Approached by the local authority, we were asked to design and execute an underpinning scheme to correct the severe ground movement causing large cracks in the walls in part of the Laycock Centre.
The primary cause of the ground movement was the desiccation of the clay-based subsoil to a depth of five meters. To tackle this and cause minimal disturbance to the building interior a piled cantilevered scheme was proposed.
Working with the Existing Structure and Services
The piles and ground beams were carefully designed in-house to ensure that the scheme did not conflict with the plant room, which was located on the other side of the failing wall. We undertook all the works externally so that we did not disturb the plant room and in doing so reduced overall project cost. We achieved this by using Pynford Stools to support the existing walls, allowing the masonry tobe removed and the beams to be installed above the existing foundation. We formed a continuous beam within the existing wall to span between the ends of the cantilevered ground beams.
Due to the high plasticity of the London Clay, the reinforced concrete ground beams were installed on Clayboard to provide a heave void beneath. These anti-heave precautions will accommodate any future ground movement without disturbing the structure above.