Sweet Street
Throughout April and May 2024, VolkerGround Engineering was on site in Leeds for valuable client Winvic, installing bearing piles to enable the construction of a new student accommodation development.
Prior to mobilisation, the preconstruction team worked in close collaboration with the client’s team to ensure constructability and the best value solution for the scheme. VolkerGround Engineering designed the 600mm/750mm diameter Continuous Flight Auger (CFA) bearing piles, with appropriate partial safety factors eliminating the need for static load testing. This provided valuable programme savings for the project.
The VolkerGround Engineering design team worked closely with the client’s engineers to produce a pile layout and design which generated the least interaction with existing foundations and obstructions. The team remained flexible throughout and were on hand to carry out design checks for unforeseen obstructions and changes to rock level and strength. By maintaining regular communication with the site team, and having carried out extensive preparatory work, any design changes made had little impact on the programme.
Once the design was agreed, VolkerGround Engineering mobilised its versatile Soilmec SR95 to site, to begin the installation of 395 bearing piles into varying ground conditions which included made ground, glacial till and mudstone.
To prevent the risk of smearing the pile shaft and potentially compromising the piles’ bearing capacity or promoting differential settlement, the team restricted auger revolutions per metre when drilling through the mudstone.
The site previously housed a structure with existing piled foundations, posing a risk of obstruction to the new bearing piles. Although 392 out of 395 piles were drilled to the design depth using the CFA technique, three piles encountered refusal at approximately three meters below platform level. Anticipating this risk, VolkerGround Engineering configured the Soilmec SR95 rig to allow quick change from CFA to rotary drilling on site.
Using the rotary technique, VolkerGround Engineering successfully cored through the obstruction, which appeared to be an existing uncharted concrete slab. The team completed the remaining three piles in accordance with the design. This approach was a major success for our client and the principal designer, as it avoided costly and time-consuming redesigns.
