ABSTRACT
A new method of tunnel construction is employed which minimizes the underground space required in densely populated areas. Using a smaller size of tunnel boring machine, ground can be bored to create one-by-one small-size tunnel as the outer perimeter of a large cross sectional tunnel. However, little is known about ground response due to these multi-excavation stages. The objectives of this study are to investigate the earth pressure changes on each smaller tunnel and displacement within the ground throughout the multi-excavation stages. The tunneling method is simulated by a physical modeling of two-dimensional trap door tests. The results suggest a new approach for predicting them when a large tunnel should be constructed by this technique. In this paper the simple method of a plotted graph is described in order to introduce for a practical use.
