Laboratory measurement of shear strength and related acoustic properties

Tang, Zhuo-hua (1993) Laboratory measurement of shear strength and related acoustic properties. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (18MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The general purpose of this research is to pursue the correlationship between acoustic properties and strength properties of sands. Conventional methods for correlating these characteristics rely on in-situ measurements of the wave velocity and shear strength. These measurements are subject to error from contamination by many unknown influences. A combined laboratory acoustic-triaxial testing equipment was developed to study reliably the interrelationship between shear strength and shear wave velocity by using piezoelectric ceramic benders to measure shear wave velocity in the triaxial tests. In processing the wave signals, the Hilbert transform technique was applied to precisely determine the wave propagation time. -- An unified stress-strain model is proposed for predicating sand behavior under loading conditions. It is found that the popular hyperbolic equation is a special case of the new model that can be applied to sands with a wide range of relative densities. -- Shear wave velocity increases with increasing confining pressure but decreases with increasing void ratio. It is found that shear wave velocity increases with increasing axial strain until reaching its peak strength and then drops. The rate of decrease depends on the type of sand and confining pressure. -- The microstructural analyses and experimental results indicate that the shear wave velocity-axial strain relationship follows the same mechanism controlling stress-strain behavior of sands. Therefore the new stress-strain model is modified further according to experimental results to correlate shear wave velocity and shear strength. Unambiguous results in shear wave velocity have been established as a function of stress ratio and axial strain. The comparisons between model and measured data indicate that the proposed equation can describe well wave velocity changes with stress and strain.

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