The construction of a dam at Empingham, Rutland has provided an opportunity to investigate the nature and effect of cambering and valley bulging. A detailed lithostratigraphic sequence has been established and the Upper Lias has been divided into a series of micropalaeontological zones. These features have enabled the internal structure of the Upper Lias to be determined in boreholes and at outcrop. The cambering process results in a progressive valley ward thinning which affects almost the entire Upper Lias sequence. The valley bulges are complex anticlinal structures developed in the valley floors. At depth the steeply inclined strata caught up in the valley bulge gives way along a possible decollement plane to largely undisturbed strata. The valley bulge structures occur throughout the valley and their courses are reminiscent of the trends of the modern valley system. This suggests that they may have been developed in the floors of the ancestral drainage system. The superficial structures were developed at the time of the Chalky Boulder Clay glaciation. Subsequent development of the valley has been a process of continued downcutting with landslipping and solifluxion being the dominant processes since the last glaciation. Possible mechanisms for the development of the superficial structures are discussed in the Appendix.
The 25 m high Cow Green embankment dam has been constructed in the upper Pennines on a deep boulder clay foundation with the aid of sand drains. The design of the core and filter received special attention following erosion of the rolled clay core of a neighbouring dam. The embankment design was based on a conventional factor of safety of 1·5. The sand drains did not achieve the predicted performance and the factor of safety in terms of effective stress approached 1·0 at completion. This condition does not represent failure in boulder clay, which is non-brittle in undrained shear, but rather the onset of relatively large displacements. The performance of the embankment supports the view that under these circumstances construction stability may best be monitored by measurements of deformation. The failure of the sand drains to attain the degree of consolidation anticipated in the design is discussed, as is the control of placing of the boulder clay core and the behaviour of the gravel fill. Le remblai du barrage Cow Green, haut de 25 m, a été construit dans les hautes Pennines sur une fondation profonde d'argile à blocaux avec l'aide de drains de sable. Le projet du noyau et du filtre a reçu une attention spéciale à la suite de l'érosion du noyau en argile roulée d'un barrage voisin. Le projet du remblai était basé sur un coefficient de sécurité conventionnel de 1·5. Les drains de sable n'ont pas permis d'atteindre la performance prédite et le coefficient de sécurité en termes de contraintes effectives approcha 1·0 à l'achèvement. Cette condition ne représente pas la rupture dans l'argile à blocaux qui n'est pas fragile dans un cisaillement non drainé, mais plutôt l'annonce de déplacements relativement importants. La performance du barrage confirme le point de vue que dans ces circonstances la stabilité de construction peut être mieux contrôlée par mesure des déformations. L'échec des drains de sable pour atteindre le degré de consolidation prévu dans le projet est discuté, ainsi que le contrôle de la mise en place du noyau d'argile à blocaux et le comportement du remblai en gravier.
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