Various existing CPT-based prediction models for profiling stress history of marine clay at the southern coast in Korea has been investigated by regression analysis. Preconsolidation pressures and overconsolidation ratio predicted by using both empirical correlations and piezocone penetration tests are compared with those of laboratory oedometer tests. Preconsolidation pressures are calculated by both empirical methods of the Chen and Mayne(1996) and theoretical method of Konrad and Law(1987) based on the effective stress method. Comparison results are smaller than those of the existing methods. It is estimated that prediction method with pore water pressure is more reliable than other methods. Overconsolidated ratio are selected by comparing with the equations of Chang''s, Mayne & Holtz,''s, Mayne & Bachus''s, Schmertmann''s methods, and laboratory test results. The suggested equations; Mayne & Holtz, and Mayne & Bachus are more proper than those of others in this area. Using the empirical methods by the results of in situ cone penetration tests are limited due to the values of stress history are not same at different sites and soil properties.
In the case of soft ground improvement, the reliability of stress history is very important, for it is a soil parameter which enables us to predict the design settlement and to judge the economy of a construction work. In general, the stress history obtained from laboratory standard consolidation test (oedometer test) is unreliable owing to a lot of uncertain factors during the test. Besides, laboratory test takes a lot of cost and time. In comparison with laboratory test, in-situ piezocone test is reliable because it enables us to test many times and to get continuous soil parameters. Besides, it takes much less time and cost than oedometer test. In this study the results of piezocone test were compared with those of oedometer test.
