Simultaneous Laboratory Measurement of Acoustic and Hydraulic Properties of Unsaturated Soils

George, Lindsay; Dewoolkar, Mandar M.; Znidarčić, Dobroslav

doi:10.2136/vzj2008.0139

Cited by 16 publications

(6 citation statements)

References 55 publications

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“…A systematic hysteresis between imbibition and drainage was observed in V P and versus S w , as commonly measured in rocks (Knight & Nolen‐Hoeksema 1990; Cadoret et al 1995, 1998) but rarely in unconsolidated porous media (Domenico 1977; George et al 2009). To properly analyse our data, we have developed a generalized Biot’s model including the following physical effects.…”

Section: Discussionmentioning

confidence: 57%

“…Other studies (Domenico 1977;Berge & Bonner 2002) in unconsolidated media showed that the effective fluid model remains valid in this high frequency range even if some discrepancies can be attributed to microscopic patchy saturation at high pressure and water saturation. At lower frequencies (20 kHz), George et al (2009) showed that the seismic velocity and attenuation strongly depend on the fluid saturation history in compacted heterogeneous soils similarly to some observation in rocks (Cadoret et al 1995(Cadoret et al , 1998. For unconsolidated media, many laboratory data sets exist but they were mainly obtained on dry, saturated or nearly saturated sediments (Prasad 1992(Prasad , 2002Bardet & Sayed 1993;Ayres & Theilen 2001).…”

Section: Introductionmentioning

confidence: 69%

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Laboratory monitoring of <italic>P</italic> waves in partially saturated sand

2012

Geophysical Journal International

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SUMMARY Energy dissipation is observed on seismic data when a wave propagates through a porous medium, involving different frequency regimes depending on the nature of rock and fluid types. We focus here on the role of partial fluid saturation in unconsolidated porous media, looking in particular at P‐wave phase velocity and attenuation. The study consists in running an experiment in a sand‐filled tank partially saturated with water. Seismic propagation in the tank is generated in the kHz range by hitting a steel ball on a granite plate. Seismic data are recorded by buried accelerometers and injecting or extracting water controls the partial saturation. Several imbibition/drainage cycles were performed between the water and gas residual saturations. A Continuous Wavelet Transform applied on seismic records allowed us to extract the direct P wave at each receiver. We observe an hysteresis in phase velocities and inverse quality factors between imbibition and drainage. Phase velocities and inverse quality factors are then jointly inverted to get a final poro‐viscoelastic model of the partially saturated sand that satisfactorily reproduces the data. The model formulation consists in generalizing the Biot theory to effective properties of the fluid and medium (permeability and bulk modulus) to properly explain the phase velocity variation as a function of the saturation. The strong level of attenuation measured experimentally is further explained by an anelastic effect due to grain to grain sliding, adding to Biot’s losses. This study shows that fluid distribution at microscopic scale has strong influence on the attenuation of direct P waves at macroscopic scale and confirms that seismic prospection may be a powerful tool for the characterization of transport phenomena in porous media.

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Section: Discussionmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 69%

Laboratory monitoring of <italic>P</italic> waves in partially saturated sand

2012

Geophysical Journal International

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“…The amplitude of the hysteresis loop increased as the isotropic confining stresses decreased. George et al (2009) and Khosravi & McCartney (2012) reported similar observations for Bonny silt, while Ng & Xu (2012) analysed the experimental data in terms of the current suction ratio (CSR) and reported that the small strain shear modulus (G 0 ) increased by about 20% when the CSR increased from 1 to 2.…”

Section: Introductionmentioning

confidence: 65%

“…compression and shear waves) propagating through a partially saturated medium are also affected by suction and associated degree of saturation. Compression waves (P-waves) induce the motion of soil grains in the direction of wave propagation and they are mainly affected by the bulk modulus of the medium, which causes them to respond to the variation of the degree of saturation (Inci et al, 2003;George et al, 2009;Barrière et al, 2012). In contrast, shear waves propagate perpendicularly to the direction of their motion, so shear distortion is applied.…”

Section: Introductionmentioning

confidence: 99%

The role of compaction energy on the small strain properties of a compacted silty sand subjected to drying–wetting cycles

