| With the vigorous construction of the city and the quick development of underground space,the deep foundation pit engineering of Urban Medium has sprung up and the accidents therewith occur often.The underground water seepage is one of the main causes of the accident,so the problem of underground water in deep foundation pit engineering has been paid great attention by engineers and technicians,and the waterproof curtain is often used to water seal before the foundation pit excavation.Besides the surrounding environment of the deep foundation pit engineering in the city is very complicated,which also puts forward higher requirements for reducing the influence of foundation pit excavation on the surrounding environment.Therefore,it is of great practical significance to study the ground settlement around the foundation pit in the rich water area.Taking the foundation pit of the Hualong station and Chongqing West Railway Station of Chongqing rail transit as the research background,this paper analyzes the pre and post grouting ground settlement around the foundation pit by means of theoretical analysis,numerical simulation and field monitoring research methods.The main contents of this paper are as follows:(1)This paper introduces the engineering background and supporting structure of the foundation pit of Hualong station and Chongqing West Railway Station of Chongqing city rail transit.The excavation process and the brace pre axial force are used to calculate the formula of the lateral displacement curve of the foundation pit supporting structure.Five different sections of the foundation pit are selected,and the ground settlements of them are calculated by the use of the deduced formula.(2)The three-dimensional finite element model is established to analyze the relationship between the ground settlement range and the excavation depth of the foundation pit under the different depth of foundation pit excavation,and the formula of ground settlement is deduced by using the soil loss theory and the lateral displacement curve of supporting structure.The results of theoretical calculation and numerical simulation are compared.The results are similar to each other,which can provide theoretical support for ground settlement calculation in the case of similar geologic conditions.(3)From comparing the ground settlement considering and without considering the groundwater seepage by using the finite element analysis software,it can be seen that groundwater seepage is one of the important causes of ground settlement around the foundation pit.Through the analysis and comparison of field monitoring data and numerical simulation results,the reliability of numerical simulation results is verified,and the numerical simulation results can meet the needs of practical engineering.(4)This paper elaborates the mechanism of reducing ground settlement by the waterproof curtain and grouting reinforcement,and improves the calculation formula of ground settlement so that it can be applied to the case when there are waterproof curtain or the grouting reinforcement around the foundation pit.The results of finite element simulation of ground settlement before and after grouting are analyzed and it is concluded that the waterproof curtain and grouting reinforcement significantly reduces the ground settlement,which can greatly reduce the influence of the foundation pit excavation on surrounding environment.In this paper,the results of theoretical research are applied to practical engineering,and numerical simulation and field monitoring data validate reliability of the theory.The research results of this paper have important reference significance for the design and construction of engineering under similar geological environment. |
PDF Full Text Request