Research On The Influence Of Vibration Source On Rayleigh Wave Propagation

Rayleigh wave is a kind of surface wave.In a semi-infinite body,the energy is mainly concentrated in the 1/2 wavelength range.Under the action of a point source,the energy of the Rayleigh wave accounts for about 2/3 of the total energy,and the P wave accounts for 7%,SV wave accounts for 26%.The surface wave gradually decays with depth,and the particle moves in an elliptical counterclockwise direction,that is,the horizontal movement lags behind the vertical movement.The surface particle response is most affected by the R wave.Therefore,Rayleigh wave is widely applied in the fields of geological engineering exploration,physical and mechanical parameter testing of geotechnical and other fields.In this paper,the propagation law of Rayleigh waves in homogeneous and layered media is studied analytically,and the propagation characteristics of Rayleigh waves excited by the source are analyzed by numerical methods.The main content and results are as follows:Based on the plane wave front hypothesis,the frequency characteristics of Rayleigh waves in layered media under free state are studied.The transfer characteristics of the layered semi-infinite body in normal mode are obtained by using transfer matrix,stiffness layer matrix,and thin layer matrix.Considering that the thin layer stiffness matrix method can simulate the modal response and total response of each order under a point source or surface source,and can simplify the second-order eigenvalue problem into a first-order eigenvalue problem,and can simplify the elements in the stiffness matrix Is algebra.The thin layer stiffness matrix method is mainly described.Using MATLAB to realize the program design of the thin layer method,it is concluded that the variation law of the Rayleigh wave dispersion curve is closely related to the medium conditions,and combined with numerical simulation,the surface wave dispersion curves under various medium model parameters are obtained feature.It not only enriches the surface wave theory,deepens the understanding of the surface wave dispersion curve,but also has important theoretical value and practical significance for surface wave exploration and nondestructive testing in practical applications.The Rayleigh wave modes and their dispersion curves in several different layered media models are analyzed.From the perspective of the excitation intensity of each mode,the jump between modes is correctly explained.From the energy point of view,the analysis of the gradual trend of the high-frequency and low-frequency of the apparent phase velocity is analyzed;the effects of the offset,the track pitch,and the frequency resolution on the dispersion curve are investigated.It provides a basis for practical applications such as stratigraphic exploration and ultrasonic detection.