Power Technology and Engineering Volume 25 Issue 9 1991 [Doi 10.1007%2Fbf01836484] Yu. E. Khechinov -- Disperse-reinforced Concrete in Hydrotechnical Construction

8/10/2019 Power Technology and Engineering Volume 25 Issue 9 1991 [Doi 10.1007%2Fbf01836484] Yu. E. Khechinov -- Dis

1/7

F R O M I D E S T O T H E I R R E L I Z T I O N

D I S P E R S E - R E I N F O R C E D C O N C R E T E I N H Y D R O T E C H N I C A L

C O N S T R U C T I O N

Yu. E. Khechinov

U D C 6 9 1 . 3 2 8 : 6 2 1 . 3 1 1 . 2 1 . 0 0 2 . 2

Orien tatio n of the development of Soviet hydropower engi neering toward the further

develop ment of mountain and piedmont regions of the country with their richest hydropow er

resources will mak e it possible, to a considerabl e extent, to avoid a serious technog enic

impact on the environment.

Under groun d layouts of mountain hydrost ations in compariso n with others have obvious

ecological advantages.

This is confirmed by world practice of constructing mounta in hydrostati ons in France,

Italy, Sweden, Japan, Canada, Switzerl and, and other countries.

The solution of technical and economic problems is directly rel ated to reducing the

amount of materials for undergro und structures by involving them in the combined work with

the rock mass and by the wide introduction of new progressi ve materials and technological

schemes.

A prospect ive way to reduce the cost of underground structures is the use of disperse-

reinforc ed conc rete tran sported to the placement site by concrete pumps, concrete spreaders,

and devices for spraying concrete [ i]. For these purposes, the Central Construction Lab-

oratory of the Inguri Hydroelec tric Station Construction Administ ration ori ginall y conducted

a cycle of tests of disperse-rei nforced concretes and mortars, in which as fiber was used

steel wire 25 mm long and 0.3 mm in diameter, whic h corre sponded to the recommende d ratio

s = 80 based on the condition of the combined work of the fiber with concrete [2 ]. The

techn ology of i ntroducing the fiber into the concrete mix was perfected and the effect of

the vibrating process on the uniformity of the distribu tion of fiber in the concrete mass

or sand--cement mortar and character of the change in the strength and defo rmation char-

acteristi cs of the material in relation to disperse reinforcemen t were studied.

During loading of the proportion ed steel wire into the concrete mix and during its

mixing the main shortcoming of such fiber--lumpiness was found, owing to which a non-

unifo rm volume distribut ion of the steel segments of the wire in the mortar component

and hence a scatter of the values both of the strength and deform ation indices of the

concrete occur.

Furthermore, it was established that during vibration, an ordering of the orientatio n

of the fiber dependin g on the type of vibrator occurs. Thus, for example, a study of

sections of disper se-re inforc ed concrete specimens showed that in all cases the distri-

bution of the wire fiber in the volume of a standard cube is nonuniform, and during vibra-

tion on a vibrat ing table or by internal vibrators a tendency toward an arrangemen t of the

fiber parallel to the plane of vibration was noted.

These circumstance s, in our opinion, could substanti ally affect the strength char-

acteris tics of concrete specimens with fraction size 5-20 mm subjected to the tests. A com-

parison of the results of testing dis perse-r einforc ed concrete specimens with the indices

of a standar d unreinfo rced specimen (Table i) did not reveal noticeable correlations bet-

ween an increase of the percent of reinforce ment and bending-ten sile strength, esp eciall y

at an early age.

The tests were conducted by the standard method correspond ing to State Standard GOST

10180-78 and the specimen s of small concrete beams measur ing i00 i00 400 mm intended

for bending- tensil e tests and cubes measurin g i00 i00 I00 mm intended for compressive

tests were st ored in a room of the concrete laboratory at a relative hum idity within 80-95%.

Transl ated f rom Gidrote khniche skoe Stroitel'stvo, No. 9, pp. 41-44, September, 1991.

