A 310 km heavy haul railway is planned to link unexploited iron ore deposits in the Pilbara with export facilities at Port Hedland. Careful planning will minimise the life cycle costs of the infrastructure

SPECTACULAR growth in China is driving up the price of iron ore, with the excess of demand over supply constraining the development of the country's steel industry.

As owner of significant iron ore deposits in Western Australia, Fortescue Metals Group aims to take advantage of this opportunity. FMG is planning a railway to link an export terminal at Port Hedland with its proposed opencast mine at Christmas Creek, in the Chichester Ranges of East Pilbara.

The line will start from an unloading loop on the south side of Port Hedland harbour, then cross the existing BHP Billiton Iron Ore heavy haul line to Goldsworthy, sharing tracks for a short distance. There will be a marshalling yard to the north of a level crossing over the Great Northern Highway.

The railway will then run south, paralleling BHP's Newman line for 145 km. A bridge will take the new line over the existing route, then the lines will run parallel as far as Redmont. The FMG line will turn east through the Chichester Ranges to the north flank of the Fortescue Valley, terminating in a loading loop at the Christmas Creek Mine, 310 km from Port Hedland.

Detailed modelling

Construction contracts are currently being negotiated, and the project is expected to take 22 months from the start of civil engineering to the dispatch of the first loaded train.

Maunsell completed a pre-feasibility study in March 2004, producing a preliminary alignment which was then refined using the Quantm planning tool, with improved geographical information and revised design criteria.

Fugro Spatial Solutions provided a digital terrain model created from 1:13000 scale aerial photographs. This contains spot heights and contours at 1m intervals, as well as major topographical features such as roads and creeks. Manual evaluation of the results with terrain modelling software from 12d produced the final alignment.

TMG used MTrain performance simulation software to determine speeds and running times, with Quantm used for capital and operating cost modelling to determine gradients and the preferred train configuration. Whole-life analysis led to a reduction in the proposed grade for loaded trains from 0·33% to 0·225%, the additional capital cost being offset by better operating flexibility.

The design is based on trains of three GE Dash-9 locos or their equivalent hauling 200 ore wagons of 126 tonne payload. The 0·225% ruling grade against loaded trains is less than BHP's 0·55%, and the grade against empty trains is equal to the grade on that line.

Average empty running time between the marshalling yard and the mine was put at 4h 27min, including loop stops, with a 4h 38min non-stop time for the loaded train. Loading will take 5·6h, and unloading 3·3h. The bare cycle time is 20h, but Monte Carlo simulations suggested 22h would be sustainable, and a 24h cycle would be sufficiently robust in the event of disruption.

This will result in six trains operating at once, with four crossing loops approximately 1h apart. Each loop will have a refuge for on-track plant, and three 250m sidings at Camp at the base of the Chichesters will be used to stable maintenance equipment, locos and wagons. Additional refuges between the crossing loops will reduce disruption to the ore trains from track maintenance.

Operating plan

The marshalling yard will initially have two through tracks, with space for expansion. On arrival at the yard, locos of loaded trains will be removed for refuelling and trip servicing before taking the next available empty rake to the mine.

Yard locos will take the loaded wagons to the unloading loop, after attaching air compressor wagons to maintain brake pressure during unloading. A loaded train will be able to arrive at the dumper as an empty train leaves the loop.

The tracks through the unloader will be graded to ensure the train is always in tension and under control. The wagons will be in semi-permanently coupled pairs with a fixed drawbar, each pair being emptied by a rotary tippler in 90sec and moved by an indexing arm without the need for locomotive power. Another loco will take empty rakes back to the yard and detach the compressors ready for inspection of the wagons prior to departure. A run-round track will allow shunting or the unloader to be bypassed in the event of any disruption.

The maintenance facility will be equipped for a fleet of 23 diesel locos and 1260 ore wagons. Three locos will be serviced simultaneously using six fuel nozzles, with sand, oil and coolant supplied as required. There will be extraction facilities for removal of waste oil, oil filters, coolant and sludge. The depot will be able to replace bogies, traction motors, wheelsets and engines. It will be equipped to carry out welding, wheel and bogie repairs on up to 50 wagon pairs, with sidings for 20 pairs on both the inbound and outbound roads. Separate tracks will be provided for running repairs and major bogie and wheel work.

Line control

Adjacent to the workshops will be the administration office, accommodating operating personnel and the CTC. This will use Union Switch & Signal computerised train order management, crossing loop controls and train location displays, as well as asset management and system supervision equipment. Proven technology will be used, with a high level of diagnostic information to expedite maintenance, particularly for remote equipment. Provision for expansion will be made where it can be done economically; in particular FMG hopes to adopt cab signalling once the traffic merits it. Arrangements for controlling the section of track near Boodarie shared with BHP have still to be agreed.

