基于应变非线性软化的海底隧道围岩力学特性

Mechanical characteristics of surrounding rock in sub-sea tunnel based on strain nonlinear softening

采用弹性、峰后具有拐点的应变非线性软化本构模型,且同时考虑中主应力效应,在海水渗流和不同排水工况下,对海底隧道围岩弹塑性区应力分布规律、围岩与支护之间作用关系以及最小支护阻力进行研究,分析海水压力、上覆岩层厚度、有效孔隙度对围岩力学特性的影响,提出渗流作用下隧道围岩稳定的海水压力临界值的概念,并绘制围岩(支护)特性曲线。研究结果表明:海底隧道排水越充分,围岩有效孔隙度越大,则塑性区开展范围越大,且递增幅度较大,围岩(支护)特性曲线也不同;当隧道埋深较浅时,在隧道周围只形成塑性区域,只有当埋深进一步加大时,才可能形成松弛区域。

By using the constitutive model composed of elastic, strain nonlinear softening segment with inflexion, the effect of intermediate principle stress, the permeation of sea water and various work conditions of controlled drainage, the stress distribution laws in elastic and plastic zone of sub-sea tunnel, interaction principle between surrounding rock and reinforcement and the least supporting resistance were studied. The impacts of sea-water pressure, upper rock covers and effective porosity on the mechanical character of surrounding rock were discussed. The concept of critical sea-water pressure of rocks around tunnel was put forward by taking the water permeation effect into account, and corresponding ground （support） reaction curves were drawn. The results show that a fuller drainage and larger value of effective porosity make a bigger scope of plastic area and increasing-range and different ground （support） reaction curves, and when the burial depth of tunnel is shallow, the plastic region is merely formed. The slack region is possibly formed when the burial depth is further enlarged.