What is it about?

ABSTRACT: Besides other elastic, petrophysical, and hydrophysical parameters, the acoustic coupling factor (coupling factor or structure factor, s ) is a critical micro-geometrical parameter in the Biot's theory of elasticity. The coupling factor exerts a specific influence on the mechanisms of propagation and attenuation of vibrations (seismic waves and acoustic signals) in porous media. It is a measure of the internal structure (geometry and shape of pores and pore tubes) of a porous medium, and thus it is a good indicator of the degree of coupling between pore fluid and solid grains. It is unity for no coupling and infinity for perfect coupling. In this study, the coupling factor is obtained for surface soils and shallow sediments, using compressional wave velocity ( x p ) determined from in situ seismic refraction measurements. The investigated soils and underlying sediments (aeration zone and aquifer) exhibit a general s range of 1.22-3.19 (average = 1.82), corresponding to a general x f range of 134-2060 m/s (average = 1134 m/s). The s values are correlated to the bulk modulus-shear modulus ratio (K/ w ) and the porosity (). A direct linear correlation between s and K/ w and an inverse polynomial correlation between s and are obtained, with coefficients of correlation of 0.91 and 0.98, respectively. Also, various items related to the coupling factor, Biot's theory, attenuation mechanisms, fast and slow compressional waves (first and second kinds), and shear waves are discussed. FOR CITATION: Salem, H.S. 2001. Determination of the acoustic coupling factor of Biot’s theory of elasticity, using in situ seismic measurements. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 23(10-December): 917–936. (Published by Taylor & Francis, USA). https://www.tandfonline.com/doi/abs/10.1080/009083101317071360 and https://www.researchgate.net/publication/232964663_Determination_of_the_Acoustic_Coupling_Factor_of_Biot's_Theory_of_Elasticity_Using_in_situ_Seismic_Measurements

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Why is it important?

The Biot's Theory coupling factor is a function of several influences. For example, an increase in the coupling factor's value indicates a greater pressure and greater cementation, compaction, and consolidation, as well as a greater saturation. The coupling factor is a significant parameter in understanding the mechanisms of propagation and attenuation of vibrations in porous media

Perspectives

In the present study, the acoustic coupling factor (coupling factor or structure factor), as one of the critical micro-geometrical parameters in Biot’s theory of elasticity, has been determined using the compressional wave velocity obtained from in situ seismic refraction measurements for the surface soils and the underlying sediments in the study area. To the author’s knowledge, this is the first time that the coupling factor, which contributes effectively to the mechanisms of the propagation and attenuation of vibrations (seismic waves and acoustic signals) through porous media, is obtained from in situ seismic measurements. In this study, the coupling factor has been investigated statistically, theoretically, analytically, and numerically.

Prof. Dr. Hilmi S. Salem

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This page is a summary of: Determination of the Acoustic Coupling Factor of Biot's Theory of Elasticity, Using in situ Seismic Measurements, Energy Sources, December 2001, Taylor & Francis, DOI: 10.1080/009083101317071360.
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