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Permafrost studies at the Kelsey Hydro-Electric Generating Station:
research and instrumemtation
NATIONAL RESEARCH COUNCIL CANADA
DIVISION OT' BUILDING RESEARCH
PERMAFROST STUDIES AT THE KELSEY HYDRO-ELECTRIC GENERATING STATION
RESEARCH AND INSTRUMENTATION -by
G . H . J o h n s t o n
A.I'J
AI,"YZED
T e c h n i c a l P a p e r N o . 1 7 8 of the
Division of Building Research
O T T A W A M a r c h 1 9 6 5
TABLE OF. CONTENTS 1 . 0 2 . 0 ?,. L
z . z
2 . 3 INTRODUCTIONDESCzuPTION OF' SITE Clirnate
Geology and Topography Soils and Perrnafrost
3.. O RESEARCH CONSIDERATIONS 3 . i D y k e D e s i g n 3 . 2 G r o u n d T h e r r n a l R e g i r n e 3 . Z . I T h e o r e t i c a l A n a l y s l s 3 . 2 . ? F i e l d S t u d l e s 3 . 2 . 2 . 1 M e a s u r e r n e n t o f d e p t h o f t h a w 3 . 2 . 2 . 2 T h a w u n d e r r e s e r v o i r 3 . 2 . 2 . 3 T h a w u n d e r d y k e 3 . Z . 2 . 4 E x i s t i n g t h e r m a l r e g i r n e 3. 3. Dyke Movernents 3. 4 Dyke Stability 4. A INSTRUMENTATION 4 . I G r o u n d T e r n p e r a t u r e s 4 . l . I T h e r m o c o u p l e C a b l e s 4 . I . Z S w i t c h B o x 4. L.3 Measurfu:g Equiprnent 4. Z Dyke Movernents 4 . 3 F r o s t I n d i c a t o r s
5. O INSTALLATION OT' INSTRUMENTATION
5 . I R e s e r v o i r A r e a 5. ? Undisturbed Area 5 . 3 D y k e s 5 . 3 . I C a b l e s a n d G a u g e s 5 . 3 . 2 B e n c h M a r k s 5 " 3 . 3 F r o s t I n d i c a t o r s 6.0 oBSERVATIoNAL PRoGRAM 6. I Meteorological Observatlons
6.2 Dyke Movement Observations
6 . 3 G r o u n d T e r n p e r a t u r e O b s e r v a t i o n s PAGE 6 6 I I 9 9 I O 1 I
t z
t z
t 4 I 4 t 4 1 5 L 6 L 7 l 8 I 9z
z
4 5r 9
I 9 ? 0zo
2 0z z
z z
z 3
z 3
z4
z4
7 . 0 ACKNOWI.EDGEMENT REFERENCES BIBLIOGRAPHY APPENDIX AI - AI I PAGE
z4
z 6
z7
PERMAFROST STUDIES AT THE KELSEY HYDRO-ELECTRIC GENERATING STATION
RESEARCH AND INSTRUMENTATION -b y
G. H. .fohnston I . O I N T R O D U C T I O N
The Kelsey Generating Station of Manitoba Hydro is located i n N o r t h e r n M a n i t o b " ( s 6 " 0 z t N , 96"3rtE) 4 rniles upstrearn frorn split
Lake on the Nelson River and about 4?5 rniles north of Winnipeg (Figure 1).
A l4-rnile spur line connects the site with the Hudsotr Bay Railway at Pit
siding (rnile 256 frorn The Pas). rt was constructed to supply power to
the International Nickel Cornpany of Canada, Lirnited at Thornpson, Manitoba,
approxirnately 53 rniles to the southwest. The hydro-electric plant is
situated at a site on the river, forrnerly known as Grand Rapid, where a
drop of about 20 ft occurred. The river at this point, after flowing on a
true course in a NNE direction for about 55 rniles, turns nearly 90 deg to the east to flow through the rapids and then reverses 180 deg to flow westward for about a rnile before continuing northward.
Construction began at Kelsey in June 195? and was cornpleted by the fall of 1960. Filling of the headpond took place in stages beginning in May 1960 and was cornpleted by late Novernber 1960. First power was delivered to Thornpson in June 1960. The initial installed capacity of the p l a n t i s 2 1 0 , 0 0 0 h o r s e p o w e r , w i t h a possible ultimate capacity of. 4ZO,O00 h o r s e p o w e r .
The design and construction aspects of the project and the
problerns encountered have been described in detail.in a paper by MacDonald,
Pillrnan and Hopper (l). O.ly brief reference wiLl here be rnade, therefore,
to the main features of the developrnent.
The natural drop through the rapids on the river, together with
the construction of a srnall darn and sorne low dykes, allowed a head of
sorne 50 ft to be utilized. A 120-ft rnaxirnurn height, rockfill-type darn
founded cornpletely on rock was constructed across the rapids section.
Irnrnediately adjacent to the darn a gated sluiceway structure was built in
a large channel excavated through perennialLy frozen overburden and the
underlying bedrock. The powerhouse is located on the north side of the
rock-controlled isthmus forrned by the river at the rapids section; the
intake channel was cut through this prornontory. Several dykes were
constructed at low spots in the topography to irnpound water in the reservoir.
-z-During the exploratory stage of the project perrnafrost was encountered at rnany locations in the area. Most of the rnajor structures at the site were not directly affected by the existence of perrnafrost because they were founded on bedrock, although excavation of the perennially
frozel overburden posed sorne interestirrg problerns. The design and
construction of the water-retaining dykes were, however, influenced greatly by the presence of perrrrafrost. The ultirnate perforrnance of these structures was of special concern because of the thawing effect of the reservoif water on the underlying perennially frozen ground.
The construction at Kelsey provided a valuable opportunity to carry out a study of the thawing effect of water under and adjacent to
several of the relatively srnall dykes erected on perrnafrost. In Decernber I 9 5 6 d i s c u s s i o n s w e r e h e L d w i t h r n e r n b e r s o f H . G . A c r e s a n d C o . L t d . , Consulting Engineers retained by Manitoba Hydro, concerning various
problerns related to construction in perrnafrost areas. Further rneetings with Manitoba Hydro and H.G. Acres and Co. Ltd. were held tn 195? and 1958 t o d i s c u s s d y k e d e s i g n a n d c o n s t r u c t i o n a n d t o c o n s i d e r p r o p o s a l s f o r research studles that rnight usefully be carried out at the Kelsey site. As a result of these discussions, a prograrn of fteld observations to deterrnine the thawing effect of water and the perforrnance of the dykes by rneans of ground ternp6rature and dyke rnovernent measurernents was drawn up by ,' ' DBR/NRC.
The field studies, in which the Division and Manitoba Hydro are jointly participating, were initiated in the fall of 1958 when the first of the instrurnentation was installed and observations were begun. Over-all supervision of the prograrn has been under the direction of the staff of the Dlvision who have designed, fabricated and installed all instrurnentation
required for the studies. Manitoba Hydro has provided the labour assistance and equiprnent at the site necessary for installing the various instrurnents. Mernbers of the H.G. Acres staff rnad.e the initial observations frorn October I958 to Septernber 1960. Mernbers of the Operating Division of Hydro
h a v e c a r r i e d o n t h e o b s e r v a t i o n s from Septernber 1960.
