University of Leeds
Lithos were commissioned to undertake site investigations on two parcels of land within the University of Leeds’ campus - the Purple Zone Car and the Western Campus. Development proposals for both sites included a network of temporary structures forming office blocks and lecture theatres, to be used by students and staff over a period of 5 years whilst renovations to existing buildings took place.
What we did
Lithos carried out site investigations comprising machine-excavated trial pitting and window sample drilling. Soakaway testing was also carried out at the Purple Zone Car Park site in accordance with BRE Digest 365.
The Western Campus site formerly comprised the grounds of the University’s law school and later a car park. Ground conditions encountered by Lithos comprised granular made ground, including ash & clinker with weathered residual soils below and bedrock at depths of less than 3m. Upon completion of the trial pitting at the Western Campus, full reinstatement of the ground was undertaken involving the use of a turf cutter and trench rammer.
Foundations for the proposed temporary structures comprised concrete pads of three different sizes founded on compacted hardcore that had to withstand point loads from the temporary cabin legs. With respect to proposed loads, it was concluded that the weathered natural strata would provide adequate bearing capacity for the temporary structures.
The proposed temporary structures at the Purple Zone Car Park site were two-storey and consequently the anticipated loads were significantly higher. Ground conditions at the Purple Zone Car Park site were much more variable, as sporadic deeper areas of made ground were encountered along with cohesive and granular residual soils at differing depths beneath the footprint of the proposed structure. Due to the ground variability and high loads, foundations comprising concrete pads of 1m2 founded in underlying sandstone bedrock were recommended.
The proposed location of a soakaway chamber was underlain by deep made ground of up to around 3m depth, likely associated with backfilled cellars from former terraced housing on site. Soakaway tests within the sandstone bedrock beneath the made ground proved unsuccessful and it was concluded that soakaways would not provide a feasible option for storm water drainage at the site.See more case studies