Numerical analysis to better understand the mechanism of the effects of ground supports and reinforcements on the stability of tunnels using the distinct element method

In order to understand the mechanism of the effects of ground supports and reinforcements on tunnel stability, numerical simulations are conducted using the distinct element method. Four cases of simulations are carried out in this paper for tunnels excavated in a sandy ground to investigate the effects of (1) dowels and a lining on a single tunnel, (2) dowels and a lining on two parallel tunnels, (3) forepoling and face bolts on a single tunnel face, and (4) forepoling and face bolts on two tunnels which face each other. It is found that the use of ground supports causes a discontinuous ground to behave as a continuous one. In addition, it is revealed that supports help to form ground arches in the sandy ground. Detailed discussions are given considering the stress paths and the stress distributions.