DEVELOPMENT MECHANIZED SHIELD

OF A PROCEDURE COAL

CANOPIES

FOR

EXTRACTION

IN T H I C K

L. P. T o m a s h e v s k i i

and

STEEP

BENEATH SEAMS

L. A . S h c h e r b a k o v

UDC 622 : 232 : 65.011.56-783.41

The shield system gives good results in thick seams with a dip of 55-90* and a thickness of 3.5-8.0 m. As mine workings become deeper, the use of this system is c o m p l i c a t e d by the increase in rock pressure and by the heightened effect of abuwnent pressure on the supports in the d e v e l o p m e n t workings and on the shield canopies, and there is an increase in expenditure on m a i n t e n a n c e of the d e v e l o p m e n t workings, particularly the c o a l chutes, driven at 6 - m intervals. The v o l u m e of development work m a y be reduced by cutting down the number of chutes in the shield pillar. It is therefore necessary to develop a method for continuous horizontal extraction, transporting the m i n e d c o a l b e tween the chutes, cutting c o a l in the support pillars, and controlling the shield canopy, which will m a k e it possible to increase the output per manshift by a factor of 2-3, to reduce the production cost of coal, and to increase the e l ficiency of the system in deeper horizons. Attempts have been m a d e to m e c h a n i z e coal extraction beneath canopies, but for various reasons the powered supports proposed for steep seams have not proved popular. Based on ShchK-KSShch and ShchK-2 shield units [3], which have passed their p r a c t i c a l tests in Donbass pits, the Dongiprouglemash Institute has developed the Ashch aggregate, e x p e r i m e n t a l trials of which have shown good results [4]. However, such aggregates, which are a combination of extraction and haulage machines and powered supports of the protective-supporting type, operate on the ptinciple of thrust between the wall rocks. In Kuzbass collieries, in seams of medium thickness with stable wall rocks, KVKP supports [5] may in p r i n c i ple be used. However, their use is l i m i t e d by shortcomings in the design of the plough unit and by the low t e c h n i cal and economic performance obtained in trials. In addition to shield aggregates which have passed =ials in mines, we must deal with proposals regarding m e chanized extraction of coal beneath shields. The authors of [6-8] suggest aggregates for extracting steep thin or m e d i u m - t h i c k seams, operating in conjunction with b r a c e - t y p e supports. However, their use is restricted to thin or m e d i u m - t h i c k seams witfi stable w a l l rocks. Bodendorf and Solov'ev [9] proposed a method for working thick steep seams, in which the coal is extracted beneath the shield by a cutting head from dish-shaped funnels. Itowever, this design has not solved the problem of canopy control, because extraction of the support pillars m a y be a c c o m p a n i e d by collapse of the shield and j a m m i n g of the cutting unit of the extraction machine. Of the haulage units, principal interest attaches to a m u h i b u c k e t scraper for the shield system [10], which consists of several r e l a t i v e l y small buckets connected sequentially by a round-link chain. However, it can be used only for transporting broken-up coal. The following comments m a y be made on recently proposed shield units and aggregates: a) the field of a p p l i cation of m e c h a n i z e d shield units of proved efficiency is l i m i t e d to m e d i u m - t h i c k seams with stable wall rocks; b) to work thick seams, a procedure must be developed for m e c h a n i z e d extraction beneath shield canopies with a new principle of shield control, because if the seam is more than 3.5 m thick, cumbersome and costly equipment is r e quired to hold the shield by bracing between the wail rock; c) it is necessary to develop essentially new e x t r a c t i o n Kuzbass Scientific-Research C o a l Institute, Prokop'evsk. Translated from F i z i k o - T e k h n i c h e s k i e Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 53-57, March-April, 1971. Original article submitted January 6, 1970. @1972 Consultants Bureau, a division o f Plenum P u b l i s h i n g Corporation, 227 g'est 17th Street, New York, N. Y. 10011. All rights reserved. This article cannot be reproduced for any purpose w h a t s o e v e r without permission of the publisher. A copy o[ this article is available from the publisher for $15.00.

