s o i b a i n v o l v e s s o i l s t r u c t u r e . According t o Green and Weltmann ( 7 ) t h i x o t s o p y cannot e x i s t w i t h o u t f l o c c u l a t i o n b u t t h e converse
i s
n o t n e c e s s a r i l y t r u e .The term t h i x o t r o p y , a s used i n t h i s p a p e r , i n c l u d e s t h e s t a t e of " f a l s e body" as d e f i n e d by Psyce-Jones
(8)
as t h e two t e r n s are s o c l o s e l y a l l i e d , and t h i x o t r o p y h a s been used by many w r i t e r s t o c o v e r b o t h t r u e t h i x o t r o p y and f a l s e body.T e s t s t o d e t e r m i n e t h e d e g r e e of t h i x o t r o p y of s o i l s a r e d i f f i - c u l t t o r e l a t e t o f i e l d c o n d i t i o n s . The l a b o r a t o r y i n v e s t i g a t i o n was d i r e c t e d toward merely p r o v i n g t h e e x i s t e n c e of a t h i x o t s o p i c s t a t e . The procedure f o l l o w e d was a c c o r d i n g t o Ackermann ( 9 ) and y i e l d s a r e s a l t e x p r e s s e d i n t e r m s of w a t e r c o n t e n t c a l l e d t h e " s t i f f e n i n g l i m i t " .
- Y
-
',LLLS metnod i s as f o l l o w s . H Y I I ~ L - L ~ arnoult of s o i l i s mixed w i t h
d i s t i l l e d w a t e r i n a t e s t t u b e . S u f f i c i e n t w a t e r i s added i n s m a l l
i n c r e m e n t s and t h o r o u g h l y mixed until t h e p o i n t i s reached when the s o i l p a s t e w i l l begin t o flow when t h e t e s t t u b e i s i n v e r t e d a f t e r a
one-minute r e s t . The w a t e r c o n t e n t c o r r e s p o n d i n g t o t h i s c o n d i t f o n X s termed t h e s t i f f e n i n g l i m i t .
Again, a s t r i k i n g d i f f e r e n c e between t h e l i g h t and d a r k l a y e r s i s r e v e a l e d i n t h e i r s t i f f e n i n g l i m i t s . Table 1 g i v e s v a l u e s obta.%ned f o r sample 2-123 and may be compared w i t h F i g u r e
4,
Other t e s t r e s u l t s showed t h e same d i f f e r e n c e between d a r k and l i g h t l a y e r s . A few samples of t h e S t e e p Rock varved c l a y were t e s t e d by Boswell ( 1 0 ) u s i n g a s l i g h t l y d i f f e r e n t t e s t . He r e p o r t s v a l u e s of
65
f o r t h e l i g h t l a y e r s and 120 f o r t h e d a r k l a y e r s . A l l t h e t h i x o t r o p i c t e s t s show t h a t b o t h t h e l i g h t and d a r k l a y e r s of t h e varvad c l a y a r e t h i x o t r o p i c , and hence must be i n a f l o c c u l a t e d c o n d i t i o n .( e ) Mineral A n a l y s i s
The m i n e r a l components of t h e varved c l a y s were determined q u a l i t a t i v e l y by t h e t e c h n i q u e s of d i f f e r e n t i a l t h e r m a l a n a l y s i s and X-ray d i f f r a c t i o n . T h i s work w a s done by t h e C r y s t a l Chemistry S e c t i o n
of t h e Department of Mines and T e c h n i c a l Surveys, Ottawa, and r e v e a l e d t h e f o l l o w i n g components f o r t h e l i g h t l a y e r s : quarDz, c a r b o n a t e s , f e l d s p a r , c l a y ( s m a l l amount), o r g a n i c m a t t e r ( t r a c e ) ; d a r k l a y e r s :
q u a r t z , f e l d s p a r , c l a y , p r o b a b l y m o n t m o r i l l o n i t e , more t h a n l i g h t l a y e r s , o r g a n i c m a t t e r
-
s m a l l amount, s l i g h t l y more t h a n l i g h t l a y e r s .The above a n a l y s i s i s borne o u t by t h e " A c t i v i t y C h a r t " ( F i g u r e 2 ) . Both t h e l i g h t and d a r k l a y e r s p l o t as " i n a c t i v e c l a y s " , w i t h t h e d a r k m a t e r i a l d i s p l a y i n g more a c t i v i t y t h a n t h e l i g h t , T h i s can be a t t r i b u t e d t o t h e r e l a t i v e l y g r e a t e r q u a n t i t y of c l a y i n t h e d a r k l a y e r s . Normally m o n t m o r i l l o n i t e c l a y i s c o n s i d e r e d t o be a n
TABLE
IWater Content R e l a t i o n s h i p s f o r Sample 2-123
( i n
$oven-dry weight)
Natural
P l a s t i -Sample
Typeof
Water
Liquid
P l a s t i c
c i t y
No.
