Evolution And Control Mechanism Of Rockburst Induced By TBM Excavation In Deep Mixed Ground Tunnel

With the development of TBM equipment and construction technology,TBM will become the inevitable trend of the transportation,water conservancy and resources mine deep tunnel construction in China.Rockburst has become one of the most serious problems in TBM construction of deep tunnel engineering.According to the special geological environment in deep,to study the mechanism and control of rockburst in deep TBM tunnel is of great theoretical and engineering significance.Motivated by the rockburst in the tunnel excavated by TBM,the evolution mechanism,control theory and technology of the rockburst induced by TBM excavation in deep mixed ground were investigated comprehensively by the combined method of laboratory test,theoretical analysis and numerical simulation.The main conclusions are as follows:(1)Mechanics experiments of rock in mixed ground under different experiment schemes had systematically been launched by using self-developed true triaxial rock mechanics test system.The deformation regularity,strength characteristics and failure modes of the different soft and hard rocks under true triaxial condition were obtained.The feature and spatial distribution of acoustic emission of different soft and hard rocks under true triaxial condition were analysed.And the mechanical properties and damage characteristics of different soft and hard rocks under deep complex stress state were revealed.(2)Based on the results of true triaxial rock mechanics test,considering the influence of plasticity and damage on mechanical properties of rock,the elastoplastic damage constitutive model of rocks based on Mogi-Coulomb criterion was established.And the corresponding incremental constitutive equation of this model was obtained.Based on the theory of plasticity potential,the formulas of difference calculation of the elastoplastic damage constitutive model were deduced detailedly.The secondary development of this model in FLAC3 D software was realized under VC++.Furtherly,the process and result of true triaxial rock mechanics test of different soft and hard rocks were verified by numerical simulation,and the simulation results were in good agreement with the experimental results.The simulation results show that the mechanical properties and deformation characteristics of rock in mixed ground can be described preferably by the elastoplastic damage constitutive model of rocks based on Mogi-Coulomb criterion.(3)Based on the structural feature of mixed ground and the characteristics of TBM excavation,the developed elastoplastic damage constitutive model was used to simulate the TBM tunnel excavation process.The two typical mixed ground of upper-hard lower-soft ground in vertical direction and soft and hard multilayer ground in horizontal direction were considered in numerical simulation.And The distribution and evolution of main stress,failure and energy of tunnel surrounding rock along with TBM excavation in deep mixed ground had been systematically investigated.The criterion for rockburst induced by TBM excavation in deep mixed ground tunnel was put forward,and the formation mechanism and evolution process of rockburst induced by TBM excavation in deep mixed ground tunnel were revealed.(4)According to the developed elastoplastic damage constitutive model,the control effect of different surrounding rock transformation methods on rockburst induced by TBM excavation in deep mixed ground tunnel were investigated systematically.What’s more,the related control parameters had been optimization analysed,and the rockburst control mechanism of TBM tunnel in deep mixed ground based on surrounding rock transformation was revealed.And the control theory of surrounding rock transformation has been formed.Finally,the technical scheme of rockburst control and the corresponding measures for different intensity rockbursts were put forward contrapuntally which provide a significant guidance for the rockburst prevention of deep TBM tunnel.