T h i s r e p o r t h a s b e e n p r e p a r e d t o r e c o r d a n d d e s c r i b e t h e scope of the research prograrn and the details of the instrurnentation designed
and installed at Kelsey to assess the thawing effect of water on the perforrnance of dykes constructed on perennially frozen ground.
Z.O DESCzuPTION Or' SITE 2 . 1 C l i m a t e
3
-places it in an interior continental position in North Arnerica. Desplte the proxlrnity of Hudson Bay, 250 rniles to the east, thls large body of water has little effect on the clirnate pf the Kelsey area because of the p r e v a i l i n g w e s t t o e a s t c i r c u l a t i o n of air masses and disturbances. A s a result, the clirnate is essentially continental in character, with long cold winters and short warrn surrrrners. Because of the lack of rnajor rellef features between Hudson Bay and the Cordlllera, the factors affecting the clirnate of Kelsey prevail throughout the Prairie provinces, wlth variations related prirnarily to latitude.
The nearest Departrnent of Transport meteorological stations are Wabowden and Gillarn, located approxirnately 110 rniles southwest and 7 0 r n i l e s e a s t r e s p e c t i v e l y , o f K e l s e y ( F i g u r e 1). A cornparison of the alr ternperatures and precipitation recorded at these stations (z) and at
Thornpson was undertaken in a previous study (3).
Daily air ternperature observations were begun at Kelsey in July 1957, and to date fairly cornplete records have been obtalned, with the exception of I961, for which only partial records are available for April to August, inclusive. Although the four sites are situated fairly close togethe.r at approxirnately the sarne ground. elevatlon, the slight differences in latltude result in differences in air ternperature and preclpi-tation- le spite of the short periods of record (4 years) at Thornpson and. Kelsey, values interrnediate to those of Wabowden ancl Gillarrr are indicated. A reasonably valid picture of the clirnate at Kelsey can be obtained,
therefore, by using data frorn Wabowden and Gillarn. Significant clirnatlc data for the four locatlons are surnrnatized. ln Table I. Exarnination of the air ternperature records glves the folLowing inforrnation:
M e a n J a n u a r y d a i l y ternp. r l r r l l rnin. ternp. r l r r r r rnax. temp. Mean July daily ternp.
r r l r l r r n i n . t e r n p . l l l l I t r n a x . ternp. Mean Annua1 ternperature
r r r r d a i l y r n i n . t e r n p . t l r l t r r n a x . ternp. Wabowden
r 9 4 4 - L g 6 r
- 1 0 .
z
- r 8 . 7
- r , 7
6 2 . 4 5 1 . 5 7 3 . 3z 7
. 6
1 8 . 0 3 7 .2 Thompson l 9 5 8 - r 9 6 r - 1 3 . 3 - 2 3 . 0 - 3 . 6 6 0 . 3 4 9 . Z 7 7 . 4 2 4 . 9 1 4 . 0 3 5 . 7 K e l s e y I 9 5 8 - 6 0 , r g 6 2 _ r 4 . 0 - 2 4 . 0 _ 3 . 9 6 r . 7 5 0 . z 7 3 . 2 2 5 . 0 t 3 . 8 3 6 . Z Gillarnr 9 4 3 - r 9 6 t
- 1 4 . 3 - ? 2 . 9 - 5 . 7 5 9 . 4 4 7 .8 7 0 . 9 2 3 . Lt 3 . z
3 3 . 04
-Freezlng and thawing indices cornputed frorn air temperatures are useful in that they give an indication of the arnount of heat added to or
extracted frorn the ground at a locality. Indices calculated frorn the air
t e r n p e r a t u r e r e c o r d s t a k e n a t K e l s e y ( i 9 5 8 - 6 0 , 1 9 6 2 l a n d a t T h o r n p s o n
( l g S g - 5 1 ) g i v e a v e r a g e v a l u e s t h a t l i e b e t w e e n those cornputed for \Mabowden a n d G i l l a * ( 9 - y e a r a v e r a g e s ) a s s h o w n b e l o w : W'abowden Thompson K e l s e y Gillarn Thawing Index ( D e g r e e -d a y s ) 3 5 5 3
3r49
3240 2850 4872 5 5 3 5 5639 5 8 1 5At Kelsey, the average period free frorn frost each surnrrrer is about 105 days frorn early June to rnid Septernber.
P r e c i p i t a t l o n r e c o r d s f o r K e l s e y a r e l n c o r n p l e t e , b u t t h e r e c o r d s
for 'Wabowden and Gillarn indicate that the rnean annual precipitation is about
16.5 in. Of this total, approxirnately 5 in. occur as snow (10 in. snow = I in. water).
Z . Z G e _ o l o g v a n d T o p o g r a p h v G, 4l
The Kelsey slte is located in the Precarnbrian Shield - the largest and
oldest geologlcal region of Canada. The rocks of the Shield are predominantly
lgneous and rnetarnorphic in Manitoba and were forrned during the Precarnbrian
era. During the Palaezoic era and Cretaceous period'rnuch of the Shield
underwent marine subrnergence. Following uplift in late Tertiary tirne ,
extensive ice sheets advanced over rnost of the Shield during the Pleistocene
epoch. As they retreated, Iarge areas were inundated by glacial lakes, which
subsequently drained leaving the land fur rnore or less its present forrn.
Lake Agassiz, perhaps the largest of the glacial lakes that occurreo in Canada, covered much of central and southern Manitoba for thousands of years followlng the retreat of the lce in the rnost recent of the gLacial periods,
the '\4risconsin. During this period the Laurentide ice sheet eroded the bedrock
surface, rounding hills, deepenlng valleys and deposlting drift as it advanced; on retreat it deposlted a variety of coarse-and fine-grained rnaterlals.
t
-Kelsey is within the area covered by glacial Lake Agassiz, but near its northern boundary. The final stage of Lake Agassiz dralned northward into Hudson Bay more than 3600 years ago, perhaps as long as
7000 years ago. Extensive and continuous larninated silt and clay deposits were left in the area it covered. These distinctly stratified rnaterlals rest on bedrock, t111 or thinly stratifled drift deposits overlying the tilI. Thelr deposltion on the htlly and knobby Shletd relief has produced an alrnost flat to gently rolling plateau-like surface.
The forrnation of a new surface drainage systern has been progresslng since the cornparatively recent disappearance of the last glacler, but because of the flat topography and the nature of the overburden this systern is still highly disorganized and contains innurnerable lakes, rivers and swarnpy areas" The chief processes affecting the landscape at present are strearn erosion and deposition, weathering and frost action.
The Nelson River flows f.or 375 rniles frorn Lake Wlnnlpeg to Hudson Bay through this country and drops in elevatlon a total of.7lZ ft,. The average ground surface elevation at Kelsey is about 600 ft A. s. L.
