The use of piezoelectric ring-actuator technique (P-RAT) in shear wave velocity measurement in granular media

Mohamed Ben Romdhan, Mahmoud N. Hussien, Mourad Karray, Mohamed Chekirad, Varvara Roubtsova

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Soil Mechanics

ABSTRACT: Shear wave velocity is a key design parameter in major geotechnical applications involving deep excavations besides existing buildings, tunneling, integral bridge abutments, bridge piers, pile foundations, liquefaction evaluation, and earthquake ground response analysis. Numerous field and laboratory investigations have been focused on measuring shear wave velocity. However, it is a difficult task to verify that the obtained shear wave velocities are correct and accurate. This paper focuses on the description of a new technique: piezoelectric ring-actuator (P-RAT) as well as its unique interpretation method of signals. This technique incorporated with odometer apparatus. The P-RAT technique is employed in this study to obtain shear wave velocity of different granular material with different particle size distribution curves. Initial results show that the influence of D50 on shear wave velocity could be attributed to the difference in (emin-emax) range. RÉSUMÉ La vitesse des ondes de cisaillement est un paramètre clé dans les grandes applications géotechniques impliquant des excavations profondes, construction de tunnels, de culées de pont intégrés, piles de pont, des fondations sur pieux, l'évaluation de liquéfaction ou analyse de la réponse dynamique du sol. De nombreuses recherches sur le terrain et ou dans le laboratoire ont été axées sur la corrélation de la vitesse des ondes de cisaillement avec des paramètres géotechniques typiques. Cependant, des études sur la relation entre la vitesse des ondes de cisaillement et la taille et les formes des particules sont limitées. Dans cette étude, les effets de la distribution de taille de grain sur la vitesse des ondes de cisaillement est évaluée sur la base d'une série d'essais œdométriques équipés d'un dispositif de mesure de la vitesse de l'onde de cisaillement sur les différents milieux granulaires de différentes courbes de distribution de taille des particules. Les premiers résultats montrent que la vitesse des ondes de cisaillement est affectée à la fois par le diamètre médiane des particules et le coefficient d'uniformité des échantillons de sol. 1 INTRODUCTION Obtaining elastic soil properties measured at small strain level (less than 10-3), such as shear wave velocity (Vs) and Young modulus (Emax) had been a topic of interest in the geotechnical field for many decades. There have been continuing strides to improve the measurement and technology used to acquire these parameters as they play an important role in estimation the response of soils subjected to dynamic loading. In particular, Vs is considered as a key design parameter in major geotechnical applications involving deep excavations besides existing buildings, tunneling, integral bridge abutments, bridge piers, pile foundations, liquefaction evaluation (e.g., Andrus et al. 2004), and earthquake ground response analysis (Kramer 1996). Moreover, Santamarina and Cascante (1996); Mitchell and Soga (2005) suggested that Vs can be employed to assess the state and natural soil structure or quality of soil samples without altering the soil fabric. Insitu Vs can also be used to indirectly estimate other soil engineering properties, such as residual undrained shear strength, via empirical relationships (Campanella, 1994). In the last several decades, extensive research effort has been devoted to measure shear wave velocity and to correlate it with typical geotechnical parameters such as void ratio and confining pressure, mainly through well-controlled laboratory experiments, particularly using resonant column (RC) tests as they offer high reliability and accuracy at this small strain level (Hardin and Richart, 1963; Iwasaki and Tatsuoka, 1977; Yang and Gu 2012; Hussien and Karray 2013). It can be determined also in-situ using several wave propagation tests namely; seismic cross-hole, down-hole, up-hole and Multi-channel Analysis of Surface Waves (MASW) These different methods provide very different resolutions for Vs measurements, and it is a difficult task to verify that the obtained shear wave velocities are correct and accurate due to the lack of a reliable reference for comparison. In actuality, direct measurement of Vs requires specialized equipment and technical expertise in order to ensure that the data are properly obtained and evaluated. This paper focuses on the description of a new technique: piezoelectric ring-actuator (P-RAT) as well as its unique interpretation method of signals. This technique incorporated with odometer apparatus. Two piezo-electric rings sensors were attached at the base (emitter) and at the top (receiver) of the odometer cell. In this study, P-RAT technique is employed to obtain shear wave velocity

RÉSUMÉ: se of piezoelectric ring-actuator technique

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Mohamed Ben Romdhan; Mahmoud N. Hussien; Mourad Karray; Mohamed Chekirad; Varvara Roubtsova (2014) The use of piezoelectric ring-actuator technique (P-RAT) in shear wave velocity measurement in granular media in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper307,author = Mohamed Ben Romdhan; Mahmoud N. Hussien; Mourad Karray; Mohamed Chekirad; Varvara Roubtsova,title = The use of piezoelectric ring-actuator technique (P-RAT) in shear wave velocity measurement in granular media ,year = 2014}