0 0 1 8 - 8 2 2 0 / 9 1 / 2 5 0 9 - 0 5 7 5 5 1 2 . 5 0 9 1 9 92 P l e n u m P u b l i s h i n g C o r p o r a n i o n 5 7 5


2/7

T A B L E 1

Bending tensile

Fiber stre ngth , Pa, at age,

c~

o f

7 28 180

vohm~e

0

0 , 5

1,0

2 ,1

1,7

1,9

2 ,2

2 .8

2 .7

3 3

2 9

3 9

Compressive strength,

MPa, at ag e, days

7 28 180

7

2,6 26

12,6 22 8 26 ,3

T A B L E 2

Parts of

prisms

divided

vertically

Quantity of I ompressive IDeviation of

steel shav-

ings in part strength of content of

of invest i- specimens, l steel shavings

gated v ol - MP a, t age of I from average,

ume,

g ! 3

days 1

II

Ill

IV

230

275

255

250

12,5

14,5

14,7

15,5

--9 I

9

0.8

- - 1 , 0

T A B L E 3

u~ ~ ~] Strength, MPa

~ I . . . . . I splitting ten- 1

~ i D e n a i n g t e n s i l e _

~'~ oi _ _ I si at age,

>an age, da s

~ Y I days

compressive

at ag e, days

0 : 2 . 1

0 .5 2 ,2

1

1,3

1 5 1 ,7

2

3 3,1

2 ,2 2 ,7

2 .5 3 ,1

2 ,2 3 ,2

2 ,3 3 .5

3 .2 4 ,1

4 ,2 4 ,4

1

1,2

1,2 1,4

0 ,8 0 ,9

0,8 1,1

1,6 1.9

2 ,7 2 .7

7 1 7 . 5 1 2 5 . 8

1 .8 [ m 5 [ 2 4 2

1 7 [ 1 4 L 1 8 5

1 8 114 1119 2

2.4 123 129

28

28 ,5

28

28 ,5

28 .6

37

44

T A B L E 4

Material of

specimens

Weight of

specimen, g

before :after

test test

i ~ C o e f f . o f

~ ~ relative

~ ~u~ wa te r

9 ~ I ' - ~

wear re-

-~ > o sistance

Granite

Concrete

Disperse-rein-

forced con-

crete

2485

11 729

11 545

2470

l! 89!

11 525

i s

38

20 8 ,2

1

0 ,35

0 ,6 8

I t w a s n o t e d t h a t o n a l l t e s t e d s p e c i m e n s , n o t a b r e a k b u t r a t h e r a d r a w i n g - o u t o f t h e

e n d s o f t h e w i r e f r o m t h e h a r d e n e d m o r t a r c a u s e d b y i t s i n s i g n i f i c a n t c o h e s i o n w i t h t h e

s m o o t h s u r f a c e o f t h e r e i n f o r c e m e n t o c c u r r e d .

A r t i f i c i a l l y c a l i b r a t e d b a r s a r e u s e d a b r o a d t o i n c r e a s e c o h e s i o n o f t h e w i r e w i t h t h e

m o r t a r c o m p o n e n t s o f c o n c r e t e , o r t h e g e o m e t r y o f t h e w i r e i s c h a n g e d ( w i t h b e n t e n d s , Z -

s h a p e d , w i t h f l a t t e n e d e n d s , e t c .) , w h i c h r e q u i r e s s p e c i a l t e c h n o l o g y o f m a n u f a c t u r i n g t h e

f i b e r o r i t s t r e a t m e n t a n d , i n t u r n , l e a d s t o a s h a r p i n c r e a s e o f it s c o s t , b u t d o e s n o t

e l i m i n a t e t h e p r o p e r t i e s o f l u m p i n e s s [ i, 2 ].

S h a v i n g s , b e i n g t h e w a s t e o f m e t a l - m a c h i n i n g e n t e r p r i s e s , w e r e t e s t e d i n t h e s e a r c h

f o r m o r e e c o n o m i c a l s o l u t i on s . S h a v i n g s o b t a i n e d d u r i n g m i l l i n g o f m e t a l , u n l i k e s t e e l

w i r e f i b e r , h a v e f l o w a b i l i t y a n d d o n o t h a v e a n y s i g n s o f l u m p i n e s s o r s t i c k i n g t o g e t h e r .

5 7 6


3/7

M P a

#5

4 0 . .

