A purpose-built, rail-mounted concrete mixing bowl has enabled Higgins Concrete to efficiently lay foundations for 965 new steel poles along the Petone to Upper Hutt rail line north of Wellington.
Having previously worked with the Fulton Hogan-John Holland Joint Venture (JV) on the rail line around Pukerua Bay, Porirua-based Higgins Concrete Regional Manager Scott Ferguson says his firm welcomed the opportunity to continue on the Hutt Valley Line upgrade.
However, it soon became apparent that due to access difficulties, a standard truck-based concrete-pouring solution would not suffice.
“You can get trucks alongside some rail lines, but it can be pretty dicey, while on others there is no room for trucks at all,” says Scott.
“So, we came up with the idea of having a complete bowl unit – with its own power pack and water tank – mounted onto a container twistlock frame.”
“The unit was built to KiwiRail’s stringent safety standards and was transported along the tracks by a KiwiRail-supplied hi-rail trailer and a hi-rail tug unit.”
The five-cubic-metre-capacity bowl was commissioned from Waikato-based Technical Welding Services, a firm that Higgins Concrete has enjoyed an almost 30-year working relationship with.
“We went to our supplier and gave them a plan of what we wanted, and they made it up. We had to go and check it a couple of times in Hamilton to make sure it was right – and then once we used it a few times we found a couple on minor modifications were required, mainly involving the water supply to wash out, but nothing major.”
“It took about three months to sort the build, including gaining KiwiRail’s approval. However, you need to bear in mind that it was the first time anyone has done this.”
Scott estimates that up to 2,000 cubic metres of concrete were poured for the steel pole foundations by Higgins Concrete during the 18-month contract.
“Transporting the frame mounted bowl unit to the rail lines was simple. We commissioned an old concrete truck to transport the unit, this was lifted off and placed on the Hi Rail trailer by forklift, it then stayed on track until we needed to clean the bowl or service the unit.”
“Getting the concrete out of our normal trucks and into the bowl unit was achieved through the use of a concrete pump. We fitted up a 150 mm pump line onto the bowl unit and just attached a hose from the pump to the bowl unit.
“The rail unit then trundled off to wherever the holes were and discharged. A couple of custom chutes were fabricated to the required length so that the concrete could be easily tipped into the foundation hole.”
“It was all special concrete – 40 MPa with steel fibres – which avoided the need for cage reinforcing.”
Scott believes the estimated $98 million project presented some other challenges, including being predominantly night-based work, and long weekends and the Xmas shutdown period.
“There were also a few issues with the pumping due to the steel fibres, but we overcame them,” adds Scott.
“Another problem we had was how to wash the bowl out at the end of each shift. So we set up a little truck-and-trailer unit with water tanks on it, which we would take with us to the rail lines. At the end of the shift we would wash the bowl out and then bring the contaminated water back to our plant’s wash water treatment ponds.”
Scott reflects with a great deal of satisfaction how sometimes the best solutions are the simplest. “With a little bit of lateral thinking the answers presented themselves using existing technology and practices, although be it with a twist.”
Taken from Readymix News.