降雨入渗下膨胀性黄土隧道围岩破坏演化

Research on failure evolution process of surrounding rock of swelling loess tunnel under rainfall infiltration

应用FISH语言改进FLAC^(3D)软件的非饱和渗流计算功能,同时等效模拟渗流过程中土体强度折减和膨胀力增加的力学特性,提出降雨入渗下膨胀性黄土隧道围岩大变形破坏数值演化分析方法.依托某膨胀性黄土隧道工程实例,将隧道围岩变形及力学特性现场测试与计算结果比较,验证了该数值方法的适用性.结果表明:降雨持续作用下隧道围岩位移随含水率呈台阶形增长,分析得出了位移出现极大值时对应的含水率,在膨胀土隧道工程实践中可以此作为安全施工的一项监控指标;降雨持续作用60 h,隧道边墙正弯矩明显增大,初期支护向内挤出变形严重,围岩体剪切应变发育显著,且地表山体边坡发育出大面积塑性贯通区,数值分析有效揭示了隧道洞内塌方及地表山坡滑塌破坏机理.研究成果可对膨胀性黄土隧道围岩稳定性分析和变形控制提供一定的指导.

Routines for improving the capability of unsaturated seepage calculation of FLAC 3D software were programmed by using FISH language.The mechanical properties of shear strength reduction and swelling force increase of surrounding rock in unsaturated seepage calculation were also considered.A numerical evolution analysis method for the large deformation and failure of the surrounding rock of the expanded loess tunnel was proposed.Based on a swelling loess tunnel project,the applicability of the numerical simulation was verified by comparing with the measurement results of tunnel surrounding rock deformation and mechanical characteristics.The results indicate that,due to the effect of continuous rainfall,the displacement of tunnel surrounding rock increases step by step with the increase of water content.The water content corresponding to the maximum value of displacement is obtained,which can be used as a monitoring index for the safe construction of the swelling loess tunnel engineering.After the rain lasts for 60 h,the positive bending moment of the tunnel side wall increases obviously,the deformation of the initial supporting is inwardly extruded,the shear strain increment develops remarkably,and a large area of plastic transfixion zone is developed along the mountain slope.The mechanism of tunnel collapse and slope slumping is revealed.The research results can provide a guide for the stability analysis and deformation control of tunnel surrounding rock in expansive soil.