岩石单轴拉伸破坏过程的数值模拟

Numerical simulation of fracture propagation of rock under uniaxial tension

用三维梁–颗粒模型BPM3D(Beam-Particle Model in Three Dimensions)对岩石材料在单轴拉伸条件下的力学性质和破坏过程进行了数值模拟。梁–颗粒模型是在离散单元法基础上,结合有限单元法中的网格模型提出的用于模拟岩石类材料损伤破坏过程的数值模型。模型中材料在细观层次上被离散为颗粒单元集合体,相邻颗粒单元由有限单元法中的弹脆性梁单元联结。梁单元的力学性质按韦伯(Weibull)分布随机赋值,以模拟岩石材料力学参数的空间变异性。材料内部裂纹通过断开梁单元来模拟。通过自动生成的非均质材料模型对岩石材料的破坏机理进行研究。岩石在单轴拉伸状态下破坏过程细观数值模拟结果显示,岩石材料宏观破坏是由于其内部细观裂纹产生、扩展、连接的结果。数值模拟结果与实验结果的对比分析表明了模型的适用性。根据数值模拟结果对岩石材料的破坏机理进行了探讨。

A numerical model BPM^3D （Beam-Particle Model in Three Dimensions） was developed to simulate the mechanical properties and fracture process of rock under uniaxial tension. This numerical method simulating damage and fragmentation phenomena of rock-like material was presented on the basis of discrete element method （DEM） and lattice model of finite element method （FEM）. Material was schematized at mesoscale level as a three dimensional assembly of particle elements in the BPM^3D and the nearest neighboring particles were connected through a lattice of elastic beam elements of FEM. The mechanical properties of beams in BPM^3D were randomly allocated according to Weibull distribution to reflect the spatial variation of mechanical parameters in rock. Cracks in material were simulated through breaking beam elements. Compact and anisotropic synthetic media were generated automatically and were used to investigate the mechanical behavior of rock. The numerical simulation results of rock fracture process under uniaxial tension showed that the initiation, propagation and linking each other in the rock samples at mesoscale level produced the macro-failure of rock samples. The comparison of the numerical simulation result with the experimental result proved how highly appropriate this method was. The fracture mechanics of anisotropic brittle rock was discussed based on the numerical simulation results.