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Placing cohesive soils in winter in the Far North (Construction of the
Vilyuiskaya Hydroelectric Station Dam)
Batenchuk, E. N.; Biyanov, G. F.; Toropov, L. N.; Myznikov, Y. N.; National
Research Council of Canada. Division of Building Research
PREFACE Many d i f f i c u l t p r o b l e m s a r e e n c o u n t e r e d w h e n t h e c o n s t r u c t i o n o f l a r g e e a r t h f i l l s t r u c t u r e s i s u n d e r t a k e n d u r i n g t h e w i n t e r p e r i o d . M e t h o d s a n d t e c h n i q u e s f o r e a r t h m o v i n g a n d p l a c e m e n t o f m a t e r i a l s a n d s c h e d u l i n g o f c o n s t r u c t i o n a r e o f p a r t i c u l a r c o n - c e r n i n n o r t h e r n a r e a s h a v i n g a s e v e r e c l i m a t e o f l o n g d u r a t i o n e a c h y e a r . T h e c o n s t r u c t i o n o f a l a r g e r o c k f i l l dam i n e a s t e r n S i b e r i a , U . S . S . R . w h e r e m a t e r i a l s w e r e h a u l e d a n d p l a c e d a t a i r 0 t e m p e r a t u r e s a s l o w a s - 5 0 C i s d e s c r i b e d i n t h i s p u b l i c a t i o n . T h e m e t h o d s u s e d a n d t h e c o n t r o l m e a s u r e s a d o p t e d t o e n s u r e s a t - i s f a c t o r y p l a c e m e n t , c o m p a c t i o n a n d p r o t e c t i o n o f t h e f i l l m a t e r i a l a r e g i v e n i n s o m e d e t a i l . I t i s b e l i e v e d t h a t t h i s i s o n e o f t h e f e w , i f n o t t h e f i r s t , e x a m p l e s o f e a r t h w o r k c o n s t r u c t i o n t h a t h s b e e n c a r r i e d o u t ( a n d d e s c r i b e d ) a t s u c h l o w a i r t e m p e r a t u r e s , a n d s h o u l d b e o f i n t e r e s t , t h e r e f o r e , t o t h o s e e n g a g e d i n s i m i l a r p r o j e c t s . C o m m e n t s o n t h e t r a n s l a t i o n , f r o m t h o s e who h a v e e x p e r i e n c e i n t h i s f i e l d , w o u l d b e w e l c o m e d b y t h e D i v i s i o n o f B u i l d i n g R e s e a r c h . T h e D i v i s i o n i s m o s t g r a t e f u l t o M r . H . R . H a y e s o f t h e T r a n s l a t i o n s S e c t i o n , N a t i o n a l R e s e a r c h C o u n c i l , f o r t r a n s l a t i n g t h i s d o c u m e n t a n d t o G . H . J o h n s t o n o f t h i s D i v i s i o n who c h e c k e d t h e t r a n s l a t i o n . O t t a w a A p r i l 1 9 7 2 N . B . H u t c h e o n D i r e c t o r
Title:
NATIONAL RESEARCH COUNCIL O F CANADA Technical T r a n s l a t i o n 1501
Placing cohesive s o i l s i n w i n t e r in the f a r n o r t h
( C o n s t r u c t i o n of the Vilyuiskaya H y d r o e l e c t r i c Station D a m )
[ z i m n y a y a ukladka svyaznykh gruntov n a k r a i n e m s e v e r e ( S t r o i t e l ' stvo plotiny Vilyuiskoi
a s ) ]
Author s : E . N . Batenchuk, G . F . Biyanov, L . N . Toropov and Yu. N. Myznikov
R e f e r e n c e : Biblioteka Gidrotekhnika i G i d r o e n e r g e t i k a , I s sue 2 , 1968. 112 p.
T r a n s l a t o r : H.
R.
Hayes, T r a n s l a t i o n s Section, National Science L i b r a r yUDK 627.824
E d i t o r i a l B o a r d
Belyakov, A . A . , Bozhko-Stepanenko, G . M . , Borovoi, A . A . , G r i s h i n , M . M e , Kuperman, V. L .
,
M i l o s l a v s k i i , N . M . , Neporozhnii, P. S. ( C h a i r m a n ) , O r a k h e l a s h v i l i , M.M.,
P e t r o v , G . D.,
Pichuzhkin, A. A . , Razin, N. V., R u n y a n t s e v , A . M . , S a p i r , I. L . , S l i s s k i i , S . M . , T i s t r o v a , 0. N.T h i s booklet d e s c r i b e s e x p e r i e n c e gained i n the c o n s t r u c t i o n of the l o a m c o r e of the Vilyuiskaya GES D a m in the e x t r e m e l y cold weather conditions of the F a r North, including technological o p e r a t i o n s , u s e of m a c h i n e r y and equipment, and m e t h o d s of controlling the quality of s o i l p l a c e m e n t .
T h i s w o r k i s intended p r i m a r i l y f o r c o n s t r u c t i o n e n g i n e e r s and d e s i g n e r s . In addition, i t m a y be
u s e f u l t o u n i v e r s i t y s t u d e n t s specializing i n h y d r a u l i c engineering.
T a b l e of Contents
P a g e INTRODUCTION
. . . e . . . . o . . .
C H A P T E R I
.
GENERAL INFORMATION CONCERNING T H E...
HYDRO SCHEME 4 1.
E n v i r o n m e n t a l . C l i m a t i c and E n g i n e e r i n g Geology...
Conditions i n t h e C o n s t r u c t i o n A r e a 4...
.
2 C o n s t r u c t i o n of Hydro C a m p l e x 6...
3.
O r g a n i z a t i o n of W o r k P r o g r a m 7...
C H A P T E R
IT..
M A T E R U L S O F THE DAM 9...
4
.
R e q u i r e m e n t s f o r t h e C o r e M a t e r i a l 95
.
L o a m P i t s and t h e i r G e o t e c h n i c a l C h a r a c t e r i s t i c s...
1 4 C H A P T E RILI
.
T H E SEARCH FOR A METHOD O F PLACING...
COHESIVE SOILS IN WINTER 16
6
.
E r e c t i o n of Low Head D a m s i n t h e Region of M i r n y i.
16.
...
7 C o n s t r u c t i o n of t h e C o r e by P l a c i n g Fill i n W a t e r 20 C H A P T E R IV
.
METHOD O F CONSTRUCTING CORE O F DAM IN...
T H E DRY 31...
.
8 G e n e r a l S t a t e m e n t s 31...
.
9
P r e p a r a t i o n of L o a m 34 10.
E l e c t r i c a l Heating of L o a m S t o r a g e Mounds...
38 11.
U s e of I c e F o a m t o P r o t e c t S t o r a g e M o u n d s f r o m F r e e z i n g. . . o . . . o . . . e . . .
40 C H A P T E R V.
P L A C E M E N T O F LOAM IN THE DAM CORE...
4 312
.
P r e p a r a t i o n of t h e W o r k S i t e...
4 3 1 3.
Working t h e Winter S t o r a g e Mounds and T r a n s p o r t -...
i n g t h e Soil 44...
.
14 P l a c i n g t h e Soil 44 1 5.
C o m p a c t i o n of t h e S o i l...
47 1 6.
S a l t T r e a t m e n t of t h e C o n t a c t S u r f a c e s...
50CHAPTER VI
.
QUALITY CONTROL O F THE LOAM FILLING O F. . .
. . .
THE DAM BODY
.
.
.
.
59. . .
.
17 C o n t r o l of Soil Density 59 18.
M e t h o d s of D e t e r m i n i n g t h e S i m p l e s t Geotechnical. . .
C h a r a c t e r i s t i c s of t h e Soil 63 19.
Soil T e m p e r a t u r e R e g i m e a t D i f f e r e n t S t a g e s of t h e E n g i n e e r i n g P r o c e s s. . .
65 C H A P T E R VII.
SOME TECHNICAL AND ECONOMIC INDICESRELATING T O THE P L A C E M E N T O F LOAM
. . . . .
.
IN DAM CORES IN WINTER
..
...
71 C o n c l u s i o n s . . . e . e . o . . . 74 R e f e r e n c e s.
. . . . . . . . . . . . . . o . . . . o . . a ~ . . . . . . . . . . . . . . . . . 76PUBLISHER'S NOTE
L a r g e - s c a l e hydro power and w a t e r r e s o u r c e s construction i s under way in the Soviet Union. The hydro s y s t e m s and the r e s e r v o i r s c r e a t e d by t h e m a r e intended t o provide power, t r a n s p o r t , i r r i g a t i o n , w a t e r supplies, e t c .
