Seismic Water Pressure in Cracked Concrete Gravity Dams: Experimental Study and Theoretical Modeling

Water pressure variations along concrete cracks with moving walls are investigated experimentally and theoretically. Displacement control tests were conducted to measure water pressure on 0.4  m long concrete cracks during harmonic motion of crack walls. The effects of key parameters including frequency of excitation, minimum and amplitude of crack mouth opening displacement, and initial static uplift pressure on the magnitude of developed pressure is also studied. The experimental results show the possibility of cavitation in a new or existing crack opening mode. A theoretical dynamic water-crack interaction model is developed, considering the effect of cavitation phenomenon, to compute water pressure in cracks as a function of crack wall motion history, crack length, crack roughness, and crack mouth pressure. The validity of the developed method is verified by the test results and it is used to study the pressure variations in longer cracks likely to develop in the concrete gravity dams. The computed uplift pressures indicate that, in an opening seismic crack, water pressure develops near the crack mouth and there is no water pressure along the rest of crack. A simplified method is developed to estimate the dynamic uplift force and resultant position in crack opening mode to use in seismic dam stability evaluation using pseudostatic or pseudodynamic procedure.