Abstract: Water-containing cracks on concrete gravity dam are susceptible to instability due to additional water pressure generated by water compression caused by the rapid opening and closing of cracks under seismic load. In an attempt to obtain the variation law of water pressure in cracks under seismic load, we deducted the formula of additional water pressure in cracks under seismic load based on the assumption that the crack is oval. By case study, we analyzed the changes of additional pressure and factor of stress intensity at crack tip in different directions in the presence of varying crack size and drainage rate. Results revealed that the maximum additional water pressure of the calculation case reached 7.55 times of initial water pressure under seismic load. Meanwhile, with the increase of initial crack width, the maximum additional water pressures and the factor of stress intensity at crack tip declined rapidly; with the decrease of initial crack width, the influence of drainage rate on additional water pressure became more evident. In addition, the inclination angle of crack had no obvious impact on the factor of stress intensity at crack tip.

Key words: crack, seismic load, calculation model, maximum additional water pressure, stress intensity factor