Cut Face Slope – Herrington House, Gateshead College

Project Overview

As part of the redevelopment, Miller Homes wanted to increase land utilisation by excavating as close as possible to the Durham Road above the site. A 34m long excavation, 4m high and as steep as 70 degrees in sandy clay over vertically cut sandstone was required to be stabilised prior to the construction of a permanent retaining wall.

Solution

The top 2m of sandy clay was cut back to 70 degrees in 5m long sections and a polythene membrane was applied to prevent the face softening during the winter. To spread the load evenly, weldmesh was overlaid and restrained by driving two horizontal rows of anchors at 1.2m centres through the mesh and polythene, then through the sandy clay layer and into the sandstone beyond. Twin timber soldiers at each anchor position held the mesh in place. Each and every anchor was proof loaded to 25kN and locked off at 20kN. On completion of each section, the sandstone layer below was cut vertically.