A ground investigation designed by CampbellReith for a major infrastructure scheme in the south of the UK uncovered a relict shear surface within one of the trial pits encountered on site. In the front of the trial pit, you can see a polished area where the mass movement of soils has occurred and created a polished ‘slickenside’ shear surface.
Relict shear surfaces can cause cohesive soils to act at significantly weakened residual strengths, and if this is not properly accounted for in detailed design then the failure of embankments, cuttings, and foundations is likely to occur.
CampbellReith identified the potential for shear surfaces during desk study research, prior to ground investigation. We consequently scheduled trial pits to be excavated with a toothless bucket in layers under the supervision of an experienced engineering geologist, as the presence of shear surfaces can be easily missed during ground investigations.
Should you have any geotechnical design or ground investigation enquiries then please contact Josh (joshchastney@campbellreith.com) or Adam (adamfisher@campbellreith.com) in the CampbellReith Surrey office.