Experimental study on karst development characteristics of calcrete and analysis of its dissolution mechanism

Karst is widely distributed throughout the world and has a significant impact on the ecological environment and engineering construction. In this study, a 3D geological model of calcrete karst near the Liuyang River was established through field investigation. The texture and mineral composition of calcrete were investigated by thin section identification, X–ray diffraction (XRD) test, and electron probe microanalysis (EPMA). Moreover, dissolution tests and uniaxial compressive strength tests were performed to analyze the karst development characteristics and dissolution mechanism of calcrete. Experimental results demonstrated that the calcrete karst is primarily distributed near the river with a small development scale, and 85.96% of the caves are filled with gravels and clay. The cementation component of calcrete is mainly composed of calcite, accounting for approximately 20%. Meanwhile, calcrete contains a large number of insoluble clastic particles, which were deposited in the karst caves after dissolution. The dissolution test results revealed that the dissolution of calcite cement destroyed the rock texture. The dissolution rate of calcrete increased linearly with increasing H+ concentration. In addition, the strength of rock decreased with karstification, and grouting was effective in treating calcrete karst by reinforcing the fillings. These findings are theoretically important for calcrete karst geology research and highly practical for engineering construction.