Mineral dissolution effects on mechanical strength

The fabric of soil media may change due to certain factors such as the dissolution of soluble mineral particles, desiccation, and cementation. The fabric changes lead to mechanical behaviour changes. The purpose of this study is to investigate the effects of mineral dissolution on mechanical strength. Experimental studies and numerical simulations are performed by using conventional direct shear and discrete element methods. The dissolution specimens are prepared with different volumetric soluble particle fractions in sandy soils. The dissolution of the specimens is implemented by saturating the salt–sand mixtures at the different confining stresses in the experimental study and reducing the sizes of soluble particles in the numerical simulations. Experimental results show that after the particle dissolution as the soluble particle fraction increases, the peak shear strength decreases, the void ratio increases, and the vertical displacement behaviour during shearing changes from dilative to contractive behaviour. The numerical simulations exhibit that the macro-behaviours match well with the experimental results. In addition, the micro-scale observation shows that the reduction in the shear strength of the soluble particle mixtures after the particle dissolution results from the reductions of the coordination number, the stability of the fabric, the ability to develop the anisotropy of the fabric, and the increases in the local voids and anisotropy. This study reveals that the particle dissolution has a significant effect on the shear strength, deformation, and fabric change.

► As the soluble mineral fraction increases, the peak shear strength decreases.
► The vertical displacement changes from dilative to contractive behaviours.
► The mineral dissolution produces a decrease in the coordination number.
► The strength reduction results from a decrease of coordination number.
► The strength reduction comes from ability to develop the anisotropy of the fabric.