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Thomas Meier - One of the best experts on this subject based on the ideXlab platform.
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modelling of Rayleigh Type seam waves in disturbed coal seams and around a coal mine roadway
Geophysical Journal International, 2007Co-Authors: Katja Essen, Thomas Bohlen, Wolfgang Friederich, Thomas MeierAbstract:SUMMARY Wave propagation in coal seams is numerically modelled in order to identify approaches towards the reconnaissance beyond the heading face of an advancing coal mine roadway. Complete synthetic wavefields including P‐SV body waves and Rayleigh-Type seam waves are calculated using a Green’s function approach for simple, laterally homogeneous models and a parallel elastic 2-D/3-D finite difference modelling code for more realistic geometries. For a simple three-layer model the wavefield within the seam is dominated by a fundamental Rayleigh seam mode symmetrical with respect to the centre of the seam on the vertical component and antisymmetrical on the horizontal component. If the seam contains an interleaved dirt band with higher velocities and density, higher modes dominate the wave propagation, depending on the thickness of the dirt band. Wave propagation in laterally inhomogeneous coal seam models with disturbances like seam ends, faults, thinning, washouts and seam splitting is strongly influenced by the Type of disturbance. Amplitudes of seam waves reflected from these disturbances strongly depend on the fault throw and the degree of thinning or washout. In some cases, conversion to higher modes can occur. In all investigated models, those Rayleigh seam wave phases are preferably reflected, which have frequencies above the fundamental mode Airy phase. Lower frequency phases are preferably transmitted. However, seam waves are not reflected from a seam splitting disturbance. Thus a detection of seam splitting with reflected seam waves appears to be impossible. FD computations for 3-D models containing an ending tunnel parallel to the seam and a source beyond the heading face of the tunnel show that seam waves are converted into Rayleigh waves at the tunnel face. They propagate along the surface of the tunnel and interfere with the seam waves propagating beside the tunnel. This effect has to be taken into account for subsequent treatment of experimental data, where the locations of sources and receivers are restricted to a small seismic layout in the vicinity of the tunnel. As tunnel surface waves have slightly lower frequencies than seam waves, it may be feasible to separate tunnel waves from the seam wave reflections, particularly because higher frequency phases of the seam wave are preferably reflected at seam disturbances. Polarization analysis showed, that the elliptically polarized Rayleigh-Type seam waves in the vertical‐radial plane can be distinguished from Rayleigh tunnel waves propagating on the sidewall of the tunnel adjoining the coal layer with elliptical polarization in the radial‐transversal plane.
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Modelling of Rayleigh‐Type seam waves in disturbed coal seams and around a coal mine roadway
Geophysical Journal International, 2007Co-Authors: Katja Essen, Thomas Bohlen, Wolfgang Friederich, Thomas MeierAbstract:SUMMARY Wave propagation in coal seams is numerically modelled in order to identify approaches towards the reconnaissance beyond the heading face of an advancing coal mine roadway. Complete synthetic wavefields including P‐SV body waves and Rayleigh-Type seam waves are calculated using a Green’s function approach for simple, laterally homogeneous models and a parallel elastic 2-D/3-D finite difference modelling code for more realistic geometries. For a simple three-layer model the wavefield within the seam is dominated by a fundamental Rayleigh seam mode symmetrical with respect to the centre of the seam on the vertical component and antisymmetrical on the horizontal component. If the seam contains an interleaved dirt band with higher velocities and density, higher modes dominate the wave propagation, depending on the thickness of the dirt band. Wave propagation in laterally inhomogeneous coal seam models with disturbances like seam ends, faults, thinning, washouts and seam splitting is strongly influenced by the Type of disturbance. Amplitudes of seam waves reflected from these disturbances strongly depend on the fault throw and the degree of thinning or washout. In some cases, conversion to higher modes can occur. In all investigated models, those Rayleigh seam wave phases are preferably reflected, which have frequencies above the fundamental mode Airy phase. Lower frequency phases are preferably transmitted. However, seam waves are not reflected from a seam splitting disturbance. Thus a detection of seam splitting with reflected seam waves appears to be impossible. FD computations for 3-D models containing an ending tunnel parallel to the seam and a source beyond the heading face of the tunnel show that seam waves are converted into Rayleigh waves at the tunnel face. They propagate along the surface of the tunnel and interfere with the seam waves propagating beside the tunnel. This effect has to be taken into account for subsequent treatment of experimental data, where the locations of sources and receivers are restricted to a small seismic layout in the vicinity of the tunnel. As tunnel surface waves have slightly lower frequencies than seam waves, it may be feasible to separate tunnel waves from the seam wave reflections, particularly because higher frequency phases of the seam wave are preferably reflected at seam disturbances. Polarization analysis showed, that the elliptically polarized Rayleigh-Type seam waves in the vertical‐radial plane can be distinguished from Rayleigh tunnel waves propagating on the sidewall of the tunnel adjoining the coal layer with elliptical polarization in the radial‐transversal plane.
