Uplift Behaviour of Circular Plate Anchors in Cohesionless Soils

The work presented in this thesis describes an investigation into the behaviour of circular plate anchors embedded in dry cohesionless soils and subjected to vertical static uplift loading. A review of previous theoretical and experimental work provides a good insight into, and justification for, this study. A small-scale laboratory test model was constructed for experimentation purposes. A large circular steel tank was used to contain sand which was uniformly deposited using a raining device except for the dense well graded sand). A total of one hundred and thirty tests were completed in five different sands at densities varying from loose to very dense and using depth/diameter ratio (D/B) ranging from 2 to 12. A further 20 tests have been performed in a two layered system. A stereo photogrammetry technique was used to establish the different zone of displaced sand mass for shallow and deep anchors and a computer program was developed to facilitate computation of the results. From the analysis of the results, it appears that the sand grain shape and grading have a profound influence on the behaviour of circular plate anchors embedded in sand. However, it was found that grain size did not have any effect on the pull out behaviour. Other influencing factors, such as the depth of embedment and relative density have also been examined. The stereo photogrammetry results showed that the extent and the shape of the zone of disturbed sand is also a function of the aformentioned parameters. Tests in the two layered system indicated that the ultimate uplift load and the mode of failure were dependent on the thickness of the upper layer and the strength of the different layers. A theoretical analysis based on Fadl's (1981) work, was formulated in order to predict the maximum uplift load in a two layered system. Design charts for homogeneous soil have also been put forward. The validity of the design procedure was examined by comparing it with both model and field test results reported by previous investigators. A reasonable correlation has been achieved. Finally, a number of areas of related research considered suitable for further study have been outlined for the benefit of future investigators