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A basis for developing a general approach to solve geotechnical engineering problems through dynamic finite element analysis of nonlinear porous media is presented. A new series of constitutive models named here as δ* series are developed under the general hierarchical single surface (HISS) modeling approach, to include the behavior of, saturated normally consolidated and overconsolidated clay, under drained or undrained, static and cyclic loading conditions. Algorithms for determination of material parameters for these models from laboratory models are also developed. Constitutive parameters for Sabine Clay are obtained using triaxial test results from undisturbed samples and the model is verified by back predicting the laboratory behavior of this clay. Sensitivity analyses for all the material parameters have been also carried out. Efficient and reliable algorithms for calculating strain increments for given stress increments and vice versa are developed. All the models in the δ* series are implemented in the finite element program POROUS which is based on the theory of dynamics of nonlinear porous media. Here a modular approach is used to facilitate easy modification of all the functions associated with these models (yield function, potential function, hardening function and interpolation functions). Complete test procedure for field load tests on two pile segments (3 inch and 1.72 inch) are numerically simulated and compared with field measurements. Initial stresses before pile driving are estimated using results of s self boring pressuremeter test on the site. Strain distributions just after pile driving are evaluated using the strain path method. The effective stress distribution is obtained by integrating constitutive equations for given strain paths. Corresponding total stresses and pore pressure distributions are obtained using the computer program POROUS. Consolidation after pile driving and all the static and cyclic tests followed are also simulated using the program POROUS. The predicted normalized pore pressure dissipation curve matches the field behavior. This analysis provides good predictions of shear transfer from which the pile capacity can be evaluated. Even though the variation of pore pressure during a cycle is not matched exactly, the accumulation of pore pressures are predicted well. The demonstrated ability of dynamic finite element analysis of nonlinear porous media, to simulate slow consolidation and cyclic load tests provides a basis for developing a general approach for solving geotechnical engineering problems.

This study includes a systematic investigation of the bond strength of cementitious borehole plugs in welded tuff. Analytical and numerical analysis of borehole plug-rock stress transfer mechanics is performed. The interface strength and deformation are studied as a function of Young's modulus ratio of plug and rock, plug length and rock cylinder outside-to-inside radius ratio. The tensile stresses in and near an axially loaded plug are analyzed. The frictional interface strength of an axially loaded borehole plug, the effect of axial stress and lateral external stress, and thermal effects are also analyzed. Implications for plug design are discussed. Push-out tests are used to determine the bond strength by applying an axial load to the cement plugs. A total of 130 push-out tests are performed as a function of borehole size, plug length, temperature, and degree of saturation of the tuff cylinder. The use of four different borehole radii enables evaluation of size effects. A well-defined exponential strength decrease with increasing plug diameter results.