? . 3 S o i l s a n d P e r r n a f r o s t
The predorninant soils at the Kelsey site are stone-free (in rnost c a s e s ) , l a c u s t r i n e , v a r v e d t t c l a y s r r cornposed of the rock flour once held Ln suspenslon by glaclal strearns and deposited by thern as they reached the waters of glacial Lake Agassiz. A surface organlc rnantle of frorn I to 3 ft o r r n o r e c o v e r s t h e w e l l - s t r a t i f i e d r r c l a y s t t t h a t o c c u r a s b r o w n a n d g r e y depositsr the grey varved rnaterials underlyilg the brown. These deposlts; which rrlay exceed 25 ft in thickness, overlie bedrock or thlnly stratified glacial drift. The drift, from zero to rnore than 20 ft thick, ls cornposed predorninantly of a sandy gravel or a rnedium to coarge sand. Rock outcrops are uncolnrnon and ahnost invariably are confined to the shores of rivers and sorne lakes. The total thickness of overburden rrray vary frorn a few feet to rrrore than 50 ft, the greater thicknesses occurrlng in depresslons in the bedrock surface. A typical soll proflle is shown in Figure 3, Logs of several boreholes in the vicinlty of East and west Dyke" No. z and. a surrrrnary of pertinent soil test results are given in Appendix A.
Perennially frozen ground was encountered tn rnany of the exploratory holes drilled on the site and in a nurnber of excavations und.er-taken during the construction period. Kelsey is located in the southern fringe area of the perrnafrost region where perennially frozen ground occurs in scattered patches or island.s. The thlckness and areal extent of these patches of frozen ground are quite variable.
6
-Perrnafrost was found nearly everywhere over the site and
appears to occur to greater depths in low-lying areas having a thick rnoss
and organic cover. The depth of the active layer can vary considerably
within short distances laterally, but ranges frorn I to 3ft in the low-lying
areas to perhaps 6 or'7 ft on higher ground. At sorne locations perrnafrost
was found in the varved clays and tills to depths as great as 35ft, and
occasionally was encountered in bedrock. Although no atternpt was rnade
to rnap the distribution of perrnafrost over the site sorne indication of its
variability can be noted on Figure 4, which shows the occurrence of frozen
ground on typical longitudinal and cross-sections under East Dyke No. Z.
Extensive ice segregation was found in all perennialLy frozen varved clays, generally in the forrn of horizontal lenses varying in thickness from hairline to 8in. but the predorninant size range was frorn t/I5 to 1in.
thick. Spacing of lenses varied sirnilarly. Although rnost ice layera were
}rorizontal, rnany inclined or vertical lenses and randorn searns, usually
quite thin (hairline to t/+in,), wer.e also observed. In some isolated cases
srnall, randorn ice crystals (< t/ +-in. diarneter) were seen at shallow depths
(< l0ft) below the ground surface. Sorne soils, (fine sands and silt) were
bonded by ice not visible to the naked eye" Typical ice segregation is shown
in Figures 5'and 6. The distribution of ice in a vertical section is shown
in the detailed logs of three holes drilled at East Dyke No. Z, reproduced in Appendix A.
Ground ternperature rneasurernents rnade to date indicate that
the mean ground ternperature in permafrost to depths of 20ft in undisturbed
a r e a s v a r i e s f r o r n a b o u t 3 0 . 5 t o 3 1 . 5 " f ' .
3.0 RESEARCH CONSIDERATIONS
3. I Dyke Design
At Kelsey only two of the rnajor dykes, East and W'est Dykes No. Z,
had to be constructed wholly on perennially frozen ground. With the exception
of the very srnall freeboard dykes, whichwere built of clay fill and placed
on a ground surface stripped of organic material, all frozet:- overburden
was rerrroved frorn rnost of the length of the centre dyke and East and West Dykes No. I (see Figure 2) and a cornpacted clay fill placed on the bedrock.
This approach was taken because of the potentially serious problerns that
would result from thawing of the underlying frozen ground at these critical
E a s t a n d W e s t D y k e s N o . a rnaximum helght of 20 ft, were requ t h e r e s e r v o i r ( F i g u r e Z ) . L o c a t e d ab
either slde of the river, they were
to considerable depth for rnost of thei IIne could not be established for elthe occurred throughout the low areas the
of the rlver. Normal design and cons
regions usually involve founding struc prove troublesorrre upon thawing, exca
rnaterial, or preservation of the exist
natural or artificial rneans. A trouble
did not exist and excavatlon or preser not considered econornical.
When designs for the dyke ( t g S e to early 1958), a literature sear
of investigations had consldered the t
disturbance of perennially frozen g described the results of fteld observat field studies had been rnade nor was with regard to the effect of a large he
frozen ground or on water-retaining st
To the authorrs knowledge only two suc
constructed on permafrost in North
inforrnation of their perforrnance was
to the Kelsey work. A number of inve
carried out and reported, however, in references (known to date) related to the thawing effect of water are listed
The design ultirnately cho
has no known precedent and has been
and MacDonatd (Z). Briefly, the design
constructed on a foundation of frozen
thawlng by a drainage systern of sand p dependent on the height of the dyke.
Discussions with repre sent and Manitoba Hydro suggested three as investlgated in a research study by rne was realized that these observatlons co irnrnediate value during the design or c o f t h e i r n e c e s s a r i l y l o n g - t e r r n nature.
, approxlrnately 2000 ft long with red to cornplete the enclosure of
t 3000 f,t upstrearn of the darn on
rlain by perennlally frozen ground
length. A perrnafrost-free dyke
dyke because extensive permafrost crossed to within a short dlstance uction procedures in perrnafrost res on rnaterlals that wlll not
on of potentially troublesome
frozen ground conditions by free locatlon for these two dykes
tion of the frozen ground was
were under conslderation
h revealed that although a nurnber oretical aspects of the therrnal
, there were few that actually
s. In particular, no detailed
re any practical experience available source such as a lake on perennlally uctures founded on permafrost.
s t r u c t u r e s ( 5 r 5 ) h a d b e e n rica and little or no published vailable that would be of asslstance
igations and studies have been
ecent years. A11 pertinent
m constfuction on perrrlafrost and
the blbliography.
for East and W'est Dykes No. ?
scribed in detail by MacDonal.d et al (l) cons ists of a cornpacted sand flll
rved clay that ls stabilized durlng e s i t h e s p a c i n g o f t h e s e i s
t i v e s o f H . G . A c r e s a n d - C o . L t d . cts that rnight usefully be
s of fleld measurerrrents. It
not provide informatlon of
struction stage of the project because
8
-prove of value with regard to future constructlon of a sirnllar nature
and lt is hoped will provide useful inforrnation should rnaintenance or
rernedial work be required on the structures under study. The observatlone
will also serve to check the prelirninary rnathernatical analyses and
iirovide information for future analyses of the therrnal problem.
a r e :
The three rnajor aspects that mlght usefully be lnvestlgated
ground therrnal regirne,
settlernent of dyke and foundation materlal,
stability of dyke and foundation rnaterlal.
( " ) ( b ) ( . )
3 . 2 G r o u n d T h e r r n a l R e g i m e 3 " Z " 7 T h e o r e t i c a l A n a l y s i s
A knowledge of the change ln the ground therrnal regirne caused by flooding of the ground surface adjacent to and beneath the dykes is most
irnportant, particularly in a region such as this where the rnean ground
ternperature is near the thawing point (32"F).
D r . D . C . P e a r c e o f t h e D i v l s i o n of Buildlng Research carried out a mathernatical anaLysis based on conduction theory to deterrnine the
long-terrn effect of water on the ground. therrnal regirne beneath the dyke.
