DEM ANALYSIS ON STABILITY OF UNSUPPORTED TUNNELS IN JOINTED ROCK MASSES AT DIFFERENT DEPTHS
节理裂隙岩体中不同埋深无支护暗挖隧洞稳定性的离散元法数值分析

The stability of unsupported tunnels in jointed rock masses at different depths is analyzed using the distinct element method. The analysis of an autobahn tunnel shows that the unsupported shallow tunnels (for example,at a 5 m depth) are not as stable as those at a larger depth (for example,at 50 m) if the joints are steep and there exist more joint sets,and vice versa. The pressure-arch effect on the stability of jointed rock mass surrounding a shallow tunnel proves to be important.