M a t e r i a l
Content
L i m i t L i m i t 4 IndenLight
(summer)
25.1
Light (summer)
23.6
Dark ( w i n t e r )
69.5
Dark ( w i n t e r )
77.8
Dark ( w i n t e r )
84.6
Dark ( w i n t e r )
89.3
Dark( w i n t e r )
90.2
Dark ( w i n t e r )
91.2
2-123-9
Dark
( w i n t e r )
92.8
93.7
30.2
63
.
5
2-1.23-10
Dark ( w i n t e r )
93
-8
95.2
33.4
61.8
2-123-11 Dark ( w i n t e r )
92.5
91
.934.0
57.9
2-123-12
ark
( w i n t e r )
79.3
64.0
2 3 0 9
4 0 , l
2-123-13
Light (summer)
27.9
26
.921
.?5.2
2-123-14 Light (summer)
23.5
25.5
2 0 . 15 0 4
ST iffet?-Eng
2 L l m l t" a c t i v e c l a y " , but i t p l o t s as a n " i n a c t i v e c l a y " because of t h e masking e f f e c t of t h e q u a r t z and f e l d s p a r mixed w i t h t h e c l a y .
The m i n e r a l a n a l y a i s r e v e a l s two i m p o r t a n t d i f f e r e n c e s i n t h e m i n e r a l c h a r a c t e r i s t i c s of t h e d a r k and l i g h t l a y e r s . One i s t h e
r e l a t i v e amounts of t r u e c l a y m i n e r a l s , and t h e second i s t h e f a c t t h a t t h e l i g h t l a y e r s c o n t a i n c a r b o n a t e s but t h a t t h e d a r k l a y e r s do n o t ,
(f) S h e a r S t r e n g t h
A few t e s t s were conducted t o determine t h e e f f e c t t h a t t h e varved s t r u c t u r e had on s h e a r s t r e n g t h . The t e c h n i q u e s used were t h e ~mcorafined compression t e s t and t h e d i r e c t s h e a r t e s t , Procedures f o r both t h e s e t e s t s a r e w e l l e s t a b l i s h e d and a r e d e s c r i b e d i n d e t a i l by Lambe ( 1 2 ) ,
F o r t h e unconfined compression t e s t , c y l i n d e r s of u n d i s t u r b e d s ~ i l were trimmed, w i t h due r e g a r d t o t h e o r 1 e n ; a t i o n of t h e v a r v e s s t o a d i a m e t e r of 1 112 i n c h e s and l e n g t h of
3
i n c h e s . T h i s c y l i n d e r was s u b j e c t e d t o a x i a l compression, w i t h t h e s t r e s s a t f a i l u r e b e i n g termed t h e unconfined compression s t r e n g t h . The Mohr t h e a r y ofsv.pture 5125~6 + h a t t h e s h e a r s t r e n g t h l a e q u a l t o one-half the
unconfined compression s t r e n g t h f o r moat c l a y s . The test rcaealts f o r two eamples a r e p r e s e n t e d i n F i g u r e
7,
by showing t h e v a r i a t i o n i n unconfined compression s t r e n g t h w i t h o r i e n t a t i o n of t h e v a r v e s . The d i f f e r z n c e between t h e two c u r v e s can be e x p l a i n e d by t h e r e l a t i v e amourits sf d a r k and l i g h t m a t e r i a l I n t h e samplea, The d a r k l a y e r s were approximately t w i c e t h e t n i e k r ~ e s s of t h e l i g h t l a y e r s i nWhen 8 = 3 0 ° , f a i l u r e t o o k p l a c e e n t i r e l y i n t h e l i g h t l a y e r s as i n d i c a t e d i n F i g u r e 9 , Thus t h e v a l u e of unconfined c ~ m p r e s s i o n s t r e n g t h a t 3 0 O r e p r e s e n t s n e a r l y t w i c e t h e s h e a s s t r e n g t h of t h e l i g h t l a y e r s . The d a r k l a y e r s r e s i s t e d d e f o r m a t i o n t o a g r e a t e r e x t e c t t h a n t h e l i g h t l a y e z a . Because of t h i s d i f f e r e n c e
Ln
stiffness, t h e d e p a r t u r e c f t h e c u r v e s F c r t h e two samples a t 8 = 0 O i s a c t u a l l y t h e s t r e n g t h of t h e l i g h t m a t e r i a l , and because t h e e f f e c t i v e a r e s r e s i s t i n g l o a d i s l e a s t h a n I n d i c a t e d by F i g u r e7,
t h e s t ~ e n g t h j.3 s l i g h t l y lower a t 8 =3e0.