35

30;

o

10

E

/ " / 7 d a y s

o

O r 5 f ,O r f ~ O 2 f h

~ i / ' t 7 t i _ j

0 $Y 76'

a

15 6 i~Yf

kg

M P a

5 ~

qTO ~

45 ~ _

2~5 ~ i 7 days

2 ~ J days

1 5

0 5

o 0 , 5 1 , o 1 , 5 z , o z , 5

i

3~ 78 7 56 79 f k g

b

F i g , i. D e p e n d e n c e o f t h e c o m p r e s s i v e ( a ) a n d b e n d i n g

t e n s i l e ( b) s t r e n g t h a t v a r i o u s a g e s o n t he c o n t e n ~ o f

s t e e l s h a v i n g s .

T h e p a r a m e t e r s ( a r b i t r a r y d i a m e t e r ) o f s h a v i n g s d e p e n d o n t h e t y p e of m i l l i n g m a c h i n e

a n d c h a r a c t e r o f m a c h i n i n g t h e p a r t s a n d c a n be s e l e c t e d a c c o r d i n g t o s i z e s t o f i t t h e

c o n d i t i o n s o f t r a n s p o r t i n g t h e m a t e r i a l b y p i p e l i n e f r o m t he r at i o

D / d = 2 . 5 - 3 ,

w h e r e D i s t h e d i a m e t e r o f t h e c o n c r e t e - c o n v e y i n g p i p e; d is t h e a r b i t r a r y d i a m e t e r o f t h e

s h a v i n g s .

I n a d d i t i o n t o e s t a b l i s h i n g t h e a b s e n c e o f l u mp i n e s s , w h i c h t o a c o n s i d e r a b l e e x t e n t

p r o v i d e d a u n i f o r m d i s t r i b u t i o n o f s h a v i n g s i n t h e c o n c r e t e m i x , e x p e r i m e n t s w e r e c o n d u c t e d

t o d e t e r m i n e t h e e f f e c t o f v i b r a t i o n o n s e g r e g a t i o n ( s i n k i n g ) o f s h a v i n g s i n t h e f r e s h l y

p l a c e d c o n c r e t e m i x .

T h e m e t h o d o f i n v e s t i g a t i o n c o n s i s t e d i n t h e f o ll o w i n g : t h e p r e p a r e d a n d t h o r o u g h l y

m i x e d d i s p e r s e - r e i n f o r c e d c e m e n t - - s a n d m o r t a r w i t h a c o n e s l u m p of 4 c m w a s p l a c e d i n a

s t a n d a r d m o l d f o r i 0 0 x i 0 0 x 4 0 0 - m m p r i s m s p e c i m e n s . T h e n t h e m o l d w a s c l o s e d o n t o p

b y a m e t a l c o v e r a n d p l a c e d i n a v e r t i c a l p o s i t i o n o n a v i b r a t i n g t a b l e. A f t e r v i b r a t i n g

t h e s p e c i m e n s f o r 1 2 0 s e c , c o r r e s p o n d i n g i n t i m e t o n o r m a l w o r k i n g o f c on c r e t e , i n o n e of

t h e b a t c h e s ( t h r e e p r i s m s ) t h e m i x f r e s h l y p l a c e d i n t h e m o l d w a s d i v i d e d i n t o f ou r e q u a l

p a r t s , i . e ., s i z e o f t h e s t a n d a r d i 0 0 I 0 0 1 0 0 - m m c u b e , e a c h o f w h i c h w a s s u b j e c t e d t o

w e t s c r e e n i n g w i t h s e p a r a t i o n o f t h e s h a v i n g s t o d e t e r m i n e i t s w e i g h t c o n t e n t a f t e r t h o r o u g h

w a s h i n g .

T h e a v e r a g e r e s u l t s o b t a i n e d ( T a b l e 2 ) c o n f i r m e d t h e v i r t u a l a b s e n c e o f s e g r e g a t i o n

o f th e m e t a l s h a v i n g s i n t h e m o r t a r m a s s d u r i n g v i b r a t i o n o n t h e t a b le .

5 7 7


4/7

M P a ~ 0 ~

b

? If f0

i

days

Fig. 2. Grap h of the depe nden ce of the modu lus

o f e l a s t i c i t y o f u n r e i n f o r c e d ( i) a n d d i s p e r s e -

r e i n f o r c e d ( 2) c o n c r e t e s a t v a r i o u s a g e s o f t h e

specimens.

c m

3O

fO

r

I / /

I

I

K

0 f ~ 6 8 fO f2 / 18

Width of working, m

Fig. 3. Calc ulat ed data of the thick ness of the coati ng of

t h e u n r e i n f o r c e d ( d a s h e d l i n e) a n d d i s p e r s e - r e i n f o r c e d

( s o l id l i n e) g u n i t e s f o r a d i f f e r e n t w i d t h o f th e w o r k i n g

and degree of fractu ring of the rocks K.

