Short-distance arranged new and old concrete dam in dangerous reservoir dam reconstruction engineering as well as method

The invention relates to a short-distance arranged new and old concrete dam in dangerous reservoir dam reconstruction engineering as well as a method, and belongs to the field of large and medium-sized dangerous dam reconstruction. The short-distance arranged new and old concrete dam comprises an original reservoir dam and a downstream original functional building, wherein a newly-built dam is positioned on the downstream side of the original reservoir dam and the upstream side of the original functional building; the original reservoir dam and the newly-built dam communicate through a left-bank dam road and a right-bank dam road; and a diversion tunnel is positioned in the original reservoir dam and the left-bank mountain of the newly-built dam. The short-distance arranged new and old concrete dam in dangerous reservoir dam has the advantages that the newly-built dam is positioned on the downstream side of the original reservoir dam, the original reservoir dam also serves as an upstream cofferdam when servin