RU2034151C1 SU925052092A SU5052092A RU2034151C1 RU 2034151 C1 RU2034151 C1 RU 2034151C1 SU 925052092 A SU925052092 A SU 925052092A SU 5052092 A SU5052092 A SU 5052092A RU 2034151 C1 RU2034151 C1 RU 2034151C1 Authority RU Russia Prior art keywords vessel tank clamshell craft excavation Prior art date 1991-07 …