为保证上方卸载的隧道结构安全,本文提出2 阶段联合分析方法。第1 阶段根据隧道上方卸载工况建立三维地层-结构模型,计算得到作用于隧道管片的土压力和外侧土体的等效刚度。第2 阶段建立三维结构-荷载模型,借助于第1 阶段计算得到的土压力和等效刚度,分析管片应力、螺栓应力、收敛变形和接头张开量。某基坑工程北区块位于隧道上方,采用2 阶段联合分析方法对该算例进行分析。结果表明,该方法能够较为合理地估算上方卸载引起的隧道竖向变形和收敛变形,应重点关注管片连接部位和腰部内侧的开裂、掉块情况,必要时应进行钢环加固。2 阶段联合分析方法充分发挥了地层-结构模型和结构-荷载模型各自的优点,为评估上方卸载的隧道结构安全状况提供思路。

A two-stage conjoint analysis method is proposed for safety analysis on tunnel structures under unloading. In the first stage, a three-dimensional (3D) stratum-structure model is established according to the unloading condition above tunnel structures, and the earth pressure and earth equivalent stiffness around tunnel structures are calculated. In the second stage, a 3D structure-load model is established, and segment stress, bolt stress, convergence deformation and joint opening are analyzed based on the earth pressure and earth equivalent stiffness calculated in the first stage. The analysis method is applied to a tunnel with a foundation pit above. The results show that the vertical deformation and
convergence deformation of the tunnel structures under unloading can be rationally estimated, and the cracking and falling of concrete in the joints between segments and the inner side of the waist of tunnel structure should be paid attention to, where the steel ring reinforcement should be carried out when necessary. By using the two-stage conjoint analysis method, the advantages of the stratum-structure model and the structure-load model are fully played, which can provide a new idea for evaluating the safety status of tunnel structures under unloading.