| |
The cooperation and close working relationship over many years between the UK specialist piling contractor Cementation Foundations Skanska (CFS) and hydraulic foundations equipment manufacturer Junttan Oy, has proved to be a considerable advantage to both parties. Initially the numerous changes CFS made to the standard piling rigs to suit their operations are now incorporated by Junttan during manufacture at the factory and are also a benefit to other Junttan customers including potential CFS competitors.
 Prime example of this productive strategy is CFS’s latest multi purpose Junttan PM26LC, which has around 60 of the company’s changes built in by Junttan, allowing CFS to operate it as a dual discipline rig and boost its utilisation by installing either continuous flight auger (CFA) or driven cast (DCIS) in situ piles. “We have worked very closely with Junttan and have made many changes to the PM26, which we used to do ourselves, but Junttan now build them in during manufacture and ensures that they have been checked by Junttan, as the Original Equipment Manufacturer,” says CFS’s Operations Manager Graeme McWhirter. “The biggest change, since we bought our first PM26 about seven years ago, is to make them capable of both CFA and DCIS and be able to quickly switch from one to the other to suit our commitments. To assist compliance with the working at height regulations we have also incorporated a special man-riding access platform on the rig, which Junttan and CFS have jointly developed to its current form.”
Cementation Foundations Skanska was the first foundations contractor in the UK to use Junttan rigs starting out in 1989 with the PM20 for driving precast concrete piles. The company subsequently added the larger PM25, which was equipped to install precast concrete and DCIS piles. However, CFS’s belief that long DCIS piles are more economical than equivalent length precast piles incorporating joints, lead the company to a change in strategy. CFS subsequently withdrew from the UK’s precast piling business and focused more on DCIS.
 For the PM26 to install piles using the DCIS method it is equipped with a Junttan 5t HHK 5AS hydraulic hammer, extractor system and a man riding access platform. The hammer is used to drive an integral tube of the required pile diameter, with an expendable pressed pile shoe on the toe, into the ground to the required penetration. A reinforcing cage is lowered into the tube and guided by the banksman linked to a safety harness on the platform. Concrete is poured into the tube from a skip opened by the banksman and lifted by one of the rig’s winches. The tube, minus its pile shoe, is then slowly extracted to complete a pile.
The initial DCIS system used by CFS relied on a vibrator to extract the tube after driving. However, the vibrator system proved unreliable and was subsequently replaced by a pair of 18t capacity winches on the rigs. These pull up on a yoke with a collar round the enlarged diameter funnel topped tube, while at the same time the hammer just taps down on the tube top with very light blows.
The CFA piling technique with the PM26LC requires the hammer and DCIS extractor system to be replaced with a rotary head and a continuous flight auger. The hollow stemmed auger, corresponding to the pile diameter, is screwed into the ground by the rig’s mast mounted rotary head to the required depth. Concrete is then pumped down through the stem to the bottom of the auger while at the same time the auger is slowly extracted. The auger displaces the excavated spoil at ground level while concrete fills the void behind the toe of the auger until it reaches ground level. Spoil and any surplus concrete is moved away form the top of the concrete column prior to lowering in a reinforcement cage to complete the pile.
Cementation Foundations Skanska is using its latest PM26 and one of three in its fleet, together with its single PM25, to install DCIS piles on a £2M foundations project adjacent to the Manchester Ship Canal at Salford Quays for client Peel Media Ltd. The 15 hectare site is being redeveloped into mixed commercial and residential properties with associated highways, parking and open spaces under the guidance of main contractor Bovis Lend Lease.
The company is installing just over 2,800 piles on its 20 week project, which includes 2,000 DCIS piles of 370mm and 335mm diameter. The remainder are a combination of larger diameter CFA and rotary bored piles. The DCIS piles are being installed through made ground with superficial silty sands and silty clays over sandstone bedrock at between 8m and 12m below ground level. The DCIS piles are founded in the sandstone to generate the required carrying capacity and support the structural compressive working loads of up to 750kN.
“DCIS piles are often more efficient than CFA piles and are often able to carry more load per metre in the ground. They can carry the same load as a larger diameter CFA pile and use less concrete, but you need the right rig to install them and believe we have that in the PM26,” says Graeme McWhirter. “We looked at other rigs on the market, but we have a very good relationship with Junttan and are good to work with. We have given them the benefit of our varied contracting experience and they have used some of our ideas elsewhere on other rigs to allow them, for example, to develop their own rotary head for installing CFA piles.”
Junttan, which was formed in 1976, has been steadily increasing its range of hydraulically operated foundations installation equipment. The company now has an extensive line of machinery to suit a wide variety of foundations requirements and has recently entrusted Cementation Foundations Skanska with a prototype of another new rig currently under development prior to its official launch, possibly sometime during 2008.
Ends
For further information please contact:
Jeremy Pilch, Junttan UK, London House,
266 Fulham Road, London SW10 9EL
Tel: +44 (0) 207 351 3130
Email: junttanuk@aol.com
Web: www.junttan.com
|
|
