Accuracy of determining pre-consolidation pressure from laboratory tests

Shear strength and compressibility of fine-grained soils is strongly influenced by their stress history and the maximum (pre-consolidation) pressure ([Formula: see text]). Accurate determination of [Formula: see text] is thus critical for settlement and stability analysis involving fine-grained soils. Many graphical techniques are available for estimating [Formula: see text] from the interpretation of soil compression in laboratory consolidation (oedometer) tests. However, the accuracy of these methods has not been extensively proven or compared with each other. A series of 30 laboratory oedometer tests is carried out in this study based on controlled rate of strain and incrementally loaded testing techniques. Several Canadian clay specimens are subject to cycles of one-dimensional compression loading and unloading to produce a known stress history and [Formula: see text]. The imposed [Formula: see text] values are compared with the predictions of 11 methods for determining [Formula: see text]. The accuracies of these methods are subsequently evaluated by comparing their predictions with [Formula: see text] imposed during the consolidation experiments. While these methods mostly overestimate [Formula: see text], it is determined that a bilogarithmic graphical approach based on the slopes of the virgin compression and recompression segments of a soil compression curve provides the most accurate predictions of [Formula: see text]. The potential ranges of errors associated with the application of each method are also presented.