Analysis Of Deformation Effect And Prevention Measures Of Shield Tunneling Underpass Existing Buildings

In recent years,with the rapid development of urban underground rail transit in China,shield tunneling has become the main method of subway tunnel excavation and construction relying on its own advantages.Due to the unavoidable disturbance of surrounding soil during the excavation of tunnels through buildings,the safety performance of existing buildings will be affected.Therefore,it is of great significance to study the influence of shield tunnel construction on the surface and existing buildings.Based on the background of Hefei Metro Line 3 from No.3 to Xinhai Avenue Station,this paper conducts a research on the following aspects:(1)Several special points of monitoring section and monitoring data of on-site settlement of No.3 commercial building in Yuanshangyuan District were analyzed.The analysis results show that the settlement deformation rate starts to accelerate when the shield excavation surface reaches the measuring point,and the settlement rate is the largest in the shield tail detachment stage,and then slows down obviously.(2)Using MIDAS/GTS numerical simulation software,a three-dimensional numerical model of the project is established.,and the effects of different building heights and excavation sequence were studied.Through the model calculation,the following conclusions are drawn:when the left line is excavated,the ground subsidence decreases gradually with the increase of the distance centered on the tunnel axis;after the right line is excavated,the maximum subsidence is located on the left side above the right tunnel;when the two lines are excavated at the same time,the soil deformation between the two lines is the largest,and the degree of deformation is greater than that of sequential excavation;at the same time,the settlement of existing buildings is closely related to the height of the building.In addition,there are some differences between simulation data and monitoring data,but the deformation law curves obtained by the two methods are highly similar.Therefore,the establishment of three-dimensional numerical model for actual engineering deformation prediction is relatively accurate and reliable,which can provide reference for engineering.(3)Based on the collection of relevant information,the deformation control technology is analyzed according to the deformation characteristics,and the following conclusions are drawn:in actual construction,special attention should be paid to controlling the parameters of propulsion pressure and speed,excavation quantity,segment assembly quality,grouting quantity and grouting pressure,and passive measures should be taken when necessary to ensure the safety of construction.Figure 42 Table 16 Reference 50...