Deep Bore Soakaway Testing, Devon
A combination of in-situ constant and variable (falling) and constant head testing was undertaken to provide information for the design of a number of deep-bore soakaway drains at a residential development site in Torbay.
Deep-bore soakaway drains had previously been recommended by Ruddlesden geotechnical following observations made during conventional soakaway testing in accordance with BRE DG 365. Previous geotechnical investigation and near-surface geophysics, undertaken as part of a solution feature investigation, had indicated that the use of conventional shallow soakaway drains could lead to the wash-out of near surface soils through underlying cavernous limestone, potentially leading to an increased long-term subsidence risk of the ground.
Rotary open-hole boreholes were undertaken to form the deep bore soakaway at depths specified by the consulting engineers, based on information provided by Ruddlesden geotechnical from an earlier phase of geotechnical investigation, which included a period of groundwater monitoring.
Additional in-situ constant head permeability testing was also undertaken following the installation of the deep bore soakaways to verify the design parameters and to confirm the performance of the deep bore soakaways.
All testing was undertaken in accordance with BS EN ISO 22282-2:2012.