Assuming a. water ternperature of 39 deg F. and a trrean ground ternperature
of 3l deg F, lt was estirnated that:
(-) it would take rnany hundreds of years for equilibrlurn
conditions to be re-established under the rnain body
of the dyke;
(b) the long-terrn effect of water on the rna6s of perrnafrost
beneath the dyke would be negllgible, except for the
region adjacent to the water-dyke interface; at thls polnt, the boundary conditions become very cornplex so that assurnptions used in the original analysls are not applicable.
Further calculations, though only approxirnate because of the
cornplex boundary conditions, suggested that within a 50-year period
9
-interface that rnight extend into and beneath the dyke for a distance of
40 ft. During the first few years, the rate of thaw in this region rnight be
in the order of. Z to 3 ft per year, although the rate would decrease wlth tirne and with distance frorn the interface.
D r . P e a r c e a l s o a n t i c i p a t e d t h a t w i t h i n the 50-year period the perrnafrost below the reservoir would thaw completely and that, lnitiallyo the rate of thaw in this area would also be at reast z to 3 ft per year.
rt is clear, therefore, that a knowledge of. the rate of thaw
occurring beneath the reservoir and the dyke as a result of flooding the area ls of pararnount importance as regards the perforrnance of the dyke. rt would also be useful to have a knowledge of the therrnal regirne existing in this area of sporadic perrnafrost before construction and to follow the l o n g - t e r r n c h a n g e s r e s u l t i n g frorn the rise in water level. This last aspect rnay be extremely difficult to detect owing to the length of tirne required for
long-term changes to take effect. In addition the accuracy of the ground
temperature rneasurernents required rnay not be easily obtained under field
c o n d i t i o n s .
3 . Z . Z F i e l d S t u d i e s
3 . Z . Z . l M . " " o A 1 t h o u g h p e r r n a f r o s t l s
detlned on a ternperature basis, the deterrnination of the existence of perennially frozen ground by rneans of field temperature measurernents
can be extrernely difficult, particularly in an area where ground ternperatures
are close to the thawing point. Determination of frozen ground by manual
r n e t h o d s ( e . g . , u s i n g steel. probes or core drilling), although rnore reliable in some cases, can be difficult and laborious when the frozen ground occurs
at sorne depth below the ground surface, particularly when observations
are desired in an area covered. by water. When a nurnber of observations
are required at regular, relatively closely spaced, intervals of tirne, such
rnethods cannot be considered for practical reasons.
o t h e r a l t e r n a t i v e s f o r r n e a s u r i n g depth of thaw (i..., d e p t h t o t h e p e r r n a f r o s t t a b l e ) were considered. T h e u s e o f s e i s r n i c o r r e s i s t i v i t y
apparatus was a possibility, but the reliability was questionable because of
several factors, rnainly lirnited experience with their use in the field. Field trials of this equiprnent have been carrled out in perrnafrost areas
by DBR personnel, but irregularities in the operation of these instrurnents
and in the results obtained showed. fhey would be of limited value.
1 0
-t h e s -t u d i e s p r o p o s e d a -t -t h e K e l s e y s l -t e , -t h e r e f o r e , a p p e a r e d -t o b e b y
ground ternperature rrleasurernent. Several types of instrurnents are
available for rneasuring ground temperatures. These include rnercury
bulb thermorneters, resistance therrnorneters and therrnocouples.
Perhaps the rnost accurate instrurnents are therrnistors, but inherent in
their use for long terrn rrreasurernents is the problern of their possible
drift with tirne and the subsequent need for recalibration. This is not
p r a c t i c a l b e c a u s e t h e y c a n n o t easily be retrieved when they are permanently
installed. Studies by DBR/NRC cornparing the various types of rneasurlng
instrurnents have indicated that therrnocouples can give results of desired accuracy provided proper care is taken with their installation and in the rneasurernent equiprnent and techniques used. It was decided therefore to use coPPer-constantan therrnocouple cables to rneasure ground. ternpera-t u r e s . E a s t D y k e N o . 2 w a s c h o s e n a s t h e l o c a t i o n f o r these studies
because fairly detailed inforrnation on perrnafrost conditions und.er and adjacent to the dyke had been obtained.
3 . 2 . 2 . 2 T h a w U n d e r t h e R e s e r v o i r : It was proposed that two
a r e a s b e s e l e c t e d f o r s t u d y b e t w e e n the present river channel and East Dyke No. Z - one sorrle distance frorn the dyke, the other adjacent to it. It was desirable that each area should have a diarneter of at least 300 ft within which the vegetation cover was sirnilar, that the active layer should initially not be greater than 3 to 4 ft, and that perrnafrost should b e p r e s e n t t o a d e p t h o f a t l e a s t ?0 f.t. The selection of such locations could have been difficult because of the extremely variable nature of
perrnafrost distribution; but an auger hole (No. 667) llad been put down
during the exploratory site investigation about 500 ft west of the dyke
and perrnafrost was encountered at a depth of. 3.4 f.t (zz october 1957) and extended to at least the z0-ft depth (bottom of the hole).
A second location was chosen about 100 ft frorn the toe of
the dyke. No inforrnation was available for this area, but an exploratory
hole put down (24 October 1958) showed that perrnafrost was present b e t w e e n 3 - 3 f . t b e l o w the ground surface and at least zo f.t.
Three rnain factors had to be considered in choosing the type of installation for this area, which would be subrnerged when the
r e s e r v o i r w a s f i l l e d :
any instrurnentation would have to be adequately
water-p r o o f e d ;
( a )
( b )
( . )
any installation at or near the water surface of the
reservoir rnight be darnaged or destroyed by ice rnovernentl
the isolated location of the installation would rnake it
I l
-The maxirnurn length of thermocouple cable was llmlted to about 200 ft because the sensitivity of the potentiorneter to be ueed was adversely affected by the external reslstance of circuits of greater length. The switch box for the therrnocouple cable installed adjacent to the dyke could be brought up onto the top of the dyke, but sorne other provlslon would have to be rnade for reading the second installatlon, which was placed about 500 ft from the dyke. For this latter case the switch box would have to be placed on an artlflcialrrislandtr in the reservoir.
Several rnethods were consldered including the use of an anchored raft, the construction of a pile-supported platforrn and the buildtng of an earth-fill observation post. A11 had to be abandoned, however, because of the exPense involved, and ln particular because of the potential danger of destruction by ice movernent of any structure erected in the reservoir" A different type of reading instrurnent, which perrnitted the use of a longer therrnocouple cable, was therefore indicated. The designs of the therrnocouple cables and the reading instrurnents finally selected a r e d e s c r i b e d i n l a t e r s e c t i o n s o f t h i s r e p o r t .
At each of the trvo locations selected in the reservoir it was proposed tlnat a therrnocouple cable be installed to rneasure ground ternperatures to a depth of. z0 ft. Therrnocouple points were to be placed at I :ft intervals between the ground surface and the lZ-ft depth, and at I.5-ft intervals frorn lZ ft to IB ft, with a final point at the i ?0 -ft depth.
