Product category:
Ground Engineering
News Release from: Aarsleff Piling
Edited by the Buildingtalk Editorial
Team on 04 January 2008
Aarsleff expands with Junttan
Aarsleff Piling has expanded its comprehensive fleet of driven piling equipment with the purchase of a Finnish Junttan PM26 LC piling rig complete with 9t Junttan accelerated hammer.
The acquisition and fleet expansion is in direct response to Aarsleff's sustained increase in demand for its services and especially in the renewable energy sector Here there is a growing requirement for much larger precast concrete piles up to 400 mm square section needed to accommodate the high cyclical loadings generated by wind turbines
This article was originally published on Buildingtalk on 15 Jan 2007 at 8.00am (UK)
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"We have already installed foundation piles for over 50 wind turbine bases and this year we expect to install piles for another 44 bases," says Aarsleff Piling managing director Terry Bolsher.
"The Junttan PM26 LC, with the 9t HHK 9A accelerated hammer, is now the largest rig in our fleet and has been bought specifically for this type of work".
"The 9t hammer is one of a new generation of Junttan hydraulic impact hammers with an adjustable stroke of up to 1.2 m".
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"It is operated from the rig's hydraulic system and hydraulically accelerates the drop weight during the fall, boosting the impact energy and increasing by up to 20% the efficiency at full stroke over a conventional free fall drop hammer of the same weight".
"The hammer produces maximum impact energy of 106kNm at full 1.2 m stroke and impact energy, stroke height and blow rate can be infinitely adjusted by the rig operator to suit ground conditions and pile type as the hammer is suitable for driving all types of precast concrete, steel tube, sheet and timber piles".
"All relevant pile driving data is displayed on the rig's computer screen in the operator's cab".
"The first wind farm project for our new PM26LC is at Ransonmoor near March, Cambridgeshire, installing 350mm square section 26m long piles for contractor R G Carter Civil Engineering".
R G Carter is constructing the foundation bases and associated access roads for a pair of 2 MW wind turbines under an approximate GBP790,000 design and build contract for client Fenpower.
R G Carter awarded specialist driven piling contractor Aarsleff Piling an approximate GBP85,000 contract for the foundation piling.
This was won on competitive tender to supply, handle, pitch and drive the 26m long continuously reinforced precast concrete piles with joints, for the foundation bases to the design of R G Carter's German consulting engineer HCE Ingenieurgesellschaft, based in Hamburg.
Aarsleff had previously introduced R G Carter to HCE, an associate of Aarsleff's parent company Per Aarsleff based in Denmark.
HCE has considerable experience of designing wind turbine foundations in Europe and is matched with Aarsleff's experience in engineered piling solutions, which has included installing the piles for the three turbines on the first phase at Ransonmoor.
Aarsleff has also previously worked for R G Carter installing precast concrete piles for eight wind turbine bases near Swaffham, Norfolk.
For the second phase at Ransonmoor Aarsleff has to install 30 piles in each of the two bases on a ground level pitch circle diameter of 15.5m.
Every third pile is driven on a 1:5 inward rake, with the remainder on a 1:4 outer rake.
HCE's design called for 26m long piles made up of an 8m long under pile jointed to an 18m long over pile to achieve a compressive working load of 955kN and tension of just under 150kN.
The joint has to be as far down the pile as possible and if for any reason a pile drives short in the expected ground the joint is still below the 10m depth zone under the foundation base, as specified by HCE.
"Following competitive tendering Aarsleff was selected on price and for their experience on wind farm installations, as they had already been on site to pile the first phase," says RG Carter Civil Engineering general manager Michael Turner".
""Also as the over piles are 18m long and very heavy, we believe the only rig in the UK that can handle and pitch these at a backward and forward rake is the Junttan PM26LC.
We also understand that Aarsleff's subsidiary, Centrum Pile, is the only company in the UK that can make 18m long piles in a single length." The piles in the first base drove more or less as expected, but on the second the ground conditions proved to be considerably different from the first.
There was a hard band about 12.5 m below ground and then another at a depth of 18.5m to 20m and the piles could not be driven through them.
With foresight R G Carter and Aarsleff had anticipated the possibility of changing ground conditions at the start of the project".
""We worked together and came up with an engineered solution to meet HCE's design, and to accommodate the client's request to accelerate the work by 3 months," adds Turner".
""We made a design change and put the 18m pile in first and drove the 8m as the jointed over pile".
"We can't drive the 8m piles more than 1.6m, as this would compromise the reinforcement cast into the main foundation".
"But the ground was stiff enough to take the loads at that level and took away the risk of the joint being in the wrong position".
As each base piling is finished R G Carter follows on cutting piles to level and completing the heavily reinforced concrete foundation bases and other ancillary works and access roads.
The REpower Systems MM82 wind turbines, which have a hub height of 69 m and 80 m diameter blades, will then be erected, tested and commissioned by REpower and are expected to be operational by the end of the year.
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