1、翻译部分英文原文Classification of conditions for short-wall continuous mechanical mining in shallowly buried coal seam with thin bedrockLIU Yu-de ZHANG Dong-sheng MA Li-qiang ZHAO Yong-feng WANG Hong-shengSchool of Mines, China University of Mining & Technology, Xuzhou, Jiangsu 221008, China State Key Labor
2、atory of Coal Resources & Mine Safety, Xuzhou, Jiangsu 221008, China Shendong Coal Filiale of Shen-Hua Energy Sources Co. Ltd., Ordos, Inner Mongolia 232001, China Abstract:The room and pillar method is usually used to extract coal from shallowly buried seams with thin bedrock. This results in a ver
3、y low production efficiency and in a low degree of extraction. In recent years short-wall continuous mechanical mining has been extensively used in many situations except shallowly buried coal seams with thin bedrock. The principles governing movement of the overlying strata above the 2-2 coal seam
4、were deduced from in-situ experience, laboratory data, calculations and computer simulations. The thicknesses of the bedrock in the Shendong Coal Field where the coal is shallowly buried are classified into 5 types: 35 m, which was done using fuzzy clustering results. A series of reasonable, relativ
5、e parameters in each category have been calculated and analyzed. One proposed way to perform short-wall continuous mechanical mining in shallowly buried coal seams is given. This is significant for coal mines with similar geological conditions. Key words: short-wall; continuous mining; thin bedrock;
6、 fuzzy clustering; technical parameter 1 Introduction Shallowly buried coal seams are typically characterized by a single key stratum, a small thickness ratio of bedrock to load-layer and a thin overlying stratum under a thick gravel formation. The relative parameters of a shallowly buried coal seam
7、 are: The buried depth of the coal seam is less than 150 m and the thickness ratio, Jz, of the bedrock to the load-layer is usually less than 1.0.There are many effective mining methods for coal seams with a thick overlying stratum or in a normal area. In this case the long wall face is undoubtedly
8、preferred. However, shallowly buried coal seams with thin bedrock or boundary coal would be mined by the room and pillar method. In recent years the techniques of short-wall continuous mechanical mining have been extensively used under many different geological conditions but not in shallowly buried
9、 coal seams with thin bedrock. To solve this we propose a short-wall continuous mechanical mining method for shallow coal seams with thin bedrock using the 2-2 Shendong Coal Field as an example. The four steps required are: a) To analyze the geologic condition of the coal seam and the physical mecha
10、nical properties of the overlying rocks. b) To analyze the collapsed character of the overlying strata in a short-wall continuous mechanical coal face. c) To choose classification indices and methods, and to make a classification. d) To select the relative parameters for each category of short-wall
11、continuous mechanical mining. 2 Geological conditions of the 2-2 coal seam and the selection of the mining method 2.1 Geological conditions The 2-2 coal seam in Shendong Coal Field belongs to the Yanan group of the Jurassic mid-formation, with a thickness ranging from 3.93 m to 6.71 m (6.18 m averag
12、e). The coal structure is simple, with 13 parting layers 0.120.37 m in thickness most of which are mudstone and some of which are carbonaceous mudstone. Consequently, at a depth of 20.1238.4 m the 2-2 coal seam is stable (Fig. 1) . Fig. 1 Cross-section of the 2-2 coal seam1) A false roof less than 0
13、.5 m in thickness composed of weak caving rocks seen as mudstone or carbonaceous mudstone. 2) The immediate roof, whose natural compressive strength is 28.4 MPa and saturated strength is 15.6 MPa, composed of mudstone, siltstone and inter-bedded layers of these. 3) The main roof is composed of homog
14、eneous sandstone or siltstone with sparse fractures and bedding. The big equivalent weight of the initial broken pressure (9901000 kN/m2) makes the strata behavior abnormal . 2.2 Mining method 1) Height of the caving zone Taking the expansion factor of rocks into account the caving zone height of th
15、e 2-2 coal seam is calculated by: where M is the mining height, m; Kp is the expansion factor, and; is the dip angle, (). The calculated height of the caving zone ranges from 9 m to 15 m. 2) Height of the fractured zone The height of the water flowing fractured zone is: where a and b are synthetic s
16、trength coefficients of the rock. These parameters can be calculated by: a =0.1075 -0.024ln Rc, b =0.155 -0.0299ln Rcwhere Rc is the synthetic strength of the rock .The synthetic strength of the bedrock above the 2-2 coal seam is in the range of 30 MPa to 60 MPa. Hence calculations predict the height of the fractured zone to range from 27.4 m to 63.5 m.
