Fluid-driven deformation of a soft granular material

TL;DR

This study investigates fluid-driven deformation in a soft granular material, revealing how microscale particle dynamics and failure mechanisms deviate from traditional continuum poroelastic models.

Contribution

It provides high-resolution experimental insights into pore-scale interactions and deformation patterns in granular systems under fluid injection, highlighting limitations of continuum theories.

Findings

Continuum poroelastic models capture some macroscopic deformation features.

Particle-scale deformation shows rearrangements and hysteresis.

Failure involves spiral shear banding and mesoscale structures.

Abstract

Compressing a porous, fluid-filled material will drive the interstitial fluid out of the pore space, as when squeezing water out of a kitchen sponge. Inversely, injecting fluid into a porous material can deform the solid structure, as when fracturing a shale for natural gas recovery. These poromechanical interactions play an important role in geological and biological systems across a wide range of scales, from the propagation of magma through the Earth's mantle to the transport of fluid through living cells and tissues. The theory of poroelasticity has been largely successful in modeling poromechanical behavior in relatively simple systems, but this continuum theory is fundamentally limited by our understanding of the pore-scale interactions between the fluid and the solid, and these problems are notoriously difficult to study in a laboratory setting. Here, we present a high-resolution measurement of injection-driven poromechanical deformation in a system with granular microsctructure: We inject fluid into a dense, confined monolayer of soft particles and use particle tracking to reveal the dynamics of the multi-scale deformation field. We find that a continuum model based on poroelasticity theory captures certain macroscopic features of the deformation, but the particle-scale deformation field exhibits dramatic departures from smooth, continuum behavior. We observe particle-scale rearrangement and hysteresis, as well as petal-like mesoscale structures that are connected to material failure through spiral shear banding.