A new classification chart for soft soils using the piezocone test

Abstract

Three classification charts for identifying soil type from CPTU data, which have been proposed in the past, were examined and discussed. A new chart is proposed in this paper. A new parameter, the equivalent pressure σ e , was introduced to normalize the cone resistance q t , and to define a pore pressure ratio B p . The new chart plots the relationship between log ( q t/σ e ) and B p . Different kinds of soils, such as sand, silty soils and clays, are found to be located in different parts of the chart. Based on this chart, a new parameter, N h , has been established to distinguish the different kinds of soils. This parameter is obtained from the measured cone resistance, pore pressure and depth. Classification can be easily performed in the field from the N h profile. The reliability of the new chart was verified from more than 50 sets of CPTU data from all over the world. Four examples were used to illustrate the reliability of the chart.