Centrifugal Modeling of the Relationship between Tunnel Face Support Pressure and Ground Deformation in Water-Rich Sandy Soil

To investigate the ground deformation induced by the variation of excess/insufficient support pressure in water-rich sandy soil, a series of centrifuge tests in tunnels located at cover over diameter (C/D) ratios equal to 0.5, 1.0 and 1.5 were carried out. The soil pressure, pore pressure, maximum surface displacement and the ground movement induced by reduced/increased support pressure were investigated. The results show that when the burial depth is large (>= 1.5 D), the ground deformation caused by the support pressure is difficult to extend to the surface. When the burial depth is shallow (<1.5 D), the ground disturbance range induced by excess support pressure is approximately fishtail-shaped while it is approximately chimney-shaped induced by insufficient support pressure. For the former, the surface disturbance range can extend horizontally to about twice the buried depth beyond the front of the face and the maximum heave occurred at a distance of approximately buried depth beyond the front of the excavation face. For the latter, the surface disturbance range can extend horizontally to about buried depth beyond the front of the face which was larger than that in dry sandy soil. Based on the centrifuge test, the ground deformation mechanism was analyzed compared with previous studies and a supporting pressure control coefficient was proposed to conduct quantitative analysis of surface displacement induced by support pressure. Finally, the control of support pressure based on the surface displacement was discussed to provide some advice for practical engineering.