Study On Dynamic Analysis And Supprot Control Of Zonal Disintegration In Surrounding Rock Of Deep Tunnel

With the steady and rapid growth of the national economy,a series of major projects are being built and planned in China,including many deep underground projects.In addition,with the continuous exploitation and consumption of shallow resources,many underground tunnels for mining mineral resources and underground caverns for water conservancy and hydropower development have reached a depth of more than 1000 meters.In deep underground engineering,a series of special deformation and failure phenomena of surrounding rock,for example,large deformation,rock burst and zonal disintegration,appear under complex geological conditions such as high geostress,high permeability,high temperature and excavation disturbance.Zonal disintegration phenomonen is a special geological phenomenon in deep underground engineering and its special non-linear failure characteristics is different from the failure mode in shallow underground engineering.So,a satisfactory explanation about this special phenomenon can not been obtained by the traditional continuum elastic-plastic mechanics theory.The failure phenomonen will lead to large-scale destruction of deep underground engineering due to improper handing.Zonal disintegration phenomonen has become an important and difficult problem in the field of geotechnical engineering,which has aroused extensive and active research.Based on the engineering background of-910m deep tunnel in Dingji coal mine of Huainan mining area,the high geostress three-dimensional eomechanical model tests considering dynamic effect are carried out,and the generation conditions and influencing factors of zonal disintegration phenomena are systematically studied.According to the damage softening characteristics of rock mass,an elastic-plastic damage softening model is established by combining strain gradient theory and total plasticity theory.The elastic-plastic displacement field and stress field of surrounding rock in deep tunnel under dynamic excavation are calculated,the formation mechanism of zonal disintegration of surrounding rock in deep tunnel and the dynamic deformation and failure law of surrounding rock in the process of zonal disintegration formation are studied.The calculation subroutine of zonal disintegration under dynamic excavation is developed by ABAQUS numerical software and the numerical simulation in deep tunnel is carried out accordingly.The rock-anchor interaction model based on strain gradient and the support energy criterion of anchor are established,and the numerical simulation study of anchorage characteristics of surrounding rock of deep tunnel is carried out,and the support control method of zonal disintegration of surrounding rock in deep tunnel is put forward.The main contents of this paper are as follows:(1)In order to study the occurring conditions and influencing factors of zonal disintegration of deep tunnel,taking the-910m deep tunnel in Dingji coal mine of Huainan mining area as the engineering background,true three-dimensional geomechanical model tests of deep tunnel under various working conditions are carried out based on the true three-dimensional loading model test system for high geostress and ISBM geotechnical similar materials.The effects of geostress characteristics and excavation methods on the formation process of zonal disintegration in deep tunnel are studied.(2)According to the damage softening characteristics of rock mass,based on the strain gradient theory and dynamic loading method,the gradient-dependent elastic-plastic damage softening model is established.The motion equation,equilibrium equation and boundary conditions of deep roadway with strain gradient term under dynamic excavation are deduced,and the corresponding failure criteria are put forward.The additional displacement field,stress field of surrounding rock at different unloading time and total displacement field and stress field of surrounding rock after excavation are solved by Runge-Kutta method and the numerical software of matlab.The gradient-dependent elastic-plastic damage softening model proposed in this paper effectively compensates for the shortcomings of traditional continuum theory.The comparison and analysis of theoretical calculation results with field measurement values and geomechanical model test results verify the correctness and advancement of the elastic-plastic damage softening dynamic model,which can dynamically observe the failure process of surrounding rock in deep tunnel,and the formation mechanism of zonal disintegration phenomenon of deep tunnel is clearly understand.(3)The matrix form of gradient-dependent elastic-plastic damage softening constitutive equation is established.The Cl-order continuous tetrahedral element considering strain gradient effect is constructed,and the corresponding finite equation of motion is established.Based on the dynamic incremental variable plastic stiffness iteration method,the zonal disintegration calculation program relying on ABAQUS platform is developed.The correlation between rock failure and energy dissipation is analyzed.According to the theory of strain energy density,the energy damage criterion of zonal disintegration is established.The numerical simulation of deep tunnel according to the dynamic excavation mode in situ is carried out.The interaction of blasting load and initial in-situ stress transient unloading leads to the alternating oscillation of wave crest and trough in the stress field of surrounding rock,which is an important reason for the emergence of zonal disintegration of surrounding rock in deep tunnel.(4)The rock-anchor interaction model based on the strain-gradient is established.The support energy criterion of anchor according to the law of conservation of energy is proposed and the criterion is applied to the numerical simulation of zonal disintegration.Based on ABAQUS platform and the zonal rupture program developed by the author,the numerical simulation of zonal disintegration in deep tunnel under support conditions is carried out.