T h e s e c o n d b a t c h o f t h r e e p r i s m s p e c i m e n s a f t e r 3 d a y s w e r e s a w e d i n t o s t a n d a r d c u b e s

a n d s u b j e c t e d t o c o m p r e s s i o n t e s t i n g, t h e r e s u l t s o f w h i c h a l s o i n s i g n i f i c a n t l y d i f f e r

from the avera ge values.

T h e a b s e n c e o f s e g r e g a t i o n o f s te e l s h a v i n g s d u r i n g v i b r a t i o n i s r e l a t e d t o t h e

c h a r a c t e r i s t i c s h a p e o f a s h a v i n g a n d t o it s c o n s i d e r a b l e s p e c i f i c s u r f a c e , n o t a l l o w i n g

it to sink into the morta r mass.

I n o r d e r t o e l i m i n a t e t h e e f f e c t o n t he s t r e n g t h i n d i c e s o f t h e d i s p e r s e - r e i n f o r c e d

c o n c r e t e o f th e a g g r e g a t e f r a c t i o n s t h a t c a u s e d s c a t t e r i n g o f t he v a l u e s i n t h e p r e c e d i n g

e x p e r i m e n t a l s e r i e s w i t h w i r e f i b er , f u r t h e r t e s t s w e r e c o n d u c t e d o n s p e c i m e n s m a d e f r o m

c e m e n t -- s a n d m o r t a r s ( s a n d w i t h f i n e n e s s m o d u l u s M f = 3 . 5) a n d r e i n f o r c e d w i t h s t e e l

shavings.

A c e m e n t - - s a nd m o r t a r M - 3 0 0 w i t h a c e m e n t c o n t e n t o f 6 8 5 k g / m ~ a n d w i t h a c o n e s l u m p

of 4 cm was taken as the initial one. The results of testing the cement--sand spec imens

w i t h v a r i o u s c o n t e n t s o f s t e e l s h a v i n g s a r e g i v e n i n T a b l e 3 . T h e b e n d i n g - a n d s p l i t t i n g -

t e n s i l e t e s t s o f s p e c i m e n s w i t h a l o w c on t e n t o f s h a v i n g s ( w i t h i n 0 . 5 - 1 . 5 ) d i d n o t r e v e a l

a n y e x c e s s o f t h e v a l u e s o f th e s e i n d i c e s i n c o m p a r i s o n w i t h s t a n d a r d s p e c i m e n s .

H o w e v e r , w i t h a n i n c r e a s e o f t he c o n t e n t o f s h a v i n g s ( w i t h i n 2 - 3 ) t h e b e n d i n g - t e n s i l e

s t r e n g t h ( w h i c h i s e x c e p t i o n a l l y i m p o r t a n t f o r u n d e r g r o u n d s u p p o r t s t r u c t u r e s ) o f t h e s p e c i -

m e n s a t a n e a r l y a g e in c o m p a r i s o n w i t h t h e u n r e i n f o r c e d i n c r e a s e s b y 5 0 - 8 0 a n d t h e s p l i t -

t i n g - t e n s i l e s t r e n g t h b y 1 2 5 - 17 5 . T h e v a l u e s o f t h e s e i n d i c e s f o r s p e c i m e n s a t a n a g e o f

2 8 d a y s e q u a l i z e , b u t n e v e r t h e l e s s t h e be n d i n g - a n d s p l i t t i n g - t e n s i l e s t r e n g t h o f t h e

r e i n f o r c e d s p e c i m e n s a r e h i g h e r t h a n t h o s e o f t h e u n r e i n f o r c e d b y r e s p e c t i v e l y 4 0 an d 70 .

A s t he t e s t r e s u l t s s h o w e d , t h e c o n t e n t o f s te e l s h a v i n g s a f f e c t s a l s o t h e c o m p r e s s i v e

s t r e n g t h o f t h e s p e c i me n s . W h e n t h e f i b e r c o n t e n t i s m o r e t h a n 1 . 5 , t h e c o m p r e s s i v e

s t r e n g t h o f t h e c o n c r e t e s p e c i m e n s r e i n f o r c e d w i t h s t e e l s h a v i n g s i n c r e a s e s m a r k e d l y w i t h

age (Fig. I). The same such picture is observ ed also in the bending ten sile test of the

specimens.

