New methods for assessing Plasticity Index and Low-strain Shear Modulus in fine-grained offshore soils

This paper introduces a new method for predicting Plasticity Index, PI, directly from CPT data. Plasticity Index values predicted using the new method have been designated “PI_CPT” to emphasise their CPT-based origin. The new PI_CPT method has, in turn, enabled a new method of assessing Low Strain Shear Modulus, G_max, to be proposed, based on a well-established equation published by Viggiani & Atkinson (1995). As an additional benefit, the predicted PI_CPT profiles have proven very useful as a simple means of identifying soil-type variations and layer boundaries. This paper presents details of the new formulae that have been developed to estimate PI_CPT and G_max, the database that has been used to calibrate the formulae, and the results that have been obtained. Some limitations of the method are presented and discussed, as well as some of the benefits.