Dynamic cone penetration resistance of soils - Theory and evaluation

A theory based on the pore collapse concept applied to cylindrical cavity expansion is developed for evaluating Dynamic Cone Penetration (DCP) resistance and predicting Dynamic Cone Penetration Index (DCPI) in c-phi soils. A closed form solution for the penetration resistance and DCPI is developed. The present analyses assume the soil matrix to flow according to a rigid-plastic rule in the core region surrounding the cone. Thus, a free boundary defining the plastic domain develops and constitutes a part of the solution. The soil beyond that region is in its linear elastic state and is considered to have negligible contribution, since the mechanism governing the penetration is predominantly dependent on volumetric change due to pore compressibility. An energy balance criterion is utilized to calculate the DCPI, which is compared with experimental values observing good agreement. The effect of angle of internal friction phi, on penetration resistance/DCPI is much more significant than that of cohesion, c, especially at low initial porosity levels.