Some problems of tunneling system reliability are solved by using probability theory and system reliability analysis of engineering structures in light of characteristics of tunnel structure. The reliability of tunnel structural system contains reliability of lining sections

reliability of lining sections in various surrounding rock pressure. reliability of lining in the same surrounding rock sections and reliability of the whole tunnel. The whole tunnel can be regarded as a series system of the portals at two ends and lining sections rock condition in the tunnel. Damage to any section of lining or any one portal is regarded as damage to the whole system. Thereby

using the PNET method

the failure probability and reliability index can be obtained for the whole tunnel. Case calculation shows that the general reliability index of whole tunnel is lower than all single sections of structure.