Study on influence characteristics of shield tunnel depth and spacing on settlement in clay strata

Abstract

The surrounding ground disturbance and surface settlement induced by shield construction are the key problems of tunnelling control and necessary to be studied. Taking the shield tunnel project of Beijing Subway Line 14 as the research background, this paper studies the influence of tunnel spacing and depth on surface settlement distribution by numerical simulation method, and analyzes the relationship between the two factors and maximum settlement. The results indicate that the increase of tunnel depth or tunnel spacing leads to the decrease of the maximum settlement and the settlement reduction rate increases. With the increase of tunnel depth, the settlement trough presents approximately symmetrical distribution, and the symmetry axis is inclined to the first tunnel. With the increase of tunnel spacing, the superposition effect of twin tunnel excavation decreases, and the settlement trough transits from U-shaped to W-shaped with the maximum settlement decreasing relatively from single peak to double peaks. Also, the tunnel depth or spacing is highly correlated with the maximum settlement in a certain range, and the tunnel depth has a stronger linear correlation than the tunnel spacing. The research results provide certain theoretical guidance and references for the prediction of ground deformation and settlement control of shield construction.