S t r e n g t h d e t e r m i n a t i o n s on s e p a r a t e s a m p l e s sf d a r k awd l i g h t material were conducted i n the d i r e e t s h e a r box. While t h i smethod of s t r e n g t h d e t e r m i n a t i o n i s not c ~ n s i d e r e d r e l i a b l e f o r cskaeaive m i l s , i t i s c o n s i d e r e d t h a t t h e r e l a t i v e s t r e n g t h s of t h e dark and
l i g h t m a t e r i a l a r e i n d i c a t e d , With t h e d i r e c t s h e a r t e s t , it was found t h a t t h e d a r k l a y e r s had a s h e a r s t ~ e n g t h of a p p s o x i m t e l y
6
p . s , $ . andt h e l i g h t l a y e r s of a p p r ~ x ~ a t e l y
3
p . s , i . These r e s u l t s compare m a s o n a b l y w e l l w i t h s h e a r a t r e n g t h d e r i v e d from t h e m c s n f f n s d compression t e s t s .It must be p o i n t e d o u t , t h a t o n l y two samples were t e s t f e d f o r s t r e n g t h , and t h e above r e s u l t s must be r e g a r d e d as p r e l i m i n a r y , The r e s u l t s do i n d i c a t e , however, t h a t t h e v a s v e s have a n i n f l u e n c e
on s h e a r s t r e n g t h , and t h a t t h e 19ght and d a r k l a y s r s have sadPcaLLy d i f f e r e n t s t r e s s - s t r a i n c h a r a c t e r f s t f c s . The d a r k l a y e r s , i n s p i t e
QF t h e i r l o o s e s t r u c t u r e and h i g h p l a s t i c i t y and w a t e r c o n t e n t , a p p e a r t o be much s t i f f e r and have g r e a t e r s t r e n g t h t h a n t h e l i g h t l a y e r s .
( g ) S e n s i t i v i t y
S e n s i t i v i t y Is t h e Cerm a p p l l e d t o d e s c r i b e t h e l o s s of s t r e n g t h i n a c l a y when i t 1 6 changed from t h e m d l a t i m b e d t o t h e
remoulded s t a t e . R e s u l t s from t h e unconfined compression t e s t have been used a s a c r i t e r i o n f o r s e n s i t i v i t y . The d e g r e e of s e n s i t i v i t y i s d e f i n e d as t h e r a t i o of u n d i s t u r b e d s t r e n g t h t o t h e remoulded s t r e n g t h , a t t h e same watep c o n t e n t .
The l i g h t m a t e r i a l , when remoulded a t n a t u r a l w a t e r c o n t e n t , d i d n o t have s u f f i c i e n t s t r e n g t h f o r a c y l i n d e r
3
i n c h e s l o n g and1 1/2 i n c h e s i n d i a m e t e r t o s t a n d by i t s e l f . The d a r k l a y e r s had a n unconfined compression remoulded s t r e n g t h of a p p r o x i m a t e l y 1 p , s . i . o r o n e - t w e l f t h of t h a t f o r t h e same m a t e r i a l i n t h e u n d i s t u r b e d s t a t e .
Thus b o t h t h e d a r k and l i g h t l a y e r s of t h e varved c l a y can be c l a s s i f i e d as e x t r a - s e n s i t i v e s o i l s ( a f t e r Skempton ( 1 6 ) ) .
