A bulkhead is a soil retaining wall structure comprised of verticallyspanning sheet piles or other flexural members. Seawalls are forms of shore protection and are not intended for use as berthing facilities (refer to NAVFAC DM-26.2, Coastal Protection).Ģ.1.2 Bulkhead. It differs from a breakwater in its capacity as a soil retention structure. A seawall is a soil retaining or armoring structure whose purpose is to defend a shoreline against wave attack. The Jack-up Barge was then used to sequentially vibrate the straight web sheet piles to level.Īs this stage, the Specialist Sheet Piling Subcontract works was effectively complete and the structure was handed over to Van Oord ACZ who then commenced filling the cells using land based sand pump equipment which had previously been set up in readiness for the fill operations.īy use of the above construction methods, both circular cofferdams were completed safely ahead of programme and within budget.For a complete version of this document click here.Ģ.1.1 Seawall. Once the tube pile had been installed to design toe level, the crane was detached from the cell and demobilised back to the Quayside. Once this was accomplished, the tubes were immediately vibrated sequentially into the seabed whilst nominal load from the temporary frame was held by the Shear Leg Barge. The tubular support piles were designed to project beyond the underside of the temporary works frame so as to be the first members to touch the seabed. Once in position, the fabricated cells were lowered to the seabed. GPS equipment was used to assist the Shear Leg Barge Master to accurately control and position the cells with the specified tolerance. A substantial Shear Leg Crane Barge was mobilised to site and used to lift and position the fabricated cells on the pre-levelled seabed. The jack-up barge was then floated out into position some 2.0m clear of the proposed cell location in readiness for driving the tubular and sheet piles immediately the cell had been accurately located. A jack-up barge was mobilised to site and the 130Te Crawler Crane was loaded onto the jack-up along with a substantial vibratory hammer and backup percussive hammer. The completed cellular cofferdams, when standing on the Quayside, weighed some 400Te and stood 22.5m tall. The eight tubular piles were also prepositioned in the temporary works frame whilst at the Quayside in order to keep to an absolute minimum the time required for completion of marine works at the Harbour entrance. The sheet piles were accurately monitored for position and verticality before being secured to the temporary works via welded steel supporting angles. However, when placed on the prepared level seabed, it was calculated that 8no 660mm tubular piles, driven some 5.0m into the seabed would be needed to resist the predicted wave and swell forces, and to keep the structure stable whilst the sheet piles were driven and sufficient permanent granular cell fill material could be placed.Ī land based 130Te Crawler Crane was used to assemble the temporary works and to interlock the sheet piles around the circular temporary works frame. These were used to form a level assembly area for the robust steel temporary works.ĭuring fabrication and interlocking of sheet piles on the Quayside, the frame alone was capable of resisting wind loads. The Quayside was protected and formed to a level area using timber navvy mats. This was designed to resist both wind and wave forces, and also to act as a lifting frame for final positioning of the cofferdam, weighing some 400 metric tonnes. The sheet pile cofferdams were thus fabricated on the Quayside with the sheet piles being installed around a purpose designed fabricated steel frame. Due to the constraints, Sheet Piling UK Limited elected to adopt a construction method aimed at keeping the marine works elements to an absolute minimum. The harbour is located close to the River Yare Estuary, and strong tidal currents and sea swells were known to exist in this location. The sheet piling works were to be undertaken in a busy ‘live’ harbour and a tender requirement was that disruption at the harbour entrance was to be kept to an absolute minimum. The works were put out to tender in June 2012 with and end of August 2012 contract completion date. Sheet Piling UK Limited were employed by Principal Contractor Van Oord ACZ to design the temporary works and install the ArcelorMittal Sheet Piles to form the Permanent Sheet Pile Cellular Cofferdams.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |