Diffraction of elastic waves by a fluid-filled crack in a fluid-saturated poroelastic half-space

2021 ◽  
Author(s):  
Zhongxian Liu ◽  
Jiaqiao Liu ◽  
Sibo Meng ◽  
Xiaojian Sun
Keyword(s):  
Half Space ◽  
Seismic Waves ◽  
Incident Angle ◽  
Excitation Frequency ◽  
Vertical Displacement ◽  
Crack Model ◽  
P Waves ◽  
Amplification Effect ◽  
Resonance Frequencies ◽  
Angle Crack

Summary An indirect boundary element method (IBEM) is developed to model the two-dimensional (2D) diffraction of seismic waves by a fluid-filled crack in a fluid-saturated poroelastic half-space, using Green's functions computed considering the distributed loads, flow, and fluid characteristics. The influence of the fluid-filled crack on the diffraction characteristics is investigated by analyzing key parameters, such as the excitation frequency, incident angle, crack width and depth, and medium porosity. The results for the fluid-filled crack model are compared to those for the fluid-free crack model under the same conditions. The numerical results demonstrate that the fluid-filled crack has a significant amplification effect on the surface displacements, and that the effect of the depth of the fluid-filled crack is more complex compared to the influence of other parameters. The resonance diffraction generates an amplification effect in the case of normally incident P waves. Furthermore, the horizontal and vertical displacement amplitudes reach 4.2 and 14.1, respectively. In the corresponding case of the fluid-free crack, the vertical displacement amplitude is only equal to 4.1, indicating the amplification effect of the fluid in the crack. Conversely, for normally incident SV waves at certain resonance frequencies, the displacement amplitudes above a fluid-filled crack may be lower than the displacement amplitudes observed in the corresponding case of a fluid-free crack.

An Analytic Solution for the Diffraction of Plane P Waves by a Cylindrical Inclusion in Half Space

2011 ◽  
Vol 255-260 ◽  
pp. 2520-2525
Author(s):  
Da Guang Li ◽  
Xue Ping Gao ◽  
Zhang Ying
Keyword(s):  
Half Space ◽  
Analytic Solution ◽  
Incident Angle ◽  
Surface Condition ◽  
Surface Displacement ◽  
Cylindrical Inclusion ◽  
Diffraction Effect ◽  
P Waves ◽  
Plane P Waves ◽  
The Impact

This paper presents an analytic solution for the diffraction of plane P waves by a cylindrical inclusion in half space by Fourier-Bessel wave function expansion method, in which the flat surface of half space is approximated by a large curved surface. The equation can be constructed by the continue boundary and the free surface condition. Based on parametric analysis, the impact of the inclusion on surface displacement amplitude is discussed. It is illustrated that there is large difference of the diffraction characteristics between the hard inclusion and soft inclusion. The displacement response depends strongly on the incident angle and frequency. The diffraction effect can be ignored with large embedded depth of the inclusion.

A STUDY OF TWO‐DIMENSIONAL HEAD WAVES IN FLUID AND SOLID SYSTEMS

Geophysics ◽  
1963 ◽  
Vol 28 (4) ◽  
pp. 563-581 ◽  
Author(s):  
John W. Dunkin
Keyword(s):  
Half Space ◽  
Vertical Displacement ◽  
Point Of View ◽  
Head Wave ◽  
Apparent Velocity ◽  
Two Dimensional ◽  
Multiple Reflections ◽  
Transient Wave ◽  
Line Load ◽  
Head Waves

The problem of transient wave propagation in a three‐layered, fluid or solid half‐plane is investigated with the point of view of determining the effect of refracting bed thickness on the character of the two‐dimensional head wave. The “ray‐theory” technique is used to obtain exact expressions for the vertical displacement at the surface caused by an impulsive line load. The impulsive solutions are convolved with a time function having the shape of one cycle of a sinusoid. The multiple reflections in the refracting bed are found to affect the head wave significantly. For thin refracting beds in the fluid half‐space the character of the head wave can be completely altered by the strong multiple reflections. In the solid half‐space the weaker multiple reflections affect both the rate of decay of the amplitude of the head wave with distance and the apparent velocity of the head wave by changing its shape. A comparison is made of the results for the solid half‐space with previously published results of model experiments.

