• Client: UKCMRI Construction Limited
  • Principle Contractor: Laing O'Rourke Construction
  • Consulting Engineer: AKT II
  • Value: £14m
  • Completion: 2012
  • Role: Piling Contractor
  • Pile extraction
  • Bearing piles 1200mm to 2100mm diameter
  • 1000mm wide diaphragm wall to the basement perimeter
  • King post piled retaining wall supporting high pressure gas main (200mm off the face of the cast iron pipe) Over 170 steel and precast concrete plunge columns
  • Contiguous piled basement fold line
  • Preliminary pile testing incorporating fibre optic instrumentation and O-Cell technology

84,000m² of R&D laboratories and support facilities over four basement levels, including two interstitial plant floors, and eight above ground floors, all within a confined site footprint. Extensive basement works and iconic design located in central London close to Eurostar, Thameslink and tube lines. Scope of works included:

  • Pile extraction
  • Bearing piles 1200mm to 2100mm diameter
  • 1000mm wide diaphragm wall to the basement perimeter
  • King post piled retaining wall supporting high pressure gas main (200mm off the face of the cast iron pipe) Over 170 steel and precast concrete plunge columns
  • Contiguous piled basement fold line
  • Preliminary pile testing incorporating fibre optic instrumentation and O-Cell technology

Expanded Geotechnical delivered this high profile complex ground engineering project over the course of nine months.

The first operation was the installation of a 150m-long king post wall positioned only 300mm from a large-diameter cast iron, highly sensitive Victorian gas main. This service was fully instrumented and continually monitored during king post piling, capping beam and diaphragm wall activities.

After a complex set of preliminary test piles were installed and performed under the watchful eye of AKT II and the University of Cambridge, the bentonite plant was commissioned and the diaphragm wall commenced. Two large-diameter piles existed on the line of the diaphragm wall. Due to their proximity to the King's Cross underground station box, their extraction required a unique approach where traditional coring and crowd-force methods were not permissible. Expanded Geotechnical took up the challenge and designed a bespoke drilling tool to allow the piles to be extracted as a single entire element.

Over 450 linear meters of wall were installed using rope grab diaphragm walling techniques. Neighbourhood sensitivity precluded traditional noisy stop end solutions or for construction works to overrun at night. To overcome these constraints we employed a precast stop end solution that, once inserted into the panel excavation, remained in situ.

Large-scale material quantities were involved on this package – with overall concrete pours equal to four Olympic-sized swimming pools and reinforcement equating to the weight of 100 London buses.

Over 250 large-diameter piles were installed, all with plunge columns to support a programme-saving top-down solution.

The high-end specification of the sensitive laboratory and testing equipment intended for this ground-breaking research facility called for measures beyond traditional methods. To fulfil this remit we employed precast concrete columns with stainless steel reinforcement, initially manufactured at our state-of-the-art Explore precast facility and subsequently installed into piles, all to the exacting standards and tolerances.