1、英文原文 Study on Critical, Modern Technology for Mining in Gassy Deep Mines YUAN Liang Huainan Mining (Group) Co. Ltd., Huainan, Anhui 232001, China Abstract: To achieve safe and highly efficient mining in the gassy, deep mines of the Huainan collieries simultaneous coal and gas extraction, and the cor
2、responding ventilation methods were developed. This includes a set of mining procedures and principles which help insure safe and efficient production. Furthermore, green mining, meaning the comprehensive use of emitted gas, proper treatment of the environment and appropriate mine temperature contro
3、l, is now standard. The concepts of modern mining and the principles of pressure relief are described. Coal-gas simultaneous extraction and multi-pressure relief techniques were developed which require a combination of surface and underground gas extraction. The application of Y-ventilation systems,
4、 of roadways retained along goafs, of stress control techniques for highly fragile mine roofs and of powerful, automatic and reliable mining equipment contributes to safe operation of modern deep mines. Operating parameters for these techniques are described and the results of their use discussed. K
5、ey words: gassy deep mining； modern mining； coal and gas simultaneous extraction； green mining CLC number: TD 82 1 Introduction Typical in terms of gassy mines in China, the Huainan mine areas have coal reserves of 50 billion tons and gas reserves of 5.928 billion m3. The coal seam is characterized
6、as rich in gas content (1226 m3/t), deeply buried (3001500 m), extremely soft in texture (f = 0.20.8), low in permeability ( =0.0011 m2/(MPa2d) and high in gas pressure (Pmax=6 MPa). Ten production mines, with a gas emission rate of 820 m3/min, are all considered gassy mines. The area is geologicall
7、y complicated.Where multiple gassy coal seam groups are being worked, however, the bursting risk becomes high when working at depth. Highpressure soft rocks surround the seam: the horizontal stress normally is 1.11.5 times the vertical stress. Furthermore, over 80% of the roof is ranked as either IV
8、 or V on the fragility scale. These geological conditions present support problems and there are the usual underground temperature troubles. Before 1997 gas was not satisfactorily extracted. The annual extraction rate was 5.2 million m3 and this average extraction rate was merely 3% of the gas produ
9、ction. Therefore, gas accidents frequently occurred in the area and mine productivity remained at a low level. During the decade from 1987 to 1997 five extremely serious gas accidents occurred which caused a total of 293 deaths. In November of 1997 two extremely serious gas accidents occurred which
10、caused 133 deaths. As a consequence of this, the area became notorious for frequent gas accidents and the annual coal output during that period remained as low as 810 million tons. With the gradual development of gassy deep mine working technology the area has witnessed much safer production, a reco
11、rd which gets better with each passing day. 2 Simultaneous Coal-Gas Extraction Technologies Gas troubles are mainly caused by working activities. Hence, a combination of technologies, including things like working methods, working sequences, the principles of stratum movement caused by working, the
12、principles of gas pressure relief or methods for gas extraction, should be considered simultaneously when designing coal-gas extraction methods. 2.1 Decision of pressure-relief seam In the Huainan area there are 918 workable seams. They are numbered in reverse order to their levels as groups A, B, C
13、, D and E and have a total workable thickness of 2234 m. The features of the coal seams are shown in Table 1. With such a layout scientific selection of the initial working seam will be a critical decision to make. 2.1.1 Intrinsic safety principle When beginning to mine a coal seam group, for the sa
14、ke of intrinsic safe mining, a seam comparatively low in gas content and burst risk should be selected as the pressure-relief seam for the following seams. For this purpose, in the Huainan area, seam 11-2 is selected as the pressure-relief seam for seam 13-1 below it； seam B8 is selected for seam B6
15、 above it； seam B10 is selected for seam B11 below it； and seam 15 is selected for seam 13 above it. These selections, and the corresponding workings, are all successful 23. The key technique of the pressure-relief seam lies in the roof bore-hole, or roadway drainage technology. The key to successfu
16、l implementation of roof borehole, or roadway drainage, technology lies in the proper location of the gas concentration. Theoretical studies, numerical simulations and in-situ surveys and measurements all show that under the present seam and roof conditions in the Huainan area concentration of gas a
17、re located in circular cranny rings vertically 825 m above the roof and 030 m below the air return way 46. Therefore, roof boreholes and roadway drainage devices should be arranged at the locations where gas concentrates. Also, gas extraction power and piping should satisfy the gas extraction demand
18、s. With the above demands satisfied one roof can extract gas at 30 m3/min and 70% of the gas can be extracted from the working face. For roof boreholes the optimal parameters for the negative pressure at the mouth of the hole, number of holes and the gas extraction rate are as follows: in an extract
19、ion field eight holes should be drilled, the interval between the two fields should be 100 m, the length of the hole should be 120 m and the negative extraction pressure should be 1620 kPa. 2.1.2 Principle of pressure relieving in cycle Mining affected pressure-relief is an essential tool which impr
20、oves the permeability of a seam. In the Huainan areas seam 13-1(C13) is a thick seam high in gas content. To improve the permeability of this seam, seam 112, 70 m below, was selected as the pressure-relief seam. Starting from the broken block of seam 11-2 and seam B8, 150 m below, was selected. In t
21、his way, the desired goals were successfully achieved. Based on this experience, a technique for simultaneous extraction of coal and gas is implemented by creating working pressure relieving seams located a long distance, 70150 m, away. When the inter-seam distance was 70 m, and the relative inter-
22、Seam distance (the ratio of inter-seam distance to working height) was 35 times, by mining seam 11-2 to relieve pressure upwards the permeability for seam 13-1 was increased by 2880 times 3. Relieving pressure downwards can be done only over a rather smaller distance. In this case, when the relative
23、 inter-seam distance is comparatively long multiple seams should be connected to the corresponding seam for sufficient pressure-relief. In the Huainan areas, seam 4 in group B contains the largest volume of gas. By working coal seams B9, B8, B7 and B6 above B4 to relieve downward pressure the B4 gas pressure was reduced from 4.0 MPa to 0.2 MPa. Additionally, the permeability increased hundreds of times. In this way, a cyclic technique involving simultaneous extraction
