ABSTRACT
In recent years, with the increase of tunnel construction, the problems existed in the construction of tunnel with soft surrounding rock are getting more and more tricky. The soft surrounding rocks which have poor engineering properties can be easily influenced by excavation disturbance which could lead to obvious deformation. Though many studies are focusing on the failure mechanism of soft surrounding rock and its control measures, there is yet no consensus. In this thesis, according to strength reduction theory, combined with displacement mutation and plastic strain energy mutation, a judging method for stability of tunnel face has been developed by using safety factor as a criterion. Then, the pre-reinforcement measures against instability have been categorized. The stability of tunnel face has been studied under different pre-reinforcement conditions by using safety factor as a criterion. At last, suggestions for pre-reinforcement have been given.