175

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Fig. 1. Design of conveyor-plough, with location of the working belts in the v e r t i c a l plane. haulage machines beneath the shield, because the tested and suggested conveyor-ploughs are inefficient; d) investigations should be m a d e of the feasibility of linking extraction machines and haulage e q u i p m e n t with designs of existing or improved elastic shields with timber or reinforced-concrete canopies, Mechanized extraction of c o a l beneath a shield of the guard type for working thick steep seams must include the following basic processes: extraction of a continuous horizontal "passage" and transport of the m i n e d c o a l to a chute, extraction of the guide tracks for the extraction machine, extraction of lhe support pillars, and control of the shieId canopy. To extract c o a l beneath shields in steep (more than 55*) seams, 3.5-6,5 m thick, the Kuzbass S c i e n t i f i c Research C o a l Institute has developed a m e c h a n i z e d aggregate, consisting of a shield canopy, an e x t r a c t i o n - c o n t r o l unit, and a conveyor-plough. The shield canopy m a y be of timber or reinforced concrete and can be inclined to the strike. If the canopy is of timber, one or two rows of roller units are linked to the strike by hinged guides, straps, and tie bolts. Furthermore, the design of the shield c a m p y is strengthened by ropes and bands. The shield is equipped with e n d - f a c e aprons and aprons on the underside. Depending on the seam thickness, the e x t r a c t i o n - c o n t r o l unit consists of two to four extraction machines with telescopic a u g e r - t y p e cutting heads, rotatable in two planes and mounted on a m o b i l e platform, an oil unit, four pairs of hydraulic props, two lowering jacks, four ploughs, and four skids. The hydraulic props are housed in channels in the platform. Extraction of the leading continuous horizontal trench is effected by the conveyor-plough with two working belts: an underbelt for extracting and deepening the trench, and an upper belt which operates as a conveyor, transporting the coal extracted from the support pillars. The conveyor-plough consists of a drive and tension head and pans. The conveyor-plough is flexibly suspended from the shield by hydraulic jacks; twin flexible couplings ensure m o b i l i t y of the conveyor-plough over the thickness of the seam and to the strike. To avoid displacement of the c o n veyor-plough away from the cutting side, a thrust-type j a c k is provided. The characteristic feature of the conveyorplough is that a set of cutter-scrapers and flights (ratio 1 : 5) is provided in the "business e n d ' ; some of the flights have a variable cross section; i.e., they allow some of the m i n e d coal to pass so as to obtain uniform distribution of the load being transported (Fig. 1); the working cutter-scrapers 1 allow all the broken c o a l to pass through them, being used only for cutting. The cutter-scrapers therefore operate under conditions excluding clogging by c o a l when the area under the pans is narrow. The flights 2-4 retain part of the coal, allowing the remainder to pass through orifices provided, and this part is transported by blank flights 5. The c y c l e of extraction by the shield aggregate consists of the following processes: deepening of the trench by the conveyor-plough, extraction o f the guide tracks ahead of the aggregate, and e x t r a c tion of the support pillars behind the aggregate. The auger-type extraction machines at the front and back of the aggregate extract the support pillars of the guide t~acks, depending on the direction of m o v e m e n t . The conveyor-plough is lowered by the hydraulic props, and the trench is deepened along the whole length of the shield face; the depth of the strip taken out by one cutting scraper is 30-60 ram, depending on the m e c h a n i c a l

176

Fig. 2.

