Sir Alexander Gibb & Partners was appointed by the Scottish Development Department in September 1972 to carry out a feasibility study of the possible routes for the Killiecrankie to north of Calvine section of the Perth Inverness Trunk Road Improvements. The original brief only extended to the north end of Killiecrankie Pass but this was extended to cover the section through the Pass in June 1973. The results of the geotechnical study carried out by Allen Gordon & Co., to which Allen refers, were made available to Gibb for use in their report.
Although, as Allen states, the landslide had been identified as part of a much larger feature in 1973, the interpretation was based upon very limited subsurface information. A single rotary borehole had been drilled into the landslide from which no recovery had been obtained down to 4.00 m depth and only partial recovery below this level to the base of the overburden at 9.00 m depth. This borehole had been supplemented by four nearby hand auger holes. The supplementary investigations carried out in 1981 included a series of deep trial pits and trenches into the suspected landslide. These provided data on the nature, structure and geotechnical properties of the soils necessary to arrive at the interpretation presented in the paper.
Design of the road proceeded on the basis that the embankment and cutting solution would be adopted where possible. In general this solution was adopted and the majority of the road including the section across.
- © The Geological Society 1984