济南地铁汽修厂站深大基坑拆撑过程的稳定性分析

Stability Analysis of Jinan Qixiuchang Metro Station during the Foundation Pit Temporary Supports Dismantling

[目的]地铁站深大基坑在拆撑过程中容易失稳,影响工程安全。故须针对地铁站深大基坑拆撑过程中的稳定性进行分析。[方法]依托济南地铁汽修厂站深大基坑工程,针对支撑轴力、地下连续墙变形和地面沉降,采用现场监测与三维数值模拟相结合的方法,研究深大基坑开挖拆撑期间的变形特性及力学响应动态演化规律。[结果及结论]基坑开挖完成,地下连续墙水平位移最大处深度为总开挖深度的0.7~0.8倍;拆除底部钢支撑后,地下连续墙的墙体变形速度加快,第一道混凝土支撑的轴力值为稳定时轴力的4~6倍;为保证施工安全,应尽量减少无支撑时间;基坑施工地面主要影响区域为地下连续墙后0~20 m范围,应作为监测重点。现场监测结果验证了数值模拟的有效性。

[Objective]It is prone to lose stability,affecting the engineering safety in the process of dismantling the supports for metro station deep and large foundation pit.Therefore,it is necessary to analyze the stability in the above process.[Method]Based on the deep and large foundation pit project of Jinan Qixiuchang Metro Station,on.site monitoring and three.dimensional numerical simulation are used to study the deformation characteristics and the dynamic evolution of mechanical response during deep and large foundation pit excavation and the supports dismantling,focusing on problems like supporting axial force,deformation of underground diaphragm wall and land subsidence.[Result&Conclusion]When the excavation is completed,the depth point where the underground diaphragm wall shows the maximum horizontal displacement is 0.7~0.8 times the total excavation depth.After the bottom steel support is removed,the diaphragm wall deformation accelerates and the axial force of the first support increases by 4 to 6 times.In order to ensure the construction safety,the unsupported time should be reduced as short as possible.The main ground area affected by foundation pit construction ranges from 0 to 20 m,and should be the focus of monitoring.On.site monitoring results verify the effectiveness of the numerical simulation.