Model tests on longitudinal surface settlement caused by shield tunnelling in sandy soil

The prediction of longitudinal surface settlement caused by shield tunnel construction is a concerning problem. However, despite the increasing concern on it, most existing prediction methods either assume that surface settlement is evenly distributed over the longitudinal direction of the tunnel or the soil affected by tunneling is in a homogeneous, incompressible or undrained state, which is not true in reality. This paper describes results from a series of model tests (conducted at 1g) carried out in sandy soil. In these tests, the effects of tunnel depth and ground volume loss on the longitudinal surface settlement caused by tunnel construction are demonstrated. Based on the Gaussian curve, an equation is developed to predict the distribution of the final longitudinal surface settlement caused by tunnelling.