A numerical characterisation of unconfined strength of weakly consolidated granular packs and its effect on fluid-driven fracture behaviour

TL;DR

This study introduces a numerical model to characterize the unconfined strength of weakly consolidated granular packs and examines how this affects fluid-driven fracture behavior, with validation against experimental data.

Contribution

The paper presents a simple numerical model incorporating weak consolidation in granular packs, enabling better simulation of stress behavior and fracture response in porous materials.

Findings

Model reproduces stress behavior of compacted and poorly consolidated sands.

Different consolidation levels significantly influence fluid-driven fracture patterns.

Numerical results align well with experimental data on bio-cemented sandstones.

Abstract

Soft or weakly-consolidated sand refers to porous materials composed of particles (or grains) weakly held together to form a solid but that can be easily broken when subjected to stress. These materials do not behave as conventional brittle, linear elastic materials and the transition between these two regimes cannot usually be described using poro-elastic models. Furthermore, conventional geotechnical sampling techniques often result in the destruction of the cementation and recovery of sufficient intact core is, therefore, difficult. This paper studies a numerical model that allows us to introduce weak consolidation in granular packs. The model, based on the LIGGGHTS open source project, simply adds an attractive contribution to particles in contact. This simple model allow us to reproduce key elements of the behaviour of the stress observed in compacted sands and clay, as well as in poorly consolidated sandstones. The paper finishes by inspecting the effect of different consolidation levels in fluid-driven fracture behaviour. Numerical results are compared against experimental results on bio-cemented sandstones.