scholarly journals Bender elements in stiff cemented clay: shear wave velocity (Vs) correction by applying wavelength considerations

2019 ◽  
Vol 56 (7) ◽  
pp. 1034-1041 ◽  
Author(s):  
Qasim Khan ◽  
Sathya Subramanian ◽  
Dawn Y.C. Wong ◽  
Taeseo Ku
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Near Field ◽  
Shear Stiffness ◽  
Propagation Distance ◽  
Small Strain ◽  
Bender Element ◽  
Bender Elements ◽  
Sine Signal

For the quality control of cement mixing in clays, small-strain shear stiffness Gmax is now increasingly being used due to enhanced repeatability in shear wave velocity (Vs) measurements. These stiff cemented clays have higher resonant frequencies that require the use of higher input frequencies in bender element testing for reliable Vs measurements. However, the practical requirements for suitable signals (with minimal near-field effects and wave reflections) can often be difficult to implement. To facilitate such Vs measurements, the current study proposes a methodology that can correct Vs values corresponding to lower wave propagation distance to wavelength ratios (Ltt/λ) to more reliable values of Vs at reference Ltt/λ criterion suggested in previous studies (e.g., 2, 3.33, and 4). Two clay types are mixed with ordinary Portland cement and various mix ratios are utilized to cover a wider range of soil stiffnesses. Based on the collected database, it is found that the resulting fitting functions enable the reasonable estimation of the stabilized Vs values corresponding to the suggested Ltt/λ criterion regardless of the nature of the input sine signal.

Dyadic wavelet analysis of bender element signals in determining shear wave velocity

2020 ◽  
Vol 57 (12) ◽  
pp. 2027-2030
Author(s):  
Guan Chen ◽  
Fang-Tong Wang ◽  
Dian-Qing Li ◽  
Yong Liu
Keyword(s):  
Wavelet Transform ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Near Field ◽  
Bender Element ◽  
Dyadic Wavelet ◽  
Wavelet Transform Modulus Maxima ◽  
Dyadic Wavelet Transform ◽  
Modulus Maxima

Determining shear wave velocity is a critical technique in bender element tests, as it can be readily affected by near-field effects, wave reflection, and other factors. This study proposes a new method based on the dyadic wavelet transform modulus maxima. Combining the local modulus maxima of dyadic wavelet transform approximate coefficients at fine decomposition levels and an appropriate threshold value, the proposed method can automatically detect the target point. For validation, a comparative study among the dyadic wavelet transform modulus maxima, peak-to-peak, first arrival, and cross-correlation methods was carried out using 140 sets of bender element signals. The comparison results show that the proposed method not only mitigates the adverse effects of near-field, later major peaks, and noise contamination, but is also more robust in estimating shear wave velocity.

scholarly journals Evaluation of the shear wave velocity (VS) of an artificial carbonate sand obtained with the use of bender elements test

DYNA ◽  
2021 ◽  
Vol 88 (217) ◽  
pp. 211-219
Author(s):  
Samuel Felipe Mollepaza Tarazona ◽  
Bárbara Luiza Riz de Moura ◽  
Matias Faria Rodrigues ◽  
Maria Cascão Ferreira de Almeida ◽  
Marcio De Souza Soares de Almeida
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Mechanical Response ◽  
Near Field ◽  
Triaxial Tests ◽  
Dynamic Parameters ◽  
Bender Elements ◽  
Carbonate Sand ◽  
Confining Stress

Carbonate sand is characterized by the presence of fragile grains, which may influence their mechanical response due to the imposed loading; especially cyclic loading. The shear wave velocity (VS) provides relevant information for the design of foundation inserted in this type of soil, which can be obtained from laboratory tests with the use of bender elements (BE). This paper aims to evaluate the VS value of a carbonate sand from triaxial tests with BE using three methods in the time domain. The influence of loading, unloading and cycling on VS is also evaluated. The results confirmed that the confining stress affects the dynamic parameters. At higher stress levels, the signals aremore susceptible to the near field effects and the dynamic parameters are less influenced by cycling.

