PHASE 3B BLOCK F WEST HENDON
Contiguous Bored Piled Wall and Bearing Piles
Client : Barratt London
Structural Engineer RLT Engineering Consultants
Duration of Works: 4 Months
Approximate Value: £1.3 million
We were asked by our Client to install rotary auger bored piles to the above project. The contract included the design and installation of over 400 lm of contiguous retaining wall around the perimeter of the site, and installation of high and low-level bearing piles within the basement, together with the testing of preliminary and working piles.
The scope of the works included 204 No. 600mm diameter and 189 No. 750mm diameter piles which were installed to lengths up to 20.0m to cater vertical load from the superstructure above. The walls were designed as a temporary cantilever and as a temporary propped cantilever. The temporary propped walls were initially considered using raking shores, however following design development with our client and their groundworker, the pile design was reconsidered to substitute the raking shores with temporary ground anchors to provide unfettered working space for the bulk dig excavation works.
The pile design was compliant with the latest Eurocode standards using EC7 for geotechnical design and EC2 for the Structural design of the reinforcement cages. The preliminary pile testing was carried out in an advance visit to the site and significant economy was achieved to the pile lengths by validating the design prior to installation of the main works piles.
The programme dictated the employment of up to two piling rigs and we released sections of wall to the ground worker to enable the bulk dig to take place whilst on the site. The bearing pile part of the scheme consisted approximately 450 No. 450mm and 600mm diameter piles to lengths up to 37.0m, which were installed from a high – level platform, with pile cut off levels up to 7.0m below in the basement. Piles were cast within specified tolerances avoiding the groundworker breaking down unnecessary concrete over the basement length of the piles.
Nearing successful completion of this contract we were asked by the client to undertake their further piling project on an adjacent site for Blocks G4 & H. Again, two rigs were employed to install 175 No. 450mm diameter contiguous piles 9.0 to 20.0 m long designed as temporary cantilever and temporary propped walls respectively designed to cater highway surcharges and surcharging from existing structures.
Again, the pile design was carried out to EC7 and EC2 however this time, the piles were designed with a higher model factor to facilitate the clients programme without a preliminary pile test. An additional 175 No. 450mm and 600mm diameter bearing piles were successfully installed together with working load tests of 2 No. working piles. This additional work prolonged our stay for a further 2 months and increased the overall project size to approximately £1.7 million.