含1组离散裂隙的岩体力学特性及破裂特征研究

Research on mechanical properties and crack characteristics of rock mass with a set of discrete fractures

岩石中裂隙分布对岩石的宏-微观力学性质和微裂纹的发育演化规律具有重要影响。研究含有1组裂隙岩体的单轴压缩强度、起裂强度、损伤强度等岩体宏观力学参数,研究含有1组裂隙岩体的微裂纹发育数量和演化分布规律,揭示裂隙岩体在压缩作用下裂纹扩展的细观力学响应机制。表征单元体的尺寸是裂隙平均迹长的数倍,综合考虑岩石模型、裂隙分布和计算能力,选取裂隙岩体的计算范围为15 m×15 m。研究结果表明:裂隙的倾角、迹长都对裂隙岩体的宏观力学特性存在重要影响;只含有第1组、第2组裂隙的岩体存在明显的脆性特征,峰值强度较高,脆性破坏最终形成清晰的宏观裂纹,破坏带清晰;只含有第3组裂隙的岩体和包含3组裂隙的岩体存在明显的塑性特征,塑性破坏的剪切带不如脆性破坏清晰,模型呈多点粉碎性破坏;同时包含3组裂隙的岩体模型的特征与只含有第3组裂隙的岩体模型特征相近,说明第3组裂隙对岩体的影响最大。

The distribution of cracks in rock has an important influence on the macroscopic and microscopic mechanical properties of rock and the development and evolution of micro-cracks.The macroscopic mechanical parameters such as uniaxial compressive strength,crack initiation strength and damage strength of rock mass containing a group of cracks are studied,and the number and evolution distribution of micro-cracks in rock mass containing a group of fractures are studied to reveal the mesoscopic mechanical response mechanism of crack propagation in fractured rock mass under compression.As the size of the representative elementary volume is several times of the average trace length of the fracture,comprehensively considering the rock model,fracture distribution and computing abilities,the calculation range of the fractured rock mass selected is 15 m×15 m.The rock mass model with a set of discrete fractures shows that the dip angle,trace length have important influences on the macroscopic mechanical properties of fractured rock mass.The rock mass containing only the first group and the second group of fractures has obvious brittleness characteristics and high peak strength,and the brittle failure eventually forms clear macroscopic cracks with clear failure zones.The rock mass containing only the third group of fractures and the rock mass containing the three groups of fractures have obvious plastic characteristics,the shear zone of plastic failure is not as clear as that of brittle failure,and the model shows multi-point comminuted failure.The characteristics of the rock mass model containing three groups of fractures are similar to those of the rock mass model containing only the third group of fractures,indicating that the third group of fractures has the greatest influence on the rock mass.