Qiang Jiang - One of the best experts on this subject based on the ideXlab platform.
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Rayleigh-Type nondegenerate four-wave mixing: ultrafast measurement and field correlation.
Physical review letters, 2002Co-Authors: Qiang JiangAbstract:We report on an ultrafast longitudinal time measurement by a nonresonant Rayleigh-Type nondegenerate four-wave mixing (NFWM). We investigated the field-correlation effects on Rayleigh-Type NFWM by examining the time-delayed dependence of the NFWM spectra. Based on the field-correlation effects, a time-delayed method is proposed to suppress the thermal effect, and ultrafast relaxation time can be measured even in an absorbing medium.
A Chattopadhyay - One of the best experts on this subject based on the ideXlab platform.
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Dispersion of Rayleigh-Type Wave in an Exponentially Graded Incompressible Crustal Layer Resting on Yielding Foundation
2019Co-Authors: Amit K. Verma, A Chattopadhyay, Mriganka Shekhar Chaki, Abhishek K. SinghAbstract:The objective of this study is to develop a theory to study the propagation of Rayleigh-Type waves in an inhomogeneous layer having yielding surface. A detailed study of a Rayleigh-Type wave propag...
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Dispersion of Rayleigh-Type Wave in an Exponentially Graded Incompressible Crustal Layer Resting on Yielding Foundation
Journal of Theoretical and Computational Acoustics, 2019Co-Authors: Amit K. Verma, A Chattopadhyay, Mriganka Shekhar Chaki, Abhishek K. SinghAbstract:The objective of this study is to develop a theory to study the propagation of Rayleigh-Type waves in an inhomogeneous layer having yielding surface. A detailed study of a Rayleigh-Type wave propagating in an exponentially graded incompressible layer resting on yielding surface is considered. The frequency equation being a function of phase velocity, wave number and heterogeneity parameter associated with the yielding parameter and density of inhomogeneous layer reveals the fact that Rayleigh-Type wave propagation is greatly influenced by the above-stated parameters. In particular cases, the dispersion relation has been discussed for stress-free foundation by taking yielding parameter tending to zero. In numerical and graphical computation, the significant effects of distortional velocity have been carried out. Moreover, the obtained dispersion relation is found in well agreement to the classical case in homogeneous isotropic layer resting on a yielding foundation.
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Impact of curved boundary on the propagation characteristics of Rayleigh-Type wave and SH-wave in a prestressed monoclinic media
Mechanics of Advanced Materials and Structures, 2019Co-Authors: Shalini Saha, Abhishek K. Singh, A ChattopadhyayAbstract:AbstractThe present article delves the effect of curved boundary on the propagation characteristics of Rayleigh-Type wave and SH wave in an initially stressed monoclinic media. The present communic...
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On propagation behavior of SH-wave and Rayleigh-Type wave in an initially stressed exponentially graded fiber-reinforced viscoelastic layered structure
Waves in Random and Complex Media, 2019Co-Authors: Shalini Saha, Abhishek K. Singh, A ChattopadhyayAbstract:The present article undertakes the study of propagation of SH-wave and Rayleigh-Type wave in a layered structure with a layer overlying a semi-infinite medium composed of distinct initially stresse...
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Impact of inhomogeneous fiber-reinforced layer with frictional interface on Rayleigh-Type wave propagation
Journal of Engineering Mathematics, 2019Co-Authors: Akanksha Srivastava, A Chattopadhyay, Abhishek Kumar SinghAbstract:The effect of frictional boundary on the propagation of Rayleigh-Type wave in an initially stressed inhomogeneous fiber-reinforced layer overlying an initially stressed homogeneous semi-infinite medium has been analyzed by an approximate analytical method. A realistic model has been considered for sliding boundary friction at the interface. The frequency equation has been obtained in closed form. The substantial effects of various affecting parameters, viz. reinforcement, inhomogeneity, bonding parameter, spectral decay parameter, and horizontal initial stress on phase and damped velocity have been discussed graphically in detail. The remarkable observation has been obtained through the comparative study in the presence and the absence of reinforcement in the layer.
Abhishek K. Singh - One of the best experts on this subject based on the ideXlab platform.
