HR: 09:15h
AN: NS21A-06    [Abstracts]
TI: Rayleigh Waves Traveling Along the Impermeable Surface of an Unsaturated Poroelastic Half-space
AU: * Chen, Y
EM: samchen1220@hotmail.com
AF: South Region Water Resources Office, Water Resources Agency, Ministry of Economic Affairs, Taiwan, No.70, Mizhi Village, Nanxi Shiang, Tainan County, 71544, Taiwan
AU: * Chen, Y
EM: samchen1220@hotmail.com
AF: Department of Hydraulic and Ocean Engineering, National Cheng Kung University, No.1, University Road, Tainan, 70101, Taiwan
AU: Lo, W
EM: lowc@mail.ncku.edu.tw
AF: Department of Hydraulic and Ocean Engineering, National Cheng Kung University, No.1, University Road, Tainan, 70101, Taiwan
AU: Leu, J
EM: jmleu@mail.ncku.edu.tw
AF: Department of Hydraulic and Ocean Engineering, National Cheng Kung University, No.1, University Road, Tainan, 70101, Taiwan
AU: Cheng, A H
EM: acheng@olemiss.edu
AF: Department of Civil Engineering, University of Mississippi, P.O. Box 1848, University, MS 38677, United States
AB: This study presents an analytical model of Rayleigh waves propagating along the impermeable surface of an unsaturated poroelastic half-space. The developed equation reveals that there are three modes of Rayleigh waves, based on the poroelastic equations in a porous medium containing two immiscible viscous compressible fluids formulated by Lo et al.[Wave propagation through elastic porous media containing two immiscible fluids. Water Resour Res 2005;41:W02025]. These three Rayleigh waves induced by three modes, corresponding to three dilatational waves in a medium saturated by two fluids, can be expressed as the R1, R2, and R3 waves in the descending order of magnitude, respectively. As an excitation frequency is given, the dispersion equation of a cubic polynomial will be solved numerically to derive the three phase speeds and the attenuation coefficients of the R1, R2, and R3 waves in Columbia fine sandy loam penetrated by air and water fluids. The numerical results show that the phase speed of the R1 wave is frequency independent, approximately 93 % to 95 % of the shear wave speed, and nearly 28 % to 49 % of the first dilatational wave speed at the frequencies of 1 Hz, 10 Hz, and 100Hz related to relative water saturation ranges (0.01-0.99). Nevertheless, the R2 and R3 waves are dispersive. In the same frequency ranges, we also find the two ratios of the phase speeds of the R2 and R3 waves to the second and third dilatational wave speeds are both around 56 % to 90 %. In addition, the R1 wave attenuates least while the R3 wave has the highest attenuation coefficient along the impermeable surface. Lastly, all the three modes of Rayleigh wave satisfy the condition of decaying exponentially with the distance far away from the surface of a porous medium.
DE: 3285 Wave propagation (0689, 2487, 4275, 4455, 6934)
SC: Near-Surface Geophysics [NS]
MN: 2009 Joint Assembly