Effects of the ring-cut excavation method on the restraint of displacements ahead of a tunnel face

In order to clarify the effects of the ring-cut excavation method on the restraint of ground displacements and on the increase in tunnel face stability, centrifugal model experiments and 3-D elasto-plastic finite element analyses are conducted. A robot, which is controlled by computer programs, is employed to excavate the ground arbitrarily in three dimensions under a centrifugal loading state. The displacements in the ground ahead of the face and the stability of the face are compared using two methods, namely, the full-face excavation method and the ring-cut excavation method, and the quantitative effects of the ring-cut excavation method are described.