Analysis Of The Influence Of Jinan Shield Tunnel Construction On The Settlement Of Adjacent Building Foundations

With the continuous development of urban underground space in China,shield method has gradually become the mainstream of urban subway construction because of its strong adaptability,fast speed and high security.In the process of shield excavation of metro tunnel,it will inevitably produce certain disturbance to surrounding rock,which leads to the deformation of the stratum and the uplift or settlement of the surface.And then affect the adjacent buildings.The subway construction in Jinan area started late,and due to the special geological conditions in Jinan metro tunnel engineering area,there are few researches on the subway tunnel construction.This paper takes the double shield tunneling of R2 and M3 lines crossing an existing frame structure in Jinan as engineering background and makes different dimensions ANSYS numerical analysis of adjacent buildings ground settlement caused by shield tunneling construction.It explores the empirical formula of the specific disturbance influence range,find out the most unfavorable position in the process of shield dynamic excavation and reasonably determine the influence scope,finally providing a theoretical basis for the detection and reinforcement of buildings.From the results of ANSYS analysis,it can be seen that:(1)under the two buried depths of R2 and M3 line tunnels,ground settlement difference between adjacent pillarsat the far and near end of a building increases first and then decreases with the increase of the horizontal distance between the center line of the tunnel and building.(2)when the depth of tunnel is fixed,under the condition of large and small net distance,the influence range of ground settlement and the difference of ground settlement between adjacent pillars are significant.(3)the empirical formulas and limit values of the disturbance influence range of the shield tunneling on the R2 and M3 lines in Jinan City are basically in agreement with the numerical simulation results.(4)The settlement of the foundation perpendicular to the excavation to the building increases gradually with the excavation of the left and right tunnels until it is stable.The settlement channel of the left tunnel foundation is almost normal distribution;the settlement channel of the right tunnel foundation is bimodal distribution.The settlement of the foundation parallel to the excavation to the building appears small range ofuplift at the beginning of double tunnel excavation.With the shield excavation,the maximum settlement of the foundation gradually deepens until it is stable.(5)After the left and right tunnels are connected,the settlement of each floor of the building perpendicular to the tunnel excavation direction decreases with the increase of the number of floors,and the settlement of each floor of the building reaches the maximum near one end of the tunnel and the center line of the right tunnel respectively.(6)The settlement difference between adjacent column bases of the far and near end increases first,then decrease until it is stable with the shield tunneling.The range of 30-42 m is excavated in the right tunnel,and the settlement difference between adjacent column bases of the far and near end is the largest,which is the most unfavorable range in the dynamic excavation process of shield.(7)Strictly controlling the shield posture,strengthening the upper structure and setting up diaphragm walls to isolate the shield tunnel from the adjacent existing buildings can effectively reduce the impact of shield excavation on the foundation settlement of adjacent buildings.