Maximum shear modulus of crushable natural pumiceous sands

Abstract

This paper focuses on the maximum shear modulus (Gmax) of natural pumiceous (NP) sands, found in the central part of North Island of New Zealand. These pumiceous sands are highly crushable, compressible and lightweight due to the vesicular nature of the pumice particles, making engineering assessment of their properties problematic. Several series of bender element tests over a wide range of effective confining pressure (σ′ c) and void ratio (e) were performed on different reconstituted NP sands, as well as on hardgrained Toyoura sand. The results showed that the Gmax of NP sands are considerably lower than that of Toyoura sand under similar relative density and σ′ c and the effect of σ′ c on Gmax is more significant for NP sands compared to Toyoura sand. With respect to Gmax - e relation, the NP sands show Gmax that is less dependent to e, compared to Toyoura sand. The difference in Gmax between crushable and hard-grained sands were then explained in terms of the micro-properties of the particles, especially the occurrence particle crushing, and difference in particle properties and particle size distribution.