冲击荷载下岩石裂纹扩展研究进展

Research Progress of Rock Crack Propagation Under Impact Loading

为了给深部资源开采和大型地下空间工程中围岩体的变形机理及稳定性控制提供理论基础,通过查阅大量关于表征岩石裂纹扩展的裂纹扩展模型、应力强度因子和断裂韧性的国内外文献,总结了前人的研究成果。依据现有研究,提出了动荷载作用下岩石裂纹扩展的几点建议:(1)综合考虑弹性力学、断裂力学和损伤力学建立岩石材料从微观断裂到宏观破坏这一演变过程的理论模型,使理论模型更加适应岩石材料的非线性特征;(2)采用分形、自组织和混沌等非线性理论表征动荷载作用下岩石内部以及表面裂纹的扩展演化特征;(3)采用颗粒离散元和有限差分模拟岩石材料裂纹扩展演化特征。

In the study of rock dynamic mechanical behavior,rock crack propagation model reveals the crack propagation process of rock materials under dynamic loads theoretically,and provides theoretical support for the failure law of rock materials under dynamic loads. Rock fracture toughness can be used to characterize the fracture resistance of rock materials or the resistance to produce new cracks.Especially when there are a few main cracks acting on rock materials,fracture toughness can predict fracture failure of rock materials more effectively than other strength parameters.However,stress intensity factors are used in the calculation of fracture toughness and stress field of rock materials,the description of crack propagation process and the stability evaluation of engineering rock mass. Therefore,two important parameters,stress intensity factor and fracture toughness,are indispensable for describing the crack propagation process and evaluating the stability of rock materials.In order to provide theoretical basis for deformation mechanism and stability control of the surrounding rock mass in deep resource exploitation and large underground space engineering,the previous research results are summarized by referring to a large number of domestic and foreign literatures about crack propagation models,stress intensity factors and fracture toughness that characterize rock crack propagation. From the existing research results,it is concluded that the anisotropy of rock material structure leads to its non-linear characteristics.If only elastic mechanics or fracture mechanics are used to describe the failure process of rock,it will be difficult to obtain ideal results.Therefore,the damage mechanics is gradually introduced into the study of rock fracture failure.Among which,the introduction of damage mechanics is mainly due to the rise and application of non-linear science such as fractal,self-organization and chaos.Because the accuracy of stress intensity factor and fracture toughness is very important for predicting rock crack growth,the research on stress intensity factor and fracture toughness of rock mainly focuses on its testing methods or influencing factors.The testing methods of rock dynamic stress intensity factor mainly include strain gauge method,caustic method and photoelastic method,and the influencing factors mainly include stress factors and geometric factors of cracks and materials.Although there are many testing methods for rock dynamic fracture toughness,the commonly used ones are three-point bending dynamic fracture test technology,sharpy impact test method and split hopkinson pression bar(SHPB)test. The testing methods based on SHPB device can be divided into three categories,they are impact tensile dynamic fracture test,unilateral impact dynamic fracture test and central crack disc dynamic fracture test.Based on the existing research,several suggestions for rock crack propagation under dynamic load are proposed.(1)A theoretical model for the evolution process of rock material from microscopic fracture to macroscopic damage is established by comprehensively considering elastic mechanics,fracture mechanics and damage mechanics to make the theoretical model more suitable for the nonlinear characteristics of rock material;(2)Nonlinear theories such as fractal,self-organization and chaos are adopted to characterize the propagation and evolution of cracks in rock and surface under dynamic loading;(3)The crack propagation and evolution characteristics of rock materials are simulated by particle discrete element method and finite difference method.