3.2.2.3 Th"* U.t$u" Dyhg Relatively detailed inforrnation on soll a n d ' p e r m a f f i s o b t a i n e d d u r i n g t h e p r e 1 i r n i n a r y s i t e
investigations at three locatlons along the centreline of East Dyke No. z where dril1 holes No. 68?, 683 and 684 were put down and core sarnples taken for the full depth of each hole. The borehole logs are shown in Appendix A. The height of the dyke (crest elevation; 610 ft) at each of t h e s e l o c a t i o n s i s a b o u t 1 1 , 1 5 , a n d 6 f t , respectively, andthe depth of water at the toe of the dyke at these points with the reservoir
maintained at the design elevation of 605.0 is about 6, 10, and 1 ft, re spectively.
It was proposed, therefore, that three permanent therrnocouple installations be rnade at each of the above-noted locations on the upstrearn shoulder of the dyke to a depth of. ?0 ft below the original ground. surface. To observe the thaw that will occur under the dyke, g"o,rr.d ternperature s would be rneasured at I -ft intervals frorn the original ground surface to a depth of. 12 ft, and at 1.5-ft intervals frorn rzto Ig ft, with a final thermocouple point at the ZO-tt depth.
1 2
-3 . 2 . 2 . 4 E x i s t l n g T h e r r n a l R e g i m e : T o p r o v l d e a b a s i s f o r
cornpariso r"
" .rr.""ured und.er the reservoir and the dyke it was necessary to rnake a reference installation ln an undisturbed area. At this location, where the vegetation cover and other conditions had not been and wiII not be disturbed, the rnean ground ternperature ls being measured. rn addttion, it may be possible to pick up annual or long-terrn variatlons, if any, in the ground thermal regirne.
Three individual therrnocouple cables were therefore proposed for installation at a location about 400 ft east of the south section of East Dyke No. 2 in an undisturbed wooded area. An exploratory borehole ( N o . 5 5 8 ) had been put down ( zz october 195?) that showed the presence o f p e r m a f r o s t i n t h i s general area from I.I ft to a depth of at least
z 0 f . t . G r o u n d t e r n p e r a t u r e s were to be rneasured at depths of ?.5, 5, 10, 15, and 20 ft below the ground surface at each of these installations.
3 . 3 D y k e M o v e r n e n t s
It was expected that significant settlement of the dykes would occur following construction. Any settlernent rneasured would be the result of either consolidation of the dyke material or cornpression of the foundation rnaterial as thawing takes place, or to a combination of both factors. It was expected that any settlement rneasured before the water level is raised against the dyke would be caused prirnarily by consolidation of the fill rnaterial . of rnore irnportance, however, is the arnount of settlement (perhaps 5 to 7 ft) that would occur because of thawing of the underlying frozen rnaterial. This latter settlernent will depend on whether drainage of the water frorn the thawed ice does or does not occur. The rate at which settlement takes place will be dependent on the rnethod of d r a i n a g e .
A knowledge of the arnount and rate of settlernent will provide a further rneans of following the depth of thaw beneath the dyke and
assist in scheduling future maintenance work. rt was proposed, therefore, to rneasure the total settlernent caused by the two above-mentioned.
factors and to atternpt to dlstinguish the arnount of settlement caused by each by installing devices at various levels in the fill and in the frozen foundation rnaterial.
Many difflculties were inherent in providing an installation t o r e c o r d t h e s e r e l a t i v e l y simple rneasurements. M a j o r f a c t o r s t o b e c o n s i d e r e d w e r e :
(") the fact that any installations
rnade prior to or during the constructlon phase of the dyke would be subject to darnage
( b ) ( . ) ( d ) ( b ) ( a )
t 3
-or loss because of construction activity;
the difficulty of instal.ling suitable instruments in perennially frozen ground;
that equiprnent should be as slrnple as posslble to k e e p o b s e r v e r e r r o r t o a rninimurn:
the isolated location of the installatlon and the fact that only a very srnall staff would be present when the plant is operating dictated that any lnstallation require a rninirnum of servicing or mafurtenance w o r k .
several types of settlement gauge were considered rncludfurg:
steel plates placed in the f itl and on the original ground surface that could be located by hand borings at various intervals of tirne to determine thelr
elevation;
a telescopic type of gauge consisting of a nurnber of d i f f e r e n t - s i z e d s t e e l t u b e s c o n c e n t r i c a l . I y a r r a n g e d around a central steel datum rod;
earth auger-type anchors placed in the fill and in the frozen ground to different depths;
a number of steel rods, having auger-type tips, that would be placed in separate drilled holes to depths a t w h i c h m e a s u r e r r l e n t s a r e d e s i r e d .
( . )
( d )
A nurnber of disadvantages apply to each of the types of gauges considered above. It appeared, however, that even though the last listed rnethod requires the drilling of a nurnber of holes, the use of individual rods was the rnost practical. A nurnber of these gauges were fabricated, therefore, to be placed adjacent to the three therrnocouple cables on East Dyke No. z at S-f.t intervals of depth from a point 5 ft above the ground surface (in the dyke.fill) to a rnaxirnum depth 20 ft below the original ground surface. Movernents were to be rneasured by determining the elevation of the top of the rod, which protrudes above the top of the dyke
r 4
-3 . 4 Dyke St?bilily
Thawing of the foundation rnaterial (with its high ice content)
with slow or very little drainage of the resulting water can cause conditlons conducive to a slope fallure. Such conditions will depend directly on
the rate at which thawing takes place. If the rate of thaw, the consolidatlon of the rnaterial, and soil conditions are such that the water is able to
drain away or dissipate sufficiently to prevent a serious decrease ln the shear strength of the soiln then critical slope condltions rnay not be reached. The role of moisture and rnoisture nlovernent between the soil varves and within the soil pores is extrernely irnportant with respect to the problern
of slope stability (and rnay also have a significant effect as an agent for heat transfer within the soil).
Discussions with rnernbers of the Division regarding the stability of the dyke have shown the cornplex nature of any study of this problern, particularly in so isolated a location. It was suggested that a study of rnoisture rnovenl.ent and water pressures rnight be useful, although the value of results obtained could be rather meanlngless because of the nurnber of other variables involved. Except for periodic visual exarnlnations
of the dyke with regard to slope rnovernent, therefore, no detailed field work was cbnternplated on this aspect.
4.0 INSTRUMTENTATION
4 . I G r o u n d T e r n p e r a t u r e s
The field rneasurement of ground ternperatures poses a nurnber of problerns. Several rnethods of rneasurernent have been investigated, but experience gained by the Division of Building Research over the past I 0 t o 1 5 y e a r s h a s s h o w n t h a t t h e r r n o c o u p l e s p e r f o r m s a t i s f a c t o r i l y .
Several factors, however, can have an appreciable effect on the accuracy of the results obtained. Sorne, inherent in the rnaterials used and in the circuitry, are not too well defined and their total effect, usually srnall in rnagnitude, is not clearly understood. Others can be directly related to the fabrication and installation of the cables, the type of readlng or recording apparatus used, and the procedures followed in rnaking the rneasurerrrents. Difficult field conditions - severe clineatic extremes, b i t i n g i n s e c t s , r e r n o t e a r e a s , l o c a l t e r r a i n environrnent - can also g r e a t l y i n f l u e n c e t h e r e s u l t s o b t a i n e d t h r o u g h o b s e r v e r error.
