An assessment of the earth pressure coefficient in overconsolidated clays

Abstract

The determination of the earth pressure coefficient K0 in a natural clay deposit is a problem of considerable significance in geotechnical engineering. While the methods for evaluation of K0 are reliable for normally consolidated soils, significant difficulties still exist in evaluating K0 in overconsolidated clays, given that it is influenced by the stress history of the material, together with the age, structure, mineralogical composition and depositional environment. Indeed, some of these factors are responsible for the soil becoming anisotropic. The existing framework for prediction of K0 in overconsolidated soils does not account for any influences caused by anisotropy. The work reported in this paper evaluates the validity of a revised relationship between K0oc and OCR (overconsolidation ratio) using data obtained from laboratory investigations. The tests were performed on reconstituted and undisturbed samples of Belfast Upper Boulder Clay, London Clay and Gault Clay. Tests were also performed on reconstituted samples of kaolin. The values of K0oc were determined using various approaches, including on-sample measurements. The results have confirmed that reliable predictions of K0oc can be made using the proposed relationship.