It would be difficult t o n a m e another s p h e r e of human activity i n which environmental, technological and economic f a c t o r s a r e s o c l e a r l y i n t e r r e l a t e d . This p l a c e s a s p e c i a l responsibility on t h o s e who p a r t i c i p a t e in the c r e a t i o n of v a s t hydroengineering complexes.
The s u c c e s s f u l development of hydro power construction i s b a s e d on the introduction of new technological solutions and g r e a t e r economic
efficiency of hydro s y s t e m s in the planning stage and s y s t e m s a l r e a d y under construction.
In 1967, the publishing house "Energiya" s t a r t e d a new s e r i a l
publication, "The Hydraulic Engineering and Water P o w e r Library"':'. It i s planned t o t r e a t s y s t e m a t i c a l l y in a s e r i e s of the L i b r a r y ' s booklets a wide
r a n g e of a c t u a l p r o b l e m s relating t o the planning, r e s e a r c h , construction and operation of hydraulic engineering and w a t e r power s t r u c t u r e s and
r e s e r v o i r s . Individual i s s u e s will d e a l with c u r r e n t w a t e r r e s o u r c e and power-economics calculations, d e t e r m i n a t i o n of the economic efficiency of h y d r o e l e c t r i c power stations':'*, engineering calculations of s t r u c t u r e s , new d e s i g n s of s t r u c t u r e s and equipment, construction organization,
c u r r e n t m e t h o d s of c a r r y i n g out construction work, methods of d e t e r m i n - ing the c o s t of construction, l a b o r a t o r y and field investigations and s u r v e y s , e x p e r i e n c e i n the operation of hydraulic s t r u c t u r e s , equipment and
r e s e r v o i r s .
The booklets of "The Hydraulic Engineering and W a t e r P o w e r L i b r a r y " will s e r v e a s a p r a c t i c a l guide t o the planning, construction and operation of hydraulic s t r u c t u r e s .
C r i t i c i s m s and r e q u e s t s concerning the L i b r a r y should be s e n t to: "Ene rgiya" P u b l i s h e r s , "The Hydraulic Engineering and W a t e r P o w e r L i b r a r y " , 10, Shlyuzovaya n a b . , Moscow Zh-114***.
"Biblioteka gidrotekhnika i gidroenergetika" ( T r a n s l . )
*
GES ( T r a n s l . )***
Moskva Zh-114, Shlynzovaya nab.,
10. Izdatel' stvo "Energiya"- "Biblioteka gidrotekhnika i gidroenergetika". ( T r a n s l . )INTRODUCTION
With e a c h succeeding y e a r , the n a t u r a l wealth of the Soviet North- e a s t and F a r North i s being exploited a t an e v e r - i n c r e a s i n g tempo: new i n d u s t r i a l e n t e r p r i s e s , mining and manufacturing b r a n c h e s of i n d u s t r y and new m a i n communications r o u t e s a r e being developed. The r a p i d growth of t h e s e s e c t o r s of i n d u s t r y depends upon the p r i o r i t y development of power, and f o r t h i s r e a s o n t h e s e r e g i o n s have, i n r e c e n t y e a r s , s e e n a n i n t e n s i - fication of engineering s u r v e y s and design studies in p r e p a r a t i o n f o r con-
s t r u c t i o n , and a s e r i e s of l a r g e - s c a l e power complexes i s being c o n s t r u c t - e d , including h y d r o e l e c t r i c s t a t i o n s .
The construction of the M a m a k a n s k a y a GES h a s been completed; a l a r g e h y d r o e l e c t r i c power station i s being c o n s t r u c t e d a t full speed on the Vilyui R i v e r , a t r i b u t a r y of the Lena; a s t a r t h a s been m a d e on the con- s t r u c t i o n of the UsttKhantaiskaya GES on the Khantaika R i v e r , and the Z e i s k a y a GES on the Zeya R i v e r ; the Verkhoyanskaya GES on t h e Adycha R i v e r , the Kolyrnskaya GES on the Kolyrna R i v e r and the Amguemskaya GES on the Chukotka R i v e r a r e in the planning stage. At the s a m e t i m e , in r e c e n t y e a r s , a number of m e d i u m and s m a l l h y d r a u l i c s t r u c t u r e s
-
of g r e a t i n t e r e s t f r o m an engineering point of view-
have been e r e c t e d i n t h e s e r e g i o n s f o r v a r i o u s p u r p o s e s . However, t h e i n d u s t r i a l development of the N o r t h e a s t and F a r North i s b e s e t by s e r i o u s difficulties due t o the long, s e v e r e winter, t h e p r e sence of p e r m a f r o s t , paucity of information about the regions and a lack of e x p e r i e n c e in c a r r y i n g out construction w o r k u n d e r the conditions which p r e v a i l t h e r e . It frequently happens t h a t the n e c e s s a r y construction m a t e r i a l s a r e not p r e s e n t i n the a r e a and t h e i r d e l i v e r y i s h a m p e r e d by the r e m o t e n e s s and undeveloped n a t u r e of the r e g i o n s and the a b s e n c e of p e r m a n e n t highways. All t h i s p r e s e n t s the c o n s t r u c t o r s with additional d i f f i c u l t i e s , which a f f e c t the t i m e , cost and quality of construction.The m a x i m u m utilization of local construction m a t e r i a l s i s a v e r y i m p o r t a n t consideration in t h e s e r e g i o n s , s i n c e t r a n s p o r t a t i o n conditions a r e exceedingly difficult: m o s t of the f r e i g h t a r r i v e s during the e x t r e m e l y
s h o r t s u m m e r navigation s e a s o n ; it i s then d e l i v e r e d t o t h e s i t e by t e m - p o r a r y winter r o a d s . F o r t h i s r e a s o n , m o s t of t h e d a m s in the n o r t h e r n regions of o u r country a r e c o n s t r u c t e d of local m a t e r i a l s with anti-seepage zones in the f o r m of p e r m a f r o s t c u r t a i n s , o r d i a p h r a g m s and c o r e s of
cohesive s o i l s with rockfill t o e s .
Until v e r y recently, only a v e r y limited number of rockfill d a m s had been constructed in t h e Soviet Union, m o s t of t h e m low o r m e d i u m p r e s s u r e d a m s . The m o s t i m p o r t a n t of the completed d a m s a r e the O r t o - Takoiskaya, which i s 59 m high, the Iriklinskaya, 43 m high, and the Malo-Ul'binskaya and Shirokovskaya semi-fill'$ d a m s , 34. 5 m and 40 m
high, r e s p e c t i v e l y ( ' I ) . Both in the Soviet Union and abroad, experience i s a l m o s t completely lacking in the construction of l a r g e darns f r o m local m a t e r i a l s under the h a r s h conditions prevailing in t h e F a r North, where in the winter the t e m p e r a t u r e frequently f a l l s below -50°C. F o r example, published d a t a on foreign experience in the e r e c t i o n of t h i s type of s t r u c t u r e , p a r t i c u l a r l y in Sweden and Canada, indicate that t h e construction of d a m s f r o m local m a t e r i a l s i s governed by e x t r e m e l y rigid technical r e q u i r e - m e n t s . Even the w o r k of filling the d a m body with r o c k depends upon the
a i r t e m p e r a t u r e , which should not be lower than -30°C. The installation of anti-seepage zones i s subject t o even s t r i c t e r r e q u i r e m e n t s : t h i s should be done during the w a r m season, o r , in exceptional c a s e s , when the a i r t e m p e r a t u r e i s no lower than - 5 t o 1 0 ° C
"
Z 1 ) a This means that the work h a s to be c a r r i e d out on a s e a s o n a l b a s i s , construction t i m e and c o s t a r e c o n s i d e r a b l y i n c r e a s e d , and it i s not uncommon t o have t o r e j e c t any idea of using local m a t e r i a l s f o r d a m construction in regions with h a r s hc l i m a t i c conditions. Thus, i t i s often n e c e s s a r y f o r d e s i g n e r s and hydraulic e n g i n e e r s , working in such regions and contending with specific engineering
-
'*polunabrosnye ( T r a n s l . )
T r a n s l a t o r ' s note: In the v e r y few c a s e s w h e r e i t h a s not been possible t o identify the p r e c i s e English equivalent f o r c e r t a i n R u s s i a n t e c h n i c a l t e r m s in available s o u r c e s of information, the R u s s i a n t e r m s a r e given in foot- note s.
geology conditions, t o have to r e s o l v e complex p r o b l e m s , which a r e often without p r e c e d e n t . Any exchange of e x p e r i e n c e , including u n s u c c e s s f u l a s well a s s u c c e s s f u l solutions, i s of undoubted value in subsequent evaluations of optimal construction conditions in h a r s h n o r t h e r n r e g i o n s . T h i s booklet d e s c r i b e s e x p e r i e n c e gained in the placing of cohesive s o i l s in w i n t e r in the F a r North during the construction of the soil c o r e of the rockfill d a m of the Vilyuiskaya GES
.