DISCUSSION OF TEST RESULTS WITH REGARD TO THEORIES ON VAWING
Before d i s c u s s i n g t h e t e s t r e s u l t s , i t i s n e c e s s a r y t o review some of t h e t h e o r i e s on t h e f o r m a t i o n of varved c l a y s . The word "va.rvedn i n f e r s a d i s t i n c t l y banded d e p o s i t . Thus a v a r v e i s u s u a l l y d e f i n e d i n g e o l o g i c a l l i t e r a t u r e as m a t e r i a l which c a n be d e f i n i t e l y i d e n t i f i e d t o have been d e p o s i t e d i n one y e a r , and i s q u i t e d i s t i n c t from p r e c e d i n g o r s u c c e e d i n g y e a r s . Baron Gerard d e Geer, a Swediph g e o l o g i s t , F i r s t recognized t h e s i g n i f i c a n c e of t h e s e l a m i n a t i o n s and s u g g e s t e d t h e a n n u a l t h e o r y of d e p o s i t i o n . Each varve c o n s i s t s of a c o u p l e t , a
l i g h t - c o l o u r e d r e l a t i v e l y c o a r s e summer l a y e r , and a d a r k e r - c o l o u r e d f i n e - g r a i n e d w i n t e r f r a c t i o n . Varved c l a y s a r e u s u a l l y a s s o c i a t e d w i t h g l a c i a l l a k e s , and were formed d u r i n g a tlme of r e t r e a t of a
g l a c i e r . De Geer b e l i e v e d t h a t d u r i n g t h e summer when l a r g e volumes of melt w a t e r charged w i t h g l a c i a l d e b r i s r e a c h e d a l a k e o r s e t t l i n g b a s i n , t h e r e l a t i v e l y l a r g e p a r t i c l e s would s e t t l e o u t . In t h e w i n t e r , when t h e l a k e was covered w i t h i c e , and no f u r t h e r f r e s h m a t e r i a l was s u p p l i e d , t h e f i n e - g r a i n e d m a t e r i a l c a r r i e d i n s u s p e n s i o n was g i v e n s u f f i c i e n t time t o p r e c i p i t a t e . Thus a varved c o u p l e t was formed e a c h
y e a r .
Antevs ( 1 7 ) h a s conducted d e t a i l e d s t u d y of t h e vasved c l a y s a t S t e e p Rock and h a s w r i t t e n a n account of t h e t y p e s of v a r v e s found and d i s c u s s e d t h e i r mode of f o r m a t i o n . He d i s c o v e r e d e i g h t s e p a r a t e s e r i e s of varved c l a y s c o r r e s p o n d i n g t o e i g h t d i f f e r e n t c o n d i t i o n s of environment. A s p r e v i o u ~ l y mentioned, Anteva b e l f e v e s t h e S t e e p Rock v a r v e s t o be d i a t a c t i c and l i s t s seven c o n d i t i o n s which a f f e c t e d t h e d e p o s i t i o n of t h e S t e e p Rock c l a y s . These seven c o n d i t i o n s a r e a s f o l l o w s : ( 1 ) r e s t r i c t i o n of a p p r e c i a b l e mud s u p p l y t o t h e a m e r months; ( 2 ) f l u c t u a t i o n of mud i n f l u x and of t h e c u r r e n t s ;
( 3 )
d i f Przren-t i a l r a t e of s e t t l i n g of unequal g r a i n s and p a r t i c l e s ;
( 4 )
low tempera- t u r e and accompanying h i g h v f a c o s % t y and d e n s i t y of t h e l a k e waters;( 5 ) s e m i s t r a t i f i c a t i o n o r Isothermy of t h e l a k e w a t e r and o s c i l l a t i o n s between t h e s e s t a t e s ;
( 6 )
h e i g h t of f a l l of t h e p a r t i c l e s ; and,( 7 )
v a r i a t i o n s i n t h e c o n c e n t r a t i o n s of t h e e l e c t r o l y t e s . Antevs h a s covered t h e f o r m a t i o n of t h e S t e e p Rock c l a y s completely, and t h er e s u l t s p r e s e n t e d i n t h i s paper can o n l y supplement p a r t i c u l a r a s p e c t s i n Antevsl t h e o r y . Only on t h e p o i n t t h a t t h e S t e e p Rock v a r v e s a r e d i a t a c t i c , does t h e a u t h o r d i s a g r e e w i t h Antevs. T h i s i s on t h e p o i n t t h a t d i a t a c t i c i n f e r s a g r a d a t i o n i n p a r t i c l e s i z e w i t h i n t h e v a r v e , Before developing t h e argument f u r t h e r o i t i s n e c e s s a r y t o examine t h e c o n d i t i o n n e c e s s a r y f o r t h e f o r m a t i o n of d i a t a c t i c v a r v e s as l a i d
down by F r a s e r ( 1 8 ) .
