Deep Bore Soakaways
Deep bore soakaways can sometimes be a suitable method of surface drainage, where ground conditions are unsuitable for conventional, near surface soakaways.
Deep bore soakaways are particularly suitable where low permeability soils overlie higher permeability rocks (e.g. chalk and limestone) and in areas of solution weathering, where near surface soakaways might cause wash-out of infilled solution features (or the creation of new ones), possibly resulting in collapse/ settlement of the ground surface.
In addition to providing recommendations, including design parameters and depths, for deep bore soakaway design, Ruddlesden geotechnical also carries out in-situ testingto verify their installation.
Deep Bore Soakaways, Devon
Deep-bore soakaway drains were recommended by Ruddlesden geotechnical following observations made during conventional soakaway testing in accordance with BRE DG 365 at a proposed residential development site in Torbay.
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 loss of near surface soils through underlying cavernous limestone, potentially leading to a heightened long term subsidence risk of the ground.
It was considered that the careful use of deep bore soakaways could mitigate this risk, by transferring surface water into competent limestone at depth, beneath the weathered zone where concentrated flows could trigger subsidence of the ground.
The installation of the deep bore soakaways was supervised by Ruddlesden geotechnical, who also carried out in-situ constant head permeability testing post-installation, to confirm the performance of the soakaway drains and the design parameters.