Study on Antiseepage Measures for Earth-Rock Dam Reservoir in Super-Intense Karst Area: Research on Curtain Grouting Scheme for Comprehensive Seepage Prevention

Constructing reservoirs in karst regions is a challenge that dam engineers around the world are very unwilling to face. The antiseepage of reservoirs is one of the urgent problems to be solved in the construction of reservoirs in karst regions. Adopting the field test method combined with advanced geological exploration instruments and survey technologies, the antiseepage measures are studied in the construction of a reservoir located within a China’s super karst region. Through a detailed hydrogeological survey, the reservoir water seeps out through the downstream primary and secondary fracture points along the limestone dissolution erosion zone through the upstream sinkholes. According to the topography, lithology, submerged area, and seepage form and direction in the reservoir area, a vertical grouting curtain is proposed to block the seepage of reservoir water to the downstream. Based on the normal water level, impermeable layer (slate) distribution, and the lowest discharge datum plane, the left, right, and bottom boundaries of the vertical curtain grouting are determined, and the maximum grouting depth reaches 131.75 m. The double curtain grouting method is proposed to reduce the construction difficulty of the super-deep grouting curtain in the intense karst area, and alongside a method is put forward to integrate the upper and lower curtains into a cohesive unit. Practical validation through the Yundong Reservoir project demonstrates the efficacy of the proposed treatment scheme, ensuring seepage-free performance for 6 years under normal water levels. The findings lay the groundwork for further studies exploring specific challenges encountered during curtain grouting construction in karst environments, which include underground karst caves, strong corrosion zones, and underground large flow and high-speed pipeline inflow.