Using a s p e c i a l l y c o n s t r u c t e d t a n k i n which t h e t e m p e r a t u r e of t h e w a t e r could be c l o s e l y c o n t r o l l e d , F r a s e r conducted experiments on t h e f o r m a t i o n of varved c l a y s , e s p e c i a l l y d i a t a c t i c v a r v e s . From his experiments, F r a s e r concluded t h a t t h e f o l l o w i n g conditions were n e c e s s a r y f o r t h e f o r m a t i o n of varved c l a y s :
( a ) The l a k e was one of q u i e t w a t e r s and had a p r a c t i c a l absence of e r o s i o n ;
( b ) The supply of m a t e r i a l was n o t f l o c c u l a t e d ;
( c ) The l a k e waters contained a very low c o n c e n t r a t i o n of e l e c t r o l y t e s .
F r a s e r f s experiments l e d him t o conclude t h a t d i a t a c t i c varves were formed s u b j e c t t o t h e r e s t r i c t i o n s t h a t follow:
( i ) During t h e m e l t i n g Beason t h e r e would be a continuous supply
of m a t e r i a l , u n f l o c c u l a t e d and of a s s o r t e d s i z e s . The c o a r s e r matePfal would s e t t l e r e l a t i v e l y r a p i d l y . Because of t h e cold w a t e r , t h e f i n e m a t e r i a l would s e t t l e very slowly. The s e t t l i n g v e l o c i t y would be a d i r e c t f u n c t i o n of t h e temperature of t h e w a t e r and p a r t i c l e s i z e . Because of t h e d i f f e r e n c e i n s e t t l i n g v e l o c i t i e s between c o a r s e and f i n e m a t e r i a l , t h e sediment would have a d e f i n i t e g r a d i n g p w i t h c o a r s e r m a t e r i a l a t t h e bottom of t h e varve and becoming p r o g r e s s i v e l y f i n e r as t h e varve was b u i l t up;
( i i ) A t t h e c l o s e of t h e m e l t i n g season, t h e supply of Ereah m a t e r i a l would dwindle t o p r a c t i c a l l y zero. Thus n e a r l y a l l of t h e c o a r s e r m a t e r i a l would be d e p o s i t e d d u r i n g t h e summer, and t h e d i v i s i o n between t h e l i g h t and d a r k m a t e r i a l would correspond approximately t o t h e c l o s e of t h e melting season;
( i i i ) During t h e w i n t e r season, w i t h no f r e s h supply of m a t e r i a l t h e f i n e m a t e r i a l would be p a r t i a l l y a i d e d by f l o c c u l a t i o n . T h i s
f l o c c u l a t i o n would r e s u l t from an i n c r e a s e d s a l i n i t y because of t h e i n c r e a s e i n t h e c o n c e n t r a t i o n of e l e c t r o l y t e s s u p p l i e d over t h e m e l t i n g season. F r a s e r t s experiments showed t h a t f l o c c u l a t i o n would be r e t a r d e d by t h e cold w a t e r . In any c a s e t h e s a l i n i t y c o u l d n o t i n c r e a s e t o a p o i n t g r e a t e r t h a n o n e - f i f t i e t h of normal s e a w a t e r t o permit varving. Erases
thought that t h i s small degree of s a l i n i t y would not a f f e c t t h e c o a r s e r p a r t i c l e s s u f f i c i e n t l y t o cause f l o c c u l a t i o n , because t h e l a r g e r t h e p a r t i c l e , t h e more i n d i f f e r e n t i t i s t o f l o c c u l a t i o n ;
( i v ) The p e r i o d i c supply of m a t e r i a l t h u s o u t l i n e d would continue on an annual cycle.
