Spatial Distribution of Excess Pore-Water Pressure due to Piezocone Penetration in Overconsolidated Clay

This paper presents the results of an analysis of the spatial distribution of the excess pore-water pressure induced by piezocone penetration into overconsolidated clays. From the experimental results obtained for moderately and heavily overconsolidated clays, it was observed that the excess pore-water pressure increases monotonically from the piezocone surface to the outer boundary of the shear zone and then decreases logarithmically, approaching zero at the outer boundary of the plastic zone. It was also found that the size of the shear zone decreases from approximately 2.2 to 1.5 times the cone radius with increasing overconsolidation ratio (OCR), whereas the plastic radius is about 11 times the piezocone radius, regardless of the OCR. The expressions developed in this study based on the modified Cam clay model and the cylindrical cavity expansion theory, which take into consideration the effects of the strain rate and stress anisotropy, provide a good prediction of the initial pore-water pressure at the piezocone location. The method of predicting the spatial distribution of excess pore-water pressure proposed in this study is based on a linearly increasing (delta)ushear in the shear zone and a logarithmically decreasing (delta)uoct, and was verified by comparing the pore-water pressure measured in overconsolidated specimens in the calibration chamber.