Belfast Grand Central Station - Busway Bridge

The Belfast Transport Hub (Belfast Grand Central Station) is a modern, world class integrated transport hub with bus coach and rail links across Northern Ireland and beyond.

Graham’s involvement in the site consisted of 2 contracted phases of work. Firstly, The “Belfast Transport Hub Enabling Works Project” where they completed essential early engineering works to prepare the site for construction. The Second stage, “Belfast Transport Hub Busway Bridge & Ramps Project” included the development of a Busway Bridge to facilitate access to the new station. Quinn Piling were subcontracted by Grahams to complete the necessary Piling works required for both stages of the project.

For the main works to be carried out Grahams first had to clear the site and prepare the rest of the site for construction with provision of maintenance/welfare facilities. Furthermore, realignment works of the existing culverts that ran below the transport hub footprint had to be completed prior to the main construction works.

Piling Scope & Details

Quinn Piling was subcontracted to complete the necessary Piling works to the busway bridge with works commencing in September 2021. The scope of works delivered is as follows :

• Busway Bridge
  36No. 900mm rotary bored piles, SWL 4,500kN, 4m sandstone rock socket, c. 28m long
• East Ramp
  194no. piles in total, 450mm and 600mm CFA piles, small section of 711mm rotary bored towards the NIW Belfast Sewer. SWL 1,000-2,000kN, c. 22-28m long
• West Ramp North
  322no. piles in total, 600mm CFA and 640mm Cased CFA SWL 800-2,000kN, c. 22-26m long
• West Ramp South
  267no. pile in total, 640mm Cased CFA SWL 1,000-2,000kN c. 18-26m long, for transfer slabs spanning the Blackstaff River culvert & 900mm rotary bored piles SWL 2,000-6,000kN, up to 4.5m sandstone rock socket c. 30m long spanning the NIW sewer.

Ground Conditions

The Ground conditions on site comprised Made Ground up to 5m deep, underlain by sleech around 5-8m thick. Glacial sands and clay Tills underlay this, with weak Sherwood Sandstone [UCS 2-10MPa] at depths ranging from 28m at the east ramp[N] to 18m at the west ramp [S]. Due to the poor geotechnical properties of the sleech most of the piles were taken to a depth of 20+ metres to meet the required loading criteria, with some requiring up to 4.5m rock socket into the sandstone.

Testing

Three sacrificial Preliminary Static Load Test [SLT] piles carried out on 450mm and 600mm CFA and 900mm RB, with test loads of 2MN to 13.5MN. These Piles performed as expected under design loads. Static load tests where also carried out on working piles (1.5 x SWL), at a testing rate of 1%. Integrity testing was carried out on all 819 working piles as well as the three preliminary piles.