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Keywords: moving load, layered medium, railway track, wave propagation, Biot's theory, Fourier transform.

Summary

Based on poroviscoelastic Biot's theory, a semi-analytical approach is proposed to study the dynamic response of layered ground. The soil is subjected to a vertical harmonic rectangular moving load. The moving excitation is applied either directly over the surface of the ground or over a track model. The track model due to Sheng et al. [1] takes into account rail, sleepers, pads and ballast. A parametric study shows the effects and relative importance of the numerous parameters involved such as load speed, frequency, porosity and permeability. In the case of a load acting directly on a soil, it is shown that the dynamic effect of load speed on the dimensionless surface displacements is only limited for values of velocity near the Rayleigh wavespeed. The dimensionless displacements present the same general trends for any value of porosity considered except for values of velocity near the Rayleigh wavespeed, specially for a more permeable soil. No change is observed with a change of porosity even for high values of load velocity. Compared to the dynamic regime for which the value of frequency is equal to 64 Hz, the amplitude of displacements is higher in the quasi-static regime corresponding to a frequency equal to 1 Hz. However, the effect of permeability is more pronounced in both the quasi-static and dynamic regime. In the quasi-static regime, the porous soil presents more important displacements for a higher permeability, except for values of the load speed near the Rayleigh wavespeed for which displacements are higher for a less permeable soil. An other point under study is the comparison between a viscoelastic and a poroviscoelastic continuum. This comparison reveals that displacement response of the poroviscoelastic soil is lower that the viscoelastic one, in the quasi-static regime. The implementation of a beam on a porous soil shows differences in the amplitude of the solid vertical displacements. Indeed, they are significantly reduced when the track is taking into account. It is also shown that the effect of permeability is not significant and no change of displacement response is observed for any change of permeability, in this case. Numerical results are presented in the spatial domain for both sub- and super Rayleigh regimes varying with the beam's stiffness.

References

1: X. Sheng, C.J.C. Jones, M. Petyt, "Ground vibration generated by a harmonic load acting on a railway track", J Sound Vib, 225(1), 3-28, 1999. doi:10.1006/jsvi.1999.2232

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 100 PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: B.H.V. Topping Paper 96 Dynamic Analysis of a Porous Layered Medium under a Load Moving along a Railway Track K. Chahour¹, G. Lefeuve-Mesgouez¹, A. Mesgouez¹, A. Bouheraoua² and A. Laribi² ¹Faculty of Sciences, University of Avignon et des Pays de Vaucluse, UMR EMMAH, Avignon, France ²LAMMOMS laboratory, Mouloud Mammeri University of Tizi-Ouzou, Algeria doi:10.4203/ccp.100.96 purchase the full-text of this paper Full Bibliographic Reference for this paper K. Chahour, G. Lefeuve-Mesgouez, A. Mesgouez, A. Bouheraoua, A. Laribi, "Dynamic Analysis of a Porous Layered Medium under a Load Moving along a Railway Track", in B.H.V. Topping, (Editor), "Proceedings of the Eighth International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 96, 2012. doi:10.4203/ccp.100.96 Keywords: moving load, layered medium, railway track, wave propagation, Biot's theory, Fourier transform. Summary Based on poroviscoelastic Biot's theory, a semi-analytical approach is proposed to study the dynamic response of layered ground. The soil is subjected to a vertical harmonic rectangular moving load. The moving excitation is applied either directly over the surface of the ground or over a track model. The track model due to Sheng et al. [1] takes into account rail, sleepers, pads and ballast. A parametric study shows the effects and relative importance of the numerous parameters involved such as load speed, frequency, porosity and permeability. In the case of a load acting directly on a soil, it is shown that the dynamic effect of load speed on the dimensionless surface displacements is only limited for values of velocity near the Rayleigh wavespeed. The dimensionless displacements present the same general trends for any value of porosity considered except for values of velocity near the Rayleigh wavespeed, specially for a more permeable soil. No change is observed with a change of porosity even for high values of load velocity. Compared to the dynamic regime for which the value of frequency is equal to 64 Hz, the amplitude of displacements is higher in the quasi-static regime corresponding to a frequency equal to 1 Hz. However, the effect of permeability is more pronounced in both the quasi-static and dynamic regime. In the quasi-static regime, the porous soil presents more important displacements for a higher permeability, except for values of the load speed near the Rayleigh wavespeed for which displacements are higher for a less permeable soil. An other point under study is the comparison between a viscoelastic and a poroviscoelastic continuum. This comparison reveals that displacement response of the poroviscoelastic soil is lower that the viscoelastic one, in the quasi-static regime. The implementation of a beam on a porous soil shows differences in the amplitude of the solid vertical displacements. Indeed, they are significantly reduced when the track is taking into account. It is also shown that the effect of permeability is not significant and no change of displacement response is observed for any change of permeability, in this case. Numerical results are presented in the spatial domain for both sub- and super Rayleigh regimes varying with the beam's stiffness. References 1 X. Sheng, C.J.C. Jones, M. Petyt, "Ground vibration generated by a harmonic load acting on a railway track", J Sound Vib, 225(1), 3-28, 1999. doi:10.1006/jsvi.1999.2232 purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £50 +P&P)
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