大采高浅埋煤层工作面矿压显现特征模拟及试验分析

Analysis of the Appearance Characteristics of Mineral Pressure in the Shallow Seam

为研究浅埋煤层在大采高条件下顶板运移规律及矿压显现特征,通过构建数值模型研究了3~7 m采高条件下的顶板破断过程及来压规律,构建物理模型分析了顶板垮落及支架工作阻力变化特征。研究结果表明:随着采高的增大,顶板回转角度不断增大,且出现了明显的台阶下沉现象,采高从3 m增大到7 m地表沉降量增加了3.5 m,顶板的初次来压及周期来压步距整体呈增大趋势;煤壁支承压力峰值随采高增大往工作面前方迁移,影响范围也不断增大,在采高5 m时达到了最大值10.53 MPa,之后回落并趋于稳定,证明支承压力并非随采高增大而持续增大;随着采高的增大顶板卸荷损伤区域迅速向上扩展,使上覆岩层裂隙充分发育,诱发顶板的大范围切落,大采高形成了"悬臂梁-砌体梁"结构,形成了工作面的剧烈来压。物理模拟结果表明,切顶发生时支架工作阻力提升到了9 614 kN,较周期来压时增大了16.1%,比普通采高时有了较大的提升。因此选取合理的采高对于保证采空区稳定减少顶板灾害事故至关重要。

In order to study the movement law of roof under high mining height in shallow seam and the characteristics of pressure, the breaking process and compressive law of roof under high mining height of 3~7 m were studied by constructing numerical model. And the physical model was constructed to analyze the change characteristics of roof collapse and support working resistance. The results show that with the increase of mining height, the rotation angle of the roof continues increases, and there is an obvious step sinking phenomenon. The surface settlement increases by 3.5 m at a height of 3~7 m, and the initial pressure and cycle of the top plate are generally increasing. The peak pressure of the coal wall supports migrates to the front of the working surface with the increase of the mining height. At the height of 5 m, the maximum value of the pressure reaches 10.53 MPa, and then down back again. Thus, the support pressure value does not increase along with the increase of mining height. With the increase of mining height, the unloading damage area of the roof expands rapidly. The crack of the upper overburden rock layer is fully developed, and the large area of the roof plate is cut down. The large height of the top plate forms the structure of a shape of cantileve-masonry beam and forms a sudden pressure of the work surface. The physical simulation results show that the working resistance of the scaffold increases to 9 614 kN at the time of roof cutting, which is 16.1% higher than that at periodic pressure, and it is greatly improved at normal height. Therefore, selecting reasonable height is very important for ensuring the stability of the goaf area and reducing the top plate disaster.