Coupled models for total stress dissipation tests

Abstract

Two linear, point-symmetric, coupled consolidation model families with various embedding space dimension values (oedometer models - 1, spherical models - 3, cylindrical models - 2), differing in one boundary condition (coupled 1 - constant displacement, coupled 2 - constant stress) are analysed analytically and numerically. The method of the research is partly analytical, the models are unified into a single model with unique analytical solution, every model can be derived from this by inserting the proper boundary condition and embedding space dimension m. The constants of the solutions are determined and an approximate time factor and model law are derived for the m >1case which is identical to the one valid in the oedometer case. The convergence of the infinite series are examined in the function of the initial condition. Concerning the total stress at the pile shaft, significant decrease (with the value of the initial mean pore water pressure) is encountered for the coupled 1 consolidation models, zero stress drop is resulted by the coupled 2 models. The total stress dissipation test is suggested to be evaluated by the coupled 1 models with a time dependent constitutive law, eg., by adding a relaxation part-model. The rate of convergence is the smaller if the initial condition is the closer to the one of a zero solution (beyond the trivial one, a non-trivial zero solution exists for the coupled 1 model, at the Terzaghi initial condition).