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煤层开挖后,采空区卸载的同时侧帮产生支撑压力作用于侧帮底板上,导致底板应力重分布;根据最终应力场由初始应力场与开挖应力场叠加的特点,建立底板岩层的力学分析模型;采用Fourier积分变换方法求解双调和方程,并利用形式函数待定法求解对偶积分方程,得到底板应力场与位移场的解析表达式;然后根据Mohr-Coulomb准则判断底板岩层的塑性破坏深度。通过算例分析结果表明:在采空区底板中主应力随着深度的增加而增大至原岩应力;而在侧帮底板中最大主应力随深度的增加而逐渐减小至原岩应力;在侧帮底板深度小于10 m时,主应力发生旋转,3?变为中间主应力并且随深度逐渐减小,当随深度继续增加时又逐渐增大至原岩应力;在采空区的中心发生最大底臌位移为0.236 m,侧帮底板受支撑压力作用产生向下的位移;塑性破坏范围呈中间大两边小,最大破坏深度为31.2 m,为半开挖宽度的1.04倍。最后通过FLAC3D模拟煤层开采,发现两者计算结果虽存在一定的偏差,但总体趋势基本一致,说明该解析方法能较准确地分析底板的应力与位移,可为工程实践提供指导与计算方法。
After the coal seam is excavated, the supporting pressure exerts on the side slab at the same time when the goaf is unloaded, resulting in the stress redistribution of the slab. Based on the fact that the final stress field is superposed by the initial stress field and the excavation stress field, the bottom strata Mechanics analysis model; Fourier integral transform method to solve the biharmonic equation, and use the formal function to be determined to solve the dual integral equation, the analytical expression of the stress field and the displacement field of the floor; and then determine the depth of the plastic deformation of the floor rock floor according to the Mohr-Coulomb criterion . The results of numerical examples show that the principal stress increases with the depth to the original rock stress in the bottom of the goaf while the maximum principal stress decreases gradually to the original rock stress with the increase of depth in the side slab. When the depth of the side slab is less than 10 m, the principal stress rotates and 3? Becomes the intermediate principal stress and decreases gradually with the depth, then gradually increases to the original rock stress as the depth continues to increase. At the center of the goaf The maximum bottom displacement is 0.236 m, and the bottom slab is displaced downward by the supporting pressure. The plastic failure range is small on both sides of the middle and large, and the maximum depth of failure is 31.2 m, which is 1.04 times of the semi-excavation width. Finally, the simulation of coal seam mining by FLAC3D shows that although there is some deviation between the calculated results, the overall trend is basically the same, which shows that the analytical method can accurately analyze the stress and displacement of the floor, which can provide guidance and calculation method for engineering practice.