Interpretation of In Situ Testing of Cohesive Soils Using Rational Methods

This research uses theoretical analyses to investigate the fundamental mechanisms controlling the performance of common in-situ penetration tests which are used to estimate the engineering properties of cohesive soils. The mechanics of penetration processes are modelled using the Strain Path Method together with generalized effective stress soil models. The analytical predictions provide a rational basis for establishing how soil properties are related to in-situ measurements. The predictions are evaluated by comparison with field data from well documented test sites. Results of this research show the following 1 The cone resistance and excess pore pressures measured on the face of the cone during piezocone penetration are the most reliable measurements for estimating changes in undrained shear strength within a given clay deposit. 2 There is no rational basis for correlations between dilatometer contact pressures and in situ K sub O stresses, undrained shear strength or preconsolidation pressure. 3 Model predictions provide a reliable basis for estimating the horizontal coefficient of permeability for normally and lightly overconsolidated clays OCR4 using measurements of pore pressure dissipation on the shaft of the piezocone. 4 Installation disturbance affects significantly the interpretation of undrained shear strength in pressuremeter expansion tests. The analyses show that undrained shear strength can be estimated more reliably from measurements during the contraction phase of the pressuremeter test.