Port Hedland Railway

Port Hedland Railway
Client: 
BHP Billiton
Value: 
$2.7M
Techniques Used: 
Sheet Piling, Retaining Wall

Project Brief:  The project formed one part of the expansion of the BHP Billiton Iron Ore export facilities located in Port Hedland, one of the busiest commodity ports in the world. The works came under the Rapid Growth Project No. 5 (RGP 5), being controlled by FAST JV (Flour and SKM Team).  The project formed part of the temporary works to allow the extension of the existing Car Dumpers 2, 3 and 4 which are used to unload the ore from the trains received from the mines.

Geological Conditions: The works were spread across BHP Billiton’s two harbour facilities located within Port Hedland, with Car Dumpers 2 and 3 located at Nelson Point and Car Dumper 4 at Finucane Island. The site geology was relatively similar across the two sites.  The piling areas were located within reclaimed land, which was completed many years ago using the sands excavated during the deepening of the shipping channels.

The subsurface conditions generally consisted of a crust of iron ore dust mixed with sand and railway ballast overlying clean medium to very dense sands, with some cemented layers. Below the reclaimed material the nature occurring marine deposits can be found at depths greater than 8m.

Scope Of Work: The project consisted of the design and construction of a retaining wall structure to allow the follow on works required to expand the Car Dumper facilities on both sides of the railway tracks.  The retaining wall had very stringent defection criteria, with the railway line to remain fully operation during the excavation, of up to 2.5m depth beside the tracks.

The project was further complicated by the locations of the work sites within a fully operating facility, that normally runs around the clock. All works had to be completed within tightly controlled shut-downs, ranging in duration from 10 to 72 hours.  The retaining wall structure consisted of a sheet piled solution constructed either side of the existing railway line for distances ranging from 25m to 64m. The sheets were located within a 508mm envelope adjacent to the ends of the railway sleepers, allowing only 100mm construction tolerance based on the design width of the sheet.

The sheet pile retaining walls consisted of 6m long AU14 sheets, with tie rods installed between the two lines at 1.5m centres (every second sheet) to control the sheet and railway deflection. The tie bars had to be installed in insulated conduit below the railway tracks and between the sleepers, thus requiring the removal and recompaction of the ballast.

Conclusion: A timely, cost effective and innovative solution for the retention works for the Car Dumper retaining structures was achieved by our in house design and operation team, with co-operations with the FAST JV team.  A total of 280 lineal meters of sheets piles were installed, and 95 tie rods. This was completed in 6 No. occupations. Using purpose built piling rigs and experience site personnel.