基于Mohr-Coulomb强度准则的锚杆支护效应研究

Study on Bolt Support Effect Based on Mohr-Coulomb Strength Criterion

从围岩与锚杆相互作用的力学特性出发,基于围岩增强理论,采用数值模拟手段,探究锚杆支护作用下隧道开挖后围岩的力学特性,得到围岩特性曲线(GRC曲线)。通过对比各种锚杆支护参数下与未支护状态下围岩特性曲线的差异,建立锚杆密度与围岩收敛降低比例之间的关系。结果表明:锚杆对围岩收敛的限制作用显著,能很好地控制围岩变形,且锚杆密度越大,支护效果越明显,但当锚杆密度大于3时,收敛限制效果开始减弱;锚杆对围岩收敛的约束作用存在极限值,锚杆密度与收敛减低比例之间满足二次函数关系,Ⅳ级围岩限制比例极限为40.9%,Ⅴ级围岩限制比例极限为33.8%;锚杆支护对围岩收敛的约束作用与围岩性质有关,Ⅳ级围岩的约束效果显著优于Ⅴ级围岩。

Starting from the mechanical characteristics of the interaction between surrounding rock and bolt,based on the surrounding rock enhancement theory,this paper uses numerical simulation to explore the mechanical characteristics of surrounding rock after tunnel excavation under bolt support,and obtains the surrounding rock characteristic curve(GRC curve).By comparing the difference between the characteristic curve of surrounding rock under various bolt support parameters and the characteristic curve of surrounding rock in the unsupported state,the relationship between bolt density and the reduction ratio of surrounding rock convergence is established.The results show that the bolt has a significant limiting effect on the convergence of the surrounding rock,which can control the deformation of the surrounding rock,and the greater the density of the bolt,the more obvious the supporting effect.However,when the bolt density is greater than 3,its limiting effect on convergence begins to weaken.There is a limit value for the constraint effect of bolt on the convergence of surrounding rock,and the quadratic function relationship between bolt density and convergence reduction ratio is satisfied,and the limit of the limiting ratio of gradeⅣis 40.9%and that of gradeⅤsurrounding rock is 33.8%.The restraining effect of bolt support on the convergence of surrounding rock is related to the nature of surrounding rock,and the constraint effect of gradeⅣsurrounding rock is significantly better than that of gradeⅤsurrounding rock.