Wave Reflection Effects on Bender Element Test of Very Stiff Clay
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 149, Issue 9
Abstract
A common source of error in bender element testing lies in the determination of the shear wave arrival time arising from the near-field effect, which is attributed to shear wave–like motion of the compression wave obscuring the arrival of the shear waves, and can be mitigated by using a sufficiently high travel-distance-to-wavelength () ratio. However, the ratio also is relevant for signal interference due to side reflections, and its role in this important mechanism is far less understood. Stiff materials such as cement-treated soils, which have a very short shear wave travel time, are likely to exacerbate these errors. This paper examined the causes of travel time errors in cement-treated soil using bender element tests of standard-sized triaxial specimens, large block samples, and three-dimensional finite-element analyses. The results show that the reflection of shear waves from sample boundaries generates a second pulse in the received signal, resulting in signal distortion. This can be ameliorated at sufficiently high ratios. The reflection of the compressional waves generates spurious prearrivals and distorts the profile of the direct shear wave even at high ratios. Shear and compressional wave reflections can be mitigated by increasing the specimen diameter to decouple the latter from the direct shear wave arrival.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published paper.
Acknowledgments
This research is supported by the Ministry of National Development (MND) under its Land and Liveability National Innovation Challenge (L2 NIC Award No. L2NICCFP2-2015-2) and National University of Singapore Research Scholarship.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 149 • Issue 9 • September 2023
Copyright
© 2023 American Society of Civil Engineers.
History
Received: Nov 29, 2022
Accepted: Apr 4, 2023
Published online: Jun 19, 2023
Published in print: Sep 1, 2023
Discussion open until: Nov 19, 2023
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