Considering t h e l a b o r a t o r y t e s t s described i n t h i s paper, t h e r e s u l t s of t h e g r a i n - s i z e t e s t s revealed no g r a d a t i o n of p a r t i c l e s i z e w i t h i n t h e laminae. This suggests t h a t t h e Steep Rock varves a r e not
d i a t a c t i c . The water content t e s t s show t h e c l a y s t o have a very loose s t r u c t u r e , and because both t h e l i g h t and dark m a t e r i a l e x h i b i t t h i x s - t r o p y , it ia thought t h a t both t h e l i g h t and d a r k m a t e r i a l were f l o c c u - l a t e d . Legget and B a r t l e y ( 1 ) i n d e s c r i b i n g t h e h y d r a u l i c dredging c a r r i e d out a t p a r t of t h e mining o p e r a t i o n s , p o i n t out t h a t t h e s a i l s , when redeposited i n t h e l a k e waters, remain i n p a r t i c l e assemblages, w i t h a mean diameter of about 0.01 m i l l i m e t r e s . This i n d i c a t e s t h a t t h e
s o i l p a r t i c l e s have s t r o n g f o r c e s a c t i n g between them t o cause t h i s f l o c c u l a t i o n . The mineral a n a l y s i s revealed t h a t t h e l i g h t l a y e r s contained carbonates, although t h e dark l a y e r s were void of carbonates, This p o i n t i s worth noting i n t h e l i g h t of Burwash ( 1 9 ) and Asrheniua
120)
Burwash ( 1 9 ) suggests t h a t t h e change i n t h e c a p a c i t y of t h e l a k e waters f o r holding d i s s o l v e d carbon dioxide and hence i t s c a p a c i t y f o r d i s s o l v i n g calcium carbonate may be r e s p ~ n s i b l e f o r t h e d e p o s i t i o n of varved c l a y s . In t h e w i n t e r , with a r e l a t i v e l y l a r g e c o n c e n t r a t i o n of carbonic a c i d , t h e lake waters a r e w e l l equipped t o maintain
calcium carbonate i n s o l u t i o n . In t h e s p r i n g , a s t h e l a k e waters become warm, t h e carbonic a c i d i s given up, l e a d i n g t o p r e c i p i t a t i o n of t h e
c a r b o n a t e s . T h i s , Burwash b e l i e v e s , l e a d s t o t h e f o r q a t i o n of c a l c i t e c o n c r e t i o n s i n t h e l i g h t o r summer l a y e r s . A s r e p o r t e d by Legget and B a r t l e y ( l ) , c o n c r e t i o n s a t S t e e p Rock a r e found only i n t h e Light
l a y e r s of t h e varves.
Arrhenius ( 2 8 ) i n a t t e m p t i n g t o e x p l a i n t h e causes f o r t h e g r e a t d i f f e r e n c e i n c o l o u r between t h e d a r k and l i g h t l a y e r s , found t h a t t h e d a r k o r w i n t e r m a t e r i a l showed d i s s o l u t i o n by carbonic a c i d on a f a r g r e a t e r s c a l e t h a n t h e summer m a t e r i a l , Arrhenius r e p o r t e d on varved marls which occur i n Sweden, but i n t h e opinion 'of t h e a u t h o r t h i s f a c t
s u p p o r t s Burwash's t h e o r y .
