Major piling and remediation works are underway in north London as a full scale regeneration of the King’s Cross railway lands gets underway. NCE reports.
It is more than three years since Westpile - now Simplex-Westpile - was first on site at the King’s Cross development in north London.
Since then, the firm has returned several times as the vast redevelopment has taken shape.
The 26.8ha site is so large that it has its own postcode - N1C. It is being transformed into a new London neighbourhood complete with offices, a university, shops, parks and leisure amenities, as well as homes.
Developer is King’s Cross Central Limited Partnership. Argent is Development Manager.
Three years ago, Westpile was installing piles within the Granary Building, now home to Central Saint Martins College of Art & Design part of the University of the Arts, London.
On its latest visit, the firm’s seventh, Simplex-Westpile is installing the piled perimeter wall for the current phase of the project for which the working title is Kings Cross Zone B.
After mobilising one Soilmec 625 rig on 3 October and another on 1o October together with attendant 90t service cranes, the firm has been installing 320 linear metres of contiguous piled wall of rotary bored piles to depths of up to 30m.
The initial installations form walls for a basement bordered by a new road, called King’s Boulevard, rising from its junction with Pancras Road up to a new bridge which crosses the Regent’s Canal.
The piles are being installed with the two rigs working away from each other on 30m length piling mats.
Simplex-Westpile has been installing 320 linear metres of contiguous piled wall or rotary bored piles to depths of up to 30m
Three hundred piles of 900mm and 1050mm diameter are being installed using 10m temporary steel casings. The piles will work in free cantilevered mode, when excavated to a depth of approximately 7m.
However, around the centre point of this wall, the circumference of the remaining submerged brickwork from the base of one of the large old gas holders intersects with the new line of piles. Due to this, a different pile design has been implemented. Thirteen piles with external diameters of 1180mm have been installed using a segmental casing, with cutting teeth at the base to cut through up to 16m of brickwork.
In addition, Bachy Soletanche’s AGM division is excavating a section of approximately 50 piles to greater depth, supported by three rows of 15m long pretensioned and grouted ground anchors together with waling beams.
This is being done so Bam Nuttall can remediate ground under the old gas holder.
Nearby water main
Vibration monitoring was carried out with initial pile tests regarding the effect of operations on a nearby water main.
In addition, three inclinometer tubes per new building to be built are being installed to monitor wall deflection.
There is also an installation of a short 10m run of hard/soft secant wall which will remain unexcavated until adjacent building purchasers have been announced.
Simplex-Westpile is scheduled to complete these works which have a value of approximately £1.8M, by mid January 2012.
The firm also has a separate contract for main contractor Kier Construction on another part of the site. This involves installing a series of 450mm, 600mm, 750mm, 900mm, 1050mm and 1350mm piles using rotary and CFA techniques.