Therrnocouple cables have been used by the Division in rnany studies of perrnafrost, and experience gained with the fabrication of reliable instrurnentation has already been recorded (8). The ground ternperature installations rnade at the Kelsey site are sirnilar to those
r 5
-described in this reference and will not be -described in any detail in t h i s r e p o r t .
Three rnajor factors had to be consldered for the ground ternperature installations at KeIsey:
( a ) AII parts of the installation had to be waterproofed, for rnoisture could have an appreciable effect on any measure-rnents rnade. This applied not only to the actual ternpera-ture rneasuring junctions and the therrnocouple wire, but also to the switch box connections. This was partlcularly irnportant with regard to this study because several of t h e c a b l e s w e r e t o b e e n t i r e l y i r n m e r s e d i n w a t e r .
It was proposed that observations be rnade at regular i n t e r v a l s f o r a p e r i o d o f a t l e a s t 1 0 y e a r s . A r y
instrurnentation placed in the field, therefore, should be designed and constructed for a life expectancy of a b o u t Z 0 y e a r s .
It was expected that observers would be changing continually and, in addition, that they would not, in rnany cases, be intimately farniliar with the equiprnent or instrurnentation used. The equiprnent, therefore, should be sirnple in operation and require littIe
rnaintenance so that the procedures to be followed in rnaking observations would be easily understood.
It was realized, therefore, that special ernphasis rnust be placed on the design and fabrication of the ternperature rneasuring equiprnent.
4 . 1 . I T h e r r n o c o u p l e C a b l e s
AIl themnocouple cables were designed and fabricated as described in Reference (8). Pertinent details, however, are given in the following s e c t i o n .
Twenty-gauge copper-constantan duplex wire was used. in
all cables. Each conductor is covered with a polyvinyl chloride coating and the duplex wire has an over-a11 covering of polyvinyl chloride. When each therrnocouple junction had been prepared and the duplex wires taped together for each installation, the cable was placed inslde a l/4-in. diarneter
( b )
1 6
-length of flexible, black polyethytene pipe .(Ganadtan Government S p e c i f i c a t i o n s B o a r d S p e c . 4 1 - G P - 5 A ) .
The length of duplex wire and plastlc pipe used depended on
the installation. For the three reference thermocouple cables (KT 6r? and 8) placed in the undisturbed area and the three cables (KT 3,4 and 5) placed under East Dyke No. 2, the Z0 ga- duplex wire was encased in a continuoua length of plastic pipe and ran directly to the switch box i.e. a trshort leadtl installation.
Two identical rrlong leadtr cables 200 ft long were originally placed in the reservoir - KT I (old), 500 ft frorn East Dyke No. 2, and K T z , 2 0 0 f t f r o m t h e d y k e . J u n c t i o n b o x e s ( s e e Reference (8), Figure ?) were placed in these cables about I0 ft frorn the borehole location.
Twenty-gauge duplex wire was used for the lower section of these cables. Frorn the junction box where the splice was rnade to the switch box, an I8-pair, 2?-ga:uge copper interphone cable (individual conductors havlng a polyvlnyl chloride covering, and the whole a polyvinyl chloride coating) was used to connect all the coppers - each of the thermocouple junction
copper wires being spliced to two of the coppers in the phone cable to reduce the circuit resistance. A single l4-gauge constantan wire covered. with cotton'-wrapped rubber and waxed braid. to which all the therrnocouple junctlon constantan wires were attached was used frorn the junction box to the switch box.
Cable KT I (old) was replaced by a new cable, KT I (new), about one year after it had been installed because the original length (zoo rt) of KT I (old) dld not allow the switch box to be placed on top of the dyke. Sorne rnodifications were rnade to this new cable, inclu-dlng the installation of a slightly different junction box (Figure 7) that allowed a separate, short therrnocouple cable to be attached for rneasuring water ternperatures in the reservoir adjacent to the ground ternperature cable. A 26-pair, ZZ-gawge copper interphone cable and a single I4-gauge
constantan conductor were used in this cable frorn the junction box to the switch box. Each of the copper therrnocouple wires was agaln spliced to two of the'interphone cable coppers, and all constantan wires were
spliced to the cornrnon constantan conductor. 4 . L . 2 S w i t c h B o x
A switching arrangernent was required to facllitate the taking of readlngs because of the large nurnber of therrnocouple junctions involved in each cable. To protect the switches and connections frorn the extrernes of weather prevalent in this area, a suitable switch
enclosure was required. switch boxes of the type described in Reference (g) wef,e therefore fabricated.
L 7
-Several types of connectors were used at the terminal points
in the switch boxes during the j-nitial years of observation. The rnost
satisfactory proved to be the wlre-wound. type (Reference (g) ) and all
installations are now equipped with thern.
To reduce the effect of convection currents within the cable and to prevent or rninirnize corrosion of junctions and. terrninal points in the circuit each cable was cornpletely filled with a high qualiry
transforrner oil (Voltesso No. 35). The cornplete installation -
therrno-couple cable and the switch box - was fabricated and assernbled in Ottawa for shiprnent to the site,
4. I. 3 Measuring Equiprnent
Ground ternperatures are frequently rneasured with a portable
precision potentiorneter, particularly in rernote areas. This instrurnent
is light in weight, relatively easy to operate, and gives reasonable accuracy provided proper procedures are followed in its use. Initially, a potentiorneter was provided to rneasure ground temperatures at the
Kelsey site- Several rnod.ifications were rnade to this instrurnent, however, to rnake it rnore suitable for field use. Details of these changes and
the operating procedures to be followed in the use of the instrurnent rnay be obtained frorn the Division.
The sensitivity of the portable potentiorneter is greatly affected when the internal resistance in a therrnocouple circuit exceeds about 30 ohrns. This factor becornes increasingly irnportant when the t e r n p e r a t u r e s t o b e r n e a s u r e d are close to the reference junction
ternperature (32"F). In addition, field conditions harnper the observer
to a large degree when using this instrument which requires considerable care in its operation.
These factors lvere all pertinent consid.erations with regard to the use of the potentiorneter at Kelsey and other types of rneasuring
equiprnent were therefore investigated. Several r.r"ihoa" of irnprovirr!
the sensitivity of the potentiorneter were consid.ered but were ginerally not suitable because of the fragile nature of the accessory equiprnent
required. The advantages of ternperature recording apparatus were
investigated but the use of this type of instrurnent was ruled out because it required not only a Power source and an extensive network of connecting cables to tie-in all the installations but also frequent rnaintenance and servicing to assure that it functioned properly.
The instrurnent that appeared to be the rnost suitable on all
1 8
-indlcating type. Thls choice rneant that power would have to be supplied
by a portable generator and the indicator protected frorn below-fre ezlng
ternperatures and possible darnage during transportatlon to and frorn the
field installatlons. Although this lnstrurnent (together wlth the power
generator) is substantially heavier (about 200 lb) than the portable
potentiorneter (20 lb), it had certain advantages that would irnprove the
accuracy and reliabiltty of ground ternperature observations. It is
relatively sirnple to operate, requiring few adjustrnents by the observerl
although basically a laboratory instrurnent, it is falrly rugged in
construction and can be used in the field after certain modijications have been rnade. Details of these changes and the operating procedures to be followed in the use of the equiprnent rnay be obtained frorn the Dlvislon.
