Seismic Performance Analysis Of Deep Foundation Pit And Surrounding Buildings Under The Action Of Main And Aftershocks

In recent years,with the rapid development of rail transportation engineering in China,subway,as the most common mode of transportation in modern times,plays an increasingly important role in various large and medium-sized cities.Similarly,the subway is an important traffic sign for a modern city to become an international city.Its appearance not only highlights a country’s economic and technological level,but also improves the traffic jam in the rush hour of the metropolis.At present,it is the most common urban traffic operation mode to distribute the traveling people regionally.At present,on the basis of the relatively developed overground facilities in China,the development potential and resources need to be utilized in the construction of underground facilities,and underground rail transportation will become the core transportation mode in the future.Urban underground space rail transit is a large-scale transportation mode,which is a safe,comfortable,convenient and fast ideal transportation mode in use.This mode plays a very important role in solving the common traffic problems in large and medium-sized cities such as road congestion.Because the urban underground space rail transit has less pollution to the environment and provides indirect protection to the surrounding ecological environment,the surface air quality has been significantly improved.This mode of transportation is in line with the national sustainable development strategy for urban construction and development,and this paper will also follow the national strategy to carry out an analysis in this direction.The seismic performance of urban underground rail transit in China is accelerating research,how to meet the requirements of underground rail transit construction at the same time to minimize the loss after earthquake is the key point of domestic research.In the process of underground track construction,the seismic performance analysis of deep foundation pit engineering is particularly important.Taking the actual earthquake as an example,in the process of earthquake,the main earthquake will be accompanied by aftershocks.In order to avoid the displacement of the surrounding buildings of the foundation pit under the acceleration of the main aftershocks,including the excessive displacement of the lateral soil of the foundation pit,the actual engineering situation and the establishment of the engineering model should be analyzed together.The main research contents of this paper are as follows: Taking the deep foundation pit engineering of Beidaying Jie Station of Shenyang Metro Line 4 as the practical background,through theoretical derivation,working condition arrangement,simulation calculation,numerical analysis and other methods,based on Midas GTS NX software,the main aftershock acceleration El-Centro and Hanshin acceleration which meet the practical requirements are input.Through the analysis of the above input seismic acceleration applied to the free field interface at the bottom of the model of deep foundation pit of subway station in the construction process,the finite element calculation model of deep foundation pit engineering under the action of seismic dynamic load is established.The following stages will be divided into the establishment of the model.(1)The theoretical basis needed for the calculation of underground building structure is defined,including the selection and division of soil mass,constitutive relation of soil mass,stress-strain theory of soil mass,selection of artificial boundary of soil mass,selection of acceleration of main aftershock,etc.(2)Based on the interaction between soil mass and the supporting structure of deep foundation pit,the displacements of the supporting structure of deep foundation pit and soil mass in the construction process were calculated under the conditions of the dead weight of the structure,the ground constant and live load,the overburden load and the construction load,etc.,and the most unfavorable points of displacements of different structures were analyzed under the construction conditions.(3)Midas GTS NX software is used to truncate the infinite boundary soil,and the appropriate boundary range is selected to conduct modal analysis on the soil and the foundation pit supporting structure,obtain the natural vibration of the structure as a whole and relevant parameters,and determine the corresponding parameter range in the model.After modeling,under the action of different earthquake accelerations,the displacement and dynamic time-history responses of the internal structure of deep foundation pit,including the surrounding buildings,were compared and studied to determine the impact of ground motion on deep foundation pit and surrounding buildings.(4)Analyze the factors that affect the seismic performance of deep foundation pit,verify the influence on deep foundation pit engineering from the basic parameters of the excavation part of the soil,and optimize the influencing factors accordingly.(5)After the improvement of the construction measures of deep foundation pit engineering,each system is analyzed to study the adverse effects on the structure in the process of foundation pit optimization.By comparing with the foundation pit before optimization,the supporting system of deep foundation pit and the displacement of surrounding buildings are summarized and effective seismic measures are proposed.