SEISMIC RESPONSE OF POWER TRANSMISSION TOWER-LINE SYSTEM UNDER MULTI-COMPONENT MULTI-SUPPORT EXCITATIONS

2012 ◽  
Vol 06 (04) ◽  
pp. 1250025 ◽  
Author(s):  
TIAN LI ◽  
LI HONGNAN ◽  
LIU GUOHUAN
Keyword(s):  
Seismic Waves ◽  
Power Transmission ◽  
Incident Angle ◽  
Ground Motions ◽  
Three Dimensional ◽  
Transmission Tower ◽  
Line System ◽  
Time Stepping ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The effect of multi-component multi-support excitations on the response of power transmission tower-line system is analyzed in this paper, using three-dimensional finite element time-stepping analysis of a transmission tower-line system based on an actual project. Multi-component multi-support earthquake input waves are generated based on the Code for Design of Seismic of Electrical Installations. Geometric non-linearity was considered in the analysis. An extensive parametric study was conducted to investigate the behavior of the transmission tower-line system under multi-component multi-support seismic excitations. The parameters include single-component multi-support ground motions, multi-component multi-support ground motions, the correlations among the three-component of multi-component multi-support ground motions, the spatial correlation of multi-component multi-support ground motions, the incident angle of multi-component multi-support seismic waves, the ratio of the peak values of the three-component of multi-component multi-support ground motions, and site condition with apparent wave velocity of multi-component multi-support ground motions.

Seismic Waves in a Laterally Inhomogeneous Layered Medium, Part I: Theory

1997 ◽  
Vol 64 (1) ◽  
pp. 50-58 ◽  
Author(s):  
Ruichong Zhang ◽  
Liyang Zhang ◽  
Masanobu Shinozuka
Keyword(s):  
Wave Field ◽  
Half Space ◽  
Seismic Waves ◽  
Scattered Wave ◽  
Inhomogeneous Layer ◽  
Dislocation Source ◽  
Seismic Dislocation ◽  
Body Forces ◽  
The Mean ◽  
Layered Half Space

Seismic waves in a layered half-space with lateral inhomogeneities, generated by a buried seismic dislocation source, are investigated in these two consecutive papers. In the first paper, the problem is formulated and a corresponding approach to solve the problem is provided. Specifically, the elastic parameters in the laterally inhomogeneous layer, such as P and S wave speeds and density, are separated by the mean and the deviation parts. The mean part is constant while the deviation part, which is much smaller compared to the mean part, is a function of lateral coordinates. Using the first-order perturbation approach, it is shown that the total wave field may be obtained as a superposition of the mean wave field and the scattered wave field. The mean wave field is obtainable as a response solution for a perfectly layered half-space (without lateral inhomogeneities) subjected to a buried seismic dislocation source. The scattered wave field is obtained as a response solution for the same layered half-space as used in the mean wave field, but is subjected to the equivalent fictitious distributed body forces that mathematically replace the lateral inhomogeneities. These fictitious body forces have the same effects as the existence of lateral inhomogeneities and can be evaluated as a function of the inhomogeneity parameters and the mean wave fleld. The explicit expressions for the responses in both the mean and the scattered wave fields are derived with the aid of the integral transform approach and wave propagation analysis.

A periodic seismic isolation foundation with an extremely broad low-frequency attenuation zone: Theoretical analysis and experimental verification

2021 ◽  
pp. 136943322110646
Author(s):  
Peng Zhou ◽  
Shui Wan ◽  
Xiao Wang ◽  
Yingbo Zhu ◽  
Muyun Huang
Keyword(s):  
Seismic Isolation ◽  
Seismic Waves ◽  
Periodic Structures ◽  
Finite Size ◽  
Low Frequency ◽  
Bridge Structure ◽  
Engineering Structures ◽  
P Waves ◽  
New Type ◽  
Dominant Frequencies

The attenuation zones (AZs) of periodic structures can be used for seismic isolation design. To cover the dominant frequencies of more seismic waves, this paper proposes a new type of periodic isolation foundation (PIF) with an extremely wide low-frequency AZ of 3.31 Hz–17.01 Hz composed of optimized unit A with a wide AZ and optimized unit B with a low-frequency AZ. The two kinds of optimized units are obtained by topology optimization on the smallest periodic unit with the coupled finite element-genetic algorithm (GA) methodology. The transmission spectra of shear waves and P-waves through the proposed PIF of finite size are calculated, and the results show that the AZ of the PIF is approximately the superposition of the AZs of the two kinds of optimized units. Additionally, shake tests on a scale PIF specimen are performed to verify the attenuation performance for elastic waves within the designed AZs. Furthermore, numerical simulations show that the acceleration responses of the bridge structure with the proposed PIF are attenuated significantly compared to those with a concrete foundation under the action of different seismic waves. Therefore, the newly proposed PIF is a promising option for the reduction of seismic effects in engineering structures.

Seismic waves from a horizontal stress discontinuity in a layered solid

1982 ◽  
Vol 72 (5) ◽  
pp. 1483-1498
Author(s):  
F. Abramovici ◽  
E. R. Kanasewich ◽  
P. G. Kelamis
Keyword(s):  
Half Space ◽  
Seismic Waves ◽  
Horizontal Stress ◽  
Radial Component ◽  
Elastic Half Space ◽  
Homogeneous Layer ◽  
Approximate Methods ◽  
Crustal Layer ◽  
Finite Fault ◽  
Stress Discontinuity

