Large-scale tests on face stability of shield tunnelling in dry cohesionless soil

The shield technology has been widely used in underground construction. The face stability is the key problem in the shield tunneling. Large-scale model tests on the face stability of tunnels with the ratios of tunnel depth to diameter C/D = 0.5，1.0 and 2.0 are conducted in the dry sand. The influence of C/D on the ultimate support pressure and the settlement of ground surface are obtained. The support pressure decreases sharply with the increase of the face displacement. However, the settlement of the ground surface is not sensitive to the support pressure before the residual support pressure. Both the support pressure and the ground settlement are essential to the monitoring of the face stability in the shield tunnelling.