岩石锚杆锚固段拉拔破坏机理离散元分析

Mechanism Investigation of Rock Bolt Failure in Anchorage Segment under Pullout via DEM

为探讨锚杆锚固段的拉拔破坏机理,采用离散元进行绿片岩中锚杆拉拔试验的模拟,分析不同锚固长度、围压下锚固段破坏模式和特点。离散元中植入新型岩石微观接触模型,可以更好的模拟绿片岩力学特性。分析结果表明,拉拔荷载与位移呈多次上升-跌落关系,并在产生贯通破坏面后明显跌落;围压可以明显增大锚杆与岩石相互作用力,对拉拔极限承载力有极大影响;拉拔破坏渐进发生,将先形成"瓶"状的破坏形态,再从锚杆底部的岩体形成一个"漏斗锥形"形的破坏形态;而在高围压时,锚杆底部岩体先破坏,裂纹沿斜向上扩展,形成"漏斗锥形"形破坏形态。

In order to discuss the failure mechanism of rock bolt anchorage segment,the discrete element method was used to simulate the bolt pullout test in green schist,and the failure modes and characteristics of anchorage segment under different anchorage length and confining pressure were analyzed.A new micro contact model of rock embedded in discrete element method can better simulate the mechanical characteristics of green schist.The analysis results show that the pulling load and displacement are multiple rise and fall relation and fall obviously after producing through failure surface;the confining pressure can obviously increase the interaction force between the rock bolt and rock,and has a great influence on the ultimate bearing capacity of the drawing;the gradual failure of pullout will form a'bottle shaped'failure form first,and then form a'funnel'shaped failure form from the rock mass at the bottom of the anchor rod;the rock mass at the bottom of the rock bolt is destroyed first,and the cracks extend upward to form a'funnel'shaped failure mode at high confining pressure.