基于上海软土模型暗挖法隧道施工的力学特性

为了将暗挖法推广至软土地层轨道交通车站建设,上海市以轨道交通14号线桂桥路车站渡线段为试验段,首创性地采用管幕暗挖法进行地铁车站的施工。依托此工程,本文将上海软土精细化本构模型用于暗挖法施工数值模拟中,研究了基于上海软土模型的暗挖法隧道施工位移、应力、应变等力学特性。主要结论如下：(1)开挖阶段地层主要发生了沉降变形,最大变形发生位置基本保持在车站中心的位置,最终地表变形趋于对称分布；(2)开挖完毕后,横断面上的剪应力分布呈现对称性,在开挖土体左肩和右肩部位易产生应力集中；(3)开挖过程中,开挖土体周围的体积应变云图基本呈对称分布,开挖土体上方体积应变最大,表明开挖土体上方塌方风险极高；(4)运用上海软土模型的模拟结果更加接近实测值,这是由于上海软土模型采用的参数能更精细地反映上海地区软土的超固结性、结构性、各向异性等特征。

Construction Mechanical Properties of Underground Tunneling using the Shanghai Soft Soil Model

To promote the undercutting method to the construction of subway stations in soft stratum, the pipe-roofing method was firstly employed in Shanghai with the Guiqiao Road station of the Metro Line 14 as a trial engineering. Based on this project, a sophisticated constitutive model of Shanghai soft soil was implemented into the numerical simulation of the tunneling construction. Soil mechanical properties including displacement, stress and strain during the tunnel construction were analyzed. The main conclusions are as follows: (1) The stratum mainly settled during excavation. The position with the maximum deformation basically remained in the center of the station. The final ground deformation tended to distribute symmetrically. (2) After excavation, the distribution of the shear stress on the cross section presented symmetrical, and the stress tended to concentrate at the left and right shoulders of excavated soil. (3) During excavation, the volumetric strain contours around the excavated soil was symmetrical, and the volumetric strain above the excavation was the largest, indicating that the risk of collapse was very high above the excavated soil. (4) The simulation results using the Shanghai soft soil model were closer to the measured values because the parameters of this model can better reflect the characteristics of overconsolidation, structure and anisotropy of the Shanghai soft soil.