Water Resources and Power

The selection of the foundation surface of the flowing tuffaceous lava is a major engineering geological issue for the Shuanggangkou Arch Dam and a key factor affecting the excavation of the arch dam foundation. Taking the tuff lava foundation surface rock mass of the Shuanggangkou Arch Dam as the research object, based on a large amount of field survey data and in-situ experiments, this paper conducts research on the structural characteristics, weathering degree, and engineering geological classification of the rock mass of the Shuanggangkou Arch Dam, and selects and determines the foundation surface of the arch dam. The results show that the rock mass in the strongly weathered zone belongs to Class BⅣ₁, the rock mass in the weakly weathered upper zone belongs to Class AⅢ₂, the rock mass in the weakly weathered lower zone belongs to Class AⅢ₁, and the rock mass in the slightly new zone belongs to Class AⅡ. According to the stress distribution characteristics of the arch dam, AⅢ₂ and BⅣ are weathered unloading zone rock masses, which are not suitable for direct use as arch dam foundations. The foundation rock mass is mainly AⅢ₁, with good foundation conditions and average deformation resistance.