Computational Approach for Determination of the Hydraulic Conductivity of Soils Using Continuous Intrusion Piezocone Penetration Test.

Abstract

In order to obtain the hydraulic conductivity or the coefficient of consolidation of the soil from PCPT, the pore pressure response during dissipation test is typically used. This method, however, requires the intermittent stopping of the advancement of the piezocone penetrometer for the dissipation test. Also, this method does not fully take into account the pore pressure interaction between near and far fields as pointed out by previous researchers (Kurup and Tumay, 1997). Thus a new rational approach is investigated here. The proposed method utilizes the pore water pressure during the penetration of the piezocone penetrometer. By its nature, the pore pressure response around the cone tip is neither a fully drained nor a fully undrained condition, it is in between. Since this is a partially drained condition, the excess pore pressure during the piezocone penetration is the function of the hydraulic conductivity of the soil as well as the function of stress strain parameters. Inversely, the hydraulic conductivity of the soil can be predicted from the measured pore pressure response during piezocone penetration test. In this study, an anisotropic modified Cam Clay model with micro-mechanical consideration is derived and incorporated with coupled theory of mixtures for large strains. The derived model is used to predict the hydraulic conductivity of the soil from the excess pore pressure generated during the piezocone penetration test. Updated Lagrangian reference frame is used for a more rational modeling of large strain behavior. Formulation of the equations is based on the theory of mixtures for inelastic porous media proposed by Prevost (1980) and in an updated Lagrangian reference frame by Voyiadjis and Abu-Farsakh (1997). Model evaluation was conducted by comparing the results with the isotropic model. Comparisons were also made with the field data. The calibration chamber test results, existing field data, and the theoretically predicted results showed acceptable agreement with each other, and shed the promising light on the new method of determination of the hydraulic conductivity of soils from the continuous intrusion piezocone penetration test.