578


5/7

TABLE 5

Bending tensile strength, M~a, at age, days

specimens reinforced wi th mes h

specimens reinforced with

steel shavings

scheme scheme 2 scheme 3 scheme I

1,75 i 2,9 3,3

7 28

2 S 3 5

~ ~ 7 6 I

3 ] 7

28

1,9 2,2 2,4

3 7 28

4 05

It is nec ess ary to note the scatter of the values of the test results, which, in our

opinion, can be explained mainly by the inhomogeneity of the steel shavings with respect

to its size, shape, and quant ity in the test specimens. The results can be cons ider ably

distor ted in the case of using oiled shavings, a decrease of which will be observed at

early test times of the specimens.

Corros ion resist ance tests of the specimens reinforced with steel shavings were also

conducted . For this purpose, sp ecimen s of stand ard i00 I00 100-mm cubes were placed

for long storage in a moist air environment. Afte r 2-3 years of stora ge no signs of

corrosi on were found on sections of specimens of the dispers e-reinf orced concrete, with

except ion of those shavings which contacted the surface of the faces of the specimens.

A visual inspecti on and measuremen ts conf irmed that the penetrati on of rust inward

did not exce ed 1.5-2 mm, and the embed ded part of the shavings on the section, as all the

others, had a pure steel luster.

Tests of the deformation properties of the dispers e-reinf orced concretes showed that

their specime ns have values of the modulus of elasticity reduced (in particular, at an

early age) by as much as 30 in comparison with unrein forced specimens, which has important

signifi cance for yielding of supports constru cted from them (Fig. 2).

Shrin kage deformati ons were determined by the known method of the Leningrad Instit ute

of Railroa d Transpor tation Engineers; according to the test results the unreinf orced speci-

mens had the maximum defo rmations (0.275 mm/m) and the dispers e-rein forced concrete speci-

mens had the minimu m (less than 0.200 mm/m). This is explained by the presence in them of

a dispers e skeleton resisting deformations due to the unifor m spatial distri bution of steel

shavings in the mortar mass.

The effect of steel shavings on the occurrence of shrin kage cracks was studied on

tablet specimens. Almost radial cracks visible to the unaided eye appeared in all specimens

not co ntai ning shaving s at the end of 28 days.

Cracks were not observed in the specimens reinforced wit h steel shavings even during

3 years.

Furthermore, the water wear resistance of the specimens was invest igated to determine

the life of disperse-r einfor ced concretes in the event they are used in conveying and dis-

charg e tunnels, ope n spillways, and canals.

The water wear resistance of concrete, estimated by the coefficient of relative wear

resist ance equal to the ratio of the loss of the volume of a standard granite specimen to

loss of the volume of concrete from the effect of a wate r jet, was chec ked on a GAI-I

device accordin g to the method develope d at the Georgia n Scient ific-Re search Institute of

Power and Hydrauli c Structures. It is seen from the experime ntal results that the wear

resista nce of the disperse-rein forced concrete is almost twice greater than that of the

unrei nforc ed (Table 4).

Bending tensile tests of 200 400 80-mm concrete slabs reinforced with a 2.5-mm-dia-

meter steel mesh with a 50 50-mm mesh size were carried out to substantiat e the possibil ity

of using dispers e-reinf orced gunite for supporting walls instead of gunite on a steel mesh

(Table 5).

579


6/7

T h e a d o p t e d s c h e m e s o f t he a r r a n g e m e n t o f t h e st e e l m e s h i n t h e t e s t s l a b s w e r e d i c t a t e d

b y i ts a c t u a l p o s i t i o n r e l a t i v e t o t he u n e v e n s u r f a c e o f t he r o c k w o r k i n g c o v e r e d w i t h a

layer of gunite, the thickne ss of which for temp orary support is usua lly with in 6-10 cm.

