Study On The Theoretical Model Of Stress Wave Propagation In Three-dimensional In-situ Stress Rocks

The rapid development of national economic construction and the depletion of shallow resources nationwide have made deep underground space resources an important national land resource.Deeply buried engineering rocks are endowed with a changing three-dimensional geo-stress environment,and the dynamic load changes generated by external disturbances and other factors lead to rocks with different porosity and damage evolution degrees,density and elastic modulus,which in turn change the attenuation characteristics of stress wave propagation in rocks.In this paper,we apply the equivalent medium method to establish a dynamic intrinsic model of three-dimensional geo-stressed rocks by modifying the Kelvin-Voigt model,construct a theoretical model of stress wave propagation in three-dimensional geo-stressed rocks,and verify the theoretical model through stress wave propagation experiments.Based on the validation of the model,the effects of three-dimensional geo-stress,dynamic loading and model parameters on the propagation characteristics of stress waves are investigated and their mechanisms are revealed.The main research contents and results are as follows:(1)Applying the equivalent medium method,on the basis of the Kelvin-Voigt model,the damage body is considered to be composed of the rock pore body and the skeleton body,and the dynamic instantonal model and instantonal equations of the rock are proposed.Based on the one-dimensional stress wave propagation theory,the fluctuation equation of stress wave propagation in three-dimensional geo-stress rocks is derived based on the dynamic intrinsic constitutive equation,and the harmonic solution of stress wave propagation velocity,spatial attenuation coefficient,response frequency to vibration frequency ratio,i.e.frequency ratio,is solved using the harmonic method.(2)Stress wave propagation experiments are carried out under different three-dimensional geo-stress conditions,and the experimental data are processed to obtain the experimental results of stress wave propagation velocity,spatial attenuation coefficient and frequency ratio.Based on the basic parameters of the experiment,the theoretical results are obtained by substituting the corresponding harmonic solutions of the stress wave propagation characteristics.By comparing the experimental results of stress wave propagation velocity,spatial attenuation coefficient and frequency ratio with the theoretical results,the theoretical model of stress wave propagation proposed in this paper is effectively verified.(3)Based on the proposed and validated theoretical model of stress wave propagation,a parametric study of the equivalent elastic modulus,stress wave propagation velocity,spatial attenuation coefficient and frequency ratio of the harmonic solutions of the rock is carried out.The stress wave propagation characteristics under the single variables of surrounding pressure,axial static stress and dynamic load are discussed separately,and the effects of initial elastic modulus of rock pore body,initial elastic modulus of rock skeleton body,rock porosity,viscosity coefficient and vibration frequency on stress wave propagation characteristics are explored separately to reveal the stress wave propagation attenuation mechanism of rocks with three-dimensional geo-stress.(4)The varying three-dimensional geo-stress and dynamic load lead to different porosity and damage evolution of the rock,resulting in changes in the density and equivalent elastic modulus of the rock,and the propagation characteristics of the stress waves.As the surrounding pressure increases,the stress wave propagation velocity increases and then remains constant,the spatial attenuation coefficient decreases and then remains constant,and the frequency ratio increases and then remains constant;as the axial static stress and dynamic load increase,the stress wave propagation velocity increases and then decreases,the spatial attenuation coefficient decreases and then increases,and the frequency ratio increases and then decreases.The theoretical model of stress wave propagation proposed in this paper can effectively study the propagation characteristics of stress waves in three-dimensional geo-stress fields,which can provide a direct and effective theoretical reference for engineering safety,and help the structural stability analysis of the surrounding rock mass and the inversion of rock physical and mechanical parameters during blasting excavation of underground projects.