Research On Safety Control Technology For Existing Structures Adjacent To Open Excavated Foundation-pit In Mix Ground

With the rapid growth of urbanization rate and motorization rate,the city faces more and more traffic pressure.At present,many domestic cities have chosen to build subway to solve the problem of urban traffic congestion.Due to the dense population of the city,and buildings,bridges and tunnels are densely constructed,the construction of subway stations in the city will inevitably close to buildings,bridges and other structures.In order to protect the surrounding structures,it put forward higher requirements for the subway station construction technology.Road surface collapse,housing collapse and other accidents have occurred due to improper construction of the foundation-pit.Therefore,it is very meaningful to study the safety control technology for existing structures adjacent to urban subway station construction.In this paper,combined with the open excavated foundation-pit engineering in Shenzhen Metro Line 9,launched the following research:?1?Through the site investigation,the characteristics of the mix ground in Shenzhen Metro Line 9 are clarified,and the surface subsidence caused by the excavation of the foundation-pit in mix ground is summarized.Based on the stochastic medium theory,the method of ground subsidence prediction caused by excavation of the foundation-pit in mix ground is put forward,and the applicability of the prediction method in mix ground is verified.?2?Based on the characteristics of the surrounding environment of the open excavated foundation-pit in Shenzhen Metro Line 9,using the finite difference software FLAC^3D to analyze the influence of foundation-pit excavation on the surrounding structures under different factors,and gave the main influencing factors.?3?Based on the main influencing factors of foundation-pit excavation on the surrounding structures,this paper put forward the criteria and methods of construction impact partition,gave the influence zones of construction of open excavated foundation pit adjacent to surrounding structures,and gave the critical soil thickness which causes the appearance of the strong influence zone.?4?Through the investigation,this paper put forward the safety control measures of the foundation-pit construction adjacent to surrounding structures in different influence zones;Through numerical simulation by FLAC^3D,discussed the reinforcement effect of the sleeve valve barrel grouting and chemical churning pile strengthening for structures,and gave the recommended value of relevant construction parameters based on current conditions.