A c o m p a r i s o n o f t h e re s u l t s o f t e s t in g s p e c i m e n s o f s l a b s r e i n f o r c e d w i t h a 3 % c o n t e n t

of steel shav ings r eveale d their increase d l oad-be aring capa city by 5% (3 days), 13% (7 days),

a n d 1 6 % ( 2 8 d a y s ) i n c o m p a r i s o n w i t h s p e c i m e n s r e i n f o r c e d b y a m e s h e v e n w i t h i t s m o s t

favor able ar range ment in the exten ded zone (Table 5, scheme 3).

T o s tu d y t h e t e c h n o l o g i c a l p o s s i b i l i t i e s o f t h e p r o c e s s o f a p p l y i n g d i s p e r s e - r e i n f o r c e d

g u n i t e, e x p e r i m e n t a l w o r k s w e r e c a r r i e d o u t o n t h e a p p l i c a t i o n o f g u n i t e r e i n f o r c e d w i t h

steel shavi ngs in the roof part of the No. 2 appro ach adit to the unde rgro und mach ine hall

o f th e K h u d o n i h y d r o s t a t i o n a n d o n a s t r e t c h o f t h e r i g h t - b a n k s l o p e o n t h e u p s t r e a m e l e v a -

tions of the abutment of an arch dam [3].

N o t e c h n o l o g i c a l p r o b l e m s o c c u r r e d d u r i n g a p p l i c a t i o n o f t h e g u n i t e r e i n f o r c e d w i t h

s t e e l s h a v i n g s b y t h e B M- 6 8 m a c h i n e ; t h e d r y m i x w i t h s t e e l s h a v i n g s u n i m p e d e d l y m o v e d

t h r o u g h a r u b b e r h o s e u p to 5 0 m l o n g w i t h o u t c r e a t i n g p l u g s a n d n o t i c e a b l e w e a r o f t h e

hoses.

T h e t h i c k n e s s o f t h e l a y e r a p p l i e d o n t h e e x p e r i m e n t a l s t r e t c h e s a t o n e ti m e w a s

2.5-3 cm, and in places with an uneve n surfa ce (in depre ssion s) was inc rease d to 5-6 cm

witho ut any signs of peelin g off of the fresh ly placed layer. A decr ease of rebound

was noted, w hich did not exceed 10-15% from the walls and not more t han 20% from the

roof, and the propo rtion of shavin gs in the rebound mass was insignifica nt.

O p t i m a l c o m p o s i t i o n s o f d i s p e r s e - r e i n f o r c e d c o n c r e t e a n d g u n i t e w i t h t h e u s e of

s t e e l s h a v i n g s w e r e d e v e l o p e d o n t he b a s i s o f l a b o r a t o r y a n d f i e l d t e s t s a t t h e C e n t r a l

C o n s t r u c t i o n L a b o r a t o r y o f t h e I n g u r i H y d r o e l e c t r i c S t a t i o n C o n s t r u c t i o n A d m i n i s t r a t i o n . *

T o s u b s t a n t i a t e t h e p o s s i b i l i t y o f u s i n g t h e d i s p e r s e - r e i n f o r c e d m a t e r i a l p r o p o s e d

b y t h e b u i l d e r s i n t h e u n d e r g r o u n d w o r k i n g s o f t h e K h u d o n i h y d r o s t a t i o n f o r s u p p o r t i n g

the walls of the machi ne hall an d room of the guard gates, as well as a perm anen t lining

i n t h e a p p r o a c h t u n n e l t o t h e g u a r d g a t e s , t h e n e c e s s a r y c a l c u l a t i o n s w e r e p e r f o r m e d o n

a c o m p u t e r b y d e s i g n e r s o f t h e T b i l i s i b r a n c h o f t he A l l - U n i o n P l a n n i n g , S u r v e y i n g , a n d

S c i e n t i f i c - R e s e a r c h I n s t i t u t e . * *

T h e r e s u l ts o f c a l c u l a t i n g t h e t h i c k n e s s o f t h e g u n i t e a n d d i s p e r s e - r e i n f o r c e d

g u n i t e l i n i n g i n c o n f o r m i t y w i t h t h e D e p a r t m e n t a l B u i l d i n g C o d e s V S N 4 9 - 8 6 o f t h e U S S R

M i n i s t r y o f P o w e r a n d E l e c t r i f i c a t i o n D e s i g n of t e m p o r a r y s u p p o r t o f h y d r a u l i c t u n n e l s

f o r c o n d i t i o n s o f r o c k c o r r e s p o n d i n g t o a s t r e n g t h c o e f f i c i e n t f s t = i0 f or t h e i r v a r i o u s

f r a c t u r i n g , f r o m s li g h t l y f r a c t u r e d K l, m o d e r a t e l y K 2, t o s e v e r e l y f r a c t u r e d K 3 , a r e

give n in Fig. 3.

