Surface footings on sand under general planar loads

The thesis is concerned with the behaviour of rigid surface strip footings on sand when subjected to eccentric and/or inclined loads. Experiments have been performed in two apparatuses, the one having a three times greater sand-bed width than the other, together with a preliminary investigation in a smaller apparatus. The bearing capacity predictions from various published theoretical and semi-empirical solutions are compared with the experimental results. Contact stress distributions which were measured in each case are also presented. The effect of the tank to footing width ratio on the bearing capacity and the contact stress distribution is examined by means of comparative results from nominally identical tests. The deformation of the sand mass has been measured by both X-ray and Stereo photogrammetric techniques and representative results obtained by each method are presented and discussed. The effect of the sand-glass friction on the photogrammetrically measured displacement fields has been investigated by comparing results obtained from identical load increments in identical tests~using each of the techniques. A new rational approach to the bearing capacity problem, based upon concepts from plasticity theory, and supported by the author's experimental evidence, has been advanced. This analysis, which utilises the concept of the plastic potential, describes the planar translation of a footing in a very satisfactory way under inclined central loads both qualitatively and even quantitatively in tests carried out so far. Finally, a generalization of the analysis has been devised to cover the case of footings under general loading, its potentialities have been discussed with particular reference to offshore oil platforms and areas recommended for future research in this field.