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Ground Engineering
News Release from: Aarsleff Piling | Subject: Piling for new steel manufacturing plant
Edited by the Buildingtalk Editorial
Team on 13 June 2005
Aarsleff piles into melt shop
Cementation Foundations Skanska and Aarsleff Piling complete piling for new steel manufacturing plant.
Specialist piling, foundations and ground engineering contractors Cementation Foundations Skanska and Aarsleff Piling have successfully completed the extensive piling required to support a new GBP 100M steel manufacturing plant on the site of the former steel reinforcement producer Allied Steel and Wire in Tremorfa, Cardiff The piling is for SMS-Demag of Germany, which is building the turnkey project for client Celsa Manufacturing (UK) ., part of the Spanish steel manufacturing Celsa Group
This article was originally published on Buildingtalk on 26 May 2005 at 8.00am (UK)
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Allied Steel and Wire was a major source of steel reinforcement for the construction industry, but the company went into administration over two years ago.
The Celsa Group, based in Barcelona, took over the plant from the receiver, prior to demolishing part of the former ASW works and building a new melting shop.
The new facility will house a 140 t electric arc and ladle furnace feeding a six strand continuous billet casting machine, producing 1.2 Mt/year of different sections from steel scrap.
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The waste slag from the furnaces will be collected, processed and recycled for construction backfill.
Celsa is reproducing at Cardiff the plant layout it uses in Spain and has appointed consulting engineer Idom, based in Bilbao, to design and supervise its construction.
SMS-Demag awarded Cementation Foundations Skanska the main foundations contract to design and install piles to loadings provided by the consulting engineer.
The approximate GBP 2.1 M contract required a combination of 681 CFA and 1022 precast concrete driven piles.
CFS no longer has the facility to manufacture precast concrete piles so negotiated an approximate GBP 750,000 subcontract with Aarsleff Piling to supply, handle, pitch and drive precast concrete piles, which are made by Aarsleff's in house subsidiary Centrum Pile at Newark, Nottinghamshire.
There are several different types of CFA and driven piles to accommodate a variety of compressive loadings on the project.
The CFA piles vary in diameter from 600 mm, 750 mm and 1,050 mm and have been designed for compressive working loads ranging from 1,500 kN, on the smallest 600 mm diameter piles, up to 4,700 kN for the largest 1,050 mm diameter.
In addition there are three types of Aarsleff's 300 mm square section precast piles, which have compressive working loads varying from 210 kN to 1000 kN.
In addition, the project's approximate 1700 individual piles also have to accommodate 10% of their allotted compressive loading in tension as a minimum requirement.
Increased tension loading is required on some of the piles, some 600 mm CFA piles have a 550 kN tensile loading, increasing to 620 kN tension on the mid sized 750s.
The three types of precast concrete piles also have to absorb lateral loads ranging from 25 kN to 55 kN.
Centrum's standard 300 mm square section piles can accommodate up to 40 kN lateral loading, but on one of the other types needed at Cardiff, Centrum, using its unique to the UK computer controlled reinforcing cage fabrication and welding robot, has simply shortened the shear links on the standard reinforcing cage's longitudinal bars.
For the highest loads the pile's normal 8 reinforcing bars have been increased to 12 and combined with reducing the pitch of the helically wrapped stirrups.
CFS moved onto site at the end of October 2004 and initially designed and built the piling area working platform to accommodate the rigs, which peaked at five machines, prior to a start on the piling in November.
CFS used a combination of a Soilmec R622 and a pair of Junttan PM26 CFA rigs, while Aarsleff opted for one of its Banut 700 and Junttan PM20 self erecting, fixed leader, drop hammer rigs.
The piles are strategically located in singles, pairs and clusters ranging from 8 to 30 piles and in some instances CFA and driven piles are close together.
"Sequencing the manufacture of the precast piles has been quite critical to match their installation," says CFS's project manager Jonathan Manning.
"In those areas where the precast and CFA are in close proximity, we have ensured that the precast are driven first, thereby eliminating the risk of damaging newly-cast CFA piles or inducing additional loading." The precast concrete piles are up to 22 m long and driven to a set by Aarsleff through the made ground overlying alluvium to penetrate and found between 3 m to 4 m into the underlying mudstone.
The CFA piles, which vary in length from about 21.5 m to 26 m, are all founded between 4.5 m and 9m into the mudstone.
The vast majority of the piles have been installed without any problems.
The majority of the works was completed before Easter while the remainder of the piling was hampered and delayed by underground obstructions in an area of fused slag, dumped by the previous steelworks operations.
This area, the last Aarsleff attempted to tackle, was badly affected by fused slag obstructions.
Here the entire area, encompassing about 200 piles, around 20% of Aarsleff's total, was excavated down to about 7m to locate the fused slag, which was impossible to drive piles through.
A combination of probe drilling, by CFS and deep excavation by the main civil works contractor, to locate and remove the obstructions was employed to enable CFS and Aarsleff to respectively complete the combined installation of 1700 continuous flight auger and pre cast concrete driven piles.
The small diameter probe drilling was not able to accurately map some of the underground slag obstructions, although it confirmed that the obstructions did not extend past 7m.
Deep excavation down to this depth was required for all of the remaining piles to allow complete removal of the fused slag and replacement with compacted backfill prior to piling.
Aarsleff temporarily moved off site, while the slag was dug out and the excavation backfilled and compacted.
Aarsleff returned after the Easter break to complete its final part of the extensive piling project.
"In the affected area of fused slag obstruction the main contractor had to excavate the pile cap areas down to 7 m to remove the slag obstruction and then backfill and compact prior to installing the piles," says Manning.
"This considerably reduced our progress as we had to wait for this excavation".
"Similarly, in those instances where single precast piles have refused and been left upstanding, the obstruction had to be removed".
"Celsa's consulting engineer Idom decided whether to remove or abandon those individual piles or redesign the affected area." The main civil works contractor Laing O'Rourke started on site in February, excavating, forming the pile caps and performing other works.
The Spanish steelworks contractor Tauxme will follow on behind Laing O'Rourke, erecting the building's structural steelwork, prior to the final installation of the SMS Demag Aktiengesellschaft steel manufacturing equipment.
Celsa's new Melt Shop is expected to employ about 400 when it goes on stream sometime during the first quarter of 2006.
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