The p r o b l e m s encountered in the construction of the Vilyuiskaya Dam w e r e successfully resolved a s a r e s u l t of t h e utilization of p e r m a - f r o s t r e s e a r c h d a t a and p e r m a f r o s t construction e x p e r i e n c e , not t o mention the c r e a t i v e work of t e a m s of r e s e a r c h w o r k e r s , d e s i g n e r s and builders: t h e M . I . Kalinin Leningrad Polytechnic
institutei,
the B. E . Vedeneev All- Union Hydraulic Engineering R e s e a r c h I n s t i t u t e 2 , the V. V. Kuibyshev Moscow Construction Engineeringinstitute3,
the S. Ya,Zhuk All -UnionPlanning, Surveying and R e s e a r c h Institute4, t h e All-Union Institute f o r the Planning of E l e c t r i c P o w e r ~ r o j e c t s '
,
the Vilyuiskaya GES Construction p r o j e c t 6 , and the M i n i s t r y of P o w e r P l a n t s and the E l e c t r i c a l Industry of the U . S . S . R a 7 .It i s emphasized that this booklet should not be r e g a r d e d a s a broad g e n e r a l i z a t i o n o r a detailed scientific a n a l y s i s of the p r o b l e m s encountered and solved. I t s p r i n c i p a l a i m is to f a m i l i a r i z e the r e a d e r with the e x p e r i - ence gained i n the construction of the s o i l c o r e of a rockfill d a m under w i n t e r conditions in the F a r North. The a u t h o r s hope that this will con- t r i b u t e , i n s o m e d e g r e e a t l e a s t , t o the s u c c e s s f u l solution of one of the m o s t i m p o r t a n t p r o b l e m s of hydraulic engineering construction i n the F a r North, n a m e l y , t o d e v i s e m e t h o d s of constructing rockfill d a m s i r r e s p e c t i v e of the t i m e of the y e a r and the a i r t e m p e r a t u r e .
L P I i m e n i M
.
I. Kalinina 'VNIIG i m e n i B. E . Vedeneeva 3 ~i m e n i V. V. Kuibysheva 1 ~ ~ * ~ i d r o ~ r o e k t i m e n i S. Ya. Zhuka 5 0 r g e n e r g o s t r o i 6: Vilyuiges s t r o i 7 ~SSSR ~ i ~ The AuthorsCHAPTER 1
GENERAL INFORMATION CONCERNING THE HYDRO SCHEME 1. Environmental, C l i m a t i c and Engineering Geology Conditions
in the Construction A r e a
The Vilyuiskaya h y d r o e l e c t r i c station i s being c o n s t r u c t e d on the middle r e a c h e s of the Vilyui R i v e r , one of the l a r g e s t t r i b u t a r i e s of the Lena
.
At the s i t e of the hydro s c h e m e the r i v e r cuts deeply into the bedrock of a steep-sided valley. The width of the r i v e r a t t h i s point v a r i e s between 100 and 110 m in the low w a t e r period and 300 m during the spring flood. During t h e s e p e r i o d s the depth of the r i v e r v a r i e s f r o m 1. 3 t o 13 m , and the r a t e of flow f r o m 0.08 t o 3.1 m / s e c .The Vilyui B a s i n i s situated in t h e E a s t S i b e r i a n c l i m a t i c zone,
which i s m a r k e d l y continental. Long, cold w i n t e r s with little snow a l t e r n a t e with s h o r t , hot s u m m e r s , during which m o s t of the precipitation f a l l s .
The m e a n a v e r a g e a i r t e m p e r a t u r e i s -8.Z°C. The annual t e m p e r a t u r e r a n g e i s a l m o s t 100°C: the m i n i m u m r e c o r d e d t e m p e r a t u r e being -63°C and the m a x i m u m t 3 6 " C . The coldest m o n t h i s J a n u a r y , the w a r m e s t , July. Winter s t a r t s a t the beginning of October and l a s t s f o r a p p r o x i m a t e l y 7 months. The snow c o v e r i s negligible, and n e v e r e x c e e d s 250
-
300 m m . The l a s t f r o s t o c c u r s in m i d - J u n e and t h e f i r s t in mid-August. Thus, the length of t h e f r o s t - f r e e period i s 59 - 60 days p e r y e a r .The construction s i t e of the hydro s c h e m e i s situated in a zone of continuous p e r m a f r o s t , 250
-
300 m t h i c k in p l a c e s . The prevailing t e m - p e r a t u r e of t h e p e r m a f r o s t i s - 2 t o -6"C, depending on the e x p o s u r e of the slopes. Under the bed of the Vilyui R i v e r , a t a l i k has been found t o a depth of 80 m . The width of the t a l i k zone i s the s a m e a s the width of the r i v e r i n the s u m m e r low-water period.The depth of the active l a y e r v a r i e s f r o m 1. 5 to 2.5 m, depending
on t h e e x p o s u r e of the slope. P e r m a f r o s t phenomena in t h e region of t h e d a m s i t e c a u s e f r o s t c r a c k s and i c e f o r m a t i o n s i n the clayey d e p o s i t s , the
i c e content of which, depending on the d r a i n a g e , v a r i e s between 50 and 80
-
90%.Owing t o the p r e s e n c e of continuous p e r m a f r o s t , the s u r f a c e runoff of the Vilyui B a s i n is v e r y low. The r i v e r i s fed m a i n l y by m e l t e d snow and, to a l e s s e r extent, by precipitation i n the s u m m e r and autumn. A s a consequence of t h i s , the hydrological r e g i m e of the r i v e r i s c h a r a c t e r i z e d by a n e x t r e m e l y uneven runoff. The winter d i s c h a r g e d i m i n i s h e s t o 1
-
2 m 3 / s e c ( i n s o m e y e a r s when t h e r e i s little w a t e r and the winter i s exceptionally cold, t h e r e i s no flow a t a l l ) ; when the snow m e l t s , however, the d i s c h a r g e is thousands of t i m e s g r e a t e r f o r a s h o r t p e r i o d , and f o r s e v e r a l d a y s thew a t e r level r e a c h e s 10
-
12 m . Eighty-four p e r cent of the annual runoff i s accounted f o r in the s p r i n g , 147'0 in the s u m m e r and autumn and 27'0 in the w i n t e r , which extends o v e r the g r e a t e r p a r t of the y e a r . At the h y d r o s i t e , the m a x i m u m runoff once i n a hundred y e a r s (17'0
f r e q u e n c y ) i s 12, 300 m 3 /s e c ; once i n 20 y e a r s (57'0 frequency), 10,300 m 3 / s e c ; and once i n 10 y e a r s (107'0 f r e q u e n c y ) , 9 , 8 3 0 m 3 / s e c .
T h e r i v e r f r e e z e s up between the 10th and 20th of October and r e - m a i n s f r o z e n f o r 200 t o 230 d a y s . The t h i c k n e s s of the i c e r e a c h e s 1 . 5 to
1 . 8 m . As the r i v e r begins t o f r e e z e , t h e w a t e r l e v e l gradually d e c r e a s e s , i c e f o r m s along the s h o r e s and a d h e r e s t o boulders; in s o m e s e c t o r s the
r i v e r f r e e z e s o v e r completely.
