Theroy And Application Research Of Multi-mode Failure Strength Theory And Numerical Algorithm For Surrounding Rock Of Deep Roadway

With the rapid development of deep rock engineering,the failure modes and failure intensities of rocks and rock masses under high stress are different from those under shallowly buried conditions,and the mechanism of multi-mode failure and the transition has not been unified.Under the influence of multiple failure mechanisms,the failure mode of rock mass surface instability presents a transitional phenomenon,that is,with the failure developing from the free face to the interior of rocks,the crack penetration mode gradually transitions from the splitting type to the shear type.Therefore,it is very necessary to study the failure mechanism of deep rock edges influenced by multiple mechanisms.In this paper,combined with field tests in Sanshandao,Jinchuan,etc,this paper conducts rock mechanics tests to obtain field data and rock samples.The multimodal failure mechanism of rocks from elongation damage to shear failure is extensively explored and a strength criterion,considering the influences of multiple failure modes,is proposed combined with continuous-discontinuous numerical algorithm to realize the numerical embedment of new constitutive model.The research results are applied to the field engineering proposal and prediction.Specific research content includes:(1)Develop an experimental device for surface instability of hard rock specimens,which can carry out loading and displacement monitoring along the length direction of the specimen.Digital image technology was used to monitor the displacement field.The LVDT sensor was used to monitor the vertical free surface and acoustic emission technology was used to monitor the process of surface splitting failure.The simulation data of unstable failure on the rock surface and the development law of failure mode with depth were obtained.According to the failure modes such as tensile,splitting,shear and isobaric yield in the test,the relationship between failure mechanism and failure strength,failure form,failure region and damage development law was constructed.(2)Based on the theory of maximum linear strain and transitional strength criterion,the field and laboratory test data are fitted to propose a strength model suitable for the transition characteristics of the failure mode of deep rock mass,and the internal mechanism of low-strength failure of rock mass is revealed.At the same time,the applicability of the multi-mode transitional failure model considering the maximum linear strain is verified,and the numerical embedding of the strength criterion under the influence of multiple failure mechanisms is established.(3)A coupling method of block-granule-rod based on penalty spring is proposed,and a continuous-discontinuous cross-scale algorithm of rock bolt support to hard rock side in deep rock engineering is established,and the application of multiple failure modes in deep rock excavation and support calculation is realized.The coupling Method is based on Continuum Discontinuum Element Method(CDEM).Discrete particle clusters are used to characterize the broken rock mass within the loose circle around the tunnel,and block elements are used to characterize the complete rock mass outside the loose circle.Bolt elements are used to describe bolt and cable support structures,and the force and displacement transfer between bolt elements,discrete particles and block elements is realized by interpolation coupling method,to realize the simulation of side wall stability of deep hard rock under high-stress environment and the evaluation of support effect.(4)A complete numerical calculation model of continuum-discontinuity considering the mechanical properties of continuous and discontinuous media in deeply buried rock tunnel is constructed.With the help of the CDEM,the influence of structural plane dip angle,horizontal in-situ stress and performance weakening of water-bearing rock mass on the stability and failure mode of the chamber under high in-situ stress is discussed.The supporting effect under different support schemes is also analyzed.The calculation results show that,under the joint control of the structural plane and in-situ stress,the rock mass at the free surface of the roadway first appear damaged and fractured,and then gradually propagate to the interior of the roadway.The fracture form and location are directly related to the structural plane and horizontal in-situ stress coefficient,while the degree of fracture is controlled by the macroscopic strength and in-situ stress of rock mass.Through calculation and analysis,the progressive instability mechanism and deformation and failure law of roadways in mining areas under the influence of multiple factors are clarified,and reasonable parameter suggestions for roadway support design are put forward.