Measuring shear wave velocity of granular material using the piezoelectric ring-actuator technique (P-RAT)

2015 ◽  
Vol 52 (9) ◽  
pp. 1302-1317 ◽  
Author(s):  
Mourad Karray ◽  
Mohamed Ben Romdhan ◽  
Mahmoud N. Hussien ◽  
Yannic Éthier
Keyword(s):  
Granular Material ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Near Field ◽  
Soil Improvement ◽  
Bender Element ◽  
Factors Affecting ◽  
A New Technique ◽  
P Rat

A precise evaluation of shear wave velocity, Vs, is a crucial issue in the design of foundations subjected to dynamic loading, liquefaction evaluation, and soil improvement control. Laboratory techniques such as resonant column (RC) and bender element (BE) have been developed over the years to measure Vs. At low strain (γ < 10−3), techniques based on piezoelectric elements (e.g., BE) can be considered superior to RC, as they can be used in conventional geotechnical devices (e.g., triaxial, oedometer, direct simple shear, etc.). However, it is a difficult task to verify that the obtained Vs values are correct and accurate, as there are several difficulties associated with these methods, including the mixed radiation of both primary and shear waves, near-field effects, boundary effects, and uncertain detection of first arrivals. This paper presents the use of a new technique to measure Vs in granular material, called the piezoelectric ring-actuator technique (P-RAT), developed at the Université de Sherbrooke. The paper also provides a detailed description of a unique interpretation method of the signals produced from this technique to minimize the difficulties associated with other techniques. The P-RAT has been incorporated into the well-known oedometer cell to measure the Vs of Péribonka sand through a series of oedometric tests, and the obtained results have been detailed, analyzed, and discussed in light of the basic state of knowledge of Vs and factors affecting it. Particular emphasis is also placed on the validation of the accuracy of the P-RAT by means of reliable experimental measurements available in literature.

Phase and amplitude responses associated with the measurement of shear-wave velocity in sand by bender elements

2000 ◽  
Vol 37 (6) ◽  
pp. 1348-1357 ◽  
Author(s):  
J Blewett ◽  
I J Blewett ◽  
P K Woodward
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Excitation Frequency ◽  
Maximum Velocity ◽  
Finite Frequency ◽  
Bender Element ◽  
Bender Elements ◽  
Phase Sensitive ◽  
Phase Sensitive Detection

Shear-wave velocity measured by bender elements in laboratory sand samples is shown to be dependent upon the excitation frequency and exhibits a maximum velocity for a finite frequency. By comparing the relative effects of dispersion due to propagation of shear waves through sand and dispersion due to bender element performance within sand, we show that a combination of the two processes is required to explain the observations. The magnitude of the aggregate response of the bender elements and the sand implies that reliable shear-wave velocity results cannot be obtained from bender element tests without a prior knowledge of the frequency response of the entire system.Key words: shear-wave velocity, phase-sensitive detection, dispersion, attenuation, sand.

Shear Strength Monitoring System Based on Measurement of Shear Wave Velocity and Moisture Content

2014 ◽  
Vol 635-637 ◽  
pp. 750-754
Author(s):  
Peng Hu ◽  
Qing Li ◽  
Yi Wei Xu ◽  
Nan Ying Shentu ◽  
Quan Yuan Peng
Keyword(s):  
Shear Strength ◽  
Moisture Content ◽  
Shear Wave ◽  
Monitoring System ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Bender Elements ◽  
Strength Measurement ◽  
Soil Shear Strength ◽  
The Relationship

Expound the importance of soil shear strength measurement at mudslide hidden point to release the loss caused by the disaster, explain the relationship between shear wave velocity, moisture content and shear strength, design the shear strength monitoring system combining the shear wave velocity measured by Piezoelectric bender elements and moisture content.

