The critical state characterization of east coast sand (ECS) and calibration for use with an advanced critical state soil constitutive model

Abstract

This paper outlines the findings of a laboratory-based study to investigate the properties and undrained flow failure behavior of East Coast Sand (ECS). ECS is a commonly encountered coastal deposit from the upper North Island of New Zealand. This work aims to derive soil parameters for an advanced constitutive soil model (NORSAND) to enable predictive analyses of flow failure potential using the critical state framework. The emphasis in the study is placed on the undrained strength behavior under static, triaxial compressive loading conditions at confining pressures in the range of typical engineering interest and for a range of soil densities considered in loosely deposited sands common to nearshore marine and estuarine environments. The research objective of establishing the basic soil properties and intrinsic advanced geomechanical properties of ECS from Auckland was achieved through laboratory experiments and matching simulations for five different aspects of its undrained behavior under static loads. It was shown that loosely deposited ECS within mean effective stresses ranging between 50kPa and 200kPa can be susceptible to expensive flow failures of structures built on or with them. Therefore, the re-engineering of ECS by adequate soil improvement is required when used in earthworks.