True Three Dimensional Physical Simulation And Nonlinear Strength Reduction Analysis Of Surrounding Rock Stability In Deep Underground Laboratory

Nuclear energy has gradually become one of the indispensable energy sources in the sustainable development of human society.However,accompanied by the rapid development of nuclear power,a series of challenges have emerged,among which the most prominent is how to treat high-level radioactive waste(HLW)safely.Thus far,geological disposal at deep burial depths is widely accepted as a feasible approach for the safe treatment of HLW.However,creation of such a geological repository is challenging due to complicated construction conditions,high safety requirements and long service life(i.e.,tens of thousands of years).Thus,it is a complex process in terms of site selection,construction and safety assessment.Moreover,such an unprecedented disposal process must be completed without any engineering experience from existing projects.The underground research laboratories(URL)is an essential facility linking the various procedures during the disposal of HLW.At present,China is in the transition stage of underground laboratory site selection and underground laboratory engineering construction.Beishan,Gansu Province has been identified as the preferred selection area for geological disposal of HLW,and the Xinchang site is determined as the recommended site for URL.Although a lot of research achievements have been made in the construction of underground engineering in China,the construction of deep buried geological repository for high-level radioactive waste is still in its infancy.In order to effectively evaluate and optimize the overall construction scheme of underground laboratory,it is necessary to carry out analysis and research on surrounding rock stability of Beishan underground laboratory construction.This paper relies on the subject of major projects of State Administration of Science,Technology and Industry for National Defense,based on the background of the China's first URL for deep-buried geological disposal of HLW in Beishan,Gansu Province,we carried out large-scale true three-dimensional physical simulation test on excavation and support of underground laboratory.On the basis of the physical simulation test,established an energy criterion for instability analysis of surrounding rock mass of underground cavern with application of cusp catastrophe theory,proposed an improved nonlinear strength reduction analysis method based on H-B criterion.The main research results obtained are as follows:(1)This paper developed an intelligent numerical control true three-dimensional physical simulation test system through the application of module combination,numerical control needle valve and gradient loading technology.This test system can effectively simulate the uneven distribution of true three-dimensional high ground stress in underground caverns,thus realize the digitization,visualization and intelligence of true three-dimensional non-uniform loading,and voltage stabilization control of ultra-high pressure model test.(2)This paper developed a micro TBM automatic excavation device for underground engineering physical simulation test,through the application of servo electric control and profiling excavation technology.This excavation device realized the Full face excavation and bench excavation method for different cavern types(circular or non-circular caverns)and different cross-section sizes.This excavation device improves the excavation accuracy of physical simulation test and reduces the influence of traditional manual excavation on the results of physical simulation test(3)This paper carried out the large-scale true three-dimensional physical simulation test of excavation and support for Beishan underground laboratory.This paper reveals the interaction between the caverns,the influence range of excavation,the supporting and anchoring effect,the overload deformation characteristics and overload failure law of the caverns group,and obtains the overload safety factor of the caverns group system in the underground laboratory,which effectively verifies the excavation sequence,excavation mode,support type and the overall safety and stability of the underground laboratory.(4)This paper established the energy criterion for surrounding rock instability analysis based on catastrophe theory,and proposed an improved nonlinear strength reduction analysis method based on H-B criterion.Based on this,the overall safety factor of Beishan underground laboratory is calculated.Compared with the results of physical simulation test,the reliability of the calculation method is verified effectively.The research results provide theoretical support and technical guidance for optimizing the overall construction scheme of underground laboratory.