直剪作用下不共面断续节理岩桥破断试验与数值研究

Experimental and Numerical Analysis on Rupture of Rock Bridge with Non-Coplanar Intermittent Joints Under Direct Shear

在伺服控制剪切加载系统下对不共面类岩石断续节理试件进行正向、反向直剪试验,研究直剪下不共面断续节理的岩桥破断机理和剪切规律,试验研究发现,直剪作用下不共面断续节理岩桥破坏过程具有明显的阶段性,经历线弹性阶段、裂纹起裂扩展阶段、岩桥断裂贯通阶段、剪切面爬坡咬合阶段和残余摩擦阶段5个阶段,正向剪切下岩桥呈齿形破断面,反向剪切作用下岩桥产生沿直剪方向贯通的带形破断面,与正向剪切相比,反向剪切下节理的初裂抗剪强度和峰值抗剪强度较大,裂纹倾角、法向应力和相邻节理搭接比例是影响试件初裂抗剪强度和峰值抗剪强度的主要因素。采用FLAC3D对正向、反向直剪作用下不共面断续节理的岩桥破断、剪切破断面的形成过程进行数值试验,数值试验结果和类岩石直剪试件的试验结果基本吻合,数值试验揭示了直剪作用下不共面断续节理岩桥的拉裂破坏和破断面的剪切屈服机理。

By using servo control shear loading system ,specimens with non-coplanar rock-like intermittent joints were tested by the way of forward and reverse direct shear ,rupture mechanism and shearing law for rock bridge with non-coplanar intermittent joints were studied under direct shear .The experimental studies showed that five apparent stages are presented in the process of rock bridge rupture under direct shear , which are linear elastic stage ,initiation and extension of crack ,fracture and transfixion of rock bridge , climbing and occlusion of shear plane and residual friction .Rock bridge presented profile fracture plane under forward direct shear .While under reverse direct shear ,band form fracture plane is showed which penetrated along with the direction of forward shear ,and the shear strength of initiation and peak shear strength under reverse direct shear are bigger than that under forward shear .Crack angle ,normal stress and lap proportion among adjacent joint are the main factors that influence the initiation strength and peak shear strength . The FLAC3D simulation for the process of non-coplanar intermittent joints rock bridge rupture and formation of shear rupture surface under forward and reverse direct shear was conducted .The results of numerical simulation agreed well with those of experiment . The simulation results revealed tension crack failure of non-coplanar＆nbsp;intermittent joints rock bridge and shear yielding mechanism of fracture plane .