Strain and pore pressure propagation in a water-saturated porous medium

Grinten, J.G.M. van der; Dongen, M. E. H. van; Kogel, Hans van der

doi:10.1063/1.339018

Cited by 45 publications

(25 citation statements)

References 8 publications

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“…It is worth noting, however, that values of á much larger than 0´25 were used by other authors (e.g. Berryman, 1980;Van der Grinten et al, 1987) and led to a good consistency between computed and measured velocities and amplitudes of the longitudinal waves of the ®rst and second kind.Furthermore, the authors have observed the presence of a longitudinal pulse with an amplitude similar to or larger than the amplitude of the longitudinal wave of the ®rst kind (Pwave). This pulse has been considered to be the longitudinal wave of the second kind (Biot-wave).…”

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Observation of Biot compressional wave of the second kind in granular soils

Nakagawa¹,

Soga²,

Mitchell³

2001

Géotechnique

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The authors have presented an interesting set of data on the comparison of elastic wave velocities measured on dry and saturated samples of granular soils and some considerations on a longitudinal pulse which has been interpreted as the longitudinal wave of the second kind (Biot-wave). The purpose of this discussion is to make a few notes that seem important in appreciating the signi®cance of the paper.From the comparison of the shear moduli evaluated from the shear wave velocities of dry and saturated samples, the authors conclude that the shear modulus of the saturated samples should be smaller than that of the dry sample and this could possibly be related to the wetting contacts between particles. The authors' analysis has been carried out using quite a low value of the apparent mass density: the`structural factor' á has been assumed equal to 0´25 as recommended by Stoll (1989) from an investigation of the attenuation characteristics of longitudinal waves. However, there are many evaluations of the added mass density, which are based on theoretical analyses, on analogical principles and on experimental measurements (as reviewed by Gajo, 1996), which seem to show that, for granular soils comprised of round grains, the`tortuosity' ô can be approximated bywhere â is the porosity and ô á 1. As a consequence, thè structural factor' á would be approximately equal to 0´06 for coarse Monterey sand, and approximately equal to 0´50 for medium Monterey sand and for ®ne crystal silica sand. These values would reduce the shear wave velocity (of about 2%) and would possibly render unnecessary the reduction of the shear modulus of saturated samples, proposed by the authors in order to have a theoretical shear wave velocity closer to the experimental data. However, these higher values of á would lead to a reduction in the computed velocity of the longitudinal waves of the second kind (about 10%) and this would change the interpretation of all the measurements. It is worth noting, however, that values of á much larger than 0´25 were used by other authors (e.g. Berryman, 1980;Van der Grinten et al., 1987) and led to a good consistency between computed and measured velocities and amplitudes of the longitudinal waves of the ®rst and second kind.Furthermore, the authors have observed the presence of a longitudinal pulse with an amplitude similar to or larger than the amplitude of the longitudinal wave of the ®rst kind (Pwave). This pulse has been considered to be the longitudinal wave of the second kind (Biot-wave). The relatively large amplitude of this pulse is not consistent with theoretical

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confidence: 98%

mentioning

confidence: 98%

Observation of Biot compressional wave of the second kind in granular soils

Nakagawa¹,

Soga²,

Mitchell³

2001

Géotechnique

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“…The pressure trough A is not measured. It is associated with precursor tube mode 18 in the input signal p 0 (Fig. 3).…”

Section: A Borehole Fracturesmentioning

confidence: 99%

Shock-induced wave propagation over porous and fractured borehole zones: Theory and experiments

Fan

Smeulders

2013

The Journal of the Acoustical Society of America

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Borehole waves are strongly affected by adjacent porous zones or by fractures intersecting the borehole. A theoretical description for both porous and fracture zones is possible based on the introduction of an effective borehole fluid bulk modulus, characterizing the wave attenuation via borehole wall impedance. This impedance can be calculated for both porous and fracture zones adjacent to the borehole, thus predicting borehole wave attenuation, transmission, and reflection over such zones. A shock tube setup generates borehole tube waves that are used for porous and fracture zone characterization. A PVC sample is used to introduce and vary fractures in a cylindrical sample. Shock wave experiments show that attenuation in boreholes adjacent to porous zones can be predicted by theory. The transmittivities of a borehole tube wave over 1 and 5 mm fractures are correctly predicted, thus showing the potential of borehole wave experiments for fracture detection and characterization.

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“…The frequency band width was investigated in a previous article (Chao et al 2004) and found to be between 0.5 and 80 kHz, approximately. Van der Grinten et al (1985, 1987, Sniekers et al (1989), and Smeulders and Van Dongen (1997) also performed shock-tube experiments on water-saturated and partially saturated samples, but here we focus on borehole wave along water-saturated samples.…”

Section: Introductionmentioning

confidence: 99%

Shock-Induced Borehole Waves and Fracture Effects

Fan

Smeulders

2012

Transp Porous Med

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We perform wave experiments using a vertical shock tube setup. Shock waves are generated by the rupture of a thin membrane. In the test section, the incident pressure waves generate borehole-guided waves along water-saturated samples. The tube is equipped with side wall gages and a mobile pressure probe, so that the attenuation and reflection of the wave can be measured. The computation for a single horizontal fracture intersecting a vertical borehole gives a quantitative prediction of reflection and transmission of borehole-guided waves. Three different fracture apertures are used for the calculation. Fracture aperture significantly affects both reflection and transmission coefficients. Large fractures increase reflectivity and decrease transmissivity. In the experiment, we found that both pressures above and below the fracture are influenced by the fracture aperture indeed, thus indicating the potential for fracture detection by borehole waves.

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Strain and pore pressure propagation in a water-saturated porous medium

Cited by 45 publications

References 8 publications

Observation of Biot compressional wave of the second kind in granular soils

Observation of Biot compressional wave of the second kind in granular soils

Shock-induced wave propagation over porous and fractured borehole zones: Theory and experiments

Shock-Induced Borehole Waves and Fracture Effects

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