In order to realize the characteristic and mechanism of flow washout for the crevice of core wall in an earth-rock dam,the soil samples obtained from the clay wall of a proposed reservoir in Northwest China are studied by the crack washout test.

In order to understand the characteristics and mechanism of flow washout for the crevice of core wall in earth rock dam,according to the exemple of crack washout test for the core of Heihe Dam,constant water level washout test and changing water level washout test are adopted differently,the process of test and the character of the flow washout for the core crack are gone into particulars.