填土注浆加固对深基坑支挡结构与相邻隧道的作用效果案例分析

为有效防范填土深基坑变形过大对邻近地铁隧道造成的安全风险，变形控制是基坑支护设计应考虑的首要问题。以重庆吾悦广场邻近地铁隧道一侧的填土深基坑边坡为研究背景，提出注浆加固联合多桩分阶支挡的方案，该方案结构受力合理，变形控制能力强。根据现场注浆试验区的检测数据可知，加固后的土体抗剪强度和变形模量大幅提高。通过在有限元模型中调整土体参数，计算不注浆加固和注浆加固2种工况下多阶支护桩及隧道的位移和内力值，计算结果表明： 填土注浆加固能提高支护桩前后填土体的力学性质，增大土体的抗剪强度参数及土体水平抗力系数的比例系数，有效降低支护桩内力值、减少桩身长度及截面尺寸。结合建筑物退台方案设置多阶平台，增大了坡脚与坡顶之间的水平距离，降低了每阶边坡的土压力值。注浆与分阶2种措施对控制支护桩及隧道变形起到积极作用，能有效防范基坑边坡变形过大对地铁隧道及周围环境造成的安全风险。

Case Study on Effect of Soil Filling Grouting Reinforcement onDeep Foundation Pit Support Structure and Adjacent Tunnels

The deformation control is a priority in foundation pit support design to effectively avoid safety risk of adjacent metro tunnel caused by excessive deformation of deep foundation pit. The deep foundation pit slope on the side of the metro tunnel near Chongqing Wuyue Square is taken as an example, a scheme of grouting reinforcement combined with multi pile step by step support is proposed, in which the structural stress is rational and the deformation control capacity is strong. The test data of the on site grouting test area show that the shear strength and deformation modulus of the soil after reinforcement have been greatly improved. The displacement and internal force values of multi stage retaining piles and tunnels under two working conditions with and without grouting reinforcement are calculated by finite element model. It is concluded that the soil filling grouting reinforcement can effectively improve the mechanical properties of the soil before and after the retaining pile, increase the shear strength parameters and the proportional coefficient of the horizontal resistance coefficient of the soil, and reduce the internal force of the retaining pile, the length and cross section size of the pile body. The multi stage platform is set in combination with the building retreat scheme, which increases the horizontal distance between the slope foot and the slope top, and reduces the soil pressure value of each step slope. The grouting and multi stage platform play a positive role in controlling the support pile and tunnel deformation, effectively avoid the safety risks caused by excessive deformation of the foundation pit slope on the metro tunnel and the surrounding environment.