复合岩体中深埋隧道开挖破坏机理离散元分析

Discrete Element Analysis on Excavation Failure Mechanism of Deep-buried Tunnel in Composite Rock Mass

为研究复合岩体中隧道开挖的问题,引入考虑胶结尺寸的岩石微观接触模型,以离散元方法为手段,模拟了复合岩体在不同初始地应力条件下隧道开挖引发的破坏过程,就宏观围岩扰动区、最大主应力、胶结破坏进行分析,并讨论了复合岩体情况与均质岩体情况的区别。结果表明:宏观围岩扰动区面积比随地应力的增大而增大,可能导致宏观大变形甚至破坏;地应力10 MPa时,未发生胶结破坏,20 MPa、30 MPa、40 MPa均发生破坏,胶结破坏数随地应力的增大而增多,且以拉剪和压剪破坏为主;最大主应力从环向看呈下垂水滴状且向下方向最大,在225°,270°和315°方向的最大主应力与离隧道中心的距离成正比;复合岩体在层理面处呈现应力不连续现象。

To study the problem of tunnel excavation in composite rock mass,the microscopic contact model of rock considering bond size introduced,and the destruction process of composite rock mass under different initial geostress in tunnel excavation simulated by using the discrete element method(DEM),with focus on disturbance zone,maximum principal stress and bond breakage in the surrounding rock.Finally,the difference between composite rock mass and homogeneous rock mass discussed.The results show that the disturbed area ratio will increase with the increase of geostress on the surrounding rocks which possibly results in macroscopic large deformation and even failure of surrounding rocks.In the case that the geostress is 10 MPa,no bond breakage occurs.When the geostress 20 MPa,30 MPa and 40 MPa,bond is broken and the number of bond breakage increases with the increase of geostress and the types of main failure are tensile shear failure and compression shear failure.The distribution of the maximum principal stress along the circumferential direction is teardrop-shaped with the downward principal largest.The maximum principal stress in the direction of 225°,270°,and 315°is proportional to the distance from tunnel center.The composite rock mass presents discontinuous stress at the bedding surface.