Abstract
The authors had carried out some kinds of trapdoor experiments and had discussed the mechanical behavior of a tunnel excavation. Moreover, they had developed a three-dimensional trapdoor tester and had performed tests with it. Based on the knowledge and issues in their past research works, the authors improve their three-dimensional trapdoor tester, and both single and multiple trapdoor experiments are conducted in this paper. In multiple trapdoor experiments, which are proposed for use in the excavation of tunnels, it can be confirmed that the process of lowering trapdoors, that is, the excavating process, strongly affects the distributions of earth pressure and ground surface settlement. When lowering trapdoors, deformation occurs in the direction of the loosened area because a loosened zone has already appeared due to the lowering of the previous trapdoor. Therefore, an unbalanced distribution of earth pressures can be found.
