The Mechanism Of Local Failure And Instability And Finite Deformation Analysis Of Surrounding Rock In Deep Tunnel

With the increasing demand for minerals,energy and transportation,deep underground engineering is the inevitable trend of future development,and often presents the characteristics of large-scale and deep burial.For deep underground tunnels,disasters caused by excavation are more and more frequent.The failure phenomena such as large deformation around the surrounding rock,sidewall lose stability,collapse and others are quite different from the shallow situation,and sometimes may even cause rockburst.These disasters seriously threaten the safety of life and property during the construction of underground engineering,put forward higher requirements and greater challenges to the safety and stability of underground tunnels.In order to give a detail interpret for local failure and instability of deep tunnels under high stress environment,different from the traditional methods which based on the small deformation analysis,in this research,by inserting the finite deformation theory to the realistic failure process analysis software RFPA 2D,a new analysis method is establish,the corresponding research contents can be divided into the following aspects:(1)Based on finite deformation theory,the relevant calculation procedure is prepared,and is combined with the RFPA software which considers the progressive failure analysis of rock mass,the correctness of the program is verified by several numerical examples(2)Based on the failure and instability phenomenon of straight wall and circular wall in deep hard rock tunnel under high geo-stress,the small deformation analysis(SDA)method and finite deformation analysis(FDA)method are used.The failure process at laboratory scale and engineering scale in hard rock with numerical uniaxial compression test is simulated.The results show that in the straight wall tunnel,when the strength of rock mass is relatively low,the ultimate failure of the rock is controlled by the failure of the material.With the increase of strength,the instability effect of the structure becomes more and more significant,and it is the structural instability that leads to the ultimate failure.In the circle tunnel,although the failure is mainly caused by stress induction,it is not accurate to ignore the failure analysis of structural instability.The failure of the material will lead to the instability of the structure,in turn,the instability of structure will also lead to the failure of the material.(3)The local failure and instability of engineering scale deep hard-rock straight wall tunnel is studied.The whole process of tunnel deformation,failure and instability is reproduced.The acoustic emission rule is summarized,and the corresponding mechanical mechanism is revealed.The results show that in the deep hard rock tunnel,based on the finite deformation analysis,the suddenness and abruption of failure can be well captured,the prediction using small deformation analysis without considering the structural instability may be not accurate.