隐式中墙复合式连拱隧道CD法施工模型试验研究

Experimental Study on the Construction Model with a CD Method for Composite Multi-arch Tunnels with Recessed Central Wall

为了深入研究新型连拱隧道——隐式中墙复合式连拱隧道CD法施工过程中,围岩变形和初支结构的受力特征,该文依托重庆沙坪坝站铁路综合交通枢纽工程,通过模型试验再现了隧道施工过程,分析了不同开挖步序下围岩的变形以及初支结构的受力变化规律。结果表明:(1)模型试验验证了数值模拟中对施工步序优化后围岩的沉降规律,实测沉降数值与数值模拟结果相符合;(2)双连拱隧道初支结构在加载破坏时,中墙上方的变截面处最容易开裂,并迅速形成通缝,验证了需对中墙采取优化措施的必要性;(3)双连拱隧道初支结构加载时,其内力值均较小,与数值模拟结果基本吻合,满足设计要求。

To investigate the deformation of surrounding rocks and the stress characteristics of the initial support structure during the construction process of a new type of multi-arch tunnel—the composite multi-arch tunnel with recessed central wall using the CD method,this paper,based on the Chongqing Shapingba Railway Station Comprehensive Transportation Hub Project,reproduces the tunnel construction process through model tests,and analyzes the deformation of surrounding rocks and the stress change law of the initial support structure under different excavation steps.The results indicate that:(1)the model test verifies the settlement law of the surrounding rock after optimizing the construction sequence in the numerical simulation,and the measured settlement values are consistent with the numerical simulation results;(2)When the initial support structure of a multi-arch tunnel is subjected to loading failure,the variable cross-section above the central wall is most likely to crack and straight joints quickly form,which verifies the necessity of taking optimization measures for the central wall;(3)When the initial support structure of the multi-arch tunnel is being loaded,its internal force values are relatively small,which is basically consistent with the numerical simulation results and meets the design requirements.