Abstract:
Crushable volcanic soils, such as pumice sands, are often encountered in engineering projects in the North Island of New Zealand. Due to the highly crushable nature of the pumice sand components, current empirical correlations, derived primarily from hard-grained sands, are not applicable when evaluating the liquefaction potential of pumice-rich soils. To better understand their liquefaction characteristics, cyclic undrained triaxial tests were performed on high-quality undisturbed soil samples sourced from various pumice-rich sites in the North Island. The undrained response, expressed in terms of the development of excess pore water pressure and axial strain with the number of cycles, and the shear work (or cumulative dissipated energy), defined as the energy consumed by the soil during plastic deformation until liquefaction, is examined vis-à-vis the pumice contents of the specimens. When compared to published trends for normal sands available in the literature, the results indicate that the shear work for pumice-rich sands sand is larger in specimens with higher pumice contents because some energy is spent as the particles undergo crushing. As a result, the liquefaction resistance of crushable pumice sand is higher than that of natural sand for the same level of loading applied.