Study On Safety Impact Of Deep Foundation Pit Excavation On Environment And Adjacent Tunnel And Control Measures

With the development of urbanization,there are more and more problems brought by the renewal and reconstruction of old cities,and there are more and more security risks brought by the construction of infrastructure projects in the old city.Therefore,this paper studies the characteristics and prevention and control techniques of the safety impact of deep foundation pit excavation on the surrounding environment and adjacent tunnels during the renewal and reconstruction of the old city,and mainly explores the optimization design of deep foundation pit support scheme and environmental safety prevention and control measures.The main research contents are as follows:(1)According to the characteristics of deep foundation pit and surrounding environment,according to the engineering geological exploration data,three different support schemes of underground diaphragm wall,pile-anchor structure and underground diaphragm wall combined support and soil nailing support are researched and designed,and the support schemes are analyzed by numerical simulation respectively.Then the evolution characteristics of stress field and displacement field and their influence attributes are compared and analyzed to distinguish the safety of foundation pit,surrounding environment and adjacent tunnel.Then through the cost analysis of the support scheme to determine the final optimal design scheme.(2)The excavation of deep foundation pit leads to the unbalance of horizontal confinement stress in the stratum and causes the movement and deformation of surrounding rock.Through systematic simulation,the influence characteristics of deep foundation pit excavation on adjacent tunnels and the change characteristics of surrounding rock stress and displacement were studied,the influence mechanism of different excavation depths on tunnel structure safety was revealed,and the influence zone map was established.This paper studies the superposition characteristics of tunnel surrounding rock affected by deep foundation pit excavation and tunnel balance arching effect,analyzes the stretching or squeezing action of tunnel surrounding rock and the deformation law of surrounding rock,and determines the area of stretching failure and squeezing failure of the left side wall of tunnel,which provides the basis for its safety reinforcement.(3)Three kinds of tunnel reinforcement schemes are designed for local deformation overrun and structural insecurity,and numerical simulation analysis is carried out respectively.The evolution characteristics and influence attributes of stress field and displacement field of reinforcement schemes are numerically analyzed to identify the safety of tunnels.Then through the comparison and analysis of the reinforcement effect of each scheme,the optimization design of the reinforcement scheme is determined.