2015

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Heitor, A., Indraratna, B. & Rujikiatkamjorn, C. (2015). The role of compaction energy on the small strain properties of a compacted silty sand subjected to drying -wetting cycles. Geotechnique: international journal of soil mechanics, 65 (9), 717-727.The role of compaction energy on the small strain properties of a compacted silty sand subjected to drying -wetting cycles AbstractThe elastic properties of a soil are usually investigated to describe its engineering behaviour. The results of previous studies indicate that the effect of changes in suction on the elastic response at a small strain level of soils is significant during compaction and post-compaction periods. Limited efforts have been focused on quantifying those post-compacted responses due to the changes in suction induced by wetting and drying cycles. During their service life, most earth structures experience changes in hydraulic behaviour owing to climatic changes. These seasonal fluctuations in turn impact on the geomechanical performance of compacted soil. In this paper the aspects related to the elastic properties of compacted soils subjected to cycles of drying and wetting are described. Particular emphasis is placed on the effect of compaction energy on the hysteric behaviour (i.e. amplitude of the hysteresis loop) and its dependence on the initial stress state conditions and suction history. The results not only confirm the importance of the current suction in governing the shear and compression velocities and associated moduli, but they also suggest that subsequent drying-wetting cycles or suction history can further induce hysteretic changes, particularly along the wetting paths. The elastic properties of a soil are usually investigated to describe its engineering behaviour. The results of previous studies indicate that the effect of changes in suction on the elastic response at a small strain level of soils is significant during compaction and post-compaction periods. Limited efforts have been focused on quantifying those post-compacted responses due to the changes in suction induced by wetting and drying cycles. During their service life, most earth structures experience changes in hydraulic behaviour owing to climatic changes. These seasonal fluctuations in turn impact on the geomechanical performance of compacted soil. In this paper the aspects related to the elastic properties of compacted soils subjected to cycles of drying and wetting are described. Particular emphasis is placed on the effect of compaction energy on the hysteric behaviour (i.e. amplitude of the hysteresis loop) and its dependence on the initial stress state conditions and suction history. The results not only confirm the importance of the current suction in governing the shear and compression velocities and associated moduli, but they also suggest that subsequent drying-wetting cycles or suction history can further induce hysteretic changes, particularly along the wetting paths.

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“…The Mualem-van Genuchten approach (Mualem, 1976;van Genuchten, 1980) has been widely used to predict the change in relative hydraulic conductivity with matric potential, based on the soil water release characteristic (e.g. George et al, 2009;Gribb et al, 2009;Touma, 2009). The central assumption of this approach is that soil is a rigid material and porosity remains constant over the range of matric potentials.…”

Section: Introductionmentioning

confidence: 99%

Estimating Relative Hydraulic Conductivity from the Water Release Characteristic of a Shrinking Clay Soil

Gregory

Bird

Whalley

et al. 2010

Soil Science Soc of Amer J

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To understand the hydraulic properties of soils, accurate prediction of the unsaturated hydraulic conductivity is needed, which is commonly derived from the soil water release characteristic. In fine‐textured soils, the modified Mualem–van Genuchten (MMVG) function has been used extensively to predict the change in relative conductivity with changes in matric potential, but this assumes that the soil is rigid with a constant porosity (CP), which is unrealistic for shrinking soils. We used a triaxial cell apparatus to accurately monitor soil volume changes during water release in a clay soil. From this we derived relative hydraulic conductivity functions based on either MMVG (CP), or based on geometrically similar shrinkage (GSS) of all pore sizes by a constant factor as calculated from the measured shrinking porosity (SP). The MMVG (CP) function predicted a decline in relative conductivity of up to three orders of magnitude from 0 to −400 kPa matric potential. This was similar to published data on the response of conductivity in the same soil to consolidation of larger pores. Based on SP, however, the soil remained effectively tension saturated (>0.97) down to a matric potential of −85 kPa due to normal shrinkage. The corresponding GSS (SP) function predicted only a modest decrease in relative conductivity from 1 to 0.85 across this range. In this case the larger pores, although reduced in size, are assumed to be still water filled and conducting. The GSS function was probably the most realistic portrayal of hydraulic functioning in a tension‐saturated shrinking clay soil.

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Simultaneous Laboratory Measurement of Acoustic and Hydraulic Properties of Unsaturated Soils

Cited by 16 publications

References 55 publications

Laboratory monitoring of <italic>P</italic> waves in partially saturated sand

Laboratory monitoring of <italic>P</italic> waves in partially saturated sand

The role of compaction energy on the small strain properties of a compacted silty sand subjected to drying–wetting cycles

Estimating Relative Hydraulic Conductivity from the Water Release Characteristic of a Shrinking Clay Soil

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