Case Studies

Location:- Upnor, Kent

Project Type: Berm Construction, Piling Works, Capping Beam

History
The slope adjacent to the road some two years prior, showed significant signs of instability caused primarily by spoil being discharged in an uncontrolled manner at the head of a steep slope by a resident trying to retain the edge of his property.

Initial remedial action was taken at the base of the slope which was to provide ballast bund bags. This held until significant recent rainfall.  The slope then became unstable with shear tears and deep fissuring within the slope.

With further rainfall lubricating the shear failure through the fissuring, the slope became very unstable and failed causing displacement of the bags onto the pavement.  Trees that were being monitored had moved and rotated down the slope up to 100 metres.

Remedial Proposals

Due to safety concerns, GSS were commissioned to work with Gabriel Associates, Knapp Hicks and Taylor Wimpey to stabilise the slope by designing and constructing an engineered Berm at the base of the slope, to prevent further base heave and to provide an access platform for a 14T piling rig to install a buttressed contiguous bored pile wall.

Geotechnical investigation information highlighted considerable depth of Made Ground including contaminates (asbestos, concrete, steel, timber etc.) overlying Thanet Sands.

Our proposed solution was to install a 26m length 660/600 diameter bored CFA piles to a depth of 11m reinforced with full depth 10H40 bar cages to resist the earth pressures.  The piles were designed to the maximum and were back analysed confirming the requirement of additional ground anchorages to increase the wall factor of safety.

The Works

The piles were installed as per design with slight difficulties in plunging the cages due to the underlying Thanet Sands.  This was engineered out by vibrating the cages into the piles using a bespoke top hat over the cage.  The bored pile wall was completed successfully to the full extent of the design.

The capping beam was designed to span between the buttresses as installed with additional anchorage ports cast at 20° rake for further anchor installation if required at a later date.

The works were completed successfully with O’Halloran O’Brien as principal contractor and the design team.

Piling Value: £266K
Main Contractor: Taylor Wimpey South East
Duration: Approx. 12 weeks


Location:- Pall Mall

Project Type: Bored Temporary Cased, Bearing Piles, Contiguous, Secant, Crane Base

GSS piling was contracted by Galliford Try to install a combination of contiguous bored pile walls and secant piled walls both within a restricted site within an existing sub-basement beneath limiting flying shores.  508/450mm diameter bored temporary cased piles were installed to retain the significant surcharge loads from the existing buildings surrounding the works.

Overriding constraints being the headroom limitation of 5.5m beneath flying shores and deep gravels before encountering the underlying London clays. Additional concerns with the risks to surrounding structures during the augering processes and therefore CFA piles were excluded and bored temporary cased piles were considered the most appropriate system which minimises the disturbance to the ground during the augering process and ensures that full depth reinforcement cages could be introduced to the piles as required by the contiguous wall design.

The site was further advanced into the pavement of Pall Mall where numerous services have been identified where a combination of 300/350mm diameter bored temporary cased piles and 406/350mm diameter piles were also required to form both the substation and plant area to service the site. The works can be summarised as follows:

  • Installation 58 No. of 508/450mm contiguous bored pile wall using Klemm KR709 with restricted headroom of 5.5m.
  • Installation of 60 No. 508/450mm diameter bearing piles within the existing basement using Klemm KR709 within 5.5m of restricted headroom
  • Installation of 18 No. 350/300mm diameter bored temporary cased piles from within the existing basement adjacent to the front elevation beneath the existing vault paving and behind an existing column.
  • Installation of 39 No. 350/300mm diameter piles to contiguous bore pile wall for the vault substation carried out from pavement level allowing for 13.5m temporary casing.
  • Installation of 12 No. 406/350mm diameter piles from existing pavement level using Klemm KR702 using 13m temporary casing.
  • Installation of 44 No. secant piles within the existing basement sub-basement using a Super Kitten rig using 350/300mm diameter piles.
  • Installation of 4 No. 350/300mm diameter crane base piles using Super Kitten within the basement.

Piling Value: £600K
Main Contractor: Galliford Try Limited
Client: Berry Brothers
Duration: Multi visits approx. 20 weeks


Location:- Prestigious Project within Kensington

Project Type: CFA Contiguous, secant, temporary works bearing piles, bearing piles

Geostructural Solutions Limited and GSS Piling Ltd with Bouygue UK and Price & Myers developed a scheme for a prestigious project within Kensington for a high profile Client to create a substantial basement extending to three elevations surrounding the property to form a car park, underground swimming pool and entertainment areas.

Works entailed the installation of 420 No. 450mm diameter CFA piles using a combination of Soil Mec CM50 and Klemm KR709 adjacent to existing structures to form a contiguous bored pile wall plus a further 29 No. 350/300mm diameter bored temporary cased piles adjacent to a Historic wall using a Klemm KR702.

Works were modified to include a secant piled wall using 2 No. Klemm KR702 to form 350/300mm diameter bored temporary cased piles within the newly formed basement in order to form the swimming pool below the ground water table. The works also required a series of temporary works bearing piles to act as temporary columns to facilitate top down construction together with combination of bearing piles to be used to support new reinforced concrete columns in the main structural elements.

GSS Piling worked in conjunction with Geostructural Solutions Limited (Sister Company) to deliver the whole basement project for Bouygue UK.

Piling Value: Approx. £600K
Main Contractor: Bouygues UK
Client: Confidential
Duration: Multi visits approx. 20 – 22 weeks


Location:- Prestigious Project within Kensington

Project Type: CFA secant, bearing

The works were for a high profile client working with a major contractor to form a large basement to the rear extending to the side which we worked in conjunction with Sister Company Geostructural Solutions Limited and Principle Contractor Bouygues UK. To both install a secant bored pile wall together with a combination of bearing piles to facilitate the formation of a double storey basement immediately adjacent to the rear of a significant property.

The works entailed carrying out piling works from two levels, initially to retain the rear garden and boundary walls by the installation of 600mm diameter secant piles along predominately two elevations with a nominal return and therefore after 3m excavation to install second level of secant piles using 450mm diameter secant wall using a Klemm KR709 to close the structural envelope. The overall basement dig was approximately 9m and similarly designed as a multi-tier top down construction with apertures left within the slab to facilitate access.

GSS Piling Ltd was commissioned to carry out the design and construction of the secant wall and thereafter, hand the project over to Geostructural Solutions to undertake the structural envelope and complete the basement works.

Piling Value: £255K
Main Contractor: Bouygue UK
Client: Confidential
Duration: 8 weeks


Location:- New Fitness Studio, Heckfield Place, Hampshire

Project Type: – CFA 600mm diameter contiguous bored temporary cased

GSS Piling was contracted to design and install a contiguous bored pile retaining wall for a new fitness studio to a new prestigious hotel in Hampshire.

The works required the installation of 241 No. 600mm diameter piles to form a contiguous bored pile wall to form a new basement. The works were fast tracked using two Klemm 709’s due to restricted access.

Piling Value: £435K
Main Contractor: Operis
Client: Operis
Duration: 3.5 weeks


Location: – Kidderpore Reservoir, Hampstead

Project Type: – Bored Temporary Cased Piles 305/250 Raking

GSS Piling was contracted to design and install stitch piles through 63 No columns @ 20° rake to enhance the pier capacities within the reservoir to support a new concrete cover slab.

The works required stitch coring through the existing column bases and installing 126 No. 308/250mm diameter piles 12.0m length heavily reinforced for shear and bending.

Kidderpore Drawing Showing Raking Pile – Click here to download

Piling Value: £200K
Main Contractor: GBMJV
Client: Thames Water
Duration: 6 weeks

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