Integrating Victorian engineering into an observational approach to slope design

The presence of a large Victorian railway cutting adjacent to a construction site in central Brighton, facilitated the use of an observational approach to the design of a significant rock slope on the site. Soil Engineering were tasked with investigating part of the site to aid with the design of an 80m long, 12m high retaining structure. At the time of the investigation site clearance had taken place and it was clear that Chalk was present at very shallow depth. The initial site visit also revealed that immediately bordering the site, was a Victorian railway cutting, some 30m deep and with natural cut slope angles of some 70 to 75 degrees. The condition of this 100 year old railway cutting was good, and as a result the ground investigation focus changed to one in which the aim was to demonstrate that the chalk on the site could be similarly engineered to provide a freestanding cut face. Minimal clearance of vegetation from the slope was required in order to reveal reasonably un-weathered and stable chalk. Assessment of the exposed chalk was undertaken at multiple locations along the proposed retaining wall length. As a result of the investigation and observation of the condition of the adjacent railway cutting, the need for a costly retaining structure was eliminated, and a free standing face was cut in the chalk at an angle of 75 degrees. This resulted in significant time and cost savings and enhancement of the ‘green’ credentials for the construction project.