Research On Deformation Characteristics Of Deep Foundation Pit And Support Structure Design Optimization Of Hongshan Station Of Wuhan Metro Line 8

In the process of subway construction,the accidents of foundation pit engineering appear constantly,which cause great economic losses and casualties.The design and construction of deep foundation pit of subway station directly affect the safety of foundation pit.Therefore,it is of great significance for the design and construction of metro foundation pit in Wuhan area to study the deformation law of maintenance structure and the disturbance law of surrounding soil layer caused by foundation pit excavation Based on the "foundation pit monitoring project of Hongshan station of Wuhan Metro Line 8",the specific research contents and relevant conclusions are as follows:(1)The deformation characteristics and supporting forms of foundation pit are analyzed.By referring to the relevant literature and research results at home and abroad,this paper summarizes the current situation of deep foundation pit engineering research,deep foundation pit deformation and optimization design of foundation pit support;introduces the foundation pit retaining structure,several deformation forms of surrounding surface settlement and pit bottom uplift,summarizes several common deformation estimation methods of foundation pit,and carries out the common types of foundation pit support structure induce.(2)Based on the field measurement data,the deformation law of the station foundation pit is analyzed.This paper briefly introduces the engineering background of the station foundation pit and the purpose and content of the foundation pit monitoring;the surface settlement value around the foundation pit increases gradually with the excavation process,and the deformation of the foundation pit has obvious time-space effect.The deformation of the foundation pit retaining structure presents a bow shape with two big ends and a small middle.(3)The excavation process of the deep foundation pit of the subway station is simulated by using the finite element software PLAXIS 3D.This paper introduces the PLAXIS 3D software,expounds the basic theory and advantages of HSS model,and makes use of PLAXIS 3D simulation of the excavation process of the foundation pit,the surrounding surface settlement and the displacement cloud diagram of the retaining structure are obtained,and the simulation results are compared with the field measured data.The simulation results are basically consistent with the measured results,which verifies the rationality and effectiveness of the finite element model.(4)Based on the finite element numerical simulation of orthogonal experimental method,the detailed parameters of the supporting structure of deep foundation pit are optimized.The orthogonal test can select the "partial test" which can represent the overall situation from the "overall test",which has the characteristics of "uniform dispersion,neat and comparable".The best scheme can be determined by using the range analysis method to analyze the experimental results.The optimization results show that in the deformation control range,taking the engineering cost of supporting structure as the evaluation index,the sensitivity of the main supporting structure parameters to the displacement and cost of pile body is in order: pile diameter > steel support distance > pile embedment depth > pile center distance.The optimized supporting scheme can save the engineering cost.