The Change in Dynamic Response Distribution of Double-Track Tunnel Structure Caused by Adding Middle Partition Wall

Adding a middle partition wall is an effective method to prevent the interaction between the upper and lower subway lines in a double-track tunnel, and the subsequent change in the dynamic response of the tunnel structure caused by adding a middle partition wall has drawn attention. We analyzed the displacement and acceleration responses of the upper part (zone A), the lower part (zone B), the tunnel bed and the surrounding connecting part (zone C) of the double-track tunnel by establishing a two-dimensional finite element model of the double-track tunnel and soil with and without a middle partition wall. The numerical results demonstrate that the addition of the middle partition wall improves the displacement and acceleration response distribution of the double-track tunnel structure. Compared with single-train traffic, the addition of the middle partition wall brings more obvious changes to the dynamic response of the double-track tunnel during double-train traffic. The maximum displacement response decreases from 5.881 mm to 5.335 mm, and the maximum acceleration response decreases from 18.51 m/s(2) to 16.62 m/s(2). The displacement response value in the upper part increases from 1.0 mm to 1.5 mm, the acceleration response value increases from 3.0 m/s(2) to 4.6 m/s(2), the displacement response value in the tunnel bed and the surrounding connecting part decreases from 5.0 mm to 3.0 mm, and the acceleration response value in the tunnel bed and the surrounding connecting part decreases from 18.0 m/s(2) to 10.0 m/s(2). There is no obvious change in the lower part. During double-train traffic, after adding the middle partition wall, the horizontal displacement and horizontal acceleration response values of the double-track tunnel structure decrease by about 30% to 45%; the vertical displacement response value of the connection between the middle partition wall and the lining increases from 1.337 mm to 1.774 mm, an increase of 32.7%, and the vertical acceleration of the lower half of the tunnel lining is partially transferred to the upper half. The response values of horizontal displacement and acceleration in the middle part of the middle partition wall are the largest, at 1.6 mm and 6.0 m/s(2), while the response values of vertical displacement and acceleration in the bottom of the partition wall are the largest, at 3.3 mm and 9.0 m/s(2). The research results provide a reference for the structural design of middle partition walls to ensure the safety and stability of trains running in double-track tunnels.