Obliquely incident wave propagation across rock joints with virtual wave source method

abstract The effects of anisotropy on the reflection of SH-waves (horizontally polarized shear waves) from a transition layer are studied. The transition layer is sand-wiched between two isotropic homogeneous half-spaces and is constituted by a medium which is both anisotropic and inhomogeneous. The SH-wave potentials are obtained for an anisotropic inhomogeneous medium in which both the anisotropy factor (ratio of the horizontal rigidity to the vertical rigidity) and vertical velocity vary with depth. An expression for the reflection coefficient of SH waves is obtained when the material mentioned above forms a finite transition zone between two isotropic homogeneous half-spaces. For further generalization, a second-order discontinuity along with the first-order on eis being assumed in the material properties, at the boundaries of the transition layer. The mathematical and numerical analyses show that the anisotropy factor, found at the top of the transition layer (N0/M0) produces considerable effect on the reflection coefficient for an obliquely incident SH wave. It has been noted that the greater the thickness of the transition layer, the greater is the dependence of the reflection coefficient upon the value of the anisotropy (N0/M0). The minima and maxima of the reflection of seismic energy are found dependent on the value of anisotropy. For greater values of the anisotropy, these maxima and minima shift toward the lower values of the wavelength of the propagating wave (or toward the higher values of the thickness of the transition layer). In fact, the values of the reflection coefficient at which these maxima and minima of seismic energy occur are found greater for the higher values of anisotropy. The effects of anisotropy are found more pronounced for the larger angles of incidence. This remains so until the angle of refraction becomes imaginary. However, no effects of the anistropy factor are found on the reflection coefficients for a normally incident wave. The results, mentioned above, are therefore discussed only for the obliquely incident wave. A geophysically interesting situation has been chosen for studying, quantitatively, the effects of the anisotropy factor on the reflection of SH waves.

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Numerical Simulation of Wave Propagation Across Multiple Parallel Rock Joints Using DEM

Lecture Notes in Civil Engineering - Geotechnical Characterization and Modelling ◽

10.1007/978-981-15-6086-6_65 ◽

2020 ◽

pp. 825-837

Author(s):

Resmi Sebastian ◽

T. G. Sitharam

Keyword(s):

Numerical Simulation ◽

Wave Propagation ◽

Rock Joints

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Stress Wave Propagation through Rock Joints Filled with Viscoelastic Medium Considering Different Water Contents

Applied Sciences ◽

10.3390/app10144797 ◽

2020 ◽

Vol 10 (14) ◽

pp. 4797 ◽

Cited By ~ 1

Author(s):

Xiaolin Huang ◽

Shengwen Qi ◽

Bowen Zheng ◽

Youshan Liu ◽

Lei Xue ◽

...

Keyword(s):

Wave Propagation ◽

Water Content ◽

Seismic Response ◽

Transmission Coefficient ◽

Stress Wave ◽

Viscoelastic Medium ◽

Rock Joints ◽

Stress Wave Propagation ◽

Multiple Reflections ◽

Joint Spacing

A rock mass often contains joints filled with a viscoelastic medium of which seismic response is significant to geophysical exploration and seismic engineering design. Using the propagator matrix method, an analytical model was established to characterize the seismic response of viscoelastic filled joints. Stress wave propagation through a single joint highly depended on the water content and thickness of the filling as well as the frequency and incident angle of the incident wave. The increase in the water content enhanced the viscosity (depicted by quality factor) of the filled joint, which could promote equivalent joint stiffness and energy dissipation with double effects on stress wave propagation. There existed multiple reflections when the stress wave propagated through a set of filled joints. The dimensionless joint spacing was the main controlling factor in the seismic response of the multiple filled joints. As it increased, the transmission coefficient first increased, then it decreased instead, and at last it basically kept invariant. The effect of multiple reflections was weakened by increasing the water content, which further influenced the variation of the transmission coefficient. The water content of the joint filling should be paid more attention in practical applications.

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Verification of UDEC Modeling 1-D Wave Propagation in Rocks

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.90-93.1998 ◽

2011 ◽

Vol 90-93 ◽

pp. 1998-2001

Author(s):

Wei Dong Lei ◽

Xue Feng He ◽

Rui Chen

Keyword(s):

Wave Propagation ◽

Analytical Solution ◽

Transmission Coefficient ◽

Method Of Characteristics ◽

Rock Joint ◽

Rock Joints ◽

Dynamic Problems ◽

The Method Of Characteristics ◽

Elastic Rock ◽

D Wave

Three cases for 1-D wave propagation in ideal elastic rock, through single rock joint and multiple parallel rock joints are used to verify 1-D wave propagation in rocks. For the case for 1-D wave propagation through single rock joint, the magnitude of transmission coefficient obtained from UDEC results is compared with that obtained from the analytical solution. For 1-D wave propagation through multiple parallel joints, the magnitude of transmission coefficient obtained from UDEC results is compared with that obtained from the method of characteristics. For all these cases, UDEC results agree well with results from the analytical solutions and the method of characteristics. From these verification studies, it can be concluded that UDEC is capable of modeling 1-D dynamic problems in rocks.

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Breakup of spatiotemporal pattern under electromagnetic radiation

International Journal of Modern Physics B ◽

10.1142/s0217979219501650 ◽

2019 ◽

Vol 33 (16) ◽

pp. 1950165 ◽

Cited By ~ 1

Author(s):

Fan Li ◽

Linwei Guo

Keyword(s):

Wave Propagation ◽

Electromagnetic Radiation ◽

Cardiac Tissue ◽

Signal Propagation ◽

Spatiotemporal Pattern ◽

Quiescent State ◽

Wave Source ◽

The Media ◽

Electrical Activities ◽

Target Wave

Stable wave propagation is important for heart health, however, the electromagnetic radiation could affect normal signal propagation of heart, even make a sudden cardiac arrest. In this paper, the effect of electromagnetic radiation on the propagation of stable target wave generated by linear feedback control is studied in detail. It is confirmed that there are different transitions of electrical activities in cardiac tissue, which are transitions from target wave to spiral wave, some isolated islands of pattern waves coexisted, broken pattern and even the quiescent state, are generated when the electromagnetic field is imposed on the cardiac tissue in three ways. Furthermore, it is interesting to find there are different real affected regions, in which the electrical activities of nodes are destroyed, when the radiation signal is imposed on the cardiac tissue in different ways. It is also found the kinds of dynamical behaviors in the media are dependent on the real affected region. These results state that electromagnetic radiation could change the electrical activities, even destroy and suppress the wave propagation of wave source, and the ways of electromagnetic radiation imposed on the media are also important.

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