A DEM study on microstructural behaviour of soluble granular materials subjected to chemo-mechanical loading

Experimental works provide a mere understanding of the behaviour of granular material subjected to chemo-mechanical weathering, while the microstructural behaviour is of key importance due to the presence of coupling between the chemical and mechanical loading at the grain scale. The Discrete Element Method (DEM) has proven to be a viable tool in characterizing such microstructural behaviour of granular material in the recent past. In the present study, a DEM based numerical model is proposed to simulate chemo-mechanical degradation as observed in experiments. The aim is to understand how the dissolution rate alters during the dissolution of fully soluble reactive granular assembly like calcite under flowing acetic acid solution. The DEM contact parameters are calibrated for calcite granules, while the grain dissolution due to acid flow is mimicked by reducing particle size at a specific rate. The numerical results reveal that a gradual rise in dissolution rate or particle size reduction rate leads to a drop in lateral stress followed by a steady stress state condition. Furthermore, the study demonstrates that a reduction in dissolution rate leads to an increase in lateral stress. The microstructural analysis utilizing average particle velocity indicates that the increasing dissolution rate does not enhance particle rearrangement of the same order. Hence, more voids are created within the sample, and particle contact reduces, which promotes a reduction in lateral stress within the sample.