Numerical and analytical solutions for consolidation analysis of soils without and with vertical drains

Consolidation analysis of soils with and without vertical drains taking into consideration time dependent loading is of practical and theoretical importance in geotechnical engineering. In this research, new specific analytical solutions for the consolidation analysis of a single layered soil and a double layered soil with a depth-dependent ramp loading are obtained. Many analytical solutions in sod mechanics are only special cases of these solutions.; An analytical solution for consolidation analysis of soil with vertical drainage wells under ramp load is also obtained. A new normalized time, T, is suggested. It is shown that the average degree of consolidation exhibits very good normalized feature using this new T.; A general one-dimensional (1-D) finite element (FE) procedure is derived for consolidation analysis of layered clay sods with an emphasis on a non-linear 1-D Elastic Visco-Plastic (1-D EVP) model proposed by Yin and Graham (1989, 1994). A new definition of excess porewater pressure is suggested to consider the situations that water heads at boundaries are fluctuating with time or there is an initial hydraulic gradient. Unlike many other 1-D FE approaches in which the initial in-situ stresses are considered indirectly or even not considered, the initial in-situ stress/strain states are taken into account directly. The FE modeling results are in good agreement with the measured results. The FE model and procedure is also used to analyze the consolidation of a multi-layered clay soils.; A finite element procedure for the analysis of consolidation of layered sods with vertical drain using general one-dimensional constitutive models is formulated in this research. The proposed procedure is then applied to the consolidation analysis of a number of typical problems using both linear and non-linear sod models. Results from this simplified method are compared with those from a fully coupled consolidation analysis using a well-known finite element package ABAQUS. The average degree of consolidation, excess porewater pressure and average vertical effective stress are almost the same as those from the fully coupled analysis for both the linear and non-linear cases studied. The differences in vertical effective stresses are tolerable except for the values near the vertical drain boundaries. The high vertical effective stress near the vertical dram from fully coupled finite element analysis also demonstrates that a zone of low permeability will form near the vertical dram regardless of the installation methods. The consolidation behaviour of soils below a certain depth of the bottom of vertical drain is actually one-dimensional for the partially penetrating case. The average degree of consolidation has good normalized feature with respect to the ratio of well radius to external drainage boundary for the cases of fully penetrating vertical drain. Numerical results clearly demonstrate that the proposed simplified finite element procedure is efficient for the consolidation analysis of sods with vertical drain and it has better numerical stability characteristics. This simplified method can easily account for layered systems, time-dependent loading, well resistance, smear effects and inelastic stress-strain behaviour. This method is also very suitable for the design of vertical drain. (Abstract shortened by UMI.)...