Analysis On The Influence Of Pile Foundation Construction On Disturbance Of Adjacent Subway Tunnel

With the continuous development of China’s rail transit,the subway,as a new product of urban traffic,often has other structures around the subway construction,structures to ensure their own stability,often need to carry out pile foundation construction.When the stress wave generated by pile foundation construction is too large,it will cause stress failure and other effects on the adjacent subway tunnel,which is a certain threat to the safety of the tunnel,so it is of great practical significance to study the influence of stress wave on the unfavorable disturbance of the adjacent subway tunnel.Based on the piling project of a wharf near the subway in the soft soil area,a "homogeneous soil-pile-tunnel" was established by numerical simulation.A three-dimensional numerical model of "actual soil-pile-tunnel" is used to analyze the dynamic response of stress wave to adjacent tunnel by LS-DYNA calculation.The details are as follows:(1)Based on the interaction theory of "soil-structure ",the wave propagation of elastic shock wave in " pile-soil-tunnel " model is studied.(2)Based on a layer of soil in a wharf project,a numerical model of "homogeneous soil-pile-tunnel" was established to study the influence of different distance,depth and energy piling on the disturbance of adjacent tunnels.The results show that the farther the horizontal distance from the tunnel,the less the influence of stress wave on the tunnel disturbance.The deeper the piling depth,the influence of stress wave on the disturbance near the upper right side of the tunnel pile increases first and then decreases.The greater the piling energy,the more obvious the disturbance to the tunnel.At the same time,the vibration velocity curve of the most unfavorable vibration position of tunnel section under different piling parameters and the unfavorable vibration and stress concentration area of tunnel are obtained.(3)Taking a wharf piling project as an example,the numerical model of "actual soil-pile-tunnel" is established to study the influence of pile foundation construction on adjacent tunnel disturbance in the presence of different distance,depth,energy and different angle joints,and the influence of pile foundation construction and train load coupling on adjacent tunnel disturbance is also studied.The results show that the farther the tunnel is piling,the less the disturbance is caused by the stress wave.The deeper the piling depth,the more the stress wave increases and then decreases the disturbance to the upper right side of the tunnel.the greater the piling energy,the more obvious the disturbance to the tunnel.The greater the dip angle of the joint,the smaller the disturbance to the tunnel after the stress wave passes through the joint.Pile foundation construction and train load.The most unfavorabledisturbance to the tunnel is concentrated on the lower right side of the tunnel.At the same time,the vibration velocity curve of the most unfavorable vibration position of tunnel section under different piling parameters and the unfavorable vibration and stress concentration area of tunnel are obtained.(4)Based on the numerical simulation results,it is concluded that the critical value of tunnel safety vibration velocity is 5.6 cm/s,which provides a reference for the influence of maximum vibration velocity on tunnel safety.In view of the unfavorable vibration and stress concentration area of the tunnel,the numerical simulation results show that it has important application value for daily monitoring and maintenance of subway and construction safety of engineering construction.