RAW MATERIALS

TRENCH-CUTTING

TECHNOLOGY

@UARRIES

MAGNEZIT

V.

P.

OF

THE

IN T H E

PLANT

Vylomov

UDC 622.235:622.368.22

The V o l c h ' e g o r y - S t e p n o i pits c o n s i s t s of the Stepnoi, South, North, G r e a t Polenikhin, Mel~niehnyi, and E a s t q u a r r i e s . The q u a r r i e s a r e r e m o t e f r o m each o t h e r and t h e i r geological conditions differ. The q u a r t y i n g o p e r a t i o n s a r e c h a r a c t e r i z e d by the n e c e s s i t y for w o r k i n g all q u a r r i e s s i m u l t a n e o u s l y and by the long l i n e s of t r a n s p o r t a t i o n and o t h e r c o m m u n i c a t i o n s . It is well known that the m o s t economic method of w o r k i n g a group of I o w - p r o d u c t i v i t y q u a r r i e s c o n s i s t s of c o n c e n t r a t i n g equipment and o p e r a t i o n s on one q u a r r y at a time. The depthwise advance of q u a r r y ing can be a c c e l e r a t e d by f a s t e r t r e n c h - c u t t i n g and r e d u c i n g the time r e q u i r e d f o r w o r k i n g o v e r l y i n g benches. It follows that to a c c e l e r a t e the q u a r r y i n g o p e r a t i o n s it is n e c e s s a r y to r e d u c e the time spent on t r e n c h - c u t t i n g by e m p l o y i n g the b e s t cutting method and using the b e s t combination of d r i l l i n g , b l a s t i n g , loading, and t r a n s p o r t i n g o p e r a t i o n s . The a v e r a g e annual depthwise advance of the working in the four q u a r r i e s with c o m p l e x geological (karst) and h y d r o g e o l o g i c a l conditions was planned by the A l l - U n i o n State Institute for the Planning of E s t a b l i s h m e n t s of the O r e - M i n i n g Industry (Table 1). During 1972-1973 the method of d e v e l o p m e n t - w o r k i n g was i n t r o d u c e d with account taken of the e x p e r i e n c e of l e a d i n g e s t a b l i s h m e n t s . T r e n c h - c u t t i n g in rocky flooded ground (water inflow 215-320 m3/h on a v e r a g e ) is l a b o r - i n t e n s i v e and t i m e - c o n s u m i n g b e c a u s e it m e a n s l a y e r w i s e cutting in confined space with a d r a i n i n g pit having to be e x c a v a t e d beforehand for e v e r y l a y e r . In this method the efficiency of e x c a v a t o r s and t r a n s p o r t a t i o n is low so that cutting a new h o r i z o n r e q u i r e s eight to twelve months. In 1972 the d e v e l o p m e n t of horizon +375 m of the North a u a r r y was s p e e d e d up by cutting the a c c e s s trench a f t e r f i r s t b o r i n g d r a i n i n g holes 450 m m in d i a m e t e r and 24-28 m in depth [1]. The holes w e r e b o r e d with a 2SBSh-200M r i g a f t e r which I~TsV 12-160-100-type i m m e r s i o n p u m p s , each with a d i s c h a r g e of 160 m ~ / h , w e r e s e t up in them. This method was introduced* b e c a u s e the e x i s t i n g s y s t e m of l o w e r i n g the level of underground w a t e r during the e n t i r e p e r i o d of q u a r r y i n g o p e r a t i o n s with d r a i n i n g holes b o r e d to a depth of 60-80 m along the p e r i p h e r y of the q u a r r y was ineffective owing to poor f i l t r a t i o n through the s u r r o u n d i n g rock.

TABLE 1

Quarry

Av. annual depth~cise advance of workings m/yr, for periods 11997750--

1976-1980

Stepnoi

4,9 6,2 3,3 6,8

6,6 5,2 2,5 5,8

Great-Polenikhin Mel' nichnyi

4,6 5,4

8,1 4,3

North South East

Magnezit P l a n t .

FI.

492

The holes 450 mm in d i a m e t e r w e r e d r i l l e d with a s p e c i a l m i l l i n g bit c o n s i s t i n g of a body of s t e e l grade 34KhNIM with a t h r e a d e d end. Six claws with a 1K-214 T K P - t y p e m i l l i n g c u t t e r s e c u r e d in each a r e welded at an angle of 60 ~ along the p e r i p h e r y of the bit (Fig. 1). During d r i l l i n g a c a s i n g pipe 500 m m in d i a m e t e r and 2.53.0 m in length is s e t into the b o r e h o l e . The bit is r o t a t e d at 6080 r p m , the axial p r e s s u r e is 14-16 tons, and the d r i l l i n g fines a r e r e m o v e d by the a i r - - w a t e r method used for washing out the b o r e h o l e when using a 2SBP-200M r i g . *P. A. Kochergov, A. S. K i s e l e v , V. G. Ivanov, and G. P. S a v e l ' e v p a r t i c i p a t e d in the work.

T r a n s l a t e d f r o m O g n e u p o r y , No. 8, pp. 21-24, August, 1975.

9 76 Plenum Publishing Corporation, 22 7 West 17th Street, New York, N. Y. 10011. No part o f this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission o f the publisher. A copy o f this article is available from the publisher for $15.00.