Within the r e s e r v o i r of the Vilyuiskaya D a m , the r i v e r valley c u t s into the m a s s i f of the S r e d n e -Vilyuiskoe Highlands, which c o n s i s t of
Palaeozoic and M e s o z o i c s e d i m e n t a r y and volcanic r o c k s . T h e s e d i m e n t a r y and tufogenic r o c k s contain s i l l s , dykes and fine veins, and a r e c o v e r e d with p l a s t i c and m a n t l e i n t r u s i o n s of t r a p s . P r e d o m i n a n t in the vicinity of the d a m a r e d i a b a s e s of a t r a p p e a n complex of m e d i u m and m i c r o c r y s t a l l i n e v a r i e t i e s f o r m i n g d e p o s i t s m o r e than 200 m thick, which m a k e up the bed and s l o p e s of the valley within the l i m i t s of the n o r m a l w a t e r level. No, tectonic f a u l t s w e r e found in the a r e a . The r o c k contains s m a l l f i s s u r e s , s o m e hollow, some filled. T h e d i a b a s e s , exposed t o weathering, a r e c o v e r - e d by a l a y e r of loose m a t e r i a l up t o 2 o r 3 m in depth.
2. Construction of the Hydro Complex
T h e construction of the Vilyuiskaya hydro complex i s being c a r r i e d out in two s t a g e s t o phase in with the i n c r e a s e in power consumption ( 1 , Z )
The complex of s t r u c t u r e s of stage one of the h y d r o s y s t e m c o m p r i s e s a rockfill d a m , h e a d r a c e canal, spillway with a single -span s e g m e n t a l lift g a t e , spillway canal, intake, s e m i -underground powerhouse with penstocks and a n offtake, a n enclosed 220 kv switchyard and v a r i o u s a u x i l i a r y
s t r u c t u r e s ( F i g u r e 1 )
.
T h e non-overflow rockfill d a m i s 74 m high and approximately 600 m along the c r e s t ( F i g u r e 2); the slopes vary: the u p s t r e a m slope f r o m 1 : 3 and 1 : 2. 5 t o 1 : 1 . 8 , and the d o w n s t r e a m slope f r o m 1 : 1 . 4 t o 1 : 1. 5.
B e r m s a r e s e t on the slopes at i n t e r v a l s of 10
-
1 5 m f o r t e m p o r a r y gang- ways and p e r m a n e n t r o a d s .The b a s e of the d a m i s composed of solid d i a b a s e s , which i n the s h o r e s e c t i o n s a r e c o v e r e d by a 1. 5 - 2 m l a y e r of loose d e p o s i t s of cobble- s t o n e s and loam with an a d m i x t u r e of g r u s s and r o c k d e b r i s caused by
weathering.
h
t h e r i v e r bed t h e s e d e p o s i t s a r e a b s e n t , s i n c e the d a m s i t e i s located on one of the s i l l s of the Vilyui. h p r e p a r i n g the foundation ofthe d a m the loose deposits w e r e removed. Using a h i t h e r t o u n t r i e d y e a r -
round m e t h o d , the q u a r r y - r u n r o c k f i l l i s placed in 8
-
1 0 m l a y e r s . In o r d e r t o obtain b e t t e r compaction of the f i l l during the s u m m e r period, i t i s t r e a t e d with a hydraulic m o n i t o r with a w a t e r p r e s s u r e of5 - 6 a t m and a d i s c h a r g e of 1
-
2 . 5 m 3 p e r cubic m e t r e of rockfill. Of c o u r s e , it i s not possible t o u s e hydraulic compaction i n filling the d a mbody i n w i n t e r ; then the only available m e a n s of compaction i s by the p a s s a g e of m o t o r vehicles. A s a r e s u l t of t h i s , the rockfill ( e s p e c i a l l y t h a t placed during w i n t e r ) s u b s i d e s by a s m u c h a s 5
-
670 over the construction period. This m e a n s that the quality of the c o r e h a s t o m e e t additional r e q u i r e m e n t s . In placing f i l l f o r the m a i n r o c k t o e , the r o c k s a r e s o r t e d roughly by s i z e , the l a r g e s t being placed c l o s e r to the d o w n s t r e a m slope, and the fine q u a r r y m a t e r i a l c l o s e r t o t h e u p s t r e a m slope.The t r a n s i t i o n zone is i n the f o r m of two l a y e r s of inverted f i l t e r s of 0
-
40 and 0-
150 mm c r u s h e d r o c k under the c o r e . The f i l t e r s a r e c o m - pacted t o a density of 1 . 8-
1 . 9 tons* p e r cubic m e t r e , c a r e being taken t o e n s u r e good contact between individual l a y e r s .The anti-seepage element of the d a m i s a c o r e of r o c k d e b r i s - g r u s s loam. The d o w n s t r e a m slope of the c o r e h a s a gradient of 1 : 1 . 4 , the up- s t r e a m slope, a gradient of 1 : 1.7. In o r d e r t o prevent piping during
v a r i a t i o n s in the w a t e r level, the outer s u r f a c e of the c o r e is covered with a n a t u r a l sand and g r a v e l f i l t e r . In the zone of fluctuating l e v e l s the f i l t e r i s i n two l a y e r s : a m i x t u r e of sand and g r a v e l and 0
-
150 mm rock d e b r i s . In o r d e r t o provide the c o r e with s t a t i c s t r e n g t h and t o reduce the effect of t e m p e r a t u r e v a r i a t i o n s f r o m the h e a d r a c e s i d e , i t i s s u r c h a r g e d with rockfill.The junction between the c o r e and the r o c k foundation c o n s i s t s of a weakly reinforced c o n c r e t e s l a b with a grouting g a l l e r y . Before the
r e s e r v o i r i s filled, the t a l i k i n the r i v e r b e d will be grouted f r o m the g a l l e r y , and l a t e r , a f t e r the f i s s u r e d r o c k a t the base of the d a m h a s thawed out, a continuous grout c u r t a i n will be laid along the e n t i r e outline of the dam.
B a s i c Quantities f o r the D a m in Thousands of Cubic M e t r e s
P l a c i n g the f i l l and pit run r o c k s u r c h a r g e of the d a m body 3,772 Installation of r o c k d e b r i s f i l t e r s under the c o r e 290
Placing of cohesive soil c o r e 58 0
Installation of i n v e r t e d f i l t e r of n a t u r a l sand and g r a v e l
m i x t u r e on o u t e r s u r f a c e of c o r e 104 C o n c r e t e facing of r o c k a t base of c o r e , and construction of
grouting g a l l e r y
3 . Organization of Work P r o g r a m
The organization of the g e n e r a l work p r o g r a m f o r the construction of the d a m i s l a r g e l y d e t e r m i n e d by the e x t r e m e l y i r r e g u l a r pattern of the Vilyui
runoff. T o c a r r y out t h e m a i n work of p r e p a r i n g t h e foundation of the d a m
and constructing i t in the r i v e r b e d s e c t o r during the w a r m s e a s o n would
have entailed the con-struction of c o f f e r d a m s and bypass structures':' designed
t o c a r r y d i s c h a r g e s of up t o 8 , 0 0 0
-
9 , 0 0 0 m 3 / s e c during construction, and t h i s would have m e a n t a m u c h longer construction t i m e and g r e a t l y i n c r e a s e d construction c o s t s . T h e r e f o r e , in o r d e r to p a s s the construction d i s c h a r g e s ,a d i v e r s i o n t r e n c h was m a d e in the left bank slope and a work plan was
adopted i n which a l l the work i n the r i v e r b e d connected with the p r e p a r a t i o n
of the foundation, the construction of the grouting g a l l e r y and the pouring of t h e d a m i s done in the w i n t e r , when the r i v e r runoff i s a t i t s lowest, under
c o v e r of a r e l a t i v e l y low cofferdam a c r o s s the r i v e r b e d ( F i g u r e 3). In the w i n t e r of 1963-64 s u c h a cofferdam was e r e c t e d u p s t r e a m f r o m the founda- tion excavation of the d a m . T h i s was used to d i v e r t the low w i n t e r runoff
( n o m o r e than 3
-
4 m 3 / s e c ) into the d i v e r s i o n t r e n c h ,With the a r r i v a l of the spring flood, w o r k on the foundation excavation was
discontinued, the equipment w a s removed and the foundation excavation flooded.
The 1964 spring flood and the s u m m e r and autumn non-regulated d i s c h a r g e of the Vilyui w a s p a s s e d through an opening between the right and left bank
e a r t h w o r k s of the d a m and the d i v e r s i o n t r e n c h .
