If the interlayer is connected with the reservoir water, in addition to excavating and backfilling the interlayer within the scope of the dam foundation, the inlet of the reservoir water upstream of the interlayer must be closed and the passage of the reservoir water into the interlayer must be cut off. In this case, it can be combined with the requirements of anti-seepage of the dam foundation, or first drill holes, thoroughly wash the interlayer within the scope of the curtain, and then carry out curtain grouting; Or with vertical shaft or inclined shaft excavated, excavated interlayer, and then backfill concrete; Large bore holes can also be used to remove the interlayer and backfill the concrete.