This week we’re going to be looking back at a job we undertook in 2019. This particular job was interesting because it highlighted the challenges of working in old buildings. Constructive Evaluation was instructed to assess the ground conditions underlying a pub in Hastings that dates back to the 1700s.
Upcoming renovation works required scaffolding which was to be supported by new foundations. The 18th century pub included a basement level with restricted access down stairs that were far too narrow to take our dart rig down. It was therefore necessary to come up with a solution, so that we could undertake the dart rig investigation from the ground floor. Following the removal of floorboards, and the flagstone of the basement floor, the dart rig was hand manoeuvred over the required location and connected to a hydraulic power pack left outside. The local geology is granular and so casing was required in order to prevent the hole collapsing during soil extraction. Initially, three casing lengths were joined to span the gap between the ground floor level and through the basement to 1.00mbgl; with each metre drilled, a new length of casing was added. In this example 6.00m depth was achieved, or 4.00m from the basement level, with in-situ Standard Penetration Testing at 1.00m intervals.
Cutting conduits, high voltage lines, data lines etc. can be both catastrophic and very costly. Scanning of an area before cutting can almost eliminate this risk.
Our investigations found that although granular soil is generally considered insufficient for load bearing, the soil in this instance could bear loads for a short period of time with a very limited risk of settlement. Our client set up the scaffolding with appropriate safety monitoring and proceeded with their renovations.
Our Archway Lightweight Competitor Dart rig can be demounted from its tracked base for locations where access won’t allow for a fully tracked unit and powered by a petrol/diesel power pack or a 110v/32amp electric source. Depending on the soils encountered, with the option of five 1.00m lengths of casing we can achieve depths of between 6.00-10.00mbgl.
If would like more information on our dart rig or other drilling services, click here. For a competitive quote or to discuss our services with one of our qualified geotechnical engineers, contact us here.
