Analysis Of Stability Of Deep Foundation Pit Excavation Support In Karst Areas And Deformation Response Of Surrounding Buildings

Taking the deep foundation pit project of a station on Dalian Metro Line 5 as the research background,monitoring data analysis and ABAQUS numerical simulation methods were used to study the stability of deep foundation pit excavation support and the deformation response of surrounding buildings in karst areas.The focus was on the influence of different parameters and location of karst caves on the deformation of foundation pit support,as well as the sensitivity analysis of factors affecting the deformation response of surrounding buildings during foundation pit excavation.The main work and conclusions of the paper are as follows:1.Using ABAQUS software to establish a three-dimensional model for step-by-step precipitation excavation of foundation pits for simulation analysis,it was found that the variation trend of numerical simulation results was roughly the same as the monitoring data through comparison between actual measurement and simulation results,verifying the rationality of the model.During the excavation process of the foundation pit,due to unloading,a mid high side low protrusion will form at the bottom of the foundation pit,and a groove shaped settlement zone will be formed on the surface within 20 m from the edge of the foundation pit around the foundation pit.In the foundation pit engineering,monitoring of the displacement at the bottom of the foundation pit and the surrounding ground settlement should be strengthened.2.Taking the passive zone karst cave as an example,the influence of the section width,section height,horizontal distance from the surrounding pile,and burial depth of the karst cave on the support structure was studied by controlling a single variable method.The influence of the active zone,transition zone,and passive zone karst caves on the support structure was analyzed.The results showed that the influence of karst caves in different regions on the surrounding pile was different,and the displacement of the surrounding pile was the most affected when the karst cave was in the passive zone,The impact of the transition zone and the active zone decreases sequentially.3.A numerical calculation model was established for the interaction between deep excavation and surrounding buildings.By controlling a single variable method,the effects of excavation depth,distance between buildings and excavation,stiffness of building foundations,and burial depth of building foundations on the deformation response of buildings were studied,And quantitatively describe and compare the sensitivity of various factors to the maximum settlement value and uneven settlement value of surrounding building foundations during foundation pit excavation using grey correlation analysis method.In summary,a comprehensive analysis and evaluation were conducted on the stability of deep foundation pit excavation support in karst areas and the deformation response of surrounding buildings.The research results provide reference for the design and construction of similar projects in the future.