Experimental Study on the Dissolution Law of Sandified Dolomite in Central Yunnan

Given the limited research on the dissolution mechanisms of sanded dolomite in the central Yunnan region, this study investigates the dissolution characteristics of dolomite from the Datangzi Tunnel. Considering the geological characteristics of the region, dissolution experiments were conducted under three influencing factors: acidity, stress, and temperature. The results demonstrate that as pH decreases, stress increases, and temperature rises, the mass loss rate, longitudinal wave velocity reduction rate, and pore occupation ratio of the specimens all exhibit an increase trend, and the effect of temperature on the dissolution rate of dolomite is significantly greater than that of stress. Scanning electron microscopy (SEM) analysis reveals that dissolution primarily occurs at the crystal contact points. Furthermore, changes in the ion concentration of the dissolution solution indicate that oxalic acid has a much higher dissolution reaction rate on MgCO3 in the dolomite compared to CaCO3, resulting in differential dissolution at the microstructural level and exhibiting the characteristic of "magnesium depletion and calcium enrichment". This differential dissolution accelerates the dissolution process, leading to an increase in internal fractures and porosity within the dolomite, which facilitates the breakdown of dolomite crystals and accelerates the sandification process.