A s f o l l o w s f r o m t h e c a l c u l a t e d d e p e n d e n c e s , t h e r a n g e o f u s e o f d i s p e r s e - r e i n f o r c e d

g u n i t e i n c o m p a r i s o n w i t h u n r e i n f o r c e d i s c o n s i d e r a b l y w i d e r . F o r e x a m p l e , o n t h e b a s i s

o f t h e t e c h n o l o g i c a l c o n d i t i o n s o f a p p l y i n g a g u n i t e l i n i n g w i t h a t h i c k n e s s o f 20 cm ,

t h i s r a n g e a p p l i e s t o s l i g h t l y a n d m o d e r a t e l y f r a c t u r e d r o c k s w i t h f s t = i0 w i t h i n l i m i t s

o f t h e w i d t h o f u n d e r g r o u n d w o r k i n g s f r o m 4 t o 1 2- 1 4 m . I n s e v e r e l y f r a c t u r e d r o c k s

t h i s l i m i t f o r d i s p e r s e - r e i n f o r c e d g u n i t e i s c o n f i n e d t o w o r k i n g s w i t h a w i d t h u p t o 7 m .

A c o m p u t e r c a l c u l a t i o n m a d e a c c o r d i n g t o V S N 4 9 - 8 6 s h o w e d a n o n c o r r e s p o n d e n c e t o t h e

g e n e r a l l y a c c e p t e d n o t i o n a b o u t r o c k p r e s s u r e a n d a s s i g n m e n t o f t h e l e n g t h o f t h e r o c k

bolts, as a result of which, for an unde rgro und work ing wi th widt h B = const the load on

t h e s u p p o r t a n d h e n c e t h e t h i c k n e s s o f t he l i n i n g a n d l e n g t h o f t h e r o c k b o l t r e m a i n c o n -

s t a n t w i t h i n c r e a s e o f t h e s t r e n g t h c o e f f i c i e n t o f th e r o c k a t a n e q u a l d e g r e e o f i t s

fractur ing, and when fst = 8 and more they even increase. This first of all pertai ns to

a d e t e r m i n a t i o n o f t h e d e p t h o f th e d i s t u r b e d z o n e hq a t th e s t a g e o f p r e l i m i n a r y c a l c u l a -

t i o n s , w h i c h , a s f ol l o w s f r o m V S N 4 9 - 86 , d o e s n o t d e p e n d o n t h e s t r e n g t h a n d d e f o r m a t i o n

c h a r a c t e r i s t i c s o f th e r oc k s , w h i c h d o e s n o t c o n f o r m t o r e a l i t y .

T h e r e s u l t s o f t h e i n v e s t i g a t i o n s m a d e i t p o s s i b l e t o j u d g e a l s o t h e h i g h e c o n o m y o f

u s i n g d i s p e r s e - r e i n f o r c e d g u n i t e .

*Under the dir ection of A. I. Dane liya and R. V. Pa rtsvaniy a.

**Di rect or A. A. Babalyan.

580


7/7

T h us , f o r ex a m p le , t h e e c o n o m y o f l a b o r e x p e n d i t u r e s w h e n o r d i n a r y g u n i t e o n a m e s h

i s r e p l a c e d b y d i s p e r s e - r e i n f o r c e d g u n i t e p e r i l 0 0 m 2 s u p p o r t e d s u r f a c e i s m o r e t h a n 3 0 0

m a n - h .

F o r a c o s t o f m e t a l s h a v i n g s e q u a l t o t h e c o s t o f m e t a l s c r a p ( 2 8 - 3 5 r u b l e s p e r t o n ) ,

t h e s a v i n gs f r o m u s i n g d i s p e r s e - r e i n f o r c e d g u n i t e i n c o m p a r i s o n w i t h g u n i t e o n a m e s h

r e a c h e s 1 4 0 0 r u b l e s p e r I 0 0 m 2 o f c o a t i n g [ 3] .

