Detailed collaborative modelling by structural and geotechnical teams to rationalise foundations.

Wembley EO3 is one of several sites within the Wembley masterplan area where CampbellReith has provided multidisciplinary engineering services. The EO3 site now houses six residential towers of 10 and 12 storeys and a high rise tower of 26 storeys all above a podium structure. CampbellReith was engaged to develop the detailed design for the substructure and superstructure.

At the time CampbellReith was appointed, the scheme included a conventional piled foundation with piles toeing on to the variable Lambeth Group. The piled foundations were designed such that they supported the entire load from the structures. Due to the high vertical and horizontal loading transferred by the high rise tower, the foundations were a significant element of the cost. Our geotechnical engineers considered various alternatives and a piled raft foundation type was chosen as the most cost effective foundation system.

The piled raft is efficient because the load is shared between the raft and the piles. However, it requires careful design and analysis of soil-structure interaction to understand the ratio of load sharing between the two elements and the likely deflections. At Wembley E03 this was further complicated by the need to observe tight tolerances on settlement.

Using a combination of software programmes including PDisp and SCIA, our geotechnical and structural engineers adopted an iterative process to design a piled raft system where the length and diameter of the piles were reduced compared to the original solution. This offered substantial cost and carbon savings by reducing the amount of concrete in the ground.  Additionally, it was possible to have the piles bearing entirely in the London Clay, easing the pile construction and reducing the risks associated with constructing piles into the Lambeth Group with its layers of sand with possible subartesian water.