Estimation of coefficients of consolidation and permeability via piezocone dissipation tests

Abstract

Measured excess pore pressure dissipation responses always present a different trend from those theoretically expected. A simple hyperbolic equation for estimating the coefficient of consolidation [ch(Hyp)] was thus proposed based on the indirect fit between both responses. The method was applied to dissipation test data in the normally consolidated clay of Nakdong River Delta. The result indicates that ch(Hyp) values vary with the normalized excess pore pressure (U), showing different trends according to the patterns of both curves. The mean values estimated with four theoretical solutions vary within a difference of 200%, and are close to those of the consolidation tests. The coefficients of consolidation obtained using three conventional methods, which are based on the direct fits at U = 50% and between the early or late parts of both curves, lie within or out of the range of ch(Hyp). The coefficients of permeability estimated using the mean values of ch(Hyp) underestimate those of the laboratory permeability test and those of an empirical formula based on the piezocone sounding records.