岩石锚杆界面滑移破坏的DEM数值模拟

Numerical Simulation of Sliding Failure in Rock-Bolt Interface by Discrete Element Model

锚固体与岩体之间界面滑移破坏是锚固系统失效的主要形式之一,开展岩石锚杆界面力学特性和破坏机制研究具有重要意义。基于岩石微观胶结接触模型,采用颗粒离散元(DEM)模拟了岩石锚杆的拉拔试验。首先分析了荷载-位移关系、轴力分布和界面剪应力分布规律,然后通过胶结破坏点的数目和组构研究了锚固段界面的微观破坏机制。主要结论有:模拟的荷载-位移曲线与室内试验结果基本一致;拉拔峰值荷载随锚固长度的增加而增大,界面平均粘结强度随着锚固长度的增加而减小;拉拔荷载值达到峰值后,锚固段界面产生渐进破坏;锚固段破坏在宏观上表现为界面滑移,在微观上主要表现为界面处的胶结拉伸破坏和沿轴力方向的微裂纹扩展。研究成果对开展岩石粘结锚杆的界面力学特性和破坏机制研究以及正确指导工程实践具有重要意义。

Researching the mechanical properties and failure mechanism of rock-bolt interface is of great significance since sliding between bolt and rock is a major failure form of anchorage system. With the microscopic bond model proposed by one of the authors previously,the pull-out test of rock bolts was simulated using discrete element method（ DEM）. The complete load-displacement curves,the distribution of axial force and the interfacial shear stress were investigated,respectively. Furthermore,the microscopic failure mechanism of bolt-rock interface was analyzed according to the type and fabric of broken bonds. Research results are concluded as follows： 1） the simulated load-displacement curves were consistent with those from laboratory tests; 2） with the increase of anchor length,peak load value increased while average cohesive strength of anchor interface decreased; 3） progressive failure occurred in the anchor interface after pull load reached peak; 4） on macroscopic level,the failure of anchored segment exhibited as interface sliding; whereas on microscopic level,the failure manifested as the tensile failure of bonds near interface and the propagation of micro-cracks along the direction of axial force.