Business profile
Benefit from interchange T
he Whitechapel station project will be delivered in three distinct parts - the refurbishment of the existing
Whitechapel station in the Hammersmith and City and District Line cutting, the construction of a new station bridge concourse above the East London Line cutting and the construction of a new ticket hall behind the retained building fronting on Whitechapel Road. Undertaking this project is BBMV, a
joint venture that encompasses Balfour Beatty, Morgan Sindall and VINCI Construction. The headline works are due to commence midway through this year when the main entrance to the existing station is temporarily moved, allowing work to begin to make way for the new station concourse.
Permanent foundation installation Before this work can commence, Balfour Beatty Ground Engineering (BBGE), Balfour Beatty’s specialist geotechnical division, is busy installing permanent foundations to support the new concourse as well as temporary piling to enable further construction work to be carried out.
These temporary piling works, designed
by BBGE, include piling to support tower cranes for later stages of the construction process and the installation of contiguous pile walls for the East and West stair shaft excavations. Due to the limited access to the site, mini piling rigs have had to be used in place of standard rigs. The two Klemm 702 rigs being used stand just three and a half metres tall and can install piles to depths in excess of 20 metres. In addition to their diminutive height, the rigs can install close up to adjacent structures. For the temporary works they have been installing 86 No 300 millimetre diameter piles up to a depth of ten metres for the contiguous wall that will be excavated to create the East stair shaft, and 12 No 450 mm diameter piles to a depth of 24.5 metres to support the tower cranes that will be used during the main construction phase. A specific challenge at Whitechapel
was the proliferation of obstructions. BBGE says an obstruction is ‘something that materially affects the progress of pile boring operations that could not have reasonably been foreseen at the tender stage or from the contract documentation’. At Whitechapel this includes old track
Page 186 April 2013
Whitechapel station is one of nine new stations being built as part of the Crossrail project and will become an important interchange, lying as it does at the eastern end of the central section of the Crossrail route
and both live and dead utilities services. Ranging between one and two metres in depth, the concrete track required coring before the piles could be installed. Rather than using a ground worker to undertake this work, savings could be made to the programme by utilising the mini piling rigs to core the obstructions prior to piling.
Coring is undertaken by fitting a cutting shoe to the bottom of a steel casing, which is then drilled down through the obstruction to create a pathway for a pile. A typical obstruction on this project
would take between four and five hours to core, making the process slow and painstaking.
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