Bachy in British Museum piling
Bachy Soletanche, geotechnical specialist, has commenced a five-month, multi-million pound piling contract to lay the foundations for the World Conservation and Exhibitions Centre at the British Museum in the centre of London. Working alongside project manager, Mace, work will see piling for a new building that will house state-of-the-art laboratories and science facilities, a dedicated gallery for special exhibitions, a collections management hub and world-class stores for the study collection.
The new basement is an irregular cruciform shape, due to the adjoining museum buildings, and the secanted wall piles are all installed close to the adjacent, existing Grade I listed British Museum buildings.
The piling
This piling package involves both bearing piles and secanted piles to produce the new basement. A secant piled basement was chosen as this can deliver the irregular and flexible shape required, will lead to a more efficient form of structure, and will also give the museum a better-assured product in terms of verticality tolerance and visual appearance. An innovative combination of Cased CFA and large diameter rotary has been employed by Bachy Soletanche to also deliver a speedier operation than the more traditional ‘kelly / casing’ rotary bored pile method could have produced. Cased CFA delivers the production of CFA with the verticality of LDA Rotary piling.
The basement is constructed with 330 linear metres of 880mm diameter piles to build a hard/firm secant piled wall. The 13-16m long Female/Primary piles and 23-27m long Male/Secondary piles will be used for the construction of the basement walls plus, 197 600mm, 750mm, and 900mm diameter load bearing piles up to 30m long are also being installed.
Geotechnical elements
Noise and vibration monitoring in being carried out by sister company Sol Data, using 2 two sets of Noise and vibration monitoring meters plus cameras. The results are then reported to all interested parties in real-time, via a web based in-house developed, reporting system. Both Noise and Vibration monitoring is required by the client due to the close proximity of valuable, irreplaceable, national and international treasures, museum staff and visitors. The new Centre is directly adjacent to existing Museum buildings and this monitoring will help avoid any damage to the building’s structure. These results could prove to be invaluable to Bachy Soletanche in future piling works in similar urban environments. Noise testing has been carried out on sites for many years but the demand for vibration monitoring is becoming increasingly popular. The cameras will give an indication of what may have triggered any alarms, should this arise.
An additional innovation has been the slab connection “box out” units that are being installed on the pile reinforcement cages, as an alternative to drilling and grouting dowel bars. These mean that when the wall and basement is excavated at a later stage, the “box-out units” will be exposed for connection to the floor slab reinforcements. This rarely used technique requires a high level of accuracy to get the “box-out” units in the right position and to make sure the cages don’t move when the pile casings are removed. This innovation is a faster alternative to the traditional drilling and grouting method and also delivers noise and vibration, and health and safety, improvements.
Barry Osborne, Southern Operations Manager at Bachy Soletanche, said:
“This is a really interesting scheme in a challenging environment that is using some rarely used techniques to create a modern annex next to a listed Museum building that’s home to one of the most important collections of antiquities in the world. The piling started on time and is running to schedule, and joins a number of exciting bored piling contracts we’re currently working on in the London area.”
Planning approval was granted in December 2009. The piling commenced on 14th March 2011 and is expected to run until 8th August 2011. The British Museum is a world leader in the conservation and display of objects from across the globe.