A Physical Simulation Research Of The Wave-field Characteristics Of Rayleigh Wave In Lateral Inhomogeneous Medium

In recent years,great progress has been made in the theoretical study of Rayleigh wave in homogeneous medium model and layered heterogeneous medium model.However,in geotechnical engineering,the theoretical research on the common lateral inhomogeneous medium model has little achievements.Because of the complexity of modeling and the lack of theoretical analytical solutions,this kind of model has more difficulties in practical research.Therefore,there are few researches on the heterogeneous medium model,and the lack of systematic physical simulation.In this paper,the physical simulation method is used to study the lateral inhomogeneous medium model,and the main contents are as follows:(1)Analysis and research on the basic theory of Rayleigh wave.The analytic method of the velocity dispersion of the Rayleigh wave and the dispersion of the elliptical polarizability are studied.The Fourier transform and ?-p domain transform are used in multi-channel Rayleigh wave velocity dispersion analysis method.The H/V spectral ratio method of single channel vector surface wave ellipticity polarization dispersion analysis are studied and analyzed..(2)Experimental study on physical simulation of ultrasonic and seismoelectric technology.Based on the theory of ultrasonic seismic experiment and the theory of seismoelectric effect,the physical simulation experiment of Rayleigh wave was carried out by using an ultrasonic transducer and an acoustic emission instrument.Based on the basic principles of ultrasonic and seismoelectric physical simulation,and virtual instrument technology,the physical simulation experiment platform of Rayleigh wave was built up.(3)Physical simulation of Rayleigh wave velocity dispersion.Based on the homogeneous media model and the lateral inhomogeneous medium model of different medium materials(granite material,artificial frozen sand material),acoustic velocity measurement and seismoelectric measurement method were made for the velocity dispersion analysis of point source Rayleigh wave.(4)Physical simulation of elliptical polarization dispersion of Rayleigh wave.Acoustic measurements were made on the homogeneous medium model and lateral inhomogeneous medium model of artificial frosted sand,to study the elliptical polarization dispersion of point source Rayleigh wave.The lateral resolution of the velocity dispersion and elliptical polarization rate is compared.Through the above researchs,the following main research results have been obtained:(1)The development of Rayleigh wave receiving transducer.Based on the analysis of the disadvantages of tranditional ultrasonic transducers used in the ultrasonic experiments of of Rayleigh surface waves,a three-component ultrasonic receiver transducer with a common point is studied,and a kind of anti-interference electrode based on electro-acoustic effect is developed.An electrode used as a receiver can be regarded as a dot.The experimental system of Rayleigh wave is established.(2)The influence of the frequency and scale of the transducer on the physical simulation of Rayleigh wave velocity dispersion.Point-like electrodes and ultrasonic transducers with different bandwidth and diameter are used as receivers in the experiments,the results show that in the Rayleigh wave dispersion simulation,the broadband receiver transducer is very important.In addition,the scale of the receiver transducer is an important factor affecting the longitudinal and lateral resolution of the Rayleigh wave velocity dispersion.The co-seismic signals received by the electrodes can effectively replace the ultrasonic signals received by the broadband ultrasound transducers.The study provides a potential for the development of point-like broadband receiver transducers.(3)Research on elliptic polarization dispersion characteristics of Rayleigh wave.The experiment results show that the measuuements for the elliptical polarization of Rayleigh wave should be carried out in the far field area or the surface wave dominant.The physical simulation of the point-source Rayleigh wave elliptic polarization can correctly identify the lateral heterogeneous half-space medium model,and has a higher lateral resolution than the velocity dispersion.Single-channel surface wave ellipticity polarization dispersion detection has a higher efficiency and site applicability.