Abstract
A novel small-scale model was proposed to investigate the mechanical behaviour of the full-scale shield tunnels. Because it used a fine-aggregate grout material, the dimensions of the model can be significantly scaled down, therefore, showed cost advantages. Although small, the most structural features of a practical shield tunnel, such as bolts and steel reinforcements, were retained in the model. Utilizing self-designed casting moulds, the model tunnel can be manufactured with high accuracy. Benchmark loading tests were conducted to test the performance of proposed model. Basically, both the deformation and the failure of the model tunnel showed good agreements with those in the full-scale experiment. Complex loading tests were then carried out to investigate the response of a shield tunnel under the effect of both unilateral unloading and soil arching. The results showed that horizontal unloading can be much more adverse and deserved special attention when compared with vertical unloading for a shield tunnel as it usually first exhibits a horizontal ovalling deformation after construction due to overburden pressure.