Construction method and device for blocking reserved relief well of open caisson

The invention relates to an open caisson reserved relief well plugging construction method and device. The open caisson reserved relief well plugging construction method comprises the steps that a mounting piece is mounted on a branch pipe on one side of a relief well, a first grouting pipe extends into the bottom of the relief well, a second grouting pipe extends to the upper end of the relief well, and a pipe opening extending into the upper end of the relief well is temporarily plugged; when it is detected that the liquid at the outlet of the mounting part is a thick grouting substance, grouting of the first grouting pipe is stopped, and standing is conducted; after the grouting substance injected into the first grouting pipe is initially set, secondary grouting is conducted through a second grouting pipe, the grouting pressure of the second grouting pipe is larger than that of the first grouting pipe, the temporary plug is opened, and in the later period of secondary grouting, grouting is conducted while