Research On Failure Process Of Tunnel In The Complicated Geological Condition

Along with the rapid of development of highway construction and transportation infrastructure construction in China, tunnels and underground space development prospects have also been continuously expanded. Due to the increasing number of highway tunnel construction, many harmful geological conditions appeared. Different geological structures, for example, faults, joints, cracks, weak intercalated layers, etc, which are widespread in rock mass. It often makes mechanics features of rock mass complex. In rock mass, deformation of the rock mass present much fracturing and failure phenomena which have different mechanical features. In China and abroad, NATM(new Austrian tunnel method) is as a important method of structure design and construction, along with it has been successful applied and spread in the tunnel engineering. The supporting structure of tunnel surrounding rock is endowed new supporting ideas. But due to complexity of tunnel environment, it is difficult for people to realize clearly rock mass of stress state in the process of NATM, and stability changes of tunnel surrounding rock in a long time.In this paper, the tunnel from Pengshui to Wuhang of the expressway from Chongqing to Changsha, was selected as the engineering background. To understand the deformation degree, the causes, trends, and the final state, timely and effective measures should be taken. The process of NATM construction was simulated by RFPA(Realistic Failure Process Analysis). Strength reduction method and finite element method was applied to simulate the whole process of the gradual failure. And the safety coefficient was calculated. Rock material heterogeneity parameters are introduced into the calculating unit in RFPA. Elastic modulus and strength parameter of each element obey some kind of distribution, which can better simulate complex geological conditions. The RFPA results demonstrate that the condition of the Surrounding rock stress redistribution after supporting by NATM construction. The changes of rock mass stress are displayed visually.To study the failure process and long-term stability of the tunnel surrounding rock, the stability of the tunnel surrounding rock is quantitatively analyzed in different geological conditions by strength reduction method. Their failure process were gat. It is directive and helpful to tunnel design and construction in different geological conditions.