During the s u m m e r of 1964, the rockfill w a s hauled f r o m both s i d e s of the r i v e r and placed in running w a t e r on the foundation p r e p a r e d during
the w i n t e r , gradually closing t h e gap. On 31st October 1964, the channel of the Vilyui R i v e r w a s c l o s e d ( 2 ) . T h e rockfill f r o m both s i d e s w a s joined,
the u p s t r e a m and d o w n s t r e a m c o f f e r d a m s w e r e r e b u i l t , and the runoff w a s
again d i v e r t e d into the d i v e r s i o n t r e n c h . In the foundation excavation
p r o t e c t e d by the c o f f e r d a m s , work w a s r e s u m e d on t h e e r e c t i o n of the d a m
i n the r i v e r b e d s e c t o r . During the winter period (October through M a y ) it was n e c e s s a r y t o d r a i n the foundation excavation, c l e a r it of sediment and e r e c t the d a m body with f i l t e r s t o a height of up t o 40 m , and the c o r e t o a height of approximately 25 m in o r d e r to p r e p a r e the p a r t i a l l y completed
d a m f o r the p a s s a g e of next y e a r ' s s p r i n g flood. The plans provided f o r the p a s s a g e of the flood w a t e r through the d i v e r s i o c t r e n c h and p a r t i a l seepage
through the f i l t e r s and the f i l l above the c o r e e r e c t e d t o a height of 25 m .
In o r d e r t o e n s u r e t r o u b l e - f r e e p a s s a g e of the flood w a t e r t h r o u g h the incomplete s t r u c t u r e , a c o n s i d e r a b l e amount of w o r k w a s n e c e s s a r y , i n - cluding the laying of a p p r o x i m a t e l y 180,000 m 3 of cohesive soil on the c o r e of the r i v e r b e d portion of the d a m .
The final closing of the Vilyui and t h e e r e c t i o n of the d a m i n the d i v e r s i o n t r e n c h s e c t o r w a s accomplished during the t h i r d w i n t e r (1966-67). A f t e r t h i s , the flow into the t a i l r a c e c e a s e d and the r e s e r v o i r began to f i l l . I n M a y 1967, the d a m c a m e u n d e r p r e s s u r e and t h e s u r p l u s w a t e r w a s d i v e r t e d through p e r m a n e n t spillway s t r u c t u r e s ,
CHAPTER
II
MATERLALS O F THE DAM
4 , R e a u i r e m e n t s f o r the C o r e M a t e r i a l
T h e Vilyuiskaya hydro s c h e m e i s a l a r g e hydroengineering complex which supplies power f o r the i m p o r t a n t i n d u s t r i a l e n t e r p r i s e s of Yakutia. One of i t s m o s t i m p o r t a n t s t r u c t u r e s i s the d a m , and t h e r e f o r e the quality of i t s c o n s t r u c t i o n , p a r t i c u l a r l y the c o n s t r u c t i o n of the c o r e , l a r g e l y d e t e r m i n e s t h e operational r e l i a b i l i t y of the e n t i r e s t r u c t u r e .
T h e r e q u i r e m e n t s f o r the c o r e m a t e r i a l w e r e l a r g e l y d e t e r m i n e d by the geotechnical c h a r a c t e r i s t i c s of the m a t e r i a l s available i n the c o n s t r u c - tion a r e a and which w e r e suitable f o r placing i n the a n t i - s e e p a g e zone of the d a m .
F i e l d and l a b o r a t o r y r e s e a r c h on r o c k d e b r i s - g r u s s l o a m which w a s t o be u s e d f o r the c o r e of the d a m was c a r r i e d out between 1959 and 1963 by the Scientific R e s e a r c h Station of G i d r o p r o e k t and the M . I. Kalinin Leningrad Polytechnic Institute.
T h e p u r p o s e of t h i s r e s e a r c h w a s t o d e t e r m i n e the s o i l c h a r a c t e r - i s t i c s and m e t h o d s f o r placing the soil in the c o r e , taking into account the excavation working c h a r a c t e r i s t i c s and the i n t e r i m s t o r a g e of the soil.
-
10-
L a b o r a t o r y t e s t s w e r e c a r r i e d out t o d e t e r m i n e the p e r m e a b i l i t y , compactibility and s t r e n g t h of the soils. Since the soil intended f o r the c o r e w a s rock d e b r i s - g r u s s loam, i t w a s a s s u m e d that the geotechnical c h a r a c - t e r i s t i c s of the s o i l a s a whole a r e d e t e r m i n e d p r i m a r i l y by the c h a r a c t e r - i s t i c s of the fine-grained soil ( i . e . , f r a c t i o n s i z e s l e s s than 2 m m ) ; t h e r e - f o r e , m o s t of the t e s t s w e r e c a r r i e d out with f i n e -grained soil.
The seepage coefficient w a s found t o be K = A
.
l o - * c m / s e c withL
s t r e s s e s in the m i n e r a l s o i l skeleton f r o m 0 t o 1. 5 kg/cm Special t e s t s c a r r i e d out a t the M
.
I. Kalinin Leningrad Polytechnic Institute with different s o i l compositions showed that c e r t a i n variations i n the g r a i n - s i z e composition have little effect on permeability. A seepage coefficient K = A 1 0 ' ~ c m / s e c is sufficient t o e n s u r e the r e q u i r e d i m p e r m e a b i l i t y of the c o r e and rapid consolidation of the s o i l a f t e r i t i s placed in the body of the s t r u c t u r e .The s h e a r s t r e n g t h of the s o i l was d e t e r m i n e d by s i n g l e - s h e a r
i n s t r u m e n t s under w a t e r . The t e s t s gave a v e r a g e values f o r s h e a r s t r e n g t h p a r a m e t e r s of cp = 34" and C = 0 . 0 8 k g / c m 2 . The t e s t s w e r e conducted in
a c c o r d a n c e with the consolidated d r a i n e d s h e a r test:::.
A s p e c i a l s e r i e s of t e s t s w a s conducted t o e s t a b l i s h the effect of f r e e z i n g and thawing on the s t r e n g t h of the soil. F i n e -grained soil was placed under w a t e r in a compactor. The s o i l w a s then compacted t o m a x - i m u m stabilization under loads of 0. 25, 0. 5, 1 and 1. 5 kg/crn2
.
Then, half the s a m p l e s w e r e t e s t e d f o r s h e a r s t r e n g t h and half w e r e f r o z e n a t t e m - p e r a t u r e t = - 2 0 ° C . The f r o z e n s o i l sample w a s placed in the s h e a r t e s t e r , i n a tank of w a t e r . After thawing, the s a m p l e s w e r e t e s t e d f o r s h e a rstrength.
The t e s t s showed that the f r e e z i n g and subsequent thawing of the s o i l had p r a c t i c a l l y no effect on i t s s h e a r strength. Average values Q = 30
-
33"and C = 0. 1 kg/cm2 w e r e obtained. Taking into account the fact that the g r a i n s i z e composition of the soil, despite a r t i f i c i a l mixing, would, t o s o m e ::%I. I. Kalinin Leningrad Polytechnic Institute, scientific r e p o r t "Is sledovanie
k a r ' e r n o g o g r u n t a dlya zemlyanogo e k r a n a platiny Vilyuiskoi GES" (Investi- gation of excavated s o i l f o r e a r t h c o r e of V i l ~ u i s k a y a GES Dam"), 1962.
extent, be non-homogeneous, i t w a s r e c o m m e n d e d t h a t , in o r d e r to i n c r e a s e the safety f a c t o r , cp = 27
-
28 and C = 0. 1 kg/cmz be adopted a s d e s i g n values.T h e c o n t r o l unit weight of f i n e - g r a i n e d s o i l skeleton w a s a s s u m e d t o be 1. 6
-
1 . 6 5 g/cm3.
Such a unit weight of m i n e r a l s o i l skeleton i s usually adopted a s a c o n t r o l value in the c o n s t r u c t i o n of a n t i - s e e p a g e zones of d a m s with cohesive s o i l s the m a x i m u m g r a i n s i z e of which d o e s not exceed 1-
2 m m . T h e p o r o s i t y of fine -grained s o i l i n t h i s c a s e i s 0 . 7 5-
0.80 f o r a n a v e r a g e s p e c i f i c weight of 2.88 g / c m 3 . A p a r t f r o m t h i s , i t i s p r e c i s e l y a t s u c h a unit weight of f i n e - g r a i n e d s o i l skeleton that the above s h e a r c h a r a c - t e r i s t i c s a r e a s s u r e d * .According to the "Technical Specifications" d r a w n up by
Lengidroproekt*::, the unit weight of f i n e - g r a i n e d s o i l skeleton f o r known v a l u e s of t h e unit weight of t h e s o i l a s a whole, the specific weight of t h e c o a r s e - g r a i n e d s o i l and the r e l a t i v e content by weight of c o a r s e - g r a i n e d m a t e r i a l i n the s o i l a s a whole w a s d e t e r m i n e d as follows.
