The Study On Failure Zones And Arching Failure Of Circular Tunnels

Since the new century, with the rapid development of traffic infrastructure construction, a large number of tunnel engineering has been built. However, the accidents such as landslides, ground subsidence, cracking of supporting structures, which due to the instability of surrounding rock, have occurred frequently, which not only causes great damage to the tunnel construction safety, but also gave the researchers more and more difficult subjects. Based on the classical theory of stress, people have recognized that the surrounding rock has the ability to remain stable, and found the existence of arch effect. The researchers have conducted a great deal of research for it, but there is no clear and unified method can be found to discriminate the pressure arch body, and the study on the progressive destruction of the tunnel surrounding rock remains to be improved. Therefore, this article take a certain depth of circular tunnel as the research object, combine with analytical method and numerical simulation method, analysis the distribution of surrounding rock damage area and the progressive arching destruction of the tunnel surrounding rock, the main research results are as follows:(1) By using elastic-plastic knowledge we can derive the analytic solution of circular tunnel surrounding rock damage area, and then I use matlab to analyze the impact of buried depth and lateral pressure coefficient on surrounding rock damage mode and failure partition. At last we can conclude the tunnel damage forms partitions for different buried depth and lateral pressure coefficient.(2) In view of the limitation of analytical method, the numerical simulation method based on the Mohr-Coulomb model was used to study the distribution of surrounding rock damage area, and to analyze the impact of buried depth, lateral pressure coefficient and surrounding rock mechanics parameters on it. It reveals the surrounding rock failure mode under different condition.(3) Using the numerical simulation method based on the strain-softening model to study the progressive failure mechanism of the circular tunnel surrounding rock. It is possible to describe the arching failure process of surrounding rock, and to discriminate the scope and boundary of caving arch body, which provides the theory basis for a certain depth of tunnel surrounding rock support design and construction.(4) By means of orthogonal experiment to study the sensitivity of the geometric parameters and mechanical parameters of tunnel influence on the arch height after tunnel excavation. According to the result, I select the parameters of friction, lateral pressure coefficient, cohesive, elasticity modulus to study their influence on the arching failure process of tunnel surrounding rock, and analyze the deformation and failure characteristics under different surrounding rock conditions, which has a good reference to the tunnel design and construction.