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Dispersion of Rayleigh-Type Wave in an Exponentially Graded Incompressible Crustal Layer Resting on Yielding Foundation
2019Co-Authors: Amit K. Verma, A Chattopadhyay, Mriganka Shekhar Chaki, Abhishek K. SinghAbstract:The objective of this study is to develop a theory to study the propagation of Rayleigh-Type waves in an inhomogeneous layer having yielding surface. A detailed study of a Rayleigh-Type wave propag...
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Dispersion of Rayleigh-Type Wave in an Exponentially Graded Incompressible Crustal Layer Resting on Yielding Foundation
Journal of Theoretical and Computational Acoustics, 2019Co-Authors: Amit K. Verma, A Chattopadhyay, Mriganka Shekhar Chaki, Abhishek K. SinghAbstract:The objective of this study is to develop a theory to study the propagation of Rayleigh-Type waves in an inhomogeneous layer having yielding surface. A detailed study of a Rayleigh-Type wave propagating in an exponentially graded incompressible layer resting on yielding surface is considered. The frequency equation being a function of phase velocity, wave number and heterogeneity parameter associated with the yielding parameter and density of inhomogeneous layer reveals the fact that Rayleigh-Type wave propagation is greatly influenced by the above-stated parameters. In particular cases, the dispersion relation has been discussed for stress-free foundation by taking yielding parameter tending to zero. In numerical and graphical computation, the significant effects of distortional velocity have been carried out. Moreover, the obtained dispersion relation is found in well agreement to the classical case in homogeneous isotropic layer resting on a yielding foundation.
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Impact of curved boundary on the propagation characteristics of Rayleigh-Type wave and SH-wave in a prestressed monoclinic media
Mechanics of Advanced Materials and Structures, 2019Co-Authors: Shalini Saha, Abhishek K. Singh, A ChattopadhyayAbstract:AbstractThe present article delves the effect of curved boundary on the propagation characteristics of Rayleigh-Type wave and SH wave in an initially stressed monoclinic media. The present communic...
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On propagation behavior of SH-wave and Rayleigh-Type wave in an initially stressed exponentially graded fiber-reinforced viscoelastic layered structure
Waves in Random and Complex Media, 2019Co-Authors: Shalini Saha, Abhishek K. Singh, A ChattopadhyayAbstract:The present article undertakes the study of propagation of SH-wave and Rayleigh-Type wave in a layered structure with a layer overlying a semi-infinite medium composed of distinct initially stresse...
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EFFECT OF LOOSE BONDING AND CORRUGATED BOUNDARY SUR-FACE ON PROPAGATION OF Rayleigh-Type WAVE
Latin American Journal of Solids and Structures, 2018Co-Authors: Abhishek K. Singh, Kshitish Ch. Mistri, Mukesh Kumar PalAbstract:THE PROBLEMS CONCERNS TO THE PROPAGATION OF SURFACE WAVE PROPA-GATION THROUGH VARIOUS ANISOTROPIC MEDIUMS WITH INITIAL STRESS AND IRREGULAR BOUNDARIES ARE OF GREAT INTEREST TO SEISMOLOGISTS, DUE TO THEIR APPLICATIONS TOWARDS THE STABILITY OF THE MEDIUM. THE PRESENT PAPER DEALS WITH THE PROPAGATION OF Rayleigh-Type WAVE IN A CORRU-GATED FIBRE-REINFORCED LAYER LYING OVER AN INITIALLY STRESSED ORTHO-TROPIC HALF-SPACE UNDER GRAVITY. THE UPPER FREE SURFACE IS ASSUMED TO BE CORRUGATED; WHILE THE INTERFACE OF THE LAYER AND HALF-SPACE IS CORRUGATED AS WELL AS LOOSELY BONDED. THE FREQUENCY EQUATION IS DEDUCED IN CLOSED FORM. NUMERICAL COMPUTATION HAS BEEN CARRIED OUT WHICH AIDS TO PLOT THE DIMENSIONLESS PHASE VELOCITY AGAINST DIMENSIONLESS WAVE NUMBER FOR SAKE OF GRAPHICAL DEMONSTRATION. NUMERICAL RESULTS ANALYZE THE INFLUENCE OF CORRUGATION, LOOSE BOND-ING, INITIAL STRESS AND GRAVITY ON THE PHASE VELOCITY OF Rayleigh-Type WAVE. MOREOVER, THE PRESENCE AND ABSENCE OF CORRUGATION, LOOSE BONDING AND INITIAL STRESS IS ALSO DISCUSSED IN COMPARATIVE MANNER.
Katja Essen - One of the best experts on this subject based on the ideXlab platform.
