The Arch Dam Foundation Rock Mass Unloading and Relaxation Deformation Characteristics and their Monitoring Result Analysis

After foundation excavation for a dam of a hydropower project, the rock mass would be unloaded and relaxed and its mechanical parameters would be lowered, thus influencing the dam stability. This paper makes an analysis of the deformation development law of the unloading rock mass of the dam foundation by analyzing the advance deformation of the dam foundation before excavation and the unloading rebound deformation of the dam foundation after excavation, and by analyzing the monitoring results of the compressive deformation after concreting of the dam and of the whole process deformation after impounding of the reservoir taking into account the results of both deformation test and acoustic test, which provides scientific basis for quality assessment of the arch dam foundation rock mass and for readjustment of the dam foundation rock mass mechanics design parameters, thus giving a reference to projects of the kind.