T h e weight of the fine-grained s o i l Pf ( f r a c t i o n s m a l l e r than 2 m m ) in a unit volume of s o i l m i n u s the weight of the w a t e r i s
:: With a content of c o a r s e -grained s o i l up t o 5570 ( s e e below), the s t r e n g t h and seepage p r o p e r t i e s of the s o i l will not depend s o l e l y on the unit weight of t h e fine -grained soil. C o n t r o l t e s t s should be m a d e with a n a t u r a l m i x - t u r e of t h e s o i l s , including c o a r s e and f i n e - g r a i n e d s o i l s . If the d e n s i t y of the c o r e m a t e r i a l i s e x p r e s s e d in t e r m s of the t e s t value of a unit weight of the skeleton s o i l , 1. 60
-
1 . 6 5 g/cm3,
the r e s u l t would be a n unjustifiable o v e r - e s t i m a t i o n of the d e n s i t y of the s o i l t o be used f o r the c o r e ; however, i n the final a n a l y s i s , t h i s would add t o the safety f a c t o r of the s t r u c t u r e . ( E d i t o r ' s note)**"Tekhnicheskie usloviya na ukladku gruntovogo e k r a n a plotiny Vilyuiskoi GES" ("Technical Specifications f o r the s o i l c o r e of the Vilyuiskaya GES Dam"), Lengidroproekt, 1964.
w h e r e y s . s k i s the unit weight of the skeleton of t h e s o i l a s a whole ( t h e weight of t h e m i x t u r e ) ; P i s the content by weight of c o a r s e - g r a i n e d m a t e r i a l ( f r a c t i o n l a r g e r than 2 m m ) ; the quantities in the f o r m u l a a r e given i n
f r a c t i o n s of a unit.
If the volume of the s o i l a s a whole i s taken a s unity, t h e volume of fine - g r a i n e d m a t e r i a l m i n u s the volume occupied by c o a r s e - g r a i n e d m a t e r i a l will be
w h e r e y is the specific weight of the c o a r s e - g r a i n e d m a t e r i a l .
C
B y a r i t h m e t i c t r a n s f o r m a t i o n s we obtain t h e f o r m u l a f o r d e t e r m i n i n g the unit weight of f i n e - g r a i n e d s o i l skeleton:
It should be noted t h a t i n t h i s booklet the t e r m unit weight of f i n e - g r a i n e d s o i l skeleton y is understood a s t h e d e n s i t y of the f i n e - g r a i n e d
f . s k
m a t e r i a l ( f r a c t i o n s s m a l l e r than 2 mm) in t h e p o r e s of c o a r s e skeleton soil. The f e a s i b i l i t y of compacting r o c k d e b r i s - g r u s s l o a m t o a y
3
f . s k t o 1.60
-
1. 65 g / c m w a s studied by the M . I . Kalinin L e n i n g r a d Polytechnic I n s t i t u t e u n d e r field conditions i n t h e c o n s t r u c t i o n a r e a . In M a y 1962, loamcontaining up t o 70% f r o z e n s o i l w a s placed on a n e x p e r i m e n t a l d a m in 10
-
20 c m l a y e r s and compacted by KrAZ-222 t r u c k s .F r o m t h e s e t e s t s i t w a s concluded t h a t it w a s i m p o s s i b l e t o compact s o i l containing l a r g e quantities of c o a r s e l y f r a g m e n t e d f r o z e n m a t e r i a l t o
3
1 . 6 0
-
1. 65 g / c m,
the c o n t r o l unit weight of fine - g r a i n e d s o i l skeleton, with d u m p t r u c k s . The investigations w e r e continued in A p r i l 1963. The s o i l w a s compacted by KrAZ -222 and MAZ -525 t r u c k s , the t h i c k n e s s of the l a y e r s being taken a s 25, 35, 50 and 70 c m f o r KrAZ-222 t r u c k s and 25, 40, 50 and 80 c m f o r M A Z - 5 2 5 t r u c k s . During the t i m e t h e m a t e r i a l w a s being placed on the t e s t d a m , the a i r t e m p e r a t u r e v a r i e d between -10 and + 7 " C , and the a v e r a g e t e m p e r a t u r e of t h e s o i l d e l i v e r e d t o t h e s i t e w a s -0.8"C. The s o i l containedonly 10
-
20'50 of f r o z e n l u m p s , the d i a m e t e r of which w a s approximately half the depth of a l a y e r of fill. The r e s u l t s of t h e s e t e s t s a r e given in Table I.On the b a s i s of t h e s e t e s t s c a r r i e d out by the M . I . Kalinin Leningrad Polytechnic Institute, it w a s a s c e r t a i n e d that t o achieve the c o n t r o l s o i l d e n s i t y it w a s n e c e s s a r y t o l i m i t the content of f r o z e n l u m p s . T h e r e f o r e , it was decided to compact the s o i l in the d a m with a MAZ -525 t r u c k t o
'f. s k = 1 . 6
-
1. 65 g/cm3,
the thickness of the l a y e r not exceeding 35-
40 c m . The content and s i z e of the f r o z e n lumps w a s limited t o 7'50 and 10-
1 5 c m , r e s p e c t i v e l y , and t h e t e m p e r a t u r e of the f i l l being placed on the d a m had t o be above 0 ° C .F o r a unit weight of fine-grained soil skeleton of 1 . 6 5 g/cm3 and a p e r m i s s i b l e content of c o a r s e -grained m a t e r i a l of 55'50, the unit weight of the m i n e r a l skeleton of the s o i l a s a whole, consisting of c o a r s e and f i n e - g r a i n e d
3
m a t e r i a l , should, according t o f o r m u l a ( 3 ) be 2.2
-
2. 3 g / c m,
which i s c l o s e to the unit weight of c o n c r e t e m a d e of t h e u s u a l m a t e r i a l s and having a3
specific weight of 2 . 6 5 g / c m
.
The t e s t s c a r r i e d out by Lengidroproekt on excavated s o i l s provided the b a s i s f o r the "Technical Specifications f o r the Soil C o r e of the Vilyuiskaya GES Dam", which laid down the following r e q u i r e -m e n t s f o r the r o c k d e b r i s - g r u s s s o i l f o r the c o r e of the d a m .
T h e seepage coefficient of the c o r e m a t e r i a l should not exceed A
.
1 0 ' ~ c m / s e c .The s h e a r r e s i s t a n c e p a r a m e t e r s of fine -grained s o i l ( f r a c t i o n s s m a l l e r than 2 m m ) in t e s t s in a stabilized s t a t e under w a t e r should not be l e s s thancp = 27
-
28" and C = 0 . 1 k g / c m 2 .The m o i s t u r e content of the fill should be between 6 and 14'50. The optimum m o i s t u r e content, d e t e r m i n e d by l a b o r a t o r y m e t h o d s , depending on g r a i n - s i z e composition, i s 9 - 11%.
B o u l d e r s and clods of f r o z e n soil, the d i a m e t e r of which e x c e e d s half the t h i c k n e s s of the l a y e r , m u s t not be included in the c o r e body. M a t e r i a l containing m o r e than 770 of f r o z e n lumps m u s t not be used f o r fill.
P l a n t r e m a i n s , t r e e s t u m p s , r o o t s and m o s s m u s t be s o r t e d out and removed, s i n c e the content of o r g a n i c m a t t e r in t h e c o r e m a t e r i a l is
l i m i t e d t o 5% by weight.
