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Cao S.-G.,Chongqing University | Zou D.-J.,Chongqing University | Bai Y.-J.,China Coal Technology and Engineering Co. | Wen D.-C.,Sichuan Weida Coal Industry Ltd Company | And 2 more authors.
Caikuang yu Anquan Gongcheng Xuebao/Journal of Mining and Safety Engineering | Year: 2012

In this paper, to investigate the influence of different mining sequence of sublevels on gateways in conditions of gob-side entry retaining in three-soft thin coal seam group, we carried out numerical simulation study on the upward and downward mining sequences of sublevels respectively in the three-soft thin coal seam group with ultra-close distance in one coal mine of Southern Sichuan, based on the previous field investigation and analysis, shield supporting study and experimental determination of rock mechanics parameters. The results show that extrusion and shear failures are occurred easily in the roadway roof and roof of higher side when the downward mining sequence of sublevels is used, and the rock packing of higher side has poor stability, while the vertical stress and shear stress of lower side in the range of 0.5 m decrease 1 MPa at least during upward mining, compared with the former mining sequence, and the produced horizontal stress can prevent the rock packing of lower side slip towards the gob side, which is beneficial to increase the initial strength of the rock packing.


Cao S.-G.,Chongqing University | Zou D.-J.,Chongqing University | Bai Y.-J.,China Coal Technology and Engineering Co. | He P.-J.,Sichuan Weida Coal Industry Ltd Company | Wu H.-R.,Sichuan Coal Industry Group Ltd Liability Company
Caikuang yu Anquan Gongcheng Xuebao/Journal of Mining and Safety Engineering | Year: 2011

To investigate the failure mechanism of mining roadway in the strike longwall in the thin coal seam group with short distance and "three-soft", based on the previous field investigation and analysis, shield supporting study and experimental determination of rock mechanics parameters, we analyzed the failure reasons of mining roadways in thin coal seam with short distance and "three-soft" in one mine in Southern Sichuan by using numerical simulation. The results show that the stress variation characteristics of surrounding rock are relatively complicated in the mining process of thin coal seam group with short distance and "three-soft". The mining of upper coal seam can cause multiple disturbances on the lower seam, while the exploitation of lower seam can also produce adverse effects on gob-side entry retaining in the upper one. The mining operation make the mining roadways lie in the stress concentration zone, or the stress decreasing area, further intensify the stress concentration degree of roadway surrounding rock, and make the supports of most of the roadways in the condition of "three-soft" be more difficult. Therefore, by guaranteeing the integrity of support system, the support design should consider the characteristics of surrounding rock control under "constant load".


Cao S.,Chongqing University | Wang Y.,Chongqing University | Zou D.,Chongqing University | Wen D.,Sichuan WeiDa Coal Industry Ltd Company
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2013

When gob-side roadways in inclined coal seam are retained by strike long wall mining method, the conveyor roadway are retained under ascending mining and the ventilation roadway is retained under underhand mining. In order to research the differences of roof activity in the two conditions, stack continuous layer boards model and load strips segmentation method are used and the influence of the coal seam dip angle is considered. Then the solving formulas of roadside support resistance under such conditions are obtained. Through comparison and analysis, it shows that roadside support resistance of conveyor roadway gob-side entry retaining is much greater than ventilation roadway gob-side entry retaining. When ventilation roadway gob-side entry retaining is used, roadside support resistance reduces with the coal seam dip angle increases. While conveyor roadway gob-side entry retaining is adoptel, roadside support resistance increases with the coal seam dip angle increases. But when the coal seam dip angle is larger than the natural repose angle of goaf caving gangue, the resistance can be reduced by considering the effect of goaf gangue accumulation. The conclusion provides reference for choosing mining sections order of gob-side entry retaining in inclined coal seam.

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