应变软化弹塑性岩体中TBM施工过程围岩力学状态的理论分析

 针对深埋圆形隧洞TBM施工过程，综合考虑纵向推进和双层衬砌构筑过程，对围岩–衬砌进行耦合分析，得到应变软化弹塑性岩体在不同时刻施加衬砌时的应力、位移、软化区和破裂区半径的解析解，并给出带衬砌问题围岩达到软化和出现破裂的判据。推导中同时考虑了岩体在软化阶段和残余强度阶段的体积扩容。通过算例分析初衬和二衬施加时刻对围岩位移、软化区和破裂区范围以及围岩压力的影响，讨论了荷载在两层衬砌间的分担演化规律。分析表明，算例中TBM推进至3倍洞径时施加二衬，则二衬阶段产生的位移可控制在总位移的6%以内；衬砌间的作用力对二衬施加时刻较为敏感，而衬砌对围岩的支护力将受初衬和二衬施加时间的共同影响。根据提出的解答，可以进行TBM推进速度、衬砌几何和材料参数及最佳支护时机的初步设计，并预测隧洞施工中位移、应力的时程变化。

Analytical research of mechanical response of TBM construction in strain-softening elasto-plastic rock

Coupling analysis of rock mass and liners was carried out for deeply buried tunnel in TBM excavation process and sequential installation of liners. Analytical solutions of stress，displacement and radii of softening and broken zone were presented for the tunnel constructed in the strain-softening elasto-plastic rock mass with two liners installed at different times. The criterions for softening and fracture occurring in the rock mass were also given. The dilation during the softening and residual stage was taken into account in the derivation. The influence of installation times of the first and second liners on the displacement，radii of softening zone and broken zone and supporting pressure on the rock were analyzed. The variation of the pressures between two liners was discussed. If the second liner was installed when the distance to the tunnel face is about three times of tunnel radius，the displacement occurred during the second liner stage can be controlled within 6% of total displacement. The pressure between two liners was sensitive to the installation time of the second liner，however，the supporting pressure to the tunnel was affected by both the installation times of the first and second liners. The advancing rate of TBM，the geometric and material parameters of the two liners and the optimum installation time of the liners can be preliminary determined in design phase，and the time dependent displacement and stresses can also be predicted with the solution presented in the paper.