Surface-mounted bender elements for measuring horizontal shear wave velocity of soils

2008 ◽  
Vol 9 (11) ◽  
pp. 1490-1496 ◽  
Author(s):  
Yan-guo Zhou ◽  
Yun-min Chen ◽  
Yoshiharu Asaka ◽  
Tohru Abe
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Horizontal Shear ◽  
Bender Elements

Bender Element Test and Numerical Simulation of Sliding Zone Soil with Gravels of Huangtupo Landslide

2021 ◽  
Author(s):  
Yu Chen
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Velocity ◽  
Small Strain ◽  
Testing System ◽  
Bender Element ◽  
Gravel Content ◽  
Consolidation Pressure ◽  
Bender Element Test ◽  
Sliding Zone

&lt;p&gt;In order to study the effect of the different consolidation pressure, loading-unloading path and gravel content on the shear modulus of the small strain of sliding zone soil, a set of consolidation bender element test device was developed. The device consists of three parts: a consolidation system, a deformation measuring system, and a shear wave testing system. The consolidation system is composed of a traditional consolidation instrument and the plexiglass cylinder box. The sample is cylindrical in shape and has a size of 50 mm&amp;#215;50 mm. The consolidation displacement is measured by a digital display micrometer. Shear wave testing system is a wave velocity measurement system made of piezoelectric ceramic. The experimental results show that the device can control the consolidation pressure and measure the vertical deformation, measure the shear wave velocity of the sliding zone soil in real-time, and then study the variation rule of the small strain shear modulus of the sliding zone soil with gravels. The shear modulus of the sliding zone soil increases with an increase in the consolidation pressure. The shear modulus of the unloading of sliding zone soil is larger than that of loading. Under the loading pressure of 200 kPa and 400 kPa, the shear modulus of the sliding zone soil first decreases and then increases with an increase in the gravel content. In the process of unloading, the shear modulus of the sliding zone soil increases with an increase in the gravel content.&amp;#160;&lt;/p&gt;

Measurement of small-strain shear modulus Gmax of dry and saturated sands by bender element, resonant column, and torsional shear tests

2008 ◽  
Vol 45 (10) ◽  
pp. 1426-1438 ◽  
Author(s):  
Jun-Ung Youn ◽  
Yun-Wook Choo ◽  
Dong-Soo Kim
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Shear Wave Velocity ◽  
Small Strain ◽  
Resonant Column ◽  
Test Results ◽  
Bender Element ◽  
Small Strain Shear Modulus ◽  
Torsional Shear ◽  
Saturated Sands

The bender element method is an experimental technique used to determine the small-strain shear modulus (Gmax) of a soil by measuring the velocity of shear wave propagation through a sample. Bender elements have been applied as versatile transducers to measure the Gmax of wet and dry soils in various laboratory apparatuses. However, certain aspects of the bender element method have yet to be clearly specified because of uncertainties in determining travel time. In this paper, the bender element (BE), resonant column (RC), and torsional shear (TS) tests were performed on the same specimens using the modified Stokoe-type RC and TS testing equipment. Two clean sands, Toyoura and silica sands, were tested at various densities and mean effective stresses under dry and saturated conditions. Based on the test results, methods of determining travel time in BE tests were evaluated by comparing the results of RC, TS, and BE tests. Also, methods to evaluate Gmax of saturated sands from the shear-wave velocity (Vs) obtained by RC and BE tests were investigated by comparing the three sets of test results. Biot’s theory on frequency dependence of shear-wave velocity was adopted to consider dispersion of a shear wave in saturated conditions. The results of this study suggest that the total mass density, which is commonly used to convert Gmax from the measured Vs in saturated soils, should not be used to convert Vs to Gmax when the frequency of excitation is 10% greater than the characteristic frequency (fc) of the soil.

scholarly journals Shear modulus of hydrate bearing calcareous sand-fines mixture

2019 ◽  
Vol 92 ◽  
pp. 04002
Author(s):  
Litong Ji ◽  
Abraham C.F. Chiu ◽  
Lu Ma ◽  
Chao Jian
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Hydrate Formation ◽  
Confining Pressure ◽  
Specimen Preparation ◽  
Bender Element ◽  
Calcareous Sand ◽  
Bender Element Test

This article presents a laboratory study on the maximum shear modulus of a THF hydrate bearing calcareous sand (CS)–fines mixture. The maximum shear modulus was inferred from the shear wave velocity measured from the bender elements installed in a temperature-controlled triaxial apparatus. The specimen preparation procedures were specially designed to mimic the hydrate formation inside the internal pores of CS. A trial test was conducted to validate whether the shear wave velocity is a feasible parameter to monitor the formation and dissociation of hydrate in the CS-fines mixture. Based on the bender element test results, hydrate has a more profound effect than confining pressure on enhancing the maximum shear modulus of CS-fines mixture.

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