In designing a d a m c o r e , s p e c i a l attention should be paid t o ensuring i t s r e s i s t a n c e t o seepage and s u b s u r f a c e e r o s i o n . T e s t s t o find the optimal g r a i n - s i z e composition f o r i n v e r t e d f i l t e r s showed that a n a t u r a l sandy g r a v e l m i x t u r e w a s not sufficiently r e s i s t a n t t o s u b s u r f a c e e r o s i o n . T h e r e
-
f o r e , it was planned t o m a k e t h e f i r s t l a y e r of t h e f i l t e r below the c o r e with0
-
40 m m c r u s h e d r o c k , the g r a i n s i z e composition of which e n s u r e s the i m p e r m e a b i l i t y of the c o r e , a s well a s r e s i s t a n c e to s u b s u r f a c e e r o s i o n a s s o c i a t e d with the second underlying l a y e r of r o c k waste ( 0-
150 m m f r a c t i o n s ) .Taking into account the f a c t that t h i s w a s the f i r s t t i m e that a 74 m high rockfill d a m w a s to be e r e c t e d in s u c h h a r s h c l i m a t i c conditions, and t h a t a t p r e s e n t we have no c l e a r idea of the deformations which o c c u r in pliable f i l l , i t was f e l t t h a t two l a y e r s of c r u s h e d m a t e r i a l should be used a s a t r a n s i t i o n zone, s i n c e t h i s would e n s u r e that the c o r e would be r e s i s t a n t t o s u b s u r f a c e e r o s i o n , even if c r a c k s f o r m e d right through it.
Notwithstanding t h i s , one of the p r i n c i p a l r e q u i r e m e n t s with r e s p e c t t o the composition of the m a t e r i a l is that it can be u s e d to c o n s t r u c t a homogeneous c o r e which will be effective i n preventing an accumulation of
seepage within it.
5. Loam P i t s and t h e i r Geotechnical C h a r a c t e r i s t i c s
Rock d e b r i s - g r u s s l o a m , which o c c u r s on both s i d e s of t h e Vilyui R i v e r , w a s s e l e c t e d a s the m a t e r i a l f o r the c o r e of the d a m . Eluvial- deluvial d e p o s i t s in the region of t h e s e o c c u r r e n c e s f o r m a m a n t l e on d i a b a s e s of t h e u s u a l type. T h e d i a b a s e s a r e heavily d i s i n t e g r a t e d w h e r e t h e y come in contact with unconsolidated m a t e r i a l , and can b e s t be d e s c r i b e d
a s crumbling r o c k in the f o r m of c o a r s e d e b r i s and s m a l l blocks.
T h e working profile of the p i t s c o n s i s t s of the following broadly d e - fined l a y e r s : f i r s t , f r o m the top, a 0.1
-
0. 2 5 m l a y e r of s o i l andvegetation; second, a 0.1
-
0 . 6 m l a y e r of heavy and m e d i u m r e d d i s h brown l o a m with up t o 20, and occasionally 4070, g r u s s and d i a b a s e r o c k d e b r i s ; in p l a c e s the loam changes t o heavy sandy loam; the t h i r d l a y e r , 0. 1-
0 . 4 m thick i s m a d e up of r o c k d e b r i s and g r u s s of weathered d i a b a s e , plus as m a l l quantity of loam o r sandy loam m a t e r i a l .
A well m i x e d blend of the second and t h i r d l a y e r s i s suitable f o r placing i n the c o r e body. I t s g r a i n - s i z e composition c h a r a c t e r i s t i c s f a l l within the range recommended f o r s o i l s of a n t i - s e e p a g e zones of e a r t h and rockfill d a m s ( F i g u r e 4 ) .
As i s evident f r o m the g r a p h , a f a i r l y wide range of variation in g r a i n - s i z e composition i s p e r m i t t e d . T h u s , the content of f r a c t i o n s l a r g e r than 2 m m ( c o a r s e - g r a i n e d m a t e r i a l ) forming the soil skeleton, can r a n g e f r o m 18 t o 55% by weight of the s o i l a s a whole. F r a c t i o n s l e s s than 2 m m i n s i z e a r e r e p r e s s n t e d by sand, s i l t and loam p a r t i c l e s . A s a r e s u l t , such a soil composition can be u s e d with a f a i r d e g r e e of reliability i n a c o m p a r a - tively fine non-permeable c o r e , since, having good s h e a r c h a r a c t e r i s t i c s ,
it i s a l s o sufficiently i m p e r v i o u s t o w a t e r .
The soil u n d e r consideration i s m o d e r a t e l y c o m p r e s s i b l e . The
coefficient of c o m p r e s s i b i l i t y , d e t e r m i n e d by VNIIG'g t e s t e r s with a d i a m e t e r of 205 m m , using d i s t u r b e d s a m p l e s , v a r i e s f r o m 0.022 t o 0.06 kg/cm2.
The t e s t e d loam contains up t o 5570 g r u s s and r o c k d e b r i s , 25
-
3570 s i l t and sand p a r t i c l e s , and 10-
2070 l o a m p a r t i c l e s . H e r e , the effective d i a m e t e r , D10 v a r i e s f r o m 0.002 t o 0.025 m m , D60 f r o m 0. 5 t o 5 m m . The non -uniformity coefficient, A ~ ~ / A ~ v a r i e s within wide l i m i t s.
T h e m i n e r a l o g i c a l composition of the soil of the second and t h i r d l a y e r s w a s studied under an e l e c t r o n m i c r o s c o p e , and subjected t o t h e r m a l a n a l y s i s and organic dye t e s t s in the Lengidroproekt l a b o r a t o r y . The
r e s u l t s of t h e s e investigations show that the l o a m p a r t i c l e s a r e m o n t r n o r i l - lonite with a d m i x t u r e s of organic m a t t e r and i r o n oxides.
::The B.
E.
Vedeneev All-Union Hydraulic Engineering R e s e a r c h Institute (T ransL)CHAPTER 111
T H E SEARCH FOR A METHOD O F PLACING COHESIVE SOILS IN WINTER
6. E r e c t i o n of Low Head D a m s i n the Region of M i r n y i
The b a s i c w o r k of p r e p a r i n g the foundation soil and e r e c t i n g the r i v e r bed portion of the Vilyuiskaya D a m had t o be c a r r i e d out i n the c o u r s e of t h r e e w i n t e r s . T h i s led t o s e r i o u s d i f f i c u l t i e s , since l a r g e - s c a l e c o n c r e t e pouring and excavation work* had t o be c a r r i e d out in exceptionally s e v e r e
w i n t e r conditions. The construction of the c o f f e r d a m s , the draining of the foundation excavations and t h e r e m o v a l of w a t e r , the p r e p a r a t i o n of the foundation s o i l s , the filling of t h e d a m body, and the laying of t h e f i l t e r s and t h e c o r e called f o r a c r e a t i v e a p p r o a c h and posed a n u m b e r of difficult engineering p r o b l e m s . P r i o r t o the e r e c t i o n of the Vilyuiskaya D a m ,
Vilyuigesstroi p e r s o n n e l had a l r e a d y a c q u i r e d e x p e r i e n c e in the e r e c t i o n of s t r u c t u r e s f o r controlling r i v e r flow and i n d u s t r i a l and d o m e s t i c w a t e r supplies. Thus, i n 1961 -1962 the r i v e r was d i v e r t e d i n o r d e r t o p r e v e n t flooding, by heavy r a i n s , of a l a r g e i n d u s t r i a l q u a r r y situated in t h e r i v e r valley. The s t r u c t u r e s r e q u i r e d f o r t h i s included two low d a m s with a head of 5
-
7 m. The construction conditions w e r e such a s to p r e c l u d e the e r e c t i o n of t h e s e d a m s during the w a r m s e a s o n , and a method of obtaining s o i l in sufficiently l a r g e quantities and placing it i n position had not been worked out a t that t i m e . It was decided, t h e r e f o r e , t o u s e f r o z e n s o i l f o r fill and compact i t i n l a y e r s with loaded t r u c k s . The grouted cutoff+:$ i n t h e s e d a m s consisted of a sectional wooden d i a p h r a g m held in place i n acutoff t r e n c h i n t h e bedrock by clayey loam backfill. Low capacity i t f i r e tube heaters8'*)$* w e r e u s e d t o obtain thawed loam f o r sealing the d i a p h r a g m f i r m l y into the d a m cutoff. T h i s work was c a r r i e d out i n the w i n t e r of
1961 -62, and i n t h e spring t h e s t r u c t u r e s w e r e put under p r e s s u r e .
