Study On Wave Field Response Characteristics Of Fractured Rock Mass Based On 3D Printing Technology

In this thesis,the seismic response characteristics of complex fractured media are studied based on physical model technology.In this study,four groups of single fracture models with different densities and two groups of double fracture models with different angles were designed.In view of the existing physical model is difficult to control the geometric characteristics of fractures and the limitations of complex fracture model,this paper based on FDM fused deposition printing technology to prepare complex fracture model.FDM technology can choose not to add supporting materials,design arbitrary crack parameters,make complex crack model based on equivalent medium theory model,and verify the effectiveness of physical modeling by using CT high-precision scanning.Then,the ultrasonic testing system is used to obtain the wave field data of each model in each direction,mainly including the wave velocity and amplitude information.With the help of the uniaxial compression control mode of MTS 815 high rigid rock mechanics test system,the wave field data of the model under the same axial pressure are obtained to ensure the accuracy of the wave field data.In this study,the experimental results are compared with Hudson's theoretical results,and the propagation law of seismic wave in complex fractured media is obtained.According to the single group fracture model,the results show that:(1)with the increase of fracture density,the degree of wave velocity anisotropy increases gradually,and the degree of shear wave splitting also increases,and there are different splitting characteristics in different directions;(2)SV wave in shear wave is more sensitive to fracture than SH wave,so the response characteristics of shear wave can also be used to predict fracture when identifying fracture parameters(3)when the fracture density is close to or more than 10%,Hudson's second-order approximation results are more accurate.Therefore,for the medium with high fracture density,it is necessary to choose a reasonable theoretical model for practical guidance;(4)compared with the wave velocity anisotropy,the attenuation anisotropy is more obvious,so it is more accurate to predict the fracture parameters by using the attenuation information of wave.The results show that:(1)when the incident angle is 0° and90° respectively,it is the maximum and minimum value of wave velocity,which is consistent with the expected value,showing obvious anisotropic characteristics;(2)when the azimuth angle is 45°and-45°respectively,the measured results are closer to the theoretical results than 0° and 90° respectively,which is consistent with the calculation results of Hudson's second-order model considering the interaction between cracks(3)in the direction perpendicular to the low-density fracture group,ignoring the interaction between the fractures in the theoretical calculation has the greatest impact on the results;(4)due to the polarization of the density projection of oblique fractures,the corresponding maximum and minimum values of wave velocity also increase,so the degree of anisotropy of oblique fractures is greater than that of orthogonal fractures.In conclusion,the directionally distributed fractures in the underground media have a significant impact on the seismic wave,and the seismic wave response characteristics also change with the fracture parameters.The research of this subject is of great significance to the quantitative study of petrodynamics and geophysical related oil and gas exploration problems.