采场老顶岩梁破断过程

Breaking process of the main roof

为研究采场老顶岩梁破断过程,将初始来压前后的采场老顶岩梁简化为固支岩梁与悬臂岩梁.采用花岗岩作为试验材料对采场初始来压和周期来压的老顶岩梁进行了试验模拟,结合自主研发的基于拉张破坏准则的有限元开裂包对岩梁破断进行了数值分析.结果表明:固支岩梁在均布载荷下,破坏过程分为两个阶段:裂纹首先在端部萌生阶段和岩梁中间区域裂纹萌生阶段;固支岩梁端部裂纹的扩展方向与岩梁的高度和长度比值有关,而中部裂纹扩展方向始终垂直于轴线方向;悬臂岩梁的裂纹只产生在端部,裂纹的扩展方向与岩梁的长度和高度的比值有关;随着固支岩梁的裂纹逐渐扩展,岩梁的固支部分减少,不平衡力增加,岩梁的裂纹扩展速度加快.

In order to research the fracture process of the main roof, the main roof at the workface before and after initial pressure are respectively simplified as lamped-clamped rock beam and cantilever rock beam. Theoretical analysis combined with experience in which the granite was taken to simulate the old roof rock beam under the initial and periodic compression has been adopted to study this problem. Meanwhile, numerical simulation based on tensile failure criterion, which is independently researched and developed, has been emerged to imitate the failure of the rock beam. Results show that： There are two stages of fracture process of the lamped-clamped rock beam under uniform load： the crack conceives firstly at the end of rock beam and the crack happened in the middle of rock beam; the expansion direction of the crack at the end of lamped-clamped rock beam is related with the ratio of the height and the length of rock beam, however, the expansion direction of crack in the middle of rock beam is always perpendicular to the axial direction; the crack of cantilever rock beam only happened at the end of the beam, and the expansion direction of the crack is related with the ratio of the height and the length of rock beam; with the expansion of the crack of the lamped-clamped rock beam, the fixed part of the rock beam is reducing, and the unbalanced force is increasing, which will lead the speed of crack propagation increasing.