深部复合岩体隧道开挖离散元模拟

DEM investigation on tunnel excavation of deeply-situated composite rock mass with different strength ratios

深部复合岩体隧道开挖过程中,抗压强度比是影响围岩稳定的重要因素。引入考虑胶结尺寸的微观接触模型,采用二维离散元方法对深部上软下硬复合岩体隧道开挖进行了数值模拟,分析了强度比对围岩胶结破坏、最大主应力及扰动区的影响。结果表明,随着抗压强度比的增大,隧道开挖引起的围岩胶结破坏率与扰动区逐渐增大,胶结破坏形式以拉剪破坏为主;最大主应力沿围岩环向呈下垂的滴水状分布,沿径向在软岩中先减小后增大,在硬岩中逐渐增大;随着抗压强度比的增大,最大主应力沿径向在硬岩区变化幅度减小,在软岩区变化幅度增大。

The strength ratio is an important factor affecting the stability of the surrounding rock during tunnel excavation of deeply-situated composite rock mass.A size-dependent bond contact model is implemented to the software of the two-dimensional distinct element method(DEM)to simulate the tunnel excavation of deeply-situated up-soft/low-hard composite rock mass.The influences of strength ratio on bond breakage,the maximum principal stress and disturbance zone of the surrounding rock are investigated.The results show that the bond breakage ratio and the disturbed area ratio caused by tunnel excavation gradually increase with the increase of strength ratio of composite rock mass,and the bond breakage is mainly caused by bond tensile failure.The maximum principal stress is distributed in teardrop shape in the circumferential direction of the surrounding rock,while in the radial direction it decreases firstly and then increases in the soft rock and increases in the hard rock.Moreover,in the radial direction,with the increase of the strength ratio,the variation range of the maximum principal stress decreases in the hard rock but increases in the soft rock.