Title

Relationship between shear wave velocity and stresses at failure for weakly cemented sands during drained triaxial compression

Document Type

Conference Proceeding

Date of Original Version

1-1-2011

Abstract

Small strain shear modulus (Gmax) has been a parameter of choice used to assess the strength and deformation behavior of cemented and other sensitive soils. The influence of density, effective confining stress, stress anisotropy, and cement content on shear wave velocity (vs)/shear modulus has been studied extensively and published. There are, however, very few studies on the effects of cement/strength degradation during shear on the shear wave velocity/shear modulus, which may be important for reliable and accurate prediction of mechanical behavior of cemented sands. The objective of this study is to evaluate the effect of cement degradation on shear wave velocity/shear modulus by measuring continuously the shear wave velocity during shear. A laboratory testing program was performed using samples of silty sand artificially cemented with Ordinary Portland Cement (OPC). Shear wave velocity was measured continuously within the triaxial cell during the shear phase using torsional ring transducers. Gmax was calculated using the shear wave velocity and the corresponding density during shear. Results from this study suggest that Gmax reaches a peak value before σ1 reaches a failure stress and this behavior is believed to be an indicator of bond breakage or destructuring. Gmax calculated at various stages during shear showed that the cement and modulus degradation can be represented by a simple index using Gmax. The results of this study suggest that there may be a unique relationship between small strain shear modulus and effective stresses at failure for dilative soils implying that in situ shear wave velocity measurements may be used to estimate effective stress strength parameters or as a precursor to failure in weakly cemented soils.

Publication Title

Soils and Foundations

Volume

51

Issue

4

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