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针对神东浅埋煤层关键层垮落容易造成大面积来压和动力灾害的问题,文章系统分析了关键层在工作面推进过程中的破坏过程及垮落机理。数值模拟结果表明,随着工作面的推进,关键层首先在跨中下表面受拉区发生屈服破坏,工作面中部煤壁前方关键层上表面受拉区发生屈服,并进一步沿煤壁延伸形成“O”型破裂带,与关键层下表面不断向四角延伸的受拉破坏区所形成的“X”型破坏带组合成大的“O-X”型破坏带。与弹性薄板理论相比,两者的开裂顺序不同,但最终的破坏形式相同。覆岩与关键层间保持同步变形,且随关键层一同垮落,失稳前挠度明显增加。关键层的失稳形式主要为沿“X”型破裂带发生屈曲失稳和沿“O”型破裂带发生沿煤壁的切落失稳,后者来压更为剧烈。
In order to solve the problem that the collapse of the key stratum in the shallowly-buried coal seam in Shendong County is likely to cause large-area compressive and dynamic disasters, the paper systematically analyzes the failure process and the collapse mechanism of the key stratum in the process of advancing the working face. Numerical simulation results show that with the advancement of the work surface, the key layer is first subjected to yield failure in the tension zone across the mid-lower surface, yielding on the upper surface of the key layer in front of the coal wall in the middle of the work face and further extending along the coal wall “O ” type rupture zone, combined with the “X ” type destruction zone formed by the tensile failure zone extending to the lower corners of the key layer into a large “OX” type destruction zone. Compared with the elastic thin plate theory, the cracking order of the two is different, but the final destruction is the same. The overlying strata and the key strata maintain synchronous deformation, and collapse along with the key strata, the deflection before instability increases obviously. The main failure modes of the key layers are buckling instability along the “X” type rupture zone and destabilization of the coal wall along the “O” type rupture zone, with the latter being more violently pressured.