Ground deformation behaviour induced by overlapped shield tunnelling considering vibration loads of subway train in sand

The tunnelling-induced ground deformation can be affected by the existing tunnel(s) in overlapped tunnels construction, especially when the existing tunnel is in operation. Therefore, the effect of subway train vibration loads on the ground movement induced by overlapped shield tunnelling is needed to further investigate. In this study, model tests and numerical simulations were conducted to investigate ground deformation caused by overlapped tunnelling while taking subway train vibration loads into account. The research results indicated that with increasing tunnel clearance, the settlement trough appeared to be a much steeper U-shape. At d/D = 0.5, the maximum ground settlement increased by 37.5% along the transverse section and 30.6% along the longitudinal section compared to the case of the vibration-free condition. As d/D increased from 0.5 to 1.0, the maximum value of ground settlement decreased by 34.1% along the transverse section and 31.25% along the longitudinal section. The ground lateral displacement appeared to be biconcave and flattened with increasing d/D. Based on the test results, a model was introduced to predict the ground settlement induced by overlapped tunnelling coupled with vibration loads in subway train. The findings in this study will help evaluate the ground deformation caused by overlapped tunnelling considering vibration loads of subway train in operation.