考虑岩体时效深埋隧洞施工过程的理论解析——开挖、锚喷与衬砌支护的全过程模拟与解答

Analytical solutions of deeply buried tunnel during construction considering time-dependent behaviors of rock——simulations and solutions of sequential excavation, rockbolt reinforcement and liner installation

对具有时效特性的流变岩体,施工过程对围岩力学响应有显著影响。针对黏弹性时效岩体中深埋圆形隧洞的断面及纵向开挖、锚喷和衬砌施工,用圆柱型正交各向异性弹性体模拟锚固后岩体,建立材料特性变化后锚固区力学响应的计算方法,进而导出Burgers岩体全施工过程的封闭解析解。根据解答分析了锚固区各向异性程度、锚固及衬砌支护时刻、锚固厚度对锚固区应力、位移的影响。分析表明:锚固区环向刚度的改变可显著影响岩体力学响应,而改变径向刚度则变化极小;衬砌受力与其施加时刻相关,而受锚固时刻影响不大;增加锚固区厚度可减小位移,优化锚固区受力,但对衬砌的受力影响很小。本解答可进行相似条件下隧洞初步设计。

For the rheological rock with time-dependent behaviors, the mechanical response is greatly affected by the sequential construction of the tunnel. The cross-section excavation, longitudinal advancement, rockbolt reinforcement and liner installation are accounted for during the analytical derivation for a deeply buried circular tunnel in viscoelastic rock. The characteristics of rockbolt reinforcement region are regarded as homogeneous cylindrically anisotropic elasticity, and the corresponding method is then proposed. Accounting for the whole construction process, including sequential excavation, reinforcement and liner installation, the closed form solutions are derived when the rock is simulated to Burgers viscoelastic model. Based on the solutions, an extensive parametric analysis is then performed to investigate the influences of anisotropy degree, installation time of rockbolt and liner and thickness of reinforced region on tunnel convergence and the stresses. The analysis shows that the hoop stiffness of the reinforced region has a significant impact on the mechanical response of rock, while the effect of radial stiffness is much less. The stresses of the liner are greatly affected by its installation time, and the installation time of the rockbolt has no effect on the stresses. Increasing the thickness of reinforced region can reduce the convergence and optimize the stresses of reinforcement region, but it has little effect on the stresses of the liner. The proposed solutions can be applied to the preliminary design of tunnel construction with similar conditions.