High strain rate behaviour of cohesive soils

Soil-filled wire and geotextile gabions are essential components of defensive infrastructure in military bases, leveraging the attenuating properties of soils to safeguard personnel and critical assets against blast and fragmentation effects. However, understanding the behaviour of cohesive soils under extreme loading conditions remains largely unexplored, presenting a crucial knowledge gap for design engineers tasked with developing robust soil constitutive models to address evolving threats. This study investigates the response of cohesive soils, focusing primarily on kaolin clay due to its homogeneity, widespread availability and consistent properties. Through high strain rate experimental testing of kaolin clay specimens, using the split-Hopkinson pressure bar (SHPB) apparatus, both unconfined and confined conditions are explored across varying moisture contents, spanning the spectrum from unsaturated to fully saturated states. The analysis of the experimental results uncovers the strain rate dependence of cohesive soils and identifies distinct phase behaviour for transmitted and radial stresses influenced by factors such as strain rate, moisture content and confinement. Utilising LS-DYNA, and the finite element method (FEM), the SHPB tests are modelled for comparison against experimental findings. While LS-DYNA, supplemented by Smooth Particle Hydrodynamics (SPH) node modelling, provides valuable insights, significant disparities between modelled and practical results underscore the challenges inherent with the accuracy in simulating the behaviour of cohesive soils. Nonetheless, this comprehensive exploration of cohesive soil's high strain rate behaviour yields critical insights for engineers, enabling them to adapt defensive strategies to diverse threats and loading scenarios effectively.