刀具动态作用下节理岩体破坏过程的数值模拟

Numerical simulation of fragmentation process of jointed rock mass induced by a drill bit under dynamic loading

基于细观损伤力学和动力有限元方法,模拟分析了节理岩体在刀具动态荷载作用下的损伤破裂过程,探讨了节理间距和节理角度的影响。在动力分析模型中,通过考虑黏弹性边界以排除边界应力波反射的影响,提高了计算精度。数值模拟结果表明,节理的存在改变了岩体中应力波的传播模式。一方面,节理面反射的拉伸应力波加剧了节理与刀具间岩体的碎裂;另一方面,软弱节理面破坏吸收了应力波能量,阻碍了应力波向下的传播,减弱了下部岩体的破坏程度。模拟结果还表明,节理间距越小,岩体破坏程度更加明显。倾斜节理的存在使刀具下部的裂纹出现不对称性扩展特征,影响了主裂纹向下扩展的能力,限制了其伸展的空间。节理岩体在刀具动态作用下的破坏过程研究还很少见到,研究结果对于节理岩体动态破坏的机理以及地下工程开挖等实际应用,具有一定的参考价值。

Based on the microscopic damage mechanics and the dynamic finite element method, the fragmentation pr ocess of jointed rock mass under dynamic loading is simulated. In the dynamic analysis model, the viscous boundary is considered to eliminate the influence of the reflected stress waves from the boundary. The numerical results show the joints change the stress wave propagation mode in the rock masses. On one side, the reflected tensile stress on the surface of the joints enhances the fracturing of the rock between the joint and the drill bit. On the other side, the fracturing toward the specimen bottom is restrained due to the fact that the dynamic wave propagation is absorbed by the weak joints. The fragmentation is also influenced by the joint spacing. The rock specimens are more obviously fractured with smaller joint spacing. The inclination of the joints leads to non-symmetric fragmentation at the two sides of the bit and affects the ability of the downward extension of the main crack. The simulation will be helpful for understanding the mechanism of dynamic failure of jointed rock mass and underground engineering.