Research On Tunnel Lining Damage And Crack Induced By Fault Creep And Anti-breaking Measure Of Flexible Connector

As a kind of geological structure, fault is widely distributed in Western China. In recent years, problems cause by fault is more and more often encountered during the construction because of the massive tunnel projects in western mountainous regions. The permanent deformation caused by creep and dislocation of fault can easily do harm to the tunnel structure, making structure crack or even worse damage. In view of this, based on the former studies, this paper chooses the Gaoligongshan tunnel, which crosses a large amount of faults, to be the background, and builds a three-dimensional FEM model for "surrounding rock, fault fracture zone and the tunnel’s dislocation and creep of fault" by using the non-linear finite element method. Based on the basic principles of extended finite element method, this model can be used to study the mechanical behavior of lining cracking in different situation of fault movement, such as different fault slip distance and different fault dip angle. Meanwhile, unter the condition of certain dip angle and fault distance, tunnel structures are built by connecting different length lining segments through flexible connectors in the same situation of Gaoligongshan tunnel. Then the thesis analyzes the impact of the damage and crack of the tunnel lining structure by using this method, and evaluates the effect of this anti-faulting measures.Based on the analysis above, this paper obtained the following conclusions:(1) Fault dislocation distance and dip angle affect the crossing tunnel lining a lot. The impacts include the stress, displacement, cracking degree, crack length, crack aperture and so on,which are measured on different longitudinal location or different locations of a same section.(2) Flexible connectors can significantly enhance the ability of anti-faulting for tunnel. Within a certain length, reducing the length of the tunnel segments can evidently improve the stress distribution and amplitude, and can absorb the displacement of the tunnel structure, and can also reduce the energy of the local accumulation of dislocations and cracking in tunnel lining, which greatly reduce the length and the aperture of crack, and can even make the crack localized and decentralized.(3) Flexible connectors can significantly reduce the damage caused by the dislocation and creep of fault. Tunnel Connected by flexible connectors can reduce the area and degree of the damage, localizing and decentralizing the damage in lining structure. By using the method, the tunnel lining could stay away from penetrating damage, and reduce the possibility of forming the locally weakened area and even crack.