abstract The displacement components for a horizontal stress discontinuity along a buried finite fault in an elastic homogeneous layer on top of an elastic half-space are given analytically in terms of generalized rays. For a particular case of a concentrated horizontal force pointing in an arbitrary direction, detailed time-dependent expressions are given. For a simple model of a “crustal” layer over a “mantle” half-space, the numerical seismograms in the near- and intermediate-field show some interesting features. These include a prominent group of compressional waves whose radial component is substantial at distances four times the crustal thickness. All the dominant shear arrivals (s, SS, and sSS) are important and show large variations of amplitude as the source depth and receiver distance are varied. Some of the prominent individual generalized rays are shown, and it is found that they can be grouped naturally into families based on the number of interactions with the boundaries. The subdivision into individual generalized rays is useful for analysis and for checks on the numerical stability of the synthetic seismograms. Since the solution is analytic and the numerical evaluation is complete up to any desired time, the results are useful in comparing other approximate methods for the computation of seismograms.

scholarly journals Research on the Resonance Characteristics of Rock under Harmonic Excitation

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Siqi Li ◽  
Shenglei Tian ◽  
Wei Li ◽  
Tie Yan ◽  
Fuqing Bi
Keyword(s):  
Resonance Frequency ◽  
Natural Frequency ◽  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Theoretical Research ◽  
Transform Method ◽  
Factors Affecting ◽  
Least Action ◽  
Principle Of Least Action ◽  
Resonance Frequencies

In order to study the resonance characteristics of rock under harmonic excitation, two vibration models have been presented to estimate the natural frequency of rock encountered during the drilling. The first one is a developed single-DOF model which considers the properties and dimensions of the rock. The second one is a multi-DOF model based on the principle of least action. Subsequently, the modal characteristics, as well as the influence of excitation frequency, the mechanical properties, and dimensions of the rock on its resonance frequency, are analyzed by using FEM. Finally, the ultrasonic test on artificial sandstones and materials of drill tools are carried out indoor, and the FFT transform method is adopted to obtain their resonance frequencies. Based on the analysis undertaken, it can be concluded that the natural frequency of the rock increases with the change of vibration mode. For the same kind of rock, the resonance frequency is inversely proportional to mass, while for the different kinds of rocks, the mechanical parameters, such as density, elastic modulus, and Poisson’s ratio, determine the resonance frequency of the rock together. Besides, the shape of the rock is also one of the main factors affecting its resonance frequency. At last, the theoretical research results are further verified by ultrasonic tests.

Investigation of the resonance of nonwetting droplets in constricted capillary tubes

Geophysics ◽  
2020 ◽  
Vol 85 (2) ◽  
pp. ID1-ID17 ◽  
Author(s):  
Chao Zeng ◽  
Wen Deng ◽  
Jing Fan ◽  
Kelly H. Liu
Keyword(s):  
Response Function ◽  
Oil Recovery ◽  
Environmental Remediation ◽  
Seismic Waves ◽  
Excitation Frequency ◽  
Immiscible Fluids ◽  
Dynamics Modeling ◽  
Resonance Theory ◽  
Two Phase ◽  
Amplification Ratio

Fluids in porous media could resonate due to passing seismic waves when meeting certain conditions of excitation frequency and pore geometry. This study of the resonance of fluids can contribute to applications in hydrocarbon microtremor analysis, enhanced oil recovery methods, and environmental remediation of nonaqueous phase liquid contamination. In this study, the analytical expression of the frequency response function and temporal response function is derived to characterize the resonance of two-phase immiscible fluids in the constricted tube. The computational fluid dynamics modeling is used to validate this resonance theory by achieving a good agreement in the prediction of output/input amplification ratio in the frequency and time domains.

Estimation of a point source wavelet in elastic media

Geophysics ◽  
1993 ◽  
Vol 58 (8) ◽  
pp. 1195-1199 ◽  
Author(s):  
Alexander Kagansky ◽  
Dan Loewenthal
Keyword(s):  
Point Source ◽  
Half Space ◽  
Simple Procedure ◽  
Estimation Algorithm ◽  
Vertical Displacement ◽  
Hankel Transform ◽  
P Wave ◽  
Wavelet Estimation ◽  
Acoustic Media ◽  
Correct Estimate

A new method of wavelet estimation in elastic or acoustic media is presented. The method is based on the simple procedure of weighted summation of seismic traces for all the distances of source‐receivers, with a horizontal offset r as a weight. The model treated consists of a homogeneous elastic (or acoustic) layer with the free surface above and a half‐space below. The Lamé parameters and the density of the half‐space can be any function of the depth. A P‐wave point source operates in the layer, and the vertical displacement field or the vertical particle velocity field (or the pressure in the acoustic case) is measured by two horizontal lines of receivers located at two depth levels in the same layer. To obtain the wavelet‐estimation algorithm, the Fourier‐Hankel transform of the field is used. It is shown that there are two possibilities of data measuring: (1) when both the lines of the receivers are below the source and (2) when one of the lines is above the source. Numerical examples show that the proposed method gives a correct estimate of the source wavelet.

Sign in / Sign up

Export Citation Format

Share Document