A trackside optic fibre link will be used for the signalling and monitoring equipment, as well as transferring business data between the mine and port. Radio will be used for train orders and general operational requirements, and coverage will extend around the trains, for use by drivers when out of the cab in the marshalling yards and on the main line.

Broken rail detection is to be provided along the main line, and at the loops, loading loop and yard. Dragging equipment detectors will be installed every 5 km and before and after every main line turnout. Wayside thermal, vibration, video image and laser measuring devices will monitor rolling stock, warning of serious faults as well as providing data to assist maintenance. Stream flow detection is to be provided on major river crossings.

Lifting barrier level crossings will protect the Great Northern Coastal Highway and a road to Finucane Island. On completion of the line, the unsealed roads needed during construction will be retained to give access for maintenance.

Trackwork

Standard carbon rails made in Australia to Arema specifications and 136RE profile have been selected for the project. The ore wagons will operate at 32 tonne axleloads during the build-up of production, work-hardening the rail and making it unnecessary to pay a premium for head-hardened rail.

Prestressed concrete sleepers designed for 37·5 tonne axleloads will be produced at Port Hedland, with Arema class 4 ballast similar to that used on the BHP lines being obtained from local quarries. The planned ballast depth of 250mm under the sleepers is generous by existing standards, providing additional protection to the formation. When the axleload is increased to 37·5 tonnes the track will be re-ballasted to a depth of 300mm.

Two turnout designs will be adopted. Lines used by loaded trains will have 1:20 turnouts with tangential geometry and swing-nose frogs, enabling operation at normal running speed with minimal wear. Other turnouts will be a 1:12 design with rail-bound manganese frogs, requiring speed restrictions. All will be electronically operated and detected, with in-cab displays of the routes set so that drivers will not need to leave the cab.

Flood management

The alignment is crossed by numerous creeks, from small gullies requiring culverts to rivers demanding multi-span bridges. HEC-RAS software developed by the US Army Corps of Engineers has been used to determine flood profiles for the bridges, providing estimates of head and tail water levels, head losses and water velocity.

The bridges will have a conventional girder construction with a precast ballast trough. Standardised spans of 25m will be used as far as possible, minimising complexity and on-site concreting, which is costly and time-consuming in the hot climate. The bridge over the BHP line will have a standard span, but the embankment will be supported by concrete retaining walls to provide sufficient clearance for the BHP maintenance access road and a future second track.

The South West Creek bridge adjacent to the marshalling yard will be a through structure to maximise the clearance above flood water levels. Because it must match existing road levels, the bridge will not meet the freeboard design criteria, so a floodway will be provided to minimise damage to the formation and retain ballast.

Culverts are being designed using a national indexing method, modified by state road building guidance and experience in the region. Drainage catchment and characteristics have been determined for each stream, with peak water flows estimated from analysis of the Turner River. Culverts will also be used to prevent disruption to sheet flow which could affect stands of mulga trees in the Fortescue Valley.

Corrugated steel pipe culverts will be rolled from galvanised strip at intervals of around 50 km using mobile plant, limiting the need for road transport. Problems with premature rusting of CSP culverts have occurred in the Pilbara on previous railway projects, and while a single cause has not been isolated, it is generally accepted that this commences at the soil interface. A great deal of success has been achieved by wrapping the pipes with an impermeable sheeting of Nylex XL 45, adding a small amount to the cost but reducing the risk of corrosion considerably. A heavy-gauge polymer 'trenchcoat' will be used in the corrosive environment at the port.

Surrounding areas must not be put at additional risk of flooding as a result of the levee effect of the railway embankment. The Port Hedland installations will withstand 50-year maximum flood levels, but anything in excess of this will overtop the embankment without adversely affecting surrounding buildings.

Specifications in brief

Length route-km 310

Design train length m 2600

(4 locos + 240 wagons)

Maximum grade against the train

Loaded 0·225%

Empty 0·500%

Maximum axleload tonnes 37·5

Gauge mm 1435

Rail kg/m 68

Sleepers Prestressed concrete

at 650mm centres

Minimum main line curve radius m 2000

Geology

Four main geological domains have been identified along the route. The first 60 km will be built on coastal alluvial and colluvial materials suitable for embankment construction. Soft mangrove muds in the unloading loop will require special preparation.

The bedrock between 60 km and 200 km is generally high strength granite, weathered and modified to form soils and gravels which can be used in embankments. Outcrops along the route will require blasting to form cuttings and to fracture the rock into particles suitable for embankments.

The summit of the railway will be on the Chichester Ranges between the 200 km and 270 km points. The granite bedrock is overlain by sediments and rocks which will require drilling and blasting. There are also gilgai, deposits of clay which undergo significant changes in volume in response to moisture, forming features known as crab holes which could make foundations unstable.

The alignment on the northern slopes of the Fortescue Valley from 270 km to 310 km passes through rock debris overlain by a silt layer which needs to be removed to provide a foundation for the railway.

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