Abstract: In the construction of deep tunnel, stratified surrounding rock may crack at some conditions and further become bent, causing severe consequences if the bending deformation is large.The limit stress of conversion from stratified structure to slab-rent structure is derived by limit equilibrium analysis and used to distinguish the bending failure from material failure.Given the randomness of parameters, the state function model for the bending deformation of stratified surrounding rock is constructed and a stochastic FEM model is also constructed by Monte-Carlo method.The analysis of real cases indicates that the two methods have obtained basically the same calculation results and can both calculate the probability of different deformation amounts, giving more scientific results than common deterministic methods can, which can be a reference to other similar engineering study.

Key words: Deep tunnel, Stratified surrounding rock, Bending deformation, Stochastic FEM