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Fig. 1 Fig. 2 F i g . 1. M i l l i n g b i t : -1) m i l l i n g c u t t e r ; 2) b i t c l a w ; 3) b i t body; 4) b o r i n g bar. F i g . 2. A r r a n g e m e n t of the b l a s t h o l e s : 1-7) r o w n u m b e r s , O) m a i n h o l e s , o) e a s e r h o l e s . T h e p o o r f i l t r a t i o n t h r o u g h the s u r r o u n d i n g r o c k i m p e d e d the w a t e r inflow to the d r a i n i n g h o l e s so t h a t it w a s found n e c e s s a r y to e s t a b l i s h a s y s t e m of c o m m u n i c a t i n g c r a c k s in the body of the m a g n e s i t e and d o l o m i t e f a c e s in the f o r m of " c u t - o f f s l o t " b o r e h o l e s 220 m m in d i a m e t e r and 20 m in depth a t a d i s t a n c e of 6 m f r o m the d r a i n i n g h o l e s . A 6 0 - k g e x p l o s i v e c h a r g e w a s f i r e d in e a c h b o r e h o l e . The u s u a l m e t h o d of e n l a r g i n g d r a i n i n g h o l e s with s m a l l c h a r g e s p r o v e d i n e f f e c t i v e . T h e d r a i n i n g h o l e s w e r e b o r e d a l o n g the edge of the a c c e s s t r e n c h so that a c c o u n t w a s t a k e n of the m a x i m u m e f f e c t of the d e p r e s s i o n c o n e . The d r i l l i n g s p e e d with a 4 5 0 - m m b i t w a s 3 . 5 - 6 . 0 m p e r s h i f t and the c o s t 18-20 r u b l e s p e r m e t e r . In O c t o b e r , 1972 an a c c e s s t r e n c h w a s c u t f r o m h o r i z o n +387 m to h o r i z o n +375 m in the South q u a r r y t h r o u g h a s e v e r e l y k a r s t e d z o n e . The m e t h o d of t r e n c h - c u t t i n g with d r a i n i n g h o l e s b o r e d b e f o r e h a n d p r o v e d i n e f f e c t i v e o w i n g to the w e a k inflow and r a p i d s i l t i n g of the b o r e h o l e s so that r e c o u r s e w a s had to t r e n c h c u t t i n g with d r a i n i n g p i t s b l a s t e d o u t b e f o r e h a n d [2]. T h e q u a r r i e s c o n c e r n e d a r e o f e l o n g a t e d s h a p e so t h a t the b l a s t h o l e s w e r e sunk in r o w s p e r p e n d i c u l a r to the d i r e c t i o n of the t r e n c h in o r d e r to o b t a i n b e t t e r r o c k d i s t r i b u t i o n a l o n g the pit e d g e s a f t e r blasting. TABLE 2 Horizon

w

Quarry

Mel'nichnyi North South

beginning end of of trench [trench +375 +387

+387

Method of cutting the

m

access trench

+363 [Layerwise +375 Wlthdeepboreheles sunk beforeaana +375 With dra~a~in~gpit blasted out Detoreaano

>.=~, ~ o,.~o O ~ O o

88* 71 $

58,4 7 698

52,2

9During the summer. tDuring the winter.

493

Having regard to the r~ature of the rock formation and the large distance (4 m) between the holes of the first and third and the fifth and seventh rows, easer holes were sunk in the fourth row between the main holes. The distance between the rows was 4 m, the depth of the main holes 16 m and that of the easer holes 8 m. The tamping depth was 7-8 m in the main holes and 2-3 m in the easer holes. The seismic charge so that the rows of boreholes rows with a delay

conditions of the South quarry do not set a limit to the weight of a simultaneously fired following blasting sequence was adopted: the explosive charges in the first and seventh were fired instantaneously, those in the second a~d sixth rows and in the third and fifth of 50 m/sec, and those in the fourth row 35 m/sec after those in the third and fifth rows

(Fig. 2). The explosive in the e a s e r holes was fired 50 m / s e e after that in the main holes. Specific c o n s u m p tion of explosive (Granulotol) was 1.80-1.88 k g / m 3, the weight of the main charge was 420 kg, and that of the charge in the e a s e r holes 80 kg. The blasting gave a draining pit of a volume of 4500 m 3 and a depth of 9.2 m for installing the draining equipment. The results was that trench-cutting was continued in n e a r - d r y conditions. T r e n c h - c u t t i n g with draining boreholes sunk and a draining pit blasted out beforehand gives an inc r e a s e in the cutting speed by a f a c t o r of two to two and a half while the total length of the boreholes is halved giving a saving of about 27,000 rubles. The trench is cut with dry faces so that l o w - c o s t explosives can be used at a saving of 81,000 rubies, and the volume of ancillary operations is reduced. CO N C L U S I O NS In the planning of the stripping operations for the individual horizons of the Volch'egory-Stepnoi quarry complex r e g a r d must be had to the specific conditions for cutting the a c c e s s trench in each quarry. The most efficient method consists of draining the undergound w a t e r with deep boreholes sunk beforehand o r with a draining pet blasted out beforehand. The f a s t e r trench-cutting makes it possible to reduce the time required for developing new horizons and to a c c e l e r a t e the depthwise advance in the q u a r r i e s so that the yield of magnesite f r o m the individual quarries increases. LITERATURE io

2.

494

CITED

A. M. Storozhenko, B. G. P e r m y a k o v , et al., Gornyi Zhurnal, No. 8, '72-73 (1972). R. S. Krysin, P. N. Sheherbakov, Yu. A. Soshko, et al., Authors' Certificate No. 269761; Byull. Izobr., No. 15, 6 (1970).