Experimental study on the influence of hydraulic fracturing on high concrete gravity dams

The safety of high concrete gravity dams in the presence of hydraulic fracturing is experimentally and numerical investigated. Ultimate application of this study is a new testing method for concrete hydraulic fracturing and the stress code ([σ]) for designing high concrete gravity dams (H > 200 m). A cylinder specimen with embedded crack was designed to simulate the hydraulic fracturing at gravity dam heel. Tests at different concrete ages were performed, and these specimens were subjected to an internal hydrostatic pressure, as well as to a uniaxial mechanical load. It was observed that, for the tested specimens, the hydraulic fracturing was more sensitive to the uniaxial mechanical load than to the concrete tensile strength. Then, nonlinear fracture mechanics-based finite element model was developed to investigate the influence of hydraulic fracturing on gravity dams. The analysis has been performed using discrete crack analysis. Based on those tests, properties of the finite element model were optimized. Furthermore, safety of different dams designed by specifications in China, the USA, and Switzerland were compared in considering hydraulic fracturing. It was determined that high concrete gravity dams (H > 200 m) designed by current specifications will be in risk. The vertical compressive stress on the dam upstream surface was the key for improving the dam safety, and additional studies were necessary to further quantify the permissible stress.