Comprehensive Investigation Method for Sudden Increases of Uplift Pressures beneath Gravity Dams: Case Study

Abstract

Due to the complexity and uncertainty of geological conditions, a comprehensive investigation method is proposed to identify main causes of sudden increases of uplift pressures beneath local blocks of a gravity dam, which integrated statistical analyses of in situ seepage observations, inversion analyses of seepage fields using the numerical method, and field investigations. To fully identify the natural geological condition of the foundation after several years of operation, comprehensive field investigations, including core borings, water-pressure tests, and borehole television imaging, are employed. A case study of Xixi Dam is applied to demonstrate the utilization of this method. The study focuses on the local riverbed blocks, underlying which sudden increases of uplift pressures occurred in the months of April and May 2010, as well as March 2012. The primary explanation is that the coupled external loads of low ambient temperature and high reservoir water level induce the phenomenon. Further investigations show that unsatisfactory waterproofing treatments, as well as the intensively tension joints in the broken foundation rock, are the defects responsible for reservoir leakage and sudden high uplift pressures. The proposed method could be employed in investigations of similar problems of gravity dams.