Getting down and dirty with silt
Dock operations are compromised, lockgates are not operating correctly, silt is building up, who to call?
Spotlighting marine civils projects, take a look at the refurbishment of the Hull Marina lock gates, carried out by Marine Civils at Seawork exhibitor Kaymac.
Hull Marina is accessed by vessels from the tidal River Humber by two pairs of radial sector gates operated by electrically powered winches. Each gate leaf is of steel fabricated egg-box construction bolted to radial arms which transfer the hydraulic loads into top and bottom pivot brackets and subsequently into the civil structure.Refurbishing the existing two pairs of lock gates to ensure full operation on completion required the replacement of the hinge pins/bushes, a complete set of gate seals and a full set of sacrificial anodes.
Initially, Kaymac had to design, supply and install the necessary temporary works equipment including stoplogs and all necessary pumps, pipework, sandbags, access ladders, etc. to enable safe working within the lock basin in the dry. To achieve this, the lock pit and both sets of gates were isolated from the hydraulic effects of the River Humber and the impounded water of the marina by the installation of the bespoke steel stop logs which locate into channels integrated into the civil structure at the extreme ends of the lock pit.
Prior to the installation, it was necessary to clean the submerged stop log chases on both west and east side of the lock adjacent to both the inner and outer gates by divers. Once the chasers were cleared of any debris or marine growth, the stoplogs were installed, the enclosed area could then be dewatered to provide a reasonably dry working area in order for the refurbishments to take place.
Kaymac encountered a number of challenges during the project, one of which was the amount of silt in the lock pit. As a result of being in the Humber estuary the silt had migrated into the lock, once the lock was dewatered, a vast amount of silt sat the bottom of the lock and around the working area. Not a problem for Kaymac; using the crane, an excavator was lowered into the lock pit which was then excavated with the silt being manually moved away from the gates to allow a clear working area. It was also identified that the outer stop logs were leaking significantly; to overcome this fly ash was installed to seal the leaks which worked effectively and remained dry for the duration of the works.
The works were successfully completed, along with additional works all within the program. On completion the gates were tested to ensure they were fully operational prior to handing back to the client.
See the video below - wait for the diver!