UBC Theses and Dissertations
Problems in nonlinear analysis of movements in soils Wedge, Neil Edward
The problems associated with nonlinear analysis of the load-deformation response of soils and soil structures are investigated. Methods of incremental nonlinear analysis are reviewed and their relative advantages and disadvantages discussed. Stress-strain relations commonly used for soils are critically examined and their limitations discussed. These stress-strain relations are based on the assumption that soils are isotropic, incrementally elastic materials. Evidence reported by other authors and reviewed in this study shows that the stress-strain relations commonly used for soils have two major sources of error, the anisotropy of soils and the effects of stress-path are neglected. The representation of soil stress-strain behaviour after yield is discussed. Although soils act as plastic materials after yield, it is common practice to represent post-yield behaviour by models of elastic materials. Many researchers use a constant value of Poisson's ratio and merely reduce the value of Young's modulus at yield. It is shown, with numerical examples, that this practice results in yielded soil elements being unrealistically compressible after yield. It is shown, with further numerical examples, that the predicted behaviour of yielded soil elements is more realistic if the value of the shear modulus is reduced at yield and the bulk modulus is not reduced.
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