Investigation of Dissolution Behaviors during Oedometer Tests Using DEM

This study investigates the dissolution behaviors of sand and soluble salt particle mixtures during oedometer tests using discrete-element method (DEM) models. Mixtures of sand and salt particles with the salt volume fraction [soluble fraction (SF)] from 0% to 10% were subjected to vertical loading from 5 to 640 kPa under zero lateral strain. For the dissolution process, salt particles were progressively reduced in size to simulate natural dissolution after compressing specimens at 40, 80, 160, and 320 kPa. During the experiments, wall displacements, coordination numbers, normal contact forces, stresses, and porosity were monitored. The results show that before dissolution, the compression behavior is unaffected by the presence of salt, with nearly constant compression index C c = 0.020–0.021 across different SFs. However, after dissolution, C c increases, reaching approximately 0.029 for SF = 10% because salt removal forms honeycomb voids that disrupt packing and enable sand to collapse and rearrange. Microstructurally, dissolution causes a pronounced and spatially heterogeneous reduction in the coordination number, with a stronger disruption at a higher SF; the coordination number partially recovers during postdissolution loading as sand contacts reform, although a residual dissolution memory persists. Stress redistribution accompanies this fabric degradation: K 0 rises sharply during dissolution as vertical load paths weaken and stresses reroute laterally. Consistently, stress anisotropy decreases markedly after dissolution (anisotropy coefficient reduced from 27.1% to 54.9%), indicating a collapse of vertically aligned force chains and incomplete anisotropy recovery upon recompression. This study provides further insights into the behavior of soluble mixtures, which will improve design awareness for geotechnical applications in regions having this condition.