A predictive model for fluid-saturated, brittle granular materials during high-velocity impact events

TL;DR

This paper introduces a comprehensive thermo-mechanical model for fluid-saturated granular materials, capable of predicting their behavior during high-velocity impacts by integrating deformation mechanisms and pore fluid interactions.

Contribution

It develops a unified, multi-mechanism model for granular and fluid interactions under extreme impact conditions, advancing understanding of their complex behaviors.

Findings

Model accurately predicts experimental results for sands under GPa stresses.

Simulations replicate different responses of dry and saturated sands during impacts.

The approach integrates deformation, pore collapse, and fluid coupling in a unified framework.

Abstract

Granular materials -- aggregates of many discrete, disconnected solid particles -- are ubiquitous in natural and industrial settings. Predictive models for their behavior have wide ranging applications, e.g. in defense, mining, construction, pharmaceuticals, and the exploration of planetary surfaces. In many of these applications, granular materials mix and interact with liquids and gases, changing their effective behavior in non-intuitive ways. Although such materials have been studied for more than a century, a unified description of their behaviors remains elusive. In this work, we develop a model for granular materials and mixtures that is usable under particularly challenging conditions: high-velocity impact events. This model combines descriptions for the many deformation mechanisms that are activated during impact -- particle fracture and breakage; pore collapse and dilation; shock loading; and pore fluid coupling -- within a thermo-mechanical framework based on poromechanics and mixture theory. This approach allows for simultaneous modeling of the granular material and the pore fluid, and includes both their independent motions and their complex interactions. A general form of the model is presented alongside its specific application to two types of sands that have been studied in the literature. The model predictions are shown to closely match experimental observation of these materials through several GPa stresses, and simulations are shown to capture the different dynamic responses of dry and fully-saturated sand to projectile impacts at 1.3 km/s.