Evaluation of different methods to identify preconsolidatin pressure of Champlain Sea Clay from CRS tests

Identifying precisely the preconsolidation pressure of any soil is one of the most challenging geotechnical problems. For sensitive soils, misjudging the preconsolidation pressure can lead to a large overestimation or underestimation of settlement due to the high compressibility after p’c. The performances of eleven graphical identification methods are evaluated on constant rate of strain (CRS) consolidation tests conducted on Champlain Sea clay. The tests include unloading/reloading cycles that are used to evaluate the accuracy of the methods based on known maximum past pressure. A number of numerical procedures are developed to aid in the use of the graphical methods for CRS test data, including locating the inflection point and the point of the maximum curvature on an e-logp curve. Preconsolidation pressure is calculated using straight line equations rather than interpreting it visually. These numerical methods are applied to the test data and their validities and ease of use are evaluated.