基于离散元的盾构隧道双层衬砌接触面剪切特性研究

Shear Characteristics of Contact Surface of Double-layer Lining of Shield Tunnel Based on Discrete Element Simulation

摘要:

盾构隧道双层衬砌间的共同作用机理对于隧道整体安全性能至关重要。为探究双层衬砌接触面的抗剪强度性能，基于PFC^3D离散元程序，开展了不同内衬混凝土强度、界面粗糙度及法向应力条件下的管片-内衬混凝土剪切的数值模拟试验，获得了不同工况条件下管片-内衬混凝土的剪切应力-应变关系及细观裂纹发展规律。根据试验结果，提出了剪切破坏时存在张拉剪切破坏及剪切滑移破坏两种模式，并针对两种破坏模式开展了接触面上单个微凸体的局部力学分析。研究结果表明：随着粗糙度及法向应力的增加，裂纹开展逐渐由接触面上转移至混凝土内部，即剪切破坏模式由剪切滑移破坏逐渐过渡到张拉剪切破坏；在考虑接触面剪切破坏机制的基础上，基于Mohr-Coulomb准则提出了多因素耦合作用下双层衬砌接触面的抗剪强度计算方法，为盾构隧道双层衬砌接触面的抗剪强度参数确定提供了理论支撑。

Abstract:

The interaction mechanism between the double-layer lining of shield tunnel is crucial for the overall safety performance of the tunnel. To investigate the shear strength performance of the contact surface between double-layer linings， numerical simulation tests of the shear behavior between the segment and the second lining concrete were conducted based on the PFC^3D discrete element program. The tests were performed under different conditions of the strength of the second lining concrete， interface roughness， and normal stress. Shear stress-strain curves and the development of microscopic cracks in the segment-second lining concrete were obtained under different working conditions. According to the test results， two modes of failure were proposed which are shear-crack failure and shear-sliding failure. Local mechanical analyses of individual convex bodies on the contact surface were conducted for the two failure modes. The research results indicate that with the increase of roughness and normal stress， the crack propagation gradually shifts from the contact surface to the inside of the concrete， which means the shear failure mode transitions from shear-sliding failure to shear-crack failure. Based on the shear failure mechanism of the contact surface and considering the coupling effects of multiple factors， a calculation method for the shear strength of the double-layer lining contact surface was proposed based on the Mohr-Coulomb criterion. The research results provides a theoretical basis for determining the shear strength parameters of the interface between the primary and secondary linings in shield tunnels.