Rayleigh Wave Method Research Articles

The Correlation of Dynamic Cone Penetration Blow Count of Wind Carried Sand vs. Surface Wave Velocity in West Bank of Qinghai Lake

Based on a test of wind carried sand roadbed in the west bank of Qinghai Lake, Rayleigh wave method is introduced to measure roadbed compactness of the specific soil in China, and analysis is conducted to find correlation of Rayleigh wave velocity (VR) vs. the blow count (N10) of dynamic cone penetration, then a regression formula is presented.

Finite Difference Numerical Analysis and Experimental Measurements for Beam Profiles of Ultrasonic Creeping Wave Probe

Compare with the Rayleigh wave method, ultrasonic creeping waves critically technique for surface and subsurface defects nondestructive measurement for has the prominent advantage, which not sensitive to surface roughness in coarse-grained materials such as austenitic steel, In this paper, the propagation characteristics and beam profiles of the creeping probe were investigated using finite difference method and measured experimentally. The finite difference numerical model for reflection arc part of the IIW block was established. Through the numerical analysis, wavefront snapshots of the creeping wave propagated in the IIW block are very clear to illustrate the mechanism, and the directivity characteristic of the main beam is obtained. The creeping wave sound characteristics were observed using the dynamical photoelastic experimental method. The beam profiles of the creeping wave probe was measured on the IIW block, the experimental measurement results and the numerical analysis are in good agreement. The results are really significant to design an efficient producer for the surface and sub-surface defects detection based on the ultrasonic creeping wave method.In this paper, a numerical modeling of contact conical transducers is discussed in conjunction with wave propagation analyses by a finite difference method (FDM). Although transducers are the devices to convert electrical energy into mechanical energy and vice versa, attention in this paper is paid mostly to the study of characteristics and parameters of cones and wedges influencing their performance. Cones and wedges inserted between an ultrasonic transducer and the specimen provide the transducer with enhanced capability for point or line contact with the specimen. We study the effect of the dimensions, shape and aperture on the frequency response and the angle of incidence of the wave. Through the testing transducer modeling, some conclusions have been drawn from the analysis, which is useful to as the guideline and criteria for an optimum conical wedge design.

Rayleigh-wave mode separation by high-resolution linear Radon transform

Multichannel analysis of surface waves (MASW) method is an effective tool for obtaining vertical shear wave profiles from a single non-invasive measurement. One key step of the MASW method is generation of a dispersion image and extraction of a reliable dispersion curve from raw multichannel shot records. Because different Rayleigh-wave modes normally interfere with each other in the time and space domain, it is necessary to perform mode separation and reconstruction to increase the accuracy of phase velocities determined from a dispersion image. In this paper, we demonstrate the effectiveness of high-resolution linear Radon transform (LRT) as a means of separating and reconstructing multimode, dispersive Rayleigh-wave energy. We first introduce high-resolution LRT methods and Rayleigh-wave mode separation using high-resolution LRT. Next, we use synthetic data and a real-world example to demonstrate the effectiveness of Rayleigh-wave mode separation using high-resolution LRT. Our synthetic and real-world results demonstrate that (1) high-resolution LRT successfully separates and reconstructs multimode dispersive Rayleigh-wave energy with high resolution allowing the multimode energy to be more accurately determined. The horizontal resolution of the Rayleigh-wave method can be increased by extraction of dispersion curves from a pair of traces in the mode-separated shot gather and (2) multimode separation and reconstruction expand the usable frequency range of higher mode dispersive energy, which increases the depth of investigation and provides a means for accurately determining cut-off frequencies.

High-frequency Rayleigh-Wave method

High-frequency (≥2 Hz) Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution.

Improvement in accuracy of the measurements of residual stresses due to circumferential welds in thin-walled pipe using Rayleigh wave method

To achieve an acceptable safety in many industrial applications such as nuclear power plants and power generation, it is extremely important to gain an understanding of the magnitudes and distributions of the residual stresses in a pipe formed by joining two sections with a girth butt weld. Most of the methods for high-accuracy measurement of residual stress are destructive. These destructive measurement methods cannot be applied to engineering systems and structures during actual operation. In this paper, we present a method based on the measurement of ultrasonic Rayleigh wave velocity variations versus the stress state for nondestructive evaluation of residual stress in dissimilar pipe welded joint. We show some residual stress profile obtained by this method. These are then compared with other profiles determined using a semi-destructive technique (hole-drilling) that makes it possible to check our results. According to the results, we also present a new method for adjusting the ultrasonic measurements to improve the agreement with the results obtained from other techniques.

調和振動荷重によるＰ‐ＳＶ波の地盤振動・波動伝播特性

Elastic waves generated by a controlled dynamic load applied on the surface of soil deposits yield useful tools for non destructive testing of the systems to determine the elastic properties of the soils and their variation with depth. A number of methods for the non destructive testing have been developed and are being used in practice. The objective of this paper is to examine some of the basic concepts related to P-SV wave propagation in layered media and their dynamic response due to the vertical harmonic point load applied on the soil surface. A proper understandings of these concepts is necessary for a correct interpretation of the field data and for improving the accuracy of the estimation of the soil properties at low strain values by using the spectral analysis of surface waves or the Rayleigh wave method.

Liquefaction‐Induced Damage to Buildings in 1990 Luzon Earthquake

The Luzon Earthquake of 1990 (Ms=7.8) caused soil liquefaction in a widespread area that in turn caused crucial damage to various structures. After presenting an overview of the geotechnical aspects of the earthquake, this paper describes damage patterns of buildings in Dagupan City where fine to silty sands liquefied extensively. Also presented are geomorphological conditions, Standard Penetration Test (SPT) results, and shear wave velocity (Vs) profiles determined by a Rayleigh wave method; and their relations to the building damage of the city. The buildings that suffered large settlement and tilting are found to be concentrated in the banks of active rivers and in the fills built on recently abandoned river channels. It is found that the currently available empirical correlations using SPT N‐value can well estimate the extent of liquefaction‐induced damage to buildings. The Rayleigh wave method used shows capability in determining cross sections of Vs structure in the near surface soil.

Vs determination from steady state Rayleigh wave method : Tokimatsu, K; Kuwayama, S; Tamura, S; Miyadera, Y Soils FoundV31, N2, June 1991, P153–163

Vs determination from steady state Rayleigh wave method : Tokimatsu, K; Kuwayama, S; Tamura, S; Miyadera, Y Soils FoundV31, N2, June 1991, P153–163

Vs Determination from Steady State Rayleigh Wave Method

An improved version of steady state Rayleigh wave method is presented for the determination of shear wave velocity ( V s ) profiles of a horizontally stratified soil deposit. A dispersion curve and particle orbits of Rayleigh waves can readily be determined in the field through measurements of ground motions induced by an exciter using sensors placed on the ground surface. To determine V s -profile from the dispersion curve, an inverse analysis which can take into account higher modes of Rayleigh waves is presented and used. To increase the effectiveness of the proposed method, desirable distances among the exciter and sensors are indicated, and the measured particle orbits are used to validate the inverted V s -profile. Comparative field tests are made at two sites using the proposed method and the conventional down hole method. The V s -profiles from the two methods are in good agreement with each other, indicating the effectiveness of the proposed method.