Study of Hydraulic Failure Mechanism in the Core of Eyvashan Earth Dam with the Effect of Pore Water Pressure and Arching

Continuous investigation and measurement of pore water pressure and arching depression play an important role in detecting the occurrence of hydraulic failure in earth dams. Increasing the pore water pressure during the initial impounding period reduces the effective stress and consequently decreases the shear strength of the earth dam core, which can overcome the water stress over the effective stress and consequently hydraulic failure. This research studies the hydraulic failure of Eyvashan earth dam under static loading conditions at the end of construction and the initial impounding period by Geostudio software with the Mohr-Coulomb behavioral model. The analysis shows that the values of the pore water pressure ratio (r u) and stress-strain values are acceptable and there is no stability problem for the dam. The highest percentage of arching (the lowest ratio of arching) is equal to 46%, at one-third of the lower height of the core. The critical arching ratio (maximum) is 0.44 and is in the normal range and hydraulic failure does not not occur despite the critical arching in the dam core.