This study investigates the impact of long-term water immersion on the mechanical and hydrochemical properties of cemented calcareous soil, emphasizing the critical role of carbonate content in mechanical performance. Utilizing hydrochemical analysis and triaxial testing, the research revealed that prolonged immersion disrupts the acid-base balance of the solution, resulting in an increased concentration of ions and chemicals. Significant dissolution of carbonates and soluble minerals occurs, which reacts with carbon dioxide to generate bicarbonate ions, thereby elevating the alkalinity of the soaking solution. Additionally, the gradual dissolution of clay minerals compromises the cementitious structure, leading to particle reorientation and interlocking. The study quantitatively assesses the changes in soil properties, demonstrating a substantial reduction in soil cohesion by up to 86.1% and an increase in the internal friction angle by 37.5%. Furthermore, the gradual dissolution of clay minerals compromises the cementitious structure, resulting in particle reorientation and interlocking that contribute to the observed mechanical changes. The findings underscore the importance of understanding the effects of extended immersion on the stability and engineering applicability of cemented calcareous soils.

This paper studies the Hongyan landslides with complex reactivation mechanisms induced by human engineering activities. Through field investigation, drilling, in site monitoring and numerical simulation, the reactivation characteristics and instability mechanism of the Hongyan landslide were systematically studied. The results show that the regional lithology, topographic characteristics, geological structure and engineering activities have a certain promoting effect on the reactivation of the Hongyan landslide; the existence of clay in the sliding body and the layered structure in the sliding body enhances the sensitivity of the slope. The free surface of the slope creates favorable conditions for the subsequent deformation of the sliding body; the sliding body is mainly the ancient landslide accumulation body, and the layered structure before the slope sliding is retained in the ancient landslide accumulation body; the excavation of the slope reduces the anti-sliding force and changes the free surface conditions, which directly leads to the reactivation of the landslide; during the deformation process, due to the change of the free surface conditions, the sliding body shows the characteristics of counterclockwise deflection. The reactivation of the Hongyan landslide is the result of the interaction of multiple inducing factors, and its instability mechanism is complex. This study is of great significance for the hazard evaluation of such ancient landslides.