The Study On Damage And Failure Numerical Simulation Method For The Tunnel Surrounding Rockmass During Excavation

The deformation, failure and stability of weak broken tunnel's surrounding rockmass during excavation are concerded by a lot of designers,constructors and scholars. A great many of tunnel engineerings show that the process of surrounding rockmass's failure and instability is the process of rock's progressive failure and damage over time under excavating load. So in this paper the regulations of surrounding rock's damage evolution and progressive failure during tunnel's excavating are studyed. The results could provide usefull guiding views for tunnel construction.(1) Firstly, combine the tunnel surrounding rock's failure characteristics, to wit rock's complete stress-strain relationship; discuss the energy conversion relationship of rock; and establish rock's damage and failure evolution equations. According to rock's bilinear strain-softening stress-strain constitutive relation, rock's micro-elements damage and failure criterion is established based on strain energy density theory.(2) On the basics of the theory in the above, develop rock's two-dimensional damage and failure calculation program by the FISH language in the FLAC. And the program is applied to the damage and failure simulation of Brazilian splitting and tensile test with cracks by static load-controled mode. Then on the basics of two-dimension, develop rock's three-dimensional damage and failure calculation program by FLAC3D. Then the three-dimensional damage and failure numerical simulation of Brazilian splitting is carried out by dynamic velocity loading mode. The simulation results indicate that the damage model and caculation program is correct and feasible.(3) The rock's three-dimensional damage and failure calculation program is used to simulate the tunnel over-loading test of the geomechanical model. The progressive damage and failure evolution characteristics of tunnel surrounding rockmass during loading are analyzed. The results show that the damage and failure model is feasible to simulate the tunnel surrounding rock's damage and failure process.(4) Lastly, based on the Liangshui tunnel, the developed rock damage and failure model is used to have the three-dimensional damage and failure numerical simulation of five-grade rock mass's whole section excavation and steps method excavation. Then this paper studies the tunnel surrounding rockmass's damage and failure space-time evolution characteristics under the two methods during tunnel excavation. The analytical results could provide usefull guiding views for engineering construction.