Study On Stress Wave Scattering And Dynamic Stress Concentration Of Underground Inclusion

The influences of blasting seismic waves on inclusion is crucial in the blasting excavation process.Part of the energy generated by blasting is used for the fragmentation of the rock mass,and the remaining part is propagated to a distance in the form of elastic waves.The scattering of stress waves at the structural discontinuity leads to the migration and accumulation of energy,resulting in local high energy and high stress,and then lead to rock failure.Base on the perspective of theoretical analysis,the dynamic response of the hoop stress around the circular inclusion with perfect and imperfect boundary conditions under the action of transient plane P-wave and cylindrical P-wave is solved.The main research contents are::(1)The plane P wave in the blasting seismic wave is taken as the research object and wave function expansion method is used to solve the scattering and dynamic stress concentration around the cylinder inclusion in the full plane under steady state linear elastic incident P wave.The incident plane wave is expanded into the series of Bessel function,and the full wave function is obtained from the stress boundary condition of the cylindrical inclusion,then the response of the cylindrical inclusion subjected to the steady state linear elastic stationary incident P wave is obtained.(2)Through the Fourier integral transformation of transient impact,the dynamic stress concentration of transient incident P wave around a cylindrical inclusion can be obtained.The effects of shear elastic modulus,Poisson’s ratio and wave number on the dynamic stress concentration factor are analyzed.The results show that the dynamic stress concentration factor reaches its maximum value when the wave number is 0.25,and the maximum value appears in the counterclockwise 90°and 270°directions of the inclusion.With the increase of wave number,tensile stress concentration occurs in the surrounding rock in the directions of 0°and180°,which may lead to the failure of the surrounding rock.(3)The spring model is introduced to characterize the imperfect boundary,and the scattering and dynamic stress concentration problems of plane P-wave and cylindrical P-wave incident on a jammed body with imperfect interface are solved.The spring stiffness k_r,k_θplane P-wave scattering characteristics of the incident clamp have a significant impact.The closer the spring stiffness k_r and k_θare to+∞,the closer the interface is to a perfect interface,and the smaller the DSCF around the inclusion.For cylindrical P-waves,in addition to spring stiffness and wave number,the distance between the wave source and the center of the inclusion also has a significant effect on the DSCF.(4)In addition,the finite element software LS-DYNA is used to establish a numerical model of wave incident rock mass with inclusions.The distribution and numerical value of the stress concentration factor obtained by the simulation are very close to the numerical calculation,which proves the correctness of the numerical calculation.The results show that the larger the difference between the shear elastic modulus of the surrounding rock and the inclusion,the more obvious the dynamic stress concentration,and the larger the failure area of the surrounding rock.The CSCM cap model material is used to establish a model,and the damage of surrounding rock under the action of transient wave incidence is obtained.The results show that the cracks appear in the counterclockwise 90°and270°directions,that is,the position of the maximum value of the dynamic stress concentration factor.