This instrurnent, sent to the site in October I959, can be transported ln
" j-ton truck or snowrnobile or pulled on a toboggan.
Both the portable potentiorneter and the electronic temperature indicator are being used at Kelsey to rneasure ground ternperature s. The indicator is used rnost of the tirne, but during the spring and fall when
transportation to the installations ffray not be possible by vehlcle, the
h a n d - c a r r i e d p o t e n t i o r n e t e r i s used.. Access to the undisturbed area is
difficult throughout rnost of the year so that the portable instrurnent is
nearly always used at this location.
4 . 2 P v k e M o v e r n e n t s
Each settlernent gauge of the type selected for the KeIsey studies rneasures rnovernerrts at one particular depth. Thus, if rnovements are d e s i r e d a t s e v e r a l d e p t h s a t o n e l o c a t i o n , a group of gauges is required. A total of i5 settlernent gauges (3 groups) were installed on East Dyke No. 2 adjacent to therrnocouple cables KT 3, 4 and 5. single gauges.were also placed at three locations in west Dyke No. z. All gauges were
fabricated in ottawa and shipped to the site in sections ready for
installation. Details of the construction of a typical gauge are given ln
F i g u r e B .
The gauges consist essentiarly of a central daturn rod
(Z/e-in. diarneter pipe) with a spiral foot attached to the lower end. The
daturn rod is pgotected frorn the surrounding soil by a grease-filIed,
I in. diarneter semi-rigid type plastic pipe casing (Kriiastic). Each gauge
is placed in a bored hole and the spiral foot, which protrudes through a grease seal at the bottorn of the casing, is turned into the soil at the depth at which rnovernents are to be rneasured.
The top of the plastic casing extend.s above the crest of the dyke and the top of the daturn rod protrudes above the casing. The
_ r 9 _
elevatlon of the top of the daturn rod is by means of level surveys. Extensions casing and the daturn rod as settlernent
4 . 3 F r o s t I n d i c a t o r s
deterrnined at regular lntervals can easlly be added to both the o c c u r s .
A nurnber of special frost depth indicators were lnstalled under East Dyke No. 2 in 1963 i.e. sorne tirne after the rnajor instrumentation prograrn had been cornpleted. These were included in the observational program to assist in following the depth of thaw under the dyke and to
supplement the information obtained by m.eans of ground ternperature rneasurernents. h addition to following thaw, they will provid.e infor-rnation on the depth of frost perretration below the top of the dyke each y e a r .
These indicators are sirnilar to those descrlbed by Gandahl and Bergan (9), except that they are rnuch longer than those norrnally used. The construction of a typical frost indicator gauge is shown in F i g u r e 9 . T h e i n d i c a t o r s consist.of a length of rtexilre, clear, plastic tubing (Tygon-:/e-in. r. D. and t/a-in. wltt ttickness)
fitled. with a methylene blue solution. The tubing is inserted in a l/+-in. diarneter serni-rigid plastic pipe (Krarastic), which is sealed at its lower end and serves as a protective casing. The solution is blue at ternperatures above 32"8, but becornes clear at ternperatures below 32"F. Frozen
zorLes in the ground or the depth of frost penetration can be observed by sirnply pulling the tube frorn the casing and noting the colour of the
solution and the depths at which colour .h*gu" occur; The tube is t h e n r e p l a c e d i n t h e casing.
5.0 INSTALLATION OF' INSTRUMENTATION
Ground ternperature and. d.yke rnovernent instrurnentation was installed at various tirnes in 1958 and 1959; the frost ind.icators were installed in April I963. The location of all cables, gauges and indicators f-"hoY_in Figure 2 and' pertinent details of each
""L gir.un in Tables I[, TTT and rv, respectively. A description
of the rnethods and techniques used and the difficulties encountered during the installation of the various instrurnents is presented in the following section.
5 . 1 R e s e r v o i r A r e a
Ground ternperature cabre KT t (old) , zoo ft in length, was placed to a depth of z0 ft in the reservoir near exploratory-borehole No. 667 about 500 ft frorn East Dyke No. Z in October 195g. This cable
? 0
-was replaced by KT I (new), 530 ft ln length, in late October 1959 so that thb switch box could be located on the top of the dyke. The new cable was placed lrnrnediately adjacent to the original cable at 3 depth of 20 ft. A short auxillary cable was attached to the maln cable at the junction box to rneasure water ternperatures, Ground ternperature
observatlons were rnade on both cables until Il April I960 when KT I (old) was salvaged. In October 1958 cable KT Z was installed in the reservolr ,to a depth of 20 ft, about 200 ft frorn East Dyke No. Z. llhe location of these cables is shown in Figure 10.
A11 cables were placed in 4-in. hand-augered holes. Frozen ground was broken up using a chopping bit and the cuttings were rernoved with the auger. After,the cable had been installed the hole was backfilled with well-tarnped sand and clay, and the rnoss cover was replaced around the cables at the ground surface. Borehole logs and solL test surnrnafleg for each installation and for exploratory hole No. 667 are given in
Appendix A.
The lead cables for KT I (new) and KT 2 were buried in a trench L to 2 ft deep to the toe of the dyke. On the upstrearn slope of the dyke, the cables were laid in a trench excavated through the heavy rock rip-r6.p to a depth of about 3 ft frorn the toe to the shoulder of the dyke.
At the tirne of installation Cables KT I (old) and KT 2 wdre located in undisturbed areas, i.e. wooded, but during the surnrner of
I959 the forebay, in whichthese cables are situated, was cleared of all b r u s h a n d t r e e s .
Undisturbed Area
In October 1958 cables KT 6, 7 and 8, which are attached to a cornrrlon switch box, were placed to depths of.20 ft.and positioned 30 ft frorn each other to forrn a right angle with cable KT 7 at the centre
(Figure 11) at a location near exploratory borehole No. 668, approxirnately 450 ft downstrearn frorn East Dyke No. Z. These cables weie installed fue hand-augered holes ln a sirnilar rnanner to those in the reservoir. They are located in an area that has not, and will not, be cleared of forest cover so that it is truly representative of undisturbed conditions.. Borehole logs and soll test surnmaries for each installation and for exploratory hole No. 668 are glven in Appendix A,
5 . 3 Dvkes
5. 3. I Gables and Gauge s
Three holes (No. 682, 683 and 684) had been drilled and sampled ln detail during March 1958 at selected locations on the centreline of
5 . 2
zL
-East Dyke No. z, Therrnocouple cables KT 3, 4 and 5 and settlernent
g a u g e s K S 1 - 1 t o 6 , K S Z - I t o 5 a n d K S 3 - 1 t o 4 w e r e p l a c e d r e s p e c t i v e l y
to varying depths knmediately adjacent to these holes. Settlement gauges
KS 4, 5 and 6 were placed to varying depths at selected locatloRe on West D y k e N o . Z . B o t h E a s t a n d W e s t D y k e s N o . Z were constructed during the perlod January to Mardr 1959. All installations were rnade during t h e p e r i o d 2 7 J u n e t o 5 J u l y 1 9 5 9 ,
A diarnond drill was used to bore holes for the lnstallation of cables and gauges through the dyke fill and into the underlyingfrozen
ground. After BX casing had been wash bored through the fil1, the
therrnocouple cables were placed to the bottom of an 'tArr size hole; the casing was then rernoved and the hole backfilled with sand. The settle* rnent gauges were placed inside AX casing, which had been wash bored to the desired depths in and under the dyke, the gauge foot was turned into the soi1, the casing rerrloved and the hole backfilled with sand.
