Summary
The investigation of a landslide on a slope of Etruria Marl at a site just south of the Weichselian limit in Staffordshire is described and discussed. Carefully logged trial trenches and shafts show that the stability of the slope is controlled by a 6 to 10 m thick mantle of periglacially disturbed and soliflucted Etruria Marl, and descriptions of the lithology, mineralogy and structure of this mantle are given. The landslide is shown to have involved the renewal of movement on a pre-existing slip surface. Ground water conditions at failure are reconstructed and two and three-dimensional back analyses made. At the appropriate level of normal effective stress, the estimate of residual shear strength from back analysis is shown to be lower than indicated by conventional direct shear and triaxial tests and probably higher than the value given by ring shear tests.
