In this thesis we develop the theory for two separate computer programs capable of modelling the plane strain consolidation of a soil layer under a variety of types of surface loading. We consider loading from flexible footings, rigid footings, built-up embankments and a plane frame structure on individual footings. The first program uses a simplified form of finite element analysis for the frame structure, and a method of discretizing the surface loading into a series of line-loads. A stress distribution theory applicable to a soil layer on a smooth rigid base is then combined with classical elasticity theory and a finite difference solution of the two-dimensional Terzaghi consolidation equation. The second program uses a unified finite element analysis modelling both structure and soil, and incoporating the Biot theory of consolidation. A process of smoothing the immediate nodal excess pore-pressures is developed, which allows standard types of finite element to be used in the soil model. In addition, it is shown how a set of data of void ratio against pressure from a compression test may be analysed (using smoothing splines) with a desk top computer to yield an estimate of the pre-consolidation pressure of a soil sample. Numerical results from both programs are presented and compared for a number of loading problems, and it is concluded that the finite difference program is considerably more efficient in the solution of problems involving homogeneous soils and loading from flexible and rigid footings; in contrast, the unified finite element analysis has advantages in the solution of more complex problems.
|Date of Award||1980|