Numerical Simulation Study On Surrounding Rock Deformation Induced By Excavation Unloading In Deep Buried Circular Tunnel

With the rapid development of social economy in our country,the shortage of resources and the deterioration of the environment are serious,so the underground space is widely used.And the size and depth of underground tunnel are increasing.However,in the process of deep rock excavation,the project is seriously affected by the surrounding rock damage and rock burst.In order to solve these problems,study on excavation unloading effect of rock mass is the focus of research,especially the influence of transient unloading process on surrounding rock during drilling and blasting.In this paper,a circular cavity is taken as an example.According to the excavation unloading effect of deep underground rock mass,based on the theory of elastic dynamics,the model of crustal stress transient unloading in the excavation of circular cavern is established by finite difference software.The research on the dynamic disturbance effect of the transient unloading process on the surrounding rock is carried out,and damage range of surrounding rock is determined.By comparing and analyzing the influence of different conditions,measures to reduce the damage of surrounding rock and prevent rock burst are proposed.In this paper,the following aspects of the work:1.On the theoretical basis of mechanical model of circular cavern excavation unloading,program for transient unloading of in-situ stress in cavern excavation is written using FLAC3 D software,simultaneously stress release method is applied.Then the model is built for simulation analysis.2.Correctness of simulation program is verified,and the analysis of dynamic effect of surrounding rock is carried out under the given conditions.The analysis includes the variation of stress,displacement and velocity of surrounding rock with time.At the same time,the damage range of surrounding rock is determined by Griffith strength criterion.3.By changing Influence factors of transient unloading process of in-situ stress,the dynamic effect of surrounding rock under different conditions is analyzed.According to the different influence conditions,based on the transient unloading,measures to reduce the damage of surrounding rock and prevent rock burst are proposed.