大采高长壁工作面顶板垮落的裂纹板力学模型

Cracked plate mechanical model for large mining height and langwall face of roof caving

针对大采高长壁工作面顶板垮落在空间上具有局部、分段和迁移的特征,结合煤岩体地质特征,将长壁工作面顶板视为含有一定数量边裂纹的弹性薄板,利用弹性力学中的薄板理论建立了裂纹板力学模型.以周期来压过程中长壁工作面的来压规律为研究对象,将弹性薄板在工作面推进过程中的破坏分为裂纹扩展、塑性铰失效和铰接板失稳三个阶段,利用断裂力学和弹塑性力学理论研究了各阶段顶板失稳的条件,求得了使裂纹开裂扩展的应力强度因子K1和裂纹的起裂荷载q的计算公式;得到了第二个阶段中造成塑性铰失效的极限荷载p*;通过分析薄板间的连接及破坏过程研究了第三个阶段铰接板的失稳过程.顶板破坏的三阶段力学分析方法合理地解释了工作面长度方向上顶板的来压特征;顶板第一次垮落完成后,由于应力转移,造成应力集中作用,使得长壁顶板未破断部分再次经历裂纹扩展、塑性铰失效、铰接板失稳这三个破坏过程;造成来压从破坏部位向两边迁移,形成了长壁工作面周期来压过程中矿压显现的迁移特征.研究结果从理论上解释了工作面长度方向上的顶板垮落及来压规律.并结合具体工作面监测信息对理论分析结果进行了验证.

Based on the local, migratory and subsection of main roof fall of large mining height and longwall face, combined with geological features of coal rock mass, the main roof was considered as an elastic plate containing a certain number of edge cracks, and a cracked plate mechanical model was established by the elastic plate theory. The weighing law of longwall face during the periodic weighting process was used as the research, and the destruction of the elastic plate was divided into three stages：crack propagation, plastic hinge failure and instability of hinged plate in the working face advancing process. The condition of the instability for the roof was studied by fracture mechanics and elastic-plastic mechanics theory. The calculation formula of stress intensity factor K1 and crack initia- tion load q was obtained. The limit load of plastic hinge failure p ＊ is obtained at the second stage. By analyzing the connection between plates and the failure process, the instability process of hinge plate at the third stage was studied. The three stage mechanical analysis method for the roof failure was a reasonable explanation for the pressure characteristics of the roof in the direction of the working face length. After completion of the first roof caving, because of stress transfer, the stress concentration is generated. The three failure processes, such as crack propagation, plastic hinge failure and instability of hinged plate are once again experienced in the long wall roof, causing the pressure from the damaged parts to the two sides of the migration. The roof caving and the law of pressure in the length direction of working face are explained in theory. The theoretical analysis results are verified by a specific working face monitoring information.