South Sands, Salcombe, Cornwall

Red Rock were appointed to design, direct, and verify the stabilisation works for a cut slope at a residential property.

The residential property was located on top of a cliff with exposed closely fractured rock strata of strong mica and quartz schist. However, the stability of this hard rock slopes tends to be controlled by the rock discontinuities, rather than the intact rock resulting in multiple rock fractures creating a fabric which when excavated results in the rock breaking down to cobble sized “columnar” rock blocks.  This was causing instability as a result of high angle spalling, and failure on discrete and locally adversely orientated discontinuities, which could impact the integrity of proposed structures.

It was the slope engineers' challenge to ensure stable cut slopes would meet the architects drawings. Red Rock undertook a slope stability analysis and designed a slope scheme using 32mm diameter solid thread bar at 2m spacings to account for the potential for planar instability, with small blocks retained by rockfall mesh.