A SMALL project in central London presented big challenges to foundation contractor Branlows.
Piling for a nine-storey apartment development in Pepys Street, next to Fenchurch Street Station, was carried out under very tight logistical and time constraints.
Access was very restricted - even unloading equipment and materials often meant a parking ticket.
Although there was very little room to manoeuvre rigs on site, augered, driven and drilled piles were all needed.
Branlows, working for developer and main contractor Fairpoint Properties, was originally going to predrill through existing 5m thick mass concrete bases before installing 30,273mm diameter driven piles.
But in many areas the mass concrete was not present or competent to its expected depth.
This meant a variety ofpiling methods had to be adopted.
Temporary casing and augers, complete with rock ripping attachments, were used, together with a permanent cased overburden drilling system which successfully overcame concrete obstructions within the fill material.
Branlows also used the overburden drilling system at some locations to penetrate the concrete bases and other obstructions before dril ling out the grouted plug and installing a second,168mm diameter, bottom-driven pile to a satisfactory set in the underlying clay and gravel. Safe working loads ofup to 300kN were achieved in these piles.