*
betonnye i z e m e l l n o - s k a l l n y e raboty ( T r a n s l . )**
protivofiltratsionnaya zave sa: a l s o given a s "curtain" ( T r a n s l . ) *:g'::zharovye t r u b c h a t y e pechi ( T r a n s l . )While the s t r u c t u r e s w e r e in u s e , the g e n e r a l s e t t l e m e n t of the d a m s was accompanied by local s o i l subsidences. These w e r e within calculated l i m i t s . Heavy seepage w a s observed in one of the d a m s during the filling of the r e s e r v o i r . This w a s promptly eliminated. During t h e s u m m e r period when the ground thawed, compaction of the s o i l in the embankment was completed.
Construction and operational experience h a s shown that, when the work i s carefully c a r r i e d out, t h i s method of constructing low head d a m s m a y be viable, but f o r the construction of important high head s t r u c t u r e s with f r o z e n soil, i t can only be recommended a f t e r a thorough study h a s been c a r r i e d out and m e a s u r e s have been taken t o prevent deformation of the diaphragm, s i n c e i t is impossible t o guarantee the r e q u i r e d density and homogeneity of the embankment.
If design considerations and the adopted work p r o g r a m preclude the placement of cohesive s o i l a t t e m p e r a t u r e s below freezing, we m u s t t r y t o find efficient methods of c a r r y i n g out t h i s work i n the w i n t e r , a s w a s done in the c a s e of the d a m on the l r e l y a k h River n e a r the town of
M i r n y i ' 3 9 5 9 15' 15a'0 This 2Om high dam (Figure 5) f o r m s a reservoir
with an effect;ve capacity of 12 million m 3 . The foundation s o i l of the d a m c o n s i s t s of f r o z e n t a l u s and alluvial d e p o s i t s . In o r d e r t o provide m o r e effective m e a s u r e s against seepage through the b a s e of the d a m , a wide cutoff t r e n c h was m a d e through t h i s soil extending into the bedrock ( c l a y - m a r l ) which l i e s at a depth of 8
-
10 m . The t a l i k in the r i v e r bed, thec o r e of the d a m with the cutoff, and the b a s e , f r e e z e and a r e maintained in t h i s s t a t e by m e a n s of a cold a i r frozen c u r t a i n s y s t e m which o p e r a t e s during the winter.
The Irelyakh R i v e r i s c h a r a c t e r i s t i c of r i v e r s in the F a r North: v e r y uneven runoff
-
p r a c t i c a l l y none in the winter-
and a flood peak during thesnow m e l t period.
In o r d e r t o reduce construction c o s t s , the plan provides f o r the work t o be c a r r i e d out without w a t e r d i v e r s i o n s t r u c t u r e s during the construction period. During the s p r i n g and s u m m e r , the work had t o be c a r r i e d out
above the n o r m a l and flood l e v e l s , while the c l e a r i n g of the bed and t h e p r e p a r a t i o n of t h e foundation excavation f o r t h e cutoff and the placement of thawed s o i l i n t h e cutoff was done in the winter u n d e r the protection of a non-overflow u p s t r e a m c o f f e r d a m with a full accumulation of runoff. Such a r e q u i r e m e n t again m a d e i t i m p e r a t i v e t o r e s o l v e the question of m e t h o d s of obtaining, s t o r i n g and placing thawed s o i l under heavy f r o s t conditions. The construction of the I r e l y a k h Dam was considered a definite p r e p a r a t o r y s t e p t o t h e e r e c t i o n of the m o r e i m p o r t a n t s t r u c t u r e s of the Vilyuiskaya hydro scheme. H e r e , u n d e r a c t u a l conditions, s e v e r a l d i f f e r e n t m e t h o d s of solving the p r o b l e m w e r e t e s t e d . Some of t h e m a r e d e a l t with i n m o r e d e t a i l below.
T h e filling of the d a m cutoff, which according t o t h e schedule should have been completed in F e b r u a r y
-
M a r c h , called f o r approximately20, 000 m 3 of thawed loam. Using b u l l d o z e r s , a pile of thawed loam 7
-
9
m high (approximately 30,000 m 3 ) was p r e p a r e d i n a pit during the s u m m e r . With the onset of w i n t e r , the pile was c o v e r e d with snow f o r b e t t e r heat insulation; no o t h e r s t e p s w e r e taken t o p r e v e n t i t f r o m f r e e z - ing. On opening up the pile i n M a r c h , i t w a s found t o be f r o z e n t o a depth of 3. 5 m , and out of the total amount of s o i l , only 8 , 0 0 0-
10,000 m3 of loam was in a n unfrozen s t a t e with a t e m p e r a t u r e between + 2 and + 3 " C . Attempts t o thaw the f r o z e n c r u s t with e l e c t r i c h e a t e r s did not produce the d e s i r e d r e s u l t s . The poor e l e c t r i c a l conductivity of the soil, the highpower consumption and the slow r a t e of heating, which was inadequate f o r the r e q u i r e d work schedule, m a d e it n e c e s s a r y t o r e m o v e the f r o z e n c r u s t by blasting i n o r d e r t o u s e the s m a l l r e s i d u e of thawed soil.
T e s t s w e r e m a d e t o d e t e r m i n e the feasibility of using a method of obtaining thawed l o a m by e l e c t r i c a l l y heating f r o z e n c r u s h e d f i l l with e l e c t r o d e s i n s e r t e d v e r t i c a l l y d i r e c t l y i n the cutoff foundation excavation. The ground w a s wetted with a s a l t solution t o i n c r e a s e the e l e c t r i c a l conductivity. However, on thawing the f r o z e n i c e - r i c h s o i l , i t s m o i s t u r e content was found t o be considerably above the acceptable level. As a r e s u l t , when the soil was compacted it w a s impossible t o achieve the
r e q u i r e d density. A p a r t f r o m t h i s , the a p p a r a t u s was not v e r y efficient and consumed l a r g e amounts of power.
The method of obtaining thawed soil with h e a t e r s , using the
O r g e n e r g o ~ t r o i ' : ~ s y s t e m g e n e r a l l y empl.oyed t o heat r o c k foundations, was a l s o unproductive. The h e a t e r u s e d i n t h i s c a s e was a canvas s a c k , 12
-
20 s q u a r e m e t r e s i n a r e a , fed with hot a i r (80-
100°C) f r o m a n e l e c t r i c a i r h e a t e r o r a h e a t jet. The hot a i r p a s s e s through p e r f o r a t i o n s in the bottom of t h e h e a t e r , w h e r e it c o m e s into contact with the f r o z e n s o i l , s p r e a d out i n a l a y e r 30-
40 c m thick, During the t e s t s i t became c l e a r that the capacity of the a p p a r a t u s was inadequate f o r thawing and reducing the m o i s t u r e content of the soil.Much b e t t e r r e s u l t s w e r e obtained with engineer Lyutov's s y s t e m of using a jet operating on d i e s e l fuel. The a i r and g a s m i x t u r e , at a t e m - p e r a t u r e of 150
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180°C, i s d i r e c t e d through h e a t - r e s i s t a n t s t e e l ducts onto the f r o z e n soil, which thaws quite rapidly. However, the s m a l l a r e a of the heat d i s t r i b u t o r s (12 s q u a r e m e t r e s in a l l ) precluded the effective u s e of t h i s method t o obtain thawed soil in the n e c e s s a r y quantities. It should be noted t h a t t h i s s y s t e m was subsequently g r e a t l y i m p r o v e d by i t so r i g i n a t o r . Heat d i s t r i b u t o r s with a n a r e a of approximately 180 s q u a r e m e t r e s w e r e mounted on the b a s e of a heavy t r a c t o r and the whole a s s e m b l y , known a s a g e n e r a l - p u r p o s e heat g e n e r a t o r (UTG*::), w a s widely used in the construction of the hydro s c h e m e .
The u s e of the heating a p p a r a t u s suggested the idea of utilizing a t u r b o j e t engine a s a s o u r c e of heat f o r thawing soil. A t h e r m a l reaction device consisting of a d i s c a r d e d RD-3m turbojet engine ( u s e d t o power TU-104 a i r c r a f t ) and a specially designed heat d i s t r i b u t o r was f i r s t u s e d in the construction of the Irelyakhskaya Dam. Consuming a c o m p a r a t i v e l y l a r g e amount of fuel (TS-1 k e r o s e n e ) , i. e .
,
3 tons p e r h o u r , the a p p a r a t u s thawed up t o 1 , 0 0 0 m 3 of f r o z e n s o i l packed on top of t h e d i s t r i b u t o r in a1 m l a y e r in two h o u r s .
