Abstract
In order to study the ground movement due to tunnelling at shallow depth, a series of laboratory model tests and numerical analyses were performed. On the basis of the results of the trap door experiments, the fundamental properties of rupture surface lines and the maximum ground surface subsidence were discussed.
X-ray radiographs of the deformation of sand during the cave-in of a trap door, showed a discontinuous internal surface having low sand density. The slip-line fields calculated by using the Kötter's method showed the failure zone in the upper ground of a trap door model.
