Changes in dielectric permittivity and shear wave velocity during concentration diffusion

1995 ◽  
Vol 32 (4) ◽  
pp. 647-659 ◽  
Author(s):  
J.C. Santamarina ◽  
M. Fam
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Electromagnetic Waves ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
High Concentration ◽  
Interparticle Forces ◽  
Wave Measurements ◽  
Concentration Diffusion

This paper documents a study of concentration diffusion with complementary mechanical and electromagnetic wave measurements. The paper starts with a review of the fundamentals of interparticle forces and wave–geomedia interaction. Experimental data were collected during the diffusion of a high-concentration solution of potassium chloride through different soils with different boundary conditions. Bentonite and kaolinite contracted during diffusion. The interaction between the concentration gradient, true interparticle forces, and fabric changes produced a pore-water pressure front that advanced ahead of the concentration front. The complex permittivity changed with the advance of the concentration front, reflecting the decrease in moisture content and the increase in conductivity. Concentration diffusion affected shear wave propagation through changes in true interparticle forces. Bentonite showed a significant increase in shear wave velocity, whereas the velocity of propagation in kaolinite decreased. Published differences in the behavior of bentonite and kaolinite were compiled and hypotheses are proposed to explain observed phenomena. Key words : mechanical waves, electromagnetic waves, clays, diffusion, double layer.

scholarly journals Investigation of fabric evolution using bidirectional shear wave velocity measurements

2019 ◽  
Vol 92 ◽  
pp. 03008
Author(s):  
Kazem Fakharian ◽  
Farzad Kaviani Hamedani ◽  
Iman Parandian ◽  
Morteza Jabbarpour Aghdam
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Velocity Measurements ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Fabric Evolution ◽  
Undrained Conditions

In order to characterise fabric evolution, continuous bidirectional shear wave velocity measurements are performed in vertical and horizontal directions (V&H) on triaxial soil specimens during shearing in which two horizontal piezo-electrics were mounted on samples using a new measurement technique. The specimens are prepared by wet tamping method and then subjected to strain-controlled compressional shearing under drained and undrained conditions. The shear wave velocities of all drained specimens initially increased as the loading commenced and then converged to a unique state in both horizontal and vertical directions. The shear wave velocity of undrained specimens on the other hand, for both horizontal and vertical directions initially decreased due to the rising of the excess pore water pressure and then gradually approached a unique shear wave velocity like drained specimens. The fabric condition or stiffness in V&H directions of all the examined drained and undrained specimens at critical state are found to be unique.

FORK BLADE-TYPE FIELD VELOCITY PROBE FOR MEASURING SHEAR WAVES

2008 ◽  
Vol 22 (11) ◽  
pp. 965-969 ◽  
Author(s):  
HYUNG-KOO YOON ◽  
JONG-SUB LEE ◽  
YOUNG-UK KIM ◽  
SUNGSOO YOON
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Pore Water ◽  
Shear Wave Velocity ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Disturbance ◽  
Excess Pore Water Pressure ◽  
Field Velocity ◽  
Excess Pore

The reasonable assessment of the shear wave velocity of soft soils in the laboratory is difficult due to the soil disturbance. This study presents a new apparatus, the blade-type field velocity probe, FVP, which overcomes several limitations of commonly used shear wave measurement methods in the field. The shear wave velocity of the FVP is simply calculated by using the travel distance and the travel time without inversion process. The FVP are carried out in clay soils up to 30m in depth. In addition, the dissipation of excess pore water pressure is investigated. The shear wave velocity is measured every 10cm. The velocity profiles with depth show the consolidation of the upper part of the soft clay. The shear wave velocity approaches asymptotic value after 50 minutes later due to the dissipation of excess pore water pressure. This study suggests that the blade-type FVP may be an effective device for measuring the shear wave velocity with minimized soil disturbance in the field.

Deep Shear Wave Velocity Profiles from Surface Wave Measurements in the Mississippi Embayment

2007 ◽  
Vol 23 (4) ◽  
pp. 791-808 ◽  
Author(s):  
Brent L. Rosenblad ◽  
Jianhua Li ◽  
Farn-Yuh Menq ◽  
Kenneth H. Stokoe
Keyword(s):  
Surface Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Response ◽  
Source Surface ◽  
Mississippi Embayment ◽  
Near Surface ◽  
Wave Measurements ◽  
Central United States

Shear wave velocity ( VS) profiles to depths of approximately 200 m were developed from active-source surface wave velocity measurements in the Mississippi Embayment region of the Central United States. Soil deposits in this region are hundreds of meters thick, but are poorly characterized at depths below 60 m. Measurements were performed at five locations in Arkansas and Tennessee with a maximum distance between sites of approximately 130 km. The median VS profile calculated from the five profiles is in good agreement with a generic reference VS profile for the Mississippi Embayment that has been used in recent site response studies. The near-surface VS profiles at the five sites were remarkably consistent with average shear wave velocities in the top 30 m ( VS30), varying by less than 10%. Increasing variability between the VS profiles was observed at greater depths. The variability between VS profiles was shown to be correlated with changes in lithology at two of the sites where nearby lithologic information was available.