At exploratory hole No. 682 (north end of East Dyke No. Zt
c a b l e K T 3 a n d g a u g e s K S 1 - l t o 6 w e r e successfully placed to the desired depths: KT 3 to z0 ft below the original ground surface, and the gauges
at 5-ft intervals of depth frorn KS I - I at 5 ft above the ground surface
(in the firl) to KS i- 6 at z0 ft below the original ground surface.
At exploratory hole No. 683 (centre of East Dyke No. Z\
difficulties were experienced that prevented placing all instrurnents to
t h e d e s i r e d d e p t h s . c a b l e R T 4 w a s p l a c e d 6 ft short of the d.esired d e p t h b e c a u s e b e d r o c k w a s e n c o u n t e r e d and caving of the hole occurred. Thus, instead of rneasuring ternperatures frorn the original ground
surface to a depth of 20 ft in the foundation rnaterial, the rneasuring
junctions are located frorn a point in the d.yke fiil 6 ft above the ground
surface to only 14 ft below it. In an atternpt to prevent caving of the
h o l e a n d t o a s s i s t i n p l a c i n g t h e c a b l e , a length of l-t/z-in d i a r n e t e r galvanized steel pipe was inserted through the dyke fill and left in p1ace. Thus, the top seven therrnocouple junctions in this cable are enclosed.
in steel pipe. It was proposed that six settlernent gauges be installed
at this loiation. Large boulders (or bedrock) were encountered., howevef,,
and prevented placing the deepest gauge. AI1 other gauges were placed at S-ft intervals to the desired depths - frorn Ks z-I at 5 ft above the original ground surface (in the dyke fill) to KS z-5 at a depth of l5 ft below the original gfound surface.
At exploratory hole No. 684 (south end of .East Dyke No" z)
difficulties were also experienced. that prevented the desired placernent
2 2
-below the orlgfueal ground surface lnetead of the l5 ft proposed becauee
the hole caved in, i.e. it was 3 ft short. Thus, three of the therrnocouple
junctions are located at I -ft intervale in the dyke ftII above the grorrnd
surface. Again, a length of l-l/z-in. diarneter galvanlzed steel pipe
was inserted and left in place in thls hole, so that the top eight
thermo-couple junctions of the cable are enclosed by pipe. G"ly four of the
proposed five settlernent gauges could be lnstalled because the deepest gauge could not be placed in the stony till encountered at a depth of
about l5 ft. The other gauges were placed at the desired 5-ft lntervals
frorn KS 3-l at the orlginal ground surface to KS 3-4 at a depth of 15 ft below the ground surface.
The positions of alr cabres and settlernent gauges h .East
Dyke No. 2 as at l1 July 1959 are shown in Figure lZ.
The three settlernent gauges KS 4, 5 and 6 were placed through the sand fill to the orlginal ground surface at selected locatlons
on 'West Dyke No. 2 without any difficulty.
AIl cables and gauges were lnstalled on a llne offset 6 ft upstrearn frorn the centreline of each dyke. They were placed at these
locations so that they would not intersect the sand plles drilled below
the dyke.
5 . 3 . 2 B e n c h M a r k s
Level surveys in the vicinity of East Dyke No. 2 were based on
ternporary bench rnarks during the constructlon phase of the project.
As these could not -be relied on for the long-terrn dyke settlement
observations, a perffranent daturn polnt was installed about ZOO f.t north
of the north end of .East Dyke No. 2 and 100 ft west of the centreline of
the dyke- This bench rnark consists of a 13-ft length of I -ln. diarneter
steel relnforcing rod lnserted 9 in. lnto a Z-in. hole in a large boulder
(or bedrock) encountered at a depth of II ft. A cernent grout was poured. into the hole around.the rod to within 5 ft of the ground. surface and the
hole was then backfilled to the surface with soil. This bench rnark (8. M. ZEI
is the prlmary daturn point used for all East Dyke No. Z settlernent
observations. Ternporary bench rnarks were used. initially for level
surveys on 'rvest Dyke No. ?, b:ut when these proved to be unreliable a
permanent daturn point was installed in October 1960 in a rock outcrop
about 400 ft north-east of the north end of the dyke anda1l observatlons
on 'W-est Dyke No. 2 were rnade frorn thls bench rnark.
5. 3. 3 Frost .Lndlcators
- During the course of a drilllng and sampling investlgatlon carrled,
? 3
-E a s t D y k e N o . 2 a n d t h e r e s e r v o i r , t h r e e f r o e t i n d i c a t o r s ' w e r e
installed adjacent to the instrumentation prevlously placed in the dyke
(Kf' 3 near IS.T 3, KF 4 near KT 4 and KF 5 near KT 5), and one, KF 6, was installed in the undisturbed area near cable KT 7. At these locations
holes of. 2-t/Z-indiarneter were drilled and sarnpled to varying depths
2 t o 3 f t b e l o w t h e p o s i t i o n o f t h e p e r r n a f r o s t t a b l e . A n t r A r r s l z e h o l e
(t-l/4-In diarneter ) was then bored below thls point to d.epths of frorn
26 to 39 ft below the top of the dyke or the ground surface. The Z/+-in.
diameter protective plastic casing for the indicator was then inserted
in the borehole, which was backfilled with sand (and clay in the undisturbed
a r e a ) , T h e l o c a t i o n s o f t h e t h r e e f r o s t i n d i c a t o r s p l a c e d i n E a s t D y k e No. Z are shown in Figure lZ, and that of KF 6 in the undisturbed area
in Figure Il. Pertinent details of the indicators are given in Table IV"
6.0 OBSERVATIONAL PROGRAM
T h e o b s e r v a t i o n a l p r o g r a m various aspects of the dyke studies including the types of observations,
the frequency of observations, rnay
o f B u i l d i n g R e s e a r c h . T h e s t u d i e s t h r e e s e p a r a t e h e a d i n g s :
reguired to obtain lnforrnation on the
at the Kelsey Generatlng Station, the procedures to be followed and be obtained by writJng to the Division outlined rnay be considered under
( a ) ( b ) ( " )
Meteorological obs e rvations
Dyke rnovernent observations
Ground ternperature ob servations
T h e s e a r e b r i e f l y d e s c r i b e d i n t h e f o l l o w i n g p a r a g r a p h s a n d surnrnarized in Table V. A11 observations are recorded on special forrns and copies are sent to all participants.
6 . I M g t e o r o l o g i c a l O b s e r v a t i o n s 6 . l . I A i r T e r n p e r a t u r e s
Maxirnurn and rninirnum air ternperatures are to be rneasured at
I e a s t o n c e a d a y ( a t 8 a . m . ). 6 . L . Z P r e c i p i t a t i o n
A record of the total precipitation that occurs at the site is to be
kept, including the date on which the precipitation occurs, the forrn (raln,
