Sector Case Studies - Residential


82 SFA Piles designed and Installed by Amplus Ltd in 2010 for the design by Axis Mason as a mixed-use development.

This development comprises nine 3 bedroom townhouses with commercial units below. Each townhouse has a series of private amenity spaces at various levels. These include roof top gardens, entrance level terraces, and projecting balconies.

Located just north of St Helier’s commercial centre, the site boundary on Halkett Place steps out at the South-West corner of the site which creates an opportunity to address its design. A common feature of the street are terraced townhouse style buildings with three window bays and a central or offset entrance door. We have elected to continue the three bay rhythm of the street into the proposed new building, picking up on the character and proportions of the traditional buildings but in a contemporary arrangement and detail.

Units are grouped in pairs to reflect the traditional plot ratios found in and around St Helier, with a regular pattern of varied windows adding a sense of scale and rhythm.

At the ground floor, units are provided with individual entrances and horizontally coursed stone cladding is incorporated to add a sense of quality and detail at the public realm whilst ensuring an appropriately robust cladding suitable in this urban location.





Work is now underway on the first phase of this Axis Mason designed mixed-use development on St Helier’s waterfront, comprising a range of contemporary apartments, retail and restaurant accommodation for Dandara (Jersey) Ltd.


Amplus designed and installed 1200nr piles using a combination of their Casagrande CFA 425, Casagrande B125, Casagrande C6 and Technodrill TD610 rigs.


Approximately 190metres of concrete guide wall was cast to facilitate the installation of a contiguous pile retaining wall.  The retaining wall consisted of nearly 300nr  450mm diameter contiguous wall piles approximately 13m long. 


The foundation piles included 230nr x 750mm CFA piles carrying loads of up to 2550kN and 530nr x 450mm CFA piles carrying loads of up to 900kN.  In addition, approximately 150nr rotary percussive piles were drilled through a rubble seawall using the Symmetrix system.


To withstand hydrostatic pressure on the basement slab during construction, Amplus installed 85nr  temporary anchors socketted in to rock.


Amplus completed the works ahead of schedule in 2008.


The Sandringham at 14 Gloucester Street, is a 7 storey mixed-use development designed by Axis Mason and containing retail space and a clinic at ground floor with a seperate medical centre occupying ground and first floor levels, and with 5 upper floors of apartments. There is also a part basement.

Amplus employed a variety of piling systems to create the basement and foundations of this development in challenging ground conditions.

Amplus installed 69nr 350mm and 450mm diameter, secant and contiguous wall piles using a Casagrande CFA 425 and TD610 piling rigs together with 138nr 450mm diameter  foundation piles each carrying up to 1000kN. In addition, Amplus built 18nr 450mm diameter segmental flight auger piles close to an old brick culvert using a TD610 piling rig. The work was completed in 5 weeks in 2007. 



This project consists of 6 storey mixed-use building with  42nr apartments, offices & retail with basement car parking over most of the site footprint. The superstructure is a braced steel frame supported on piles. The building was designed by Naish Waddington Architects for Spinnaker Developments Ltd


Amplus installed 332nr  250mm diameter, 11m long, permanently cased rock socketted mini-piles to carry compressive loads of up to 600kN and tensile loads of up to 300kN.  Amplus employed two piling rigs, namely a Casagrande C6 and a TD610, using ODS and Symmetrix drilling systems to complete the work in 11 weeks in 2003.



Amplus Ltd, has designed and installed up to 1,500 piles to support the new Albert Pier Waterfront housing development in Jersey.  This is the largest piling contract ever undertaken in the Channel Islands.  Five crawler mounted hydraulic piling rigs were used over a period of nine months to install the 17m long piles.  The contract for Spie-Camerons JV was completed on time and within budget in July 2001. 


Amplus Ltd bored the 250mm diameter piles using rotary percussive techniques with permanent casing through the loose fill and beach deposits.  The specified working load of 500kN was carried by the skin friction between the pile grout and the strong granite rock over the 3m length of uncased "rock socket".


The ability of the rock to carry these stresses was checked by preliminary pile tests carried out in advance of the permanent works.  Amplus Ltd made allowance in their pile design for the possibility of down-drag (negative skin friction) arising from the long term consolidation settlement of the fill.

The mild steel casing has a wall thickness of 3mm and comes in 2m and 4m lengths.  The casings are welded together.


Amplus Ltd  operate Italian built piling rigs.  The Casagrande hydraulic crawler drills used on the site included the C8 and C6 models.  The larger C8 rig weighs 21 tonne and has a 10.0m long mast.  The smaller C6 rig weighs 13 tonne and has a 6.0m long mast.


Rotary percussive drilling uses a down-the-hole hammer fitted to the bottom of the drill string.


Compressed air is fed through the hollow drill rods and drives the hammer.  After activating the hammer, the exhaust air exits through holes in the face of the bit.  Amplus Ltd   use button bits with round tungsten carbide inserts.  The air cools the bit and flushes the cuttings away and lifts them to the surface via the annulus between the casing and the drill string.


When drilling through the overburden, Amplus Ltd use casing.  An eccentric bit is fitted on the down-the-hole hammer.  When the eccentric bit extends beyond the shoe of the casing, it is made  to open out and to underream the hole to a diameter slightly larger than the casing's  outer diameter.  The casing can then be drawn down in to the enlarged hole using the bottom drive system.  When the drilling is complete, the bit retracts and can be withdrawn leaving the casing in the ground.


The hole is extended in to the rock using a down-the-hole hammer without casing to create the rock socket.







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