Procedure for mechanized extraction of coal beneath a shield canopy.

properties of the coal (Fig. 2a). After the trench has been deepened by a given amount (30-50 cm), extraction of the guide tracks for moving the aggregate and extraction of the support pillars are begun. Extraction of the guide tracks begins at one of the coal chutes, for which purpose the extraction-control unit is brought to the required depth by constantly lowering (Fig. 2b). After extraction of the guide tracks, the extraction-control unit is installed on the floor of the tracks, and the shield is opened out and set at the first chute (Fig. 2c). As it moves toward the second coal chute, the extraction-control unit extracts the guide tracks for the skids with one pair of the auger-type cutting machines and extracts the support pillars with the other pair (Fig. 2d). Extraction of the support pillars is effected as follows: part of the shield is retained in a fixed position along the strike (1.0-1.5 m) by the thrust-type props (during this period the coal-cutting machines extract the support pillars to a depth of 0.5-0.75 m). After extraction of the support pillars over a given length, the pressure in the hydraulic system of the supporting props is removed and part of the shield is lowered. The thrust-type rear props are shifted toward the extraction point by rams, the front props are pushed further, displacing the platform, and extraction of the support pillars is recommended. During this period the forward cutters extract the guide tracks. During extraction of the support pillars and the guide tracks, the mined coal is transported by the upper belt of the conveyor-plough. When the second coal chute is reached, the extraction-control unit lowers the shield in its zone (see Fig. 2e). At the time of extraction of the support pillars, the shield is also supported by the hydraulic props of the conveyorplough, which is not then operating The foUowing cycle also begins with deepening of the trench by the conveyorplough (see Fig. 2f), and the extraction-control unit moves in the opposite direction. Thus, this system of mechanized extraction of coal in thick steep seams, together with the shield system of working, makes it possible to increase its efficiency and to extend the field of application of the system in the underlying horizons of Ku zbass pits. The following conclusions may therefore be drawn: 1. When thick steep seams are worked by the shield system, mechanized extraction of coal in the miningout face may be effeeted beneath shields of the guard type with the part of the shield beneath which the coal pillar is extracted supported on the coal mass. 2. A mechanized shield face must have two coal chutes, located on the flanks of the shield pillar. To transport the coal along the face and to extract the forward horizontal trench, it is necessary m develop a self-sinking extraction-haulage machine (of the conveyor-plough type) with the working belts located in the vertical plane.

177

3. To eliminate involuntary lowering of the shield at the extraction site of the support pillars, and jamming of the "business end" of the extraction unit, this part of the shield must be supported by hydraulic props, using the coal pillar for support. LITERATURE CITED 1. 2. 3. 4. 5. 6.

G . I . Gritsko, Analysis of Formation and Calculation of the Stressed-Deformed State of the Rock Mass during the Working of Thick Steep Seams in /he Kuzbass, Author's Abstract of Dissertation, Novosibirsk (1968). K . A . Ardashev, Investigation and Analysis of Rock Pressure Manifestations during the Working of Thick Steep Seams of the Prokop'evsk-Kiselevsk Field of the Kuzbass, Author's Abstract of Dissertation, Kemerovo (1968). A . I . Bashkov, Ugol', No. 6 (1968). G . G . Vasil'ev, A. E. Tarasenko, and P. F. Didenko, Tr. "Dongiprouglemasha,* No. 4, Nedra, Moscow (1968). E. Ya. Makhno, Problems of the Working of Steep Coal Seams by the Shield System [in Russian], Ugletakhizdat, Moscow (1957). Ya. S. Bmk, A.D.Gridin, E. K. Korzyukov, et al., Author's Certificate No. 144,808, Byull. Izobretenii, No. 4

(1962). 7. 8. 9. 10.

178

S.M. Arutyunyan, A. D. Bondarenko, I. D. Gelyukh, et al., Author's Certificate No. 210,787; Isobreteniya, Promyshlennye Obraztzy, i Tovamye Znaki, No. 7 (1968). S.M. Arutyunyan, G. G. Vasil'ev, P. F. Didenko, et at., Author's Certificate No. 211,480; Izobreteniya, Pmmyshlennye Obraztsy i Tovarnye Znaki, No. 8 (1968). B.A. Bodendorf and I. N. Solov'ev, Author's Certificate No. 132,165; Byu11. Izobretenii, No. 19 (1960). P. ~ Mal'bert, N. S. Lavrov, and Yu. I. Alkasarov, Fiz.-Tekhn. Probl. Razrabotki Polema. Iskop., No. 5 (1968).