The d i f f e r e n c e i n p l a s t i c i t y between t h e d a r k and l i g h t m a t e r i a l may be due t o t h r e e c a u s e s , F i r s t , t h e d a r k l a y e r s c o n t a i n
more c l a y m i n e r a l s , which would i n c r e a s e p l a s t i c i t y , Secondly9 t h e l i g h t m a t e r i a l i s s l i g h t l y c o a r s e r , t h u s has l e s s s u r f a c e a r e a , which would
reduce i t s p l a s t i c i t y . A t h i r d cause could be a d i f f e r e n t c a t i o n complex i n t h e c l a y s , brought about by changes i n t h e d e p o s i t i o n a l e n ~ i r o ~ m e a ~ t ; . Test r e s u l t s b e a r out t h e f i r s t twc p o i n t s but t h e r e i s no proof
for
t h e Third.In
conclusion, t h e t e s t r e s u l t s p r e s e n t e d i n t h i s paperi n d i c a t e t h a t both t h e d a r k and l i g h t l a y e r s of t h e varved c l a y a t S t e e p Rock were a f f e c t e d by f l o c c u l a t i o n i n t h e i r d e p o s i t i o n , G r a i n - s i z e
r e s u l t s show t h a t t h e y cannot be termed d i a t a c t i c a s d e f i n e d by F r s a e r ( 1 8 ) . Regarding t h e i r mode of formation, t h e r e s u l t s lend support ti,
the t h e o r y put forward by Bumash, ACKNOWLEDGEMENTS
The a u t h o r wishes t o acknowledge t h e a s s i s t a n c e and f r i e n d l y co-operation extended t o him by t h e s t a f f of S t e e p Rock Ikon Mines
Manager, and K . McRorie, Chief Engineer. S p e c i a l acknowledgement i s a l s o due S. Forman, of t h e Department of Mines and Technical Surveys
(Canada), who c a r r i e d out t h e mineral a n a l y s i s and t o D r . A . MacLasen of t h e Geological Survey of Canada who supplied samples of v a ~ v e d c l a y from Amos, Quebec. The a u t h o r a l s o wishes t o express h i s a p p r e c i a t i o n f o s t h e h e l p w i t h v a r i o u s a s p e c t s of t h e work given him by h i s colleagues i n t h e Division of Building Research, e s p e c i a l l y t h e D i r e c t o r , M r . R , F. Legget, w i t h whose approval t h i s paper i s now published as a c o n t r i b u t i o n from t h e Division of Building Research of t h e National Research Council of Canada.
BIBLIOGRAPHY
1. Legget, R . F. and M . W. B a r t l e y , An Engineering Study of G l a c i a l Deposits a t Steep Rock Lake, Ontario. 3conomic l e o l o g ~ r ~ Vole 48, p. 513-540, November 1953.
2 . Hauser, E . A . and D. S. Le Beau. Colloid Cheml3try of Clay Minerals and Clay Films. ' c l l o i d Chemistry ( ~ d i t e d by Jerome ~ i e . ~ a n d e r ) , Val.
6 ,
p.191-213, R.inhold 2 ~ b . L 1 . ~ h i n g Corp.,
Neb Ycrk,1946,
3. Ahlberg, H. A Contribution t o t h e Methods of Measuring t h e P l a s t i c i t y of Clays. Transactions of Chalmers U n i v e r s i t y of Technology
No. 119. Gothenburg, Sweden. 1951.
4. American S o c i e t y f o r T e s t i n g M a t e r i a l s , Procedures f o r T e s t i n g S o i l s . 1950. 418p.
5 . Skempton, A.W. The C o l l o i d a l ' A c t i v i t y 1 of Clays. Proc. 3rd I n t . Conf. on S o i l Mechanics and Foundation Engineeringp
V O ~ . 1, p.57-61, Switzerland, 1953.
6 Casagrande, Arthur, C l a s s i f i c a t i o n and I d e n t i f i c a t i o n of S o i l s . Proceedings, American S o c i e t y of C i v i l Engineers, Vol. 739 p.783-810. 1947.
7 . Green, H. and Ruth
N.
Weltmann. Thixotropy. 3ollbid >heastry (Edfted by Jerome Alexander), Vol. 6, p.328-346, Reinhold Publishing Corg.
,
New York, 1946.8, Pryce-Jones,
.
J. The ?low ~f juspensions-
Thixotropy and Dilatancy , Psoc.
of Univer~ity of Durham Phil. Soc.
,
Vol. 10, Dart6 ,
p.427-467. March1948.
11
9.
Ackernlann, E.
k i x e t s ~ ? ! _ e a7.d Fliesseigenschaft e n ?einkoa*niger ~bldan (~hixotropy and Flow Propertiesof Fins
Grained Solls).
Geologische Rurdschau, Vol. 36, 1948. Technical Translation No.1509 National Research Council, Ottawa, Canada. April, 1950, 10. Boswell, P.G.H. The Trend of R2search on the Rheotropy of
Geological Materials, Science Progress No. 136, p .608-622. October 1951
11. Casagrande, Arthur." The Hydrometer Method for MechanicaJ Analysis of Soils and Other Granular Materials. Zambridge, Mass.
JUe, 1931. 51po
12. Lambe, T. W. Soil Testing for Engineers. John Wiley & Sons, Inc
.
