Study On The Evolution And Distribution Of Deformation Energy In Surrounding Rock Of Deep-buried Tunnel

Geological disasters in deep-buried rock mass engineering such as rock burst and large deformation of soft rock are essentially rock mass instability driven by energy.Study the deformation and failure rule of surrounding rock of deep buried tunnel from the perspective of energy could bring a new visual angle and analysis method to the prediction and mechanism research of geological disasters,and brings a breakthough of the traditional stress and strain analysis method.At the same time,it can also provide theoretical guidance for support design and construction safety of deep buried tunnel.In order to study the evolution and distribution law of deformation energy,four aspects i.e.laboratory test,analytical study,numerical study,parametric analysis and case verification were discussed,and mainly obtains the following results:1.On the basis of summarizing the existing research results of rock energy evolution,it is found that it is not comprehensive to use "strain energy" to express the energy stored or dissipated in rock mass."Strain" is only an expression of deformation.When the deformation of a rock mass unit is too large and exceeds its own size,"strain energy" is no longer applicable.Therefor the concept of "deformation energy" was introduced,and the phenomenon of energy concentration,accumulation and dissipation were described with total deformation energy,elastic deformation energy and dissipated deformation energy respectively.2.Conventional triaxial compression tests and triaxial cyclic loading and unloading tests under different confining pressures were carried out for shale and sandstone in allusion to the evolution of deformation energy in the process of rock deformation and failure.The evolution of axial deformation energy,radial diffusion deformation energy,dissipated deformation energy and elastic deformation energy were studied systematically.The concept of elastic energy consumption ratio was innovatively put forward considering the law of strain energy accumulation and dissipation during rock failure,which could be used as the failure criterion of rock strength in case of abrupt change in the process of deformation energy evolution.3.In order to study the distribution of deformation energy in the surrounding rock of deep tunnel,the analytical method was used to calculate the elastic deformation energy of the surrounding rock of deep tunnel in a continuous,uniform,isotropic and linear elastic state.Then the numerical solution was adopted in circular and rectangular tunnel cases to verifiy with the analytical results.4.Considering the advantages and disadvantages of existing energy indexes,new energy indexes with clear physical significances—ECI(Energy Concentration Index),EAE(Energy Accumulation Efficiency),EDE(Energy Dissipation Efficiency)were proposed based on the characteristics of energy concentration,accumulation and dissipation,which could characterize the degree of energy concentration,energy storage ratio and energy dissipation ratio of rock mass.The deformation energy evolution analysis system was established.By applying the research achievements to the rock burst section of the deep-buried diversion tunnel of Taipingyi hydropower station,the obtained evolution and distribution rules of deformation energy,and geological disaster prediction results are consistent with the actual situation of the site,which verifies the reliability and applicability of the above indexes and the deformation energy evolution analysis system.5.In order to study the influence of the direction of in-situ stress,tunnel size and tunnel type on the distribution law of deformation energy of deep-buried tunnels,the finite resolution numerical simulation analysis method and the deformation energy evolution analysis system were adopted.The parametric study showed that the excavation behavior will lead to energy concentration in the surrounding rock ingnoring the above factors change.The distribution of energy field in surrounding rock mass is mainly controlled by in-situ stress.The tunnel size effect is mainly reflected in energy concentration and accumulation.The larger the tunnel size is,the more intense the energy concentration and accumulation effect shows.The distribution law of energy field,energy accumulation and dissipation efficiency have nothing to do with the size of the tunnel.The tunnel type has little influence on the distribution of energy field,but energy concentration and accumulation tend to occur in the geometric singularities.6.Based on the engineering background of hard rock burst section of Linglong gold mine and large deformation section of soft rock of Yuelongmen tunnel of Chenglan railway,the aforementioned research achievements were verified.By applying the deformation energy evolution analysis system,the geological disaster forecast conclusions consistent with the actual situation in the project sites.Then the gestation and generation energy mechanism of rock burst and large deformation were expounded combing the geological disasters in site and the deformation energy evolution analysis.Finally,from the energy point of view,the construction safety protection and reinforcement measures of hard rock rockburst and soft rock large deformation are proposed.