基于数值流形元法岩石动态破坏及力学性能细观机制研究

Mechanical and fracture behavior of rock, as a heterogeneous and grained composite material, is deeply affected by its meso-structure, which is constituted by grains and grain cement. Therefore, developing an more advanced numerical model for more realistically modeling the meso-failure of rock plays key roles in investigating the meso-mechanisms underlying rock fracture and fragmentation. Based on the numerical manifold method, the present project first aims to develop a numerical model to better represent the characteristic of rock meso-failure. An orthotropic rate-dependent cohesive law is developed for NMM to capture the contact behavior and failure process between grains. A crack initiation criterion as well as corresponding crack evolution technique is developed to model the failure of rock grains. Using the developed program, the influences of meso-scale parameters such as grain size, grain strength, contact stiffness, contact strength, contact ultimate displacements and contact rate dependent characteristic on rock dynamic failure process, strength and fracture toughness are then investigated. Compare the numerical results predicted by rate-independent model with those predicted by rate-dependent model, the influence of the rate-dependent characteristic of the meso-scale contact strength on the rock observed macro-rate-dependent behavior is also studied. Finally, assuming the meso-scale strength of rock grains and grain contacts to conform to Weibull distribution, the effect of heterogeneity on rock dynamic behavior especially the rate-dependent behavior is analyzed.

岩石材料作为一种各向异性的颗粒复合材料，其力学表现和破裂过程同它的细观颗粒以及颗粒之间的粘结紧密相连。因此，发展符合岩石细观破坏特征的分析程序是研究岩石动态破坏背后细观力学影响的关键。本项目首先基于数值流形法，引入正交各项异性率相关性接触模型模拟岩石细观颗粒之间的动态表现；同时植入岩石细观颗粒破坏准则及相应的开裂技术模拟岩石细观颗粒的开裂破坏，实现岩石细观两种类型破坏—颗粒以及颗粒之间粘结同时破坏的模拟。在此基础上，拓展程序分析岩石细观参数（如细观颗粒尺寸、颗粒强度、接触刚度、接触强度、接触极限位移以及接触强度率相关性等）对于岩石动态破裂过程、破坏强度以及断裂韧度的影响；对比采用率相关与率无关接触模型分析结果，探索细观接触强度率相关性对于岩石宏观率相关性的影响。最后，通过对岩石细观接触强度以及颗粒强度采用Weibull分布，分析由此引起的材料不均匀性对于岩石动态响应特别是率相关性的影响。

岩石材料作为一种各向异性的颗粒复合材料，其力学表现和破裂过程同它的细观颗粒以及颗粒之间的粘结紧密相连。因此，了解岩石动态破坏背后的细观力学影响对于岩石动力学的发展有着深远的意义。本项目基于数值流形法，借助数字图像处理技术，开发相应图像处理程序，将岩石真实的细观结构导入到数值流形法中，同时为了处理岩石细观颗粒破碎以及局部损伤，引入细观颗粒损伤破坏准则以及相应的颗粒开裂技术，为了解决颗粒接触参数难以选取以及接触模拟计算量大的问题，采用零厚度粘聚力单元的本构来模拟颗粒之间的相互作用，利用数值流形法强大的连续-非连续处理能力，建立了能够真实反映岩石细结构的岩石破裂细观力学仿真程序。基于所发展的程序，揭示岩石细观参数如细观颗粒尺寸、接触刚度、接触抗拉强度、接触剪切强度以及接触极限位移等对于岩石动态破裂过程、破坏强度以及断裂韧度的影响。同时引入正交各项异性率相关性本构模型模拟岩石细观颗粒之间的动态力学表现，通过对比采用率相关与率无关本构模型分析结果，探索细观强度率相关性对于岩.石宏观率相关性的影响，对岩石细观颗粒界面强度以及颗粒强度采用Weibull分布，分析由此引起的材料不均匀性对于岩石动态响应特别是率相关性的影响。最后，基于研究结果，建立了岩石细观力学参、细观结构及其演化过程同动态宏观力学参数、力学特征以及破裂过程的内在联系，揭示了岩石破动态破裂灾变过程背后的宏细观机制。研究结果具有重要的理论意义和推广应用价值。