Role of the location and size of soluble particles in the mechanical behavior of collapsible granular soil: a DEM simulation

Collapsing soil structure caused by mineral dissolution is a challenge to geoenvironmental projects. Although the parameters affecting the macro-response of collapsible soil have been addressed experimentally, the micromechanical behavior of soluble soil is unclear. The aim of this study was to simulate the dissolution behavior of a granular assembly at the particle level. A DEM code was developed that considers both localized and random dissolution as well as the particle size distribution and stress level. The effect of particle dissolution was simulated by considering the role of particle size in the load-bearing skeleton. The results show that mechanical behavior of a granular assembly is strongly influenced by the location and percentage of dissolution of particles. The loss of the soluble particles decreases physical contact and transfers to neighboring particles due to the arching forces around the voids, as in a honeycomb structure. However, if the soluble areas cut across the load-bearing force chains, a honeycomb fabric cannot form because of the lack of an arching effect, leading to the collapse of the structure and large volume change. Particle loss of up to 3% will not have a serious impact on the mechanical behavior of the granular assembly. After fine particle dissolution of a binary mixture, the arching effect around them decreases the volumetric strain in comparison with the dissolution of coarse particles. Also, during dissolution, the high stress level will decrease the peak friction angle, but the opposite is true for the post-dissolution behavior above 12% strain.