We have recently completed a job, near Matlock in the Derbyshire Dales, where we were asked to provide a ground profile and soil & rock properties for a large retaining wall design in a farmyard. The boreholes were between 20m and 25m deep and located at both the base and along the crest of the proposed retaining wall. Where large geotechnical structures are proposed the quality of the information is vital, and the original specification had called for cable percussion boreholes with rotary follow-on. Based on our experience of the technique, and knowing the workmanship of our trusted partners, Borehole Solutions Ltd., we decided to tender using sonic boreholes.
The site was located on rocks from the Millstone Grit Series, of Carboniferous age. As such, it consisted of interbedded mudstones and sandstones. The rocks were extremely closely fractured in places and, to make matters worse, they were also interbedded with sand and clay beds. As you can see, the core recovery, using the sonic technique, was nearly 100%, and was considerably better than could have been achieved using alternative drilling methods. This allowed us to provide high quality engineering geology logs; with accurate measurements of TCR, SCR and RQD; alone with being able to collect and test samples for rock strength (UCS and point load), while also undertaking in-situ SPT testing. In addition to this, sonic drilling is safe, speedy and relatively clean.
Here at Geo-Integrity Ltd. we have a good experience of site investigation techniques and a wide network of high quality trusted contractors. This means we can provide you with a good value, timely, pragmatically designed, first grade ground investigation. Contact us on firstname.lastname@example.org or 01280 816409