The Use of Hall Effect Semiconductors in Geotechnical Instrumentation

Drnevich, PV; Clayton, C.R.I.; Khatrush, SA; Bica, Adriano Virgílio Damiani; Siddique, AB

doi:10.1520/gtj10676j

Cited by 107 publications

(5 citation statements)

References 8 publications

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“…In addition to the conventional external measurement of axial strain using a linear variable differential transformer (LVDT), the cyclic triaxial system is equipped with three Hall-effect transducers (Clayton et al 1989) for measuring local soil deformation at the mid-height of each specimen, as shown in Fig. 1.…”

Section: Testing Apparatus and Measuring Devicementioning

confidence: 99%

Resilient modulus of unsaturated subgrade soil: experimental and theoretical investigations

2013

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The resilient modulus, M R , of subgrade soil is an important stiffness parameter for analysing fatigue cracking in either the asphalt or concrete layer of a pavement. Although subgrade soil is often unsaturated and subject to seasonal variations of moisture content and hence suction in the field, effects of soil suction on the resilient modulus are generally not accounted for in existing testing methods. In this study, M R values of a subgrade soil under various stress and suction conditions were investigated using a suction-controlled cyclic triaxial apparatus. To enhance the accuracy of measurements, Hall-effect transducers were employed to monitor the local axial and radial deformation of each specimen. It was found that M R increases with number of load applications when a soil contracts, but decreases slightly when a soil dilates. When suction increases, the soil response tends to change from contractive to dilative due to suction-induced dilatancy. Moreover, the measured M R is highly dependent on the stress state. It decreases with cyclic stress due to the nonlinearity of the soil stress-strain behaviour, but increases significantly with suction due to the presence of water tension. At the same stress and suction conditions, M R measured along the wetting path is generally larger than that measured along the drying path. A new semi-empirical equation representing the stress-dependency of M R is proposed and was verified using experimental results of four different soils.Résumé : Le module de résilience, M R , du sol de fondation est un paramètre important de la rigidité pour l'analyse des fissures de fatigue dans l'asphalte ou la couche de béton d'une chaussée. Même si le sol de fondation sur le terrain est souvent non saturé et soumis aux variations saisonnières de teneur en eau, et conséquemment de succion, les effets de la succion du sol sur le module de résilience ne sont généralement pas considérés dans les méthodes d'essais existantes. Dans cette étude, les M R d'un sol de fondation soumis à différentes conditions de contraintes et succion ont été étudiés à l'aide d'un appareil triaxial cyclique contrôlé par la succion. Pour améliorer la précision des mesures, des capteurs à effet de Hall ont été utilisés pour suivre les déformations axiales et radiales de chaque échantillon. Il a été observé que M R augmente avec le nombre d'applications de charges lorsque le sol se contracte, mais diminue légèrement lorsque le sol se dilate. Quand la succion augmente, le comportement du sol tend à changer de contractif à dilatant en raison de la dilatation induite par la succion. De plus, le M R mesuré est fortement dépendant de l'état des contraintes. Il diminue avec les contraintes cycliques en raison de la non-linéarité du comportement en contrainte-déformation du sol, mais augmente significativement avec la succion à cause de la présence de la tension de l'eau. Pour les mêmes conditions de contrainte et succion, le M R mesuré en mouillage est généralement plus grand que celui mesuré en séchage. Une nouvelle éq...

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Section: Testing Apparatus and Measuring Devicementioning

confidence: 99%

Resilient modulus of unsaturated subgrade soil: experimental and theoretical investigations

2013

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“…Encoder sensors were used for the tests [67]. The sensors were derived from Hall effect sensors [68]. Two sensors were used to measure the sample's axial strain and one radial sensor in a system proposed by [69].…”

Section: Materials and Metodologymentioning

confidence: 99%

Characteristic of small-strain stiffness of fine-grained soils based on advanced laboratory tests

2023

Archives of Civil Engineering

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The non-linearity of the modulus in the zone of small deformations has become one of the three basic concepts of modern soil mechanics, together with "effective stresses" or "critical state". It is therefore necessary to obtain suitable parameters to describe these phenomena through the development of modern measuring equipment and new research methods. Limitations in the availability of the research area or research equipment indicate the need to create a data set, in the formula of regional assessments. The article presents a compilation of data on the deformation characteristics of soils covering about 75% of the country's area, which are the most common subsoils for building. Descriptions, images of microstructures, and a record of mechanical parameters are presented for various age-old glacial clays and marginal clays and loesses. Emphasis is placed on parameters obtained from triaxial tests, including the determination of the shear modulus at small deformations obtained from BET measurements. In combination with the patented solution of sample strain measurement, complete deformability curves of the tested samples were obtained, indicating model reference curves developed for the above soil types. The statistically significant amount of data collected allowed the creation of a specific portfolio for selected soils as a starting point for assessing deformability. This corresponds to the current expectations regarding the characteristics of the behaviour of the substrate in the full spectrum of stresses and deformations, obtained from different types of tests, which, as in the case of soil stiffness degradation, together allow the correct determination of the necessary parameters.

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“…Figure (5) shows the immediate changes in pore water volume after a change of pressure. If the volume change after initial pressurization of the cell is ignored (initial volume change is indeed ignored during a real test as the majority of the drainage lines are initially pressurized to 800 kPa) it is then possible to approximate the volume changes caused by both pressure decrease and increase by a single line.…”

Section: Calibration For the Apparent Volume Changementioning

confidence: 99%

Volume Change Measurements for Unsaturated Soils in Triaxial Equipment with Double Wall Cell

A. Al-Sharrad,

Gallipoli,

J. Wheeler

2013

ETJ

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The paper gives a brief description of double wall cell triaxial equipment for testing soil samples under unsaturated conditions and presents results of some of the calibrations necessary to achieve accurate measurements of inner cell water volume, pore water volume, pressure, load and displacement. The calibration of the measurement devices showed linear relationships b e tween the raw readings and applied values with the regression constants differ from 1 and 0. The result of apparent volume change calibrations showed significant correlation between cell water volume fluctuation and temperature fluctuation inside testing room. A correction to the measured volume was therefore required to reduce the effects of long-term temperature fluctuation on the measured volume. Investigation of the accuracy of volume change measurement with the double wall cell showed excellent matching between the inner cell volume change and pore water volume change under saturated conditions, indicating the high reliability of the double wall system for apparent volume change measurements.

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The Use of Hall Effect Semiconductors in Geotechnical Instrumentation

Cited by 107 publications

References 8 publications

Resilient modulus of unsaturated subgrade soil: experimental and theoretical investigations

Resilient modulus of unsaturated subgrade soil: experimental and theoretical investigations

Characteristic of small-strain stiffness of fine-grained soils based on advanced laboratory tests

Volume Change Measurements for Unsaturated Soils in Triaxial Equipment with Double Wall Cell

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