Generation and Dissipation of Excess Pore Water Pressure During CPTu in Clayey Soils: A Numerical Approach

Do all the clayey soils have the same behavior in terms of the generation and dissipation of excess pore water pressure during the piezocone penetration process? To find the answer, a coupled numerical simulation of CPTu in clays based on finite element analysis is presented in this paper. In this regard, the numerical modeling is verified by some laboratory tests on the samples with known initial conditions and stress states as well as field measurements of piezocone testing. Generation of excess pore water pressure during the penetration process is then investigated at different locations around the cone. This study encompasses piezocone penetration in both normally consolidated and heavily overconsolidated clayey soils. The dissipation of induced excess pore water pressures is also examined by stopping the cone after penetrating into the soil. The obtained results show that the measured excess pore water pressure at the cone shoulder is a key parameter for interpreting the soil behavior in terms of the generation and dissipation of excess pore water pressure around the piezocone during the penetration process. Caution should, therefore, be exercised to use existing correlations for estimating the flow characteristic parameters of cohesive soils (e.g. the coefficients of permeability and consolidation) from the piezocone test results.