A world of railway experience15.03.17
The successful completion of an enormously complicated project in Hong Kong adds further weight to Laing O’Rourke’s already impressive metro railway engineering experience.
As they excavated deep below Hong Kong street level, under live railway lines and one of the city’s busiest railway stations and adjacent to government buildings and police headquarters, the Laing O’Rourke team had as their focus the client’s primary goals.
Metro operators MTR did not just expect a flawless final product, they also had in mind the experience of Hong Kong locals, specifically ensuring that their safety, and the reliability of their railway system, was never threatened during construction.
That was easier said than done, considering the level of challenges faced during the Contract 901 project. Extending Admiralty Station and constructing new rail tunnels, platforms, a below-ground interchange concourse and circulation area would involve an excavation 42 m below street level of around 840,000 t of often hard rock.
The ‘hard rock’ in question was granite with a strength of up to 200 MPa, four or five times that of concrete. “We employed a variety of methods, from drilling and splitting to mechanical breaking to blasting,” says Viv Jones, Laing O’Rourke’s Project Director on the Contract 901 project.
“We employed different types of machines and brought in specialist crews, using various techniques to drive the program forward. That was one of the most challenging aspects.” But the team couldn’t blast freely. In such a sensitive urban area, with live railway lines mere metres away, blasts had to be timed between trains to ensure there were no passengers in nearby tunnels.
“We also had a four-hour window, from 1am to 5am each night, where there was no traffic,” Jones says. “Our planning meant we didn’t cause a delay to a single train during the five-and-a-half-year project, an achievement the client considered significant.”
"Our planning meant we didn’t cause a delay to a single train during the five-and-a-half-year project, an achievement the client considered significant."
A further engineering challenge came during the ‘underpinning’ segment. Existing rail tunnels went to a depth of 27 m below ground and the engineers had to dig a large cavern, 30 m high and 70 m long, under that. They supported the railway tunnels above with a combination of permanent and temporary columns and a computer-operated jacking system, which made adjustments if there were any movements.
“We were allowed three millimetres of movement underneath the live, operating railway,” Jones explains. “We put a great deal of engineering focus into the solution and ended up using just 1.2 mm.” “To give the client surety we allowed designated people on their team 24-hour access to the live movement monitoring system, creating complete transparency. We set alert levels so if anything significant happened the system would send them a text message.
So the client was actively involved.” In the railway industry, technology and innovation has been an interesting challenge in itself. With such a long history and a clear emphasis on safety, ‘tried and true’ tends to trump ‘experimental and new’.
The international reach of Laing O’Rourke means experts from other territories have been available to come to the Australian market to share knowledge and experience during the many rail engineering projects that its teams have successfully completed. Thanks to its broad experience, Laing O’Rourke is now uniquely and powerfully equipped to tackle rail projects of all shapes and sizes.
“We could see there was an infrastructure workload on its way,” says Nicole Waterman, Technical Leader at Laing O’Rourke and Technical Director of Novo Rail. “The New South Wales and Victorian governments have been speaking about this for a long time. As we have had some strategic projects, including Hong Kong and elsewhere, we have sent engineers, planners and commercial managers across to work on those projects in anticipation that they will come back with powerful experience and knowledge.”
“Currently, our UK business is working on the London underground, Crossrail and the new High Speed 2 rail. All of these opportunities build experience in engineers’ careers and build capacity and capability in a nation’s infrastructure programs.”