scholarly journals Shear-wave velocity measurements and their uncertainties at six industrial sites

2021 ◽  
pp. 875529302098802
Author(s):  
Yaniv Darvasi
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Dispersion Curves ◽  
Shallow Subsurface ◽  
Industrial Sites ◽  
Wave Measurements ◽  
Average Shear ◽  
The Individual ◽  
Industrial Zones

This study assesses the variability of shear-wave ( VS) profile determinations for a suite of methods at six industrial sites. The methods include active, consisting of multi-channel analysis of surface waves (MASW), as well as passive, consisting of refraction microtremor (ReMi), and extended spatial autocorrelation (ESAC). The purpose is to ascertain the effect of the higher level of ambient noise on the results from the different methods, as only a few of these many methods are commonly used for site characterization. The measured dispersion curves are in fair agreement with one another. The average coefficient of variation (CoV; the percentage ratio of the standard deviation to the mean) for the dispersion curves varied from 2.5% to 12.6%. In contrast, over the VS-depth domain, the average shear-wave velocity profiles to a depth z ( VS,Z) vary from 11.6% to 16.5% between the various methods at the different sites. This indicates that the variance among the individual methods can lead to significant misinterpretation of the shallow subsurface, while the average VS,Z is much more robust. This reaffirms its use (mainly as VS,30) in building codes and within ground motion prediction equations (GMPEs). At all six sites, because of inversion processes, the variability within each method ranges from 4% up to 14%. There is no correlation between the test type and the CoV. Our study focused on surface-wave measurements in noisy industrial environments, where the signals processed are typically complex. Despite this complexity, our results suggest that such tests are also applicable to industrial zones, where the noisy environment constitutes an energy source.

scholarly journals Studies on a Piezoelectric Cylindrical Transducer for Borehole Dipole Acoustic Measurements

2021 ◽  
Vol 11 (3) ◽  
pp. 1036
Author(s):  
Yinqiu Zhou ◽  
Xiuming Wang ◽  
Yuyu Dai
Keyword(s):  
Numerical Simulation ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Low Frequency ◽  
Compressional Wave ◽  
Wave Measurements ◽  
New Development ◽  
Cylindrical Transducer ◽  
Simulation Results

In this article, a novel design of a piezoelectric dipole transducer is proposed for formation acoustic velocity measurement in the vicinity of a borehole with a frequency range of 0.4–6 kHz. The transducer which actuates a cylindrical shell to generate a pure dipole mode wave by using multiple piezoelectric bender bars is analyzed theoretically and simulated numerically by using the finite element method (FEM). Moreover, the transducer is fabricated and tested to compare with the numerical simulation results, which shows that the test and simulation results are in good agreement. Finally, compared with numerical simulation results of the traditional dipole transducer, it is shown that the proposed dipole transducer has higher transmitting sensitivities than commonly used ones, especially in low frequency responses. This work lays a foundation for the new development of the transducer in borehole dipole acoustic shear wave measurements. Especially, in a slow formation where the shear wave velocity is lower than that of compressional wave in the borehole fluid, the transducer could be used for highly efficient shear wave velocity measurements.

scholarly journals In situ shear wave velocity from multichannel analysis of surface waves (MASW) tests at eight Norwegian research sites

2007 ◽  
Vol 44 (5) ◽  
pp. 533-544 ◽  
Author(s):  
Michael Long ◽  
Shane Donohue
Keyword(s):  
Surface Waves ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Small Strain ◽  
Soft Clays ◽  
Small Strain Stiffness ◽  
Wave Measurements ◽  
Multichannel Analysis

The multichannel analysis of surface waves (MASW) technique, which is used to determine shear wave velocity (Vs) and hence small strain stiffness (Gmax), has recently generated considerable interest in the geophysics community. This is because of the ease of carrying out the test and analysis of the data. The objective of this work was to assess the repeatability, accuracy, and reliability of MASW surface wave measurements for use in engineering studies. Tests were carried out at eight well-characterized Norwegian clay, silt, and sand research sites where Vs had already been assessed using independent means. As well as being easy and quick to use, the MASW technique gave consistent and repeatable results, and the MASW Vs profiles for the clay sites were similar to those obtained from other techniques. Reasonable results were also obtained for the silt and sand sites, with the best result being obtained for the finer silt. This work also confirms that MASW Vs clay profiles are comparable to those obtained by correlation with cone penetration test (CPT) data. For these sites there also seems to be a good correlation between normalized small strain shear modulus and in situ void ratio or water content, and the data fit well with published correlations for clays.Key words: soft clays, silts, sands, small strain stiffness, shear wave velocity.

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