Thermodynamics-based constitutive modeling of chemically-induced grain degradation for cohesive granular materials

This paper focuses on the chemically induced degradation of grains and bonds in cohesive granular materials, employing a thermodynamically consistent approach. To capture the stiffness degradation and bonding/debonding phenomena in cohesive granular materials, such as cemented sand, under chemo-mechanical coupling, we integrate chemical potential energy — including pore geochemistry and pressure dissolution — into the classical Modified Cam-Clay (MCC) model. The study also introduces a cross-scale relation to address microscale dissolution at grain and bond contacts. Furthermore, the contact force is determined by the evolving cumulative particle size distribution, characterized as a probability size distribution density function, which results from chemical degradation. To implement the proposed physical mechanisms, the derivations and numerical algorithms are carefully developed to ensure an accurate representation of the processes. Multiple validations and verifications of the proposed model are conducted to evaluate and compare its performance against laboratory experiments. The results demonstrate that the model successfully explains the macroscopic observations of geomaterial degradation commonly encountered in geotechnical engineering.