Shear-compaction band evolution in dry and saturated porous media using a hybrid Finite Element Method/Peridynamic model

Abstract

This study presents a hybrid Finite Element Method/Peridynamic (FEM/PD) model to simulate the evolution of shear and compaction bands in dry and saturated porous media under compressive loading. A shear damage evolution criterion, based on macro equivalent shear strain, is proposed to describe localized shear band formation within the Ordinary State-based Peridynamic (OSB-PD) framework. Additionally, a grain crushing potential is incorporated into the constitutive scalar force density function to account for shear damage associated with grain crushing and pore collapse. By combining the OSB-PD equations for solid deformation and damage with the finite element method for fluid flow, the model provides a flexible tool for investigating shear and compaction band formation under pure mechanical and hydro-mechanical action. Numerical simulations are conducted to validate the model’s effectiveness. Parameter studies reveal that higher degradation function exponents result in more concentrated shear bands with smaller inclination angles. Convergence studies reveal key discretization parameters, such as horizon radius ($\delta$) and $m$-ratio ($m_r$), which are critical for ensuring simulation stability and accuracy. Benchmark simulations demonstrate the model’s versatility, effectively simulating compaction band evolution under confining pressure and grain crushing conditions. The model also successfully captures the transition from shear bands to shear-enhanced or pure compaction bands as grain crushing or confining pressure increases. In saturated conditions, the model shows that excess pore pressure can suppress compaction band formation, particularly in low-permeability scenarios, thereby highlighting its ability to capture the influence of pore pressure on shear-compaction band evolution.