Ramboll UK Ltd has presented a specific scope of works to Discovery on behalf of Stoford Properties Ltd, the team are to inspect the northern carpark of the Rockingham Raceway and perform Plate Testing. Initially the site is to be inspected for existing monitoring wells, then after the ground investigation these are to be used with the new installations for ground and gas monitoring purposes. Ramboll will be sampling the groundwater across the site while DCE will be using Photo-ionisation detectors (PIDs) on soils samples for screening using headspace analysis undertaken every metre of excavation.
Originally it was thought that Skip Tests were appropriate for this site, but this had been changed to Plate Bearing Tests instead, plates loaded to 100kpa. This test is carried out in order to determine the settlement characteristics of the made ground of the Rockingham carpark, the tests are carried out in accordance with BS1377-9:1990:Part 4.2″. 15 No. Shallow window sample locations to 4m bgl as well as 10 No. groundwater monitoring wells with installations and 14 No. Trial Pits are what this ground investigation comprises of.
Made Ground was found to be extremely variable across the entirety of site between 15 and 22m below existing ground level. The Made Ground comprises primarily of fine soils (cohesive) but with coarse (granular) horizons and numerous obstructions within the Made Ground. Throughout the course of the dynamic sampling as well as the cable percussion and rotary drilling encountered cobbles and boulders of concrete, slag and metal. These obstructions have been frequently identified in the north and the north east of the site. There were a number of geotechnical risks identified by Discovery in regards to the site, below is a short summary of these risks:
-Due to settlement creep that was indicated on site, remodelling of the site will be required in order for the development platform to be created for the proposed five units. Thus a significant earthworks operation would be required to prepare the development platform for the structure.
-Given the geometry of the site adjacent to Gretton Brook Road, large retaining walls are likely to be required to accommodate the current layout.
-Deep backfill across the site was placed with limited or no control which will cause variable bearing capacity, long term self weight settlement of fill materials and potential collapse.
-Slopes in the north of the site, potentially affecting the local highway
-High sulphate concentrations in the Made Ground at the site affecting concrete design and soil stabilisation options
-Infiltration devices are not recommended due to the risk of inundation settlement.