Cracks and crevices on the foundation of a dam should first be washed with high-pressure water and cleaned with high-pressure air to a depth at least three times the width of the crevices. Then 20MPa cement mortar is used to fill the joint to make it completely closed. If the gap width is greater than 50mm, concrete caulking is used to make it completely closed. If the crack is small and narrow, cement paste perfusion and brushing the gap to close it, the cement paste at the crack should be about 10mm higher than the rock face.