Study On The Influence And Control Measures Of Adjacent Pit Engineering On The Construction Of The Existing Subway In The Soft Soil Area

At present,the scale of urban metro network construction is getting larger and larger.From the initial single lane to gradual cross-networking,the setting of interchange stations is more and more intensive and the surrounding environment is more and more complicated.Due to the complexity of the underground space structure,the new underground project brings great potential safety hazard to the neighboring subway tunnels and stations,which also makes it very necessary to newly build or renovate the subway next to the subway.The difficulty of underground engineering and control standards change.In soft soil area,studying the influence of foundation pit excavation on adjacent subway tunnel and adopting targeted subway protection and prevention measures are of great significance for the long-term safe operation of subway.In this paper through the analysis of adjacent foundation pit engineering construction effect on the already built subway,sums up the construction of similar rail transit facilities affect prevention measures,based on the orbit transportation structure characteristics and characteristics of soft soil mass and FLAC3 D analysis is used to calculate the subway lining displacement deformation under excavation and precipitation.According to the design of soil grouting reinforcement scheme,the stability of tunnel lining is analyzed.The main conclusions are as follows:1?The analysis shows that under the condition soil parameters,as the shield tunnel is located below the excavation depth of the foundation pit,therefore,the foundation pit excavation has little effect on the settlement deformation of the subway lining,but it has a great influence on the horizontal displacement of the subway lining.At the same time,the influence of a large-scale precipitation project in the pit after the excavation work of the precipitation pit to the settlement and deformation of the subway lining is very significant.The results of the numerical analysis show that the size of the displacement and deformation of the subway lining is inversely proportional to the distance between the subway lining and the edge of the foundation pit.According to the design scheme of grouting reinforcement,the grouting in the bottom of subway lining makes the lining rise upwards,and the grouting reinforcing measures play a certain role in rectifying the deviation.The stability analysis of the lining shows that the stress in the lining is still in the bearing capacity of the lining concrete under the design of grouting pressure,and the stability of subway lining can be ensured.2?Based on the analysis of the impact of excavation on the subway,the concrete control measures are summarized as follows:(1)applies to the soil pressure calculation model of subway facilities on one side of the foundation pit engineering,the engineering prospecting indicators as well as the corresponding adjacent excavation engineering with different levels of rail transit deformation control the minimum synthetical stiffness requirements.(2)based on the technical measures to control the deformation of foundation pit retaining structure design,including the whole process of construction of foundation pit retaining structure stiffness to strengthen measures,reinforcement measures for the typical passive area,the water reduction measure of the typical silty soil foundation,considering the effect of excavation space and time in installment retaining design measures.(3)based on the technical measures to control the deformation of tunnel facilities design,including the isolation pile of blocking sideloading transfer specific control measures,construction load,according to different unloading engineering construction activities of groundwater control measures rainfall.