Initial shear modulus of sandy soils and equivalent granular void ratio

Abstract

The small strain/initial shear modulus, G_O , for clean sands has been extensively studied over the last few decades, and it is generally accepted that G_O is a function of the effective mean stress, p′ and void ratio, e. However, natural sandy soils often contain some fines (particle size ≤ 75 μm) and systematic studies on the effect of fines on G_O are relatively limited. Two different approaches for capturing the effects of fines on G_O have been reported. However, both approaches assumed that the G_O values for a range of fines content specific to the sand and fines type are known in advance, and thus they cannot be used as predictive tools. This paper presents an alternative approach for evaluation of G_O based on the equivalent granular void ratio, e*. Unlike earlier attempts, the proposed method does not rely on back-analysis and e* can be calculated from e and other conventional grading properties of sandy soils. The proposed approach approximately leads to a single relationship between G_O and (e*, p′) irrespective of fines content. Thus, it provides a framework for estimating G_O at different fines content from data on clean sand.

Keywords:

• initial shear modulus
• sand
• fines
• void ratio

Acknowledgement

The first author would like to acknowledge that the manuscript of this paper was prepared during his postdoctoral tenure on the project “identification and mitigation of geotechnical hazards” at University of Canterbury, New Zealand. He would also like to acknowledge that the prediction approach for equivalent granular void ratio framework used in this paper was developed during his PhD at University of New South Wales at ADFA, Australia.