Exploring a Distinct Element Method Approach for Coupled Chemo-mechanical Mechanisms in Geomaterials

Chemo-mechanical interaction processes in multifarious environmental circumstances may strongly affect the evolution of the mechanical and transport properties of geomaterials. Such interaction is believed to occur at the microscopic scale at the level of inter-granular contact but its effects are often manifested at higher scales leading to critical mechanisms in many natural geomechanical processes. The present work focuses on establishing the chemo-mechanical coupling effects at the granular scale and explores the macro-scale response of siliceous and calcareous sands using Distinct Element Method as a modeling tool. The effect of the mineral dissolution on the mechanical response at the grain contact is incorporated into a modified linear contact model. Two kinetic rate formulations to account for mechanically enhanced dissolution are examined, both allowing the evolving local mechanical response to be considered in the enhanced dissolution process at each grain contact. The results show the importance of the kinetic characteristics of the mass dissolution and precipitation processes in the behavior of geomaterials. Compared to siliceous sands, the interaction of pore fluid with carbonate minerals leads to much accelerated dissolution of carbonate minerals which results in more enhanced deformation of the calcareous sands. The presented numerical analysis is a feasibility study of the use of DEM to model coupled chemo-mechanical phenomena.