Influence Of Seepage On Deformation Of Foundation Pit Supported By Diaphragm Walls

As the scale of the construction enlarging, more and more deep foundation pit appears. With the foundation pit deeper and deeper, its deformation is the most important indicator on security issues. In various foundation pit supporting schemes, underground diaphragm be more widely used because of its big stiffness, small deformation, better safety and its function of being used as main structure. Therefore, more and more researches about the deformation of foundation pit supported by underground diaphragm appear. But, as one of the main factors influencing the deformation of foundation pit, groundwater seepage action is rarely be researched, especially the separate research of the seepage flow of groundwater seepage. Finite element simulation software is used in this article and the process of dewatering is calculated independently. The different deformations before and after dewatering are compared in order to explore the seepage effects of groundwater on the deformation of foundation pit. The main researches are as follows:(1) A introduction is made about details of finite element model,such as the selection of parameters, analysis steps and the contacts. The whole process of excavation of foundation pit is divided into two steps, excavation and dewatering. Therefore the value of deformation caused by dewatering can be distinguished from that caused by excavation. A simulating about an example of foundation pit engineering is made, then the simulation results are compared with the measured relults to verify its applicability.(2) A finite element model is selected as standard to study the influence of various affecting factors. Calculating the above standard model,the deformation magnitude and feature of foundation pit can be arrived by analysising the simulation results. The lateral deformation of underground diaphragm, the soil settlement outside the foundation pit and the upheaval of foundation pit are selected as contrast data and then calculate the percentage of deformation caused by dewatering in the total deformation.(3) Built up models with different buried depth of the underground diaphragm, the strength of seepage and deformation of the foundation pit influenced by the depth of underground diaphragm can be obtained by comparing the simulation results of models above. Models with soil of different permeability, void ratio and coefficient of restitution are builted up and the percentage of deformation caused by dewatering in the total deformation are compared, to explore the effect of soil parameters on the deformation of foundation pit and the strength of seepage.(4) Two measures which can reduce the influence of seepage are researched separately: embedding the undergrounddiaphragm into bedrock and setting dewatering wells around the foundation pit. Finite element simulations of the two measures above are made. The parameters in the finite element models are the same as that of the standard model except for the parameters related to the two measures. The effect of the two measures can be concluded by comparing the simulation results with that of the standard model.