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modelling of Rayleigh Type seam waves in disturbed coal seams and around a coal mine roadway
Geophysical Journal International, 2007Co-Authors: Katja Essen, Thomas Bohlen, Wolfgang Friederich, Thomas MeierAbstract:SUMMARY Wave propagation in coal seams is numerically modelled in order to identify approaches towards the reconnaissance beyond the heading face of an advancing coal mine roadway. Complete synthetic wavefields including P‐SV body waves and Rayleigh-Type seam waves are calculated using a Green’s function approach for simple, laterally homogeneous models and a parallel elastic 2-D/3-D finite difference modelling code for more realistic geometries. For a simple three-layer model the wavefield within the seam is dominated by a fundamental Rayleigh seam mode symmetrical with respect to the centre of the seam on the vertical component and antisymmetrical on the horizontal component. If the seam contains an interleaved dirt band with higher velocities and density, higher modes dominate the wave propagation, depending on the thickness of the dirt band. Wave propagation in laterally inhomogeneous coal seam models with disturbances like seam ends, faults, thinning, washouts and seam splitting is strongly influenced by the Type of disturbance. Amplitudes of seam waves reflected from these disturbances strongly depend on the fault throw and the degree of thinning or washout. In some cases, conversion to higher modes can occur. In all investigated models, those Rayleigh seam wave phases are preferably reflected, which have frequencies above the fundamental mode Airy phase. Lower frequency phases are preferably transmitted. However, seam waves are not reflected from a seam splitting disturbance. Thus a detection of seam splitting with reflected seam waves appears to be impossible. FD computations for 3-D models containing an ending tunnel parallel to the seam and a source beyond the heading face of the tunnel show that seam waves are converted into Rayleigh waves at the tunnel face. They propagate along the surface of the tunnel and interfere with the seam waves propagating beside the tunnel. This effect has to be taken into account for subsequent treatment of experimental data, where the locations of sources and receivers are restricted to a small seismic layout in the vicinity of the tunnel. As tunnel surface waves have slightly lower frequencies than seam waves, it may be feasible to separate tunnel waves from the seam wave reflections, particularly because higher frequency phases of the seam wave are preferably reflected at seam disturbances. Polarization analysis showed, that the elliptically polarized Rayleigh-Type seam waves in the vertical‐radial plane can be distinguished from Rayleigh tunnel waves propagating on the sidewall of the tunnel adjoining the coal layer with elliptical polarization in the radial‐transversal plane.
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Modelling of Rayleigh‐Type seam waves in disturbed coal seams and around a coal mine roadway
Geophysical Journal International, 2007Co-Authors: Katja Essen, Thomas Bohlen, Wolfgang Friederich, Thomas MeierAbstract:SUMMARY Wave propagation in coal seams is numerically modelled in order to identify approaches towards the reconnaissance beyond the heading face of an advancing coal mine roadway. Complete synthetic wavefields including P‐SV body waves and Rayleigh-Type seam waves are calculated using a Green’s function approach for simple, laterally homogeneous models and a parallel elastic 2-D/3-D finite difference modelling code for more realistic geometries. For a simple three-layer model the wavefield within the seam is dominated by a fundamental Rayleigh seam mode symmetrical with respect to the centre of the seam on the vertical component and antisymmetrical on the horizontal component. If the seam contains an interleaved dirt band with higher velocities and density, higher modes dominate the wave propagation, depending on the thickness of the dirt band. Wave propagation in laterally inhomogeneous coal seam models with disturbances like seam ends, faults, thinning, washouts and seam splitting is strongly influenced by the Type of disturbance. Amplitudes of seam waves reflected from these disturbances strongly depend on the fault throw and the degree of thinning or washout. In some cases, conversion to higher modes can occur. In all investigated models, those Rayleigh seam wave phases are preferably reflected, which have frequencies above the fundamental mode Airy phase. Lower frequency phases are preferably transmitted. However, seam waves are not reflected from a seam splitting disturbance. Thus a detection of seam splitting with reflected seam waves appears to be impossible. FD computations for 3-D models containing an ending tunnel parallel to the seam and a source beyond the heading face of the tunnel show that seam waves are converted into Rayleigh waves at the tunnel face. They propagate along the surface of the tunnel and interfere with the seam waves propagating beside the tunnel. This effect has to be taken into account for subsequent treatment of experimental data, where the locations of sources and receivers are restricted to a small seismic layout in the vicinity of the tunnel. As tunnel surface waves have slightly lower frequencies than seam waves, it may be feasible to separate tunnel waves from the seam wave reflections, particularly because higher frequency phases of the seam wave are preferably reflected at seam disturbances. Polarization analysis showed, that the elliptically polarized Rayleigh-Type seam waves in the vertical‐radial plane can be distinguished from Rayleigh tunnel waves propagating on the sidewall of the tunnel adjoining the coal layer with elliptical polarization in the radial‐transversal plane.