1951.13. Krmbein, W,C. and F.G. Pettijoh. Manual of Sedimentary Petography. D, Appleton Century Company, Inc
.
,
New York, 1938.549~.
14. Otto, G.H.A
Modified Logarithmic Probability Graph for theInterpretation of Mechanical Analyses of Sediments. Journal of Sedimentary Petrology, Vol
.
9, No. 2, p -62-76. August, 1939, 15, Inman, D.L. Measures for Describing the Size Distribution ofSediments. Journal of Sedimentary Petrology, Vol, 22, No. 3, p. 125-145. September, 1952,
16. Skempton, A.W, and R.D. Northey. The Sensitivity of Clays, Gc?otechnique, Vol. 3, No, 1, p.30-51, March, 1952.
17. Antevs,
E.
G l a c i a l Clays I n S t e e p Rock Lake, Ontario, Canada. d. b
B u l l . Geol. Soc, of America, Vol. 62, p.1223-1262, October, 1951,
18.
F r a s e r , H.J. An Experimental Study of Varve Deposition. Royal S o c i e t y of Canada Proceedings and Transactions, Vol. 23,19. Burwash, E.M. The Deposition and A l t e r a t i o n of Varved Clays, Transactions, Royal Canadian I n s t i t u t e , Vol. 22, p-3-6, Toronto, Canada. 1938,
h his
paper i s p r i n t e d a s an appendix i n Legget ( 1 ) ) .20. Arrhenius, G. Den G l a c i a l a Lerans Varvighet (The Varvity of t h e G l a c i a l Clay), Sveriges Geologiste Undersakning, S e s . C , No. 486, Stockholm, 1947. 74p.
*
L N A T U R A L W A T E R C O N T E N T-
Oi0 D R Y W T . 0 2 0 4 0 6 0 8 0 100 T O Pmi
... ... ... ... ... D A R K H T W N-
V) J J 3 LL W 0-
3 I- 11 W J a U V) /a
FIG. 1 V A R I A T I O N IN N A T U R A L W A T E R C O N T E N T W I T H I N T H E V A R V E S ( S A M P L E - 2-65) p . o ~ * h 1 . / 5 4 D . 8 . n . REfOqT 9-
24G R A I N S I Z E
-
4
U N I T S 7 8 9 10 I I F I G U R E 5 \ \ M E D I A N V A R I A T I O N I N G R A I N S I Z E I N A G E O M E T R I C M E A N \ \ \ D I A M E T E R.
D I A M E T E R - \ 0 \ \ \i
h
D l A T A C T l C V A R V EC U M U L A T I V E G R A I N - S I Z E D i S T R I B U T 1 0 N C U R V E S L E G E N D L O W E R T H I R D - U P P E R H A L F L O W E R T H I R D
-
L O W E R H A L F---
F I G U R E 6 C-
L O W E R T H I R D R E S U L T S O F M I C R O S C O P I C G R A I N - S I Z E A N A L Y S I S O F L I G H T L A Y E R O F V A R V E D C L A Y ( S A M P L E 2 - 1 2 4 )2 8 F I G . 7
1
2 6 '---.
V A R I A T I O N O F U N C O N F I N E D C O M P R E S S I O N I I-
\ \\.
S T R E N G T H W I T H O R I E N T A T I O N O F V A R V E S - I I 2 4 \ I L E G E N D - \-
I
-
-B Z A N C L F -B E T W E E N V A R V E D P L A N E S 6 A X I S O F S T R E S S . S O L I D L I N E S - A V E R A C E V A L U E S P 0 z 0-
-
C - - - - 0 U P S A M P L E 2 - 6 8 W z 6 - -- 3I
i
4 -- 2 0 I o0 10' 20' 30- 4 0 - 8 50' 60 ' 7 0' 8 0- 9 0 ' 9V A R V E USED
IN TESTS-'
F I G U R E 8
F i g .
9
-
Specimen on t h e l e f t--
8 = 30'-
f a i l e d a l o n g t h e l i g h t l a y e r .-
Spscimen on t h e r i g h t--
8 = 60°-
f a i l e d t h r o u g h b o t h d a r k and l i g h t l a y e r s . ( s c a l e i n i n c h e s )Fig. 1 0
-
Typical sample of v a r v e dclay From S t e e p Rock Lake.