UBC Theses and Dissertations
Finite element analysis of creep problems in soil mechanics Emery, John Joseph
Application of the finite element method of stress analysis to problems in soil mechanics has enabled the engineer to gain much information on the deformations and stresses in earth structures under the assumption that the properties of soil are independent of time. However, both laboratory studies and field observations indicate that time is a very important factor in the behaviour of cohesive soils. The finite element method is extended to deal with typical problems in soil mechanics in which the time dependence of the mechanical properties of soil is considered. From creep studies reported in the literature, stress-strain-time relationships that have been developed for essentially uniaxial constant stress creep tests are extended to the multiaxial changing stress condition that is applicable in situ. The finite element method is used to examine problems where the soil is assumed to be linear viscoelastic. The correspondence rule of linear viscoelasticity is used as part of this development. This is an idealized case and will generally be limited to qualitative studies. Then, the incremental initial strain finite element method is developed to deal with general soil creep as described by empirical relationships. A cumulative creep law based on the strain-hardening rule is adopted in this .analysis. Creep rupture is introduced into the general incremental solution method by reducing the stiffness of elements of the earth, structure that have failed. The failure criterion used in the analysis is based on the total elapsed time from the beginning of creep and the creep strain rate. Some typical examples of problems in soil mechanics are examined to illustrate the methods developed.
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