T h e r e s u l t s o f t h e i n v e s t i g a t i o n s a n d c a l c u l a t i o n s p e r m i t t e d p r o p o s i n g a s t r u c t u re

o f d i s p e r s e - r e i n f o r c e d g u n i t e w i t h a t h i c k n e s s o f I 0 cm i n c o m b i n a t i o n w i t h d e e p r o ck b o l t s

f o r s u p p o r t i n g t h e w a l l s o f t h e u n d e r g r o u n d m a c h i n e h a l l o f th e K h u d o n i h y d r o s t a t i o n i n s t e a d

o f r e i n f o r c e d - c o n c r e t e w a l l s w i t h a d e s i g n t h i c k n e s s o f 4 0 c m, a n d a l s o as a p e r m a n e n t l i n i n g

i n t h e a p p r o a c h t u n n e l t o t h e g u a r d g a t e .

T h e s e p r o p o s a l s w e r e n o t r e a l i z e d o w i n g t o t h e d e c i s i o n i n 1 9 8 9 to s t op t h e c o n s t r u c -

t i o n o f t h e K h u d o n i h y d r o s t a t i o n .

T h e w i d e u s e o f d i s p e r s e r e i n f o r c e m e n t * i n u n d e r g r o u n d s t r u c t u r e s , w a t e r - c o n v e y i n g

a n d d i s c h a r g e s t r u c t u r e s , a s w e l l a s in t h i n - w a l l e d c r a c k - r e s i s t a n t s t r u c t u r e s a n d i n

g r o u t i n g j o i n t s w o u l d m a k e i t p o s s i b l e t o c o n s i d e r a b l y r e d u c e t h e c o s t o f c o n c r e t e

s t r u c t u r e s a n d l a b or i n t e n s i t y o f t he w o r k s, p r o v i d i n g a t th e s a m e t i me t e c h n o l o g i c a l

e f f i c i e n c y o f c o n s t r u c t i o n a n d h i g h r e l i a b i l i t y o f o p e r a t i n g t h e c o n c r e t e s t r u c t ur e s .

T h e s p e c i m en s a n d m a t e r i a l s o n d i s p e r s e - r e i n f o r c e d c o n c r e t e a n d g u n i t e p r e s e n t e d f o r

c o m p e t i t i o n w e r e a w a r d e d t h e S i l v e r M e d a l o f t he U S S R E x h i b i t i o n o f E c on o m i c A c h i e v e m e n t s

in 1990.

i

2.

3.

L I T E R A T U R E C I T E D

O . M . G e t m a n e n k o , U s e o f s t e e l f i b e r - r e i n f o r c e d c o n c r e t e in c o n s t r u c t i o n , ~ k s p.

Inf. VNIIS. Stroit el. Mater. Izd., No. 9 (1982).

G . T . M i k e l a d z e , Y u . E . K h e c h i n o v , a n d R . V . P a r t s v a n i y a , D i s p e r s e r e i n f o r c e m e n t o f

s m a l l - f r a c t i o n c o n c r e t e s a n d m o r t a r s , E n e r g . S t r o i t . , No . 6 ( 1 9 8 7 ).

Y u . E . K h e c h i n o v a n d R . V . P a r t s v a n i y a , D i s p e r s e - r e i n f o r c e d g u n i t e fo r u n d e r g r o u n d

s t r u c t u r e s of t h e K h u d o n i h y d r o e l e c t r i c s t a t i o n, I n f o r m e n e r g o S o o r u z h . G i d r o e l e k t r o -

stantsi i, No. 3 (1987).

* A d d i t i o n a l i n f o r m a t i o n a b o u t t h e p r o p e r t i e s o f d i s p e r s e - r e i n f o r c e d c o n c r e t es , o p t i m a l c o m-

p o s i t i o n s, a n d r e c o m m e n d a t i o n s o n t h e t e c h n o l o g y o f t h e i r a p p l i c a t i o n a n d p l a c e m e n t c a n b e

o b t a i n e d a t th e C e nt r a l L a b o r a t o r y o f t h e In g u r i H y d r o e l e c t r i c S t a t i o n C o n s t r u c t i o n A d m i n i -

s t r a t i o n ( G e or g i a , 3 8 3 7 4 0 , D z h v a r i , C e n t r a l C o n s t r u c t i o n L a b o r a t o r y ) .

581

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