北山花岗岩闭合裂隙剪切破坏机理研究

Study on Shear Failure Mechanism of Closed Fractures in Beishan Granite

随着我国高放废物处置库研发战略的推进,处置库花岗岩围岩工程特性成为研究重点。天然裂隙是花岗岩中的薄弱环节,岩体往往沿既有结构面发生剪切滑移。因此裂隙剪切特性和剪切破坏机理研究意义重大。天然裂隙包括张开裂隙和闭合裂隙,其剪切特性和剪切破坏机理存在差异。针对北山地下实验室场址范围花岗岩闭合裂隙,开展剪切试验。将裂隙结构面扫描数据嵌入离散元颗粒流软件(PFC),构建北山花岗岩闭合裂隙剪切颗粒模型,利用fish语言监测颗粒间接触(contact)失效并生成对应裂隙(fracture)以模拟试样剪切过程内部微裂纹的发育。试验获得了北山花岗岩典型闭合裂隙的剪切强度和闭合裂隙三维形貌。将试验与模拟结果进行对比,研究认为:构建的颗粒模型可较好地模拟裂隙三维形貌对剪切强度的影响,表征了花岗岩闭合裂隙剪切过程的微裂纹发育扩展过程,展示了闭合裂隙的剪切破坏机理。

With the advancement of China’s strategy for high-level radioactive waste disposal repositories,the engineering characteristics of granite have become a focus of research.Natural fracturess are the weak surfaces in surrounding rock,and the rock mass often shears and slips along existing structural planes.Therefore,the study of the shearing characteristics and failure mechanisms of fractures is of great significance.Natural fractures include open and closed ones,and their shearing characteristics and failure mechanisms differ.In this study,shear tests were conducted on closed granite fractures from the Beishan Underground Laboratory site.Scanning data of the fracture surface was embedded into the particle flow software,and a three-dimensional particle model of the Beishan granite closed fracture was constructed.Using the fish language,contact failure between particles was monitored and corresponding fractures were generated to simulate the development of internal micro-fractures during the shearing process of the specimen.The shearing strength parameters and the shear stress-strain curve of the typical closed granite fracture in Beishan have been obtained through experiment.Comparing the experimental and simulation results,the research found that the particle model constructed is able to simulate the influence of the three-dimensional morphology of fractures on the shearing strength,visualize the development and expansion of micro-fractures during the shearing process of granite fractures,and demonstrate the shearing failure mechanism of closed fractures.