In his capacity as Reporter for Question 55 at the International High Dams Conference in Rio de Janeiro last year, Dr A. D. M. Penman discussed the hydraulic fracture of the cores of earth dams and wrote ‘It was considered to be a cause of the failure of Teton dam in 1976 and has been suggested as the cause of failure of Dale Dyke dam in Britain in 1864 by Binnie (1978) in his reconsideration of that classical failure.’ This refers to the above paper which appeared in Volume 11, pp. 305-324 of the Quarterly Journal. Subsequent to the publication of this paper, the accompanying longitudinal section of the Dale Dyke embankment was discovered in the archives of Messrs. Watson-Hawksley and is reproduced with their permission.
The dangerous planes in a core are vertical ones passing from upstream to downstream through it but with sufficiently low strength, as would be the case with puddle clay, it should normally be possible to maintain sufficiently high stresses on these planes. Dr Penman states that ‘this fact may account for the successful behaviour of the very many puddle clay core dams’.
The longitudinal section helps to explain why theDale Dyke dam appears to have been an exception. It can be seen that below and near the centre of the part of the embankment that was washed away, there was a 35 feet high step in the cut off trench. This step, which was not disclosed at the inquest nor during the subsequent Parliamentary