A proposed reporting approach for Champlain Sea clays and other similar deposits

ABSTRACT: This paper recommends the routine inclusion of profile-based geotechnical models, Liquidity Indices and Consistency Indices to supplement the more commonly used Plasticity Indices and Sensitivity values to characterize clay soils. Provincial transportation departments in Canada currently promote the use of the Unified Soil Classification System (USCS), where mineral soils are divided into fine-grained and coarse-grained soils; fine-grained soils are sub-classified as Silt or Clay; and, clays are further sub-classified on the basis of their degree of plasticity as being of low plasticity, of intermediate plasticity or of high plasticity with corresponding Group Symbols of CL, CI and CH. The intuitively incompatible CL classification for quick clays presents a risk of misunderstanding of the anticipated soil behavior since for other non-marine deposits the group symbol CL typically indicates more favorable soils when compared to the CI and CH clays. This paper also proposes the use of a group symbol modifier such as CL-m to reflect the non-standard predicted behavior of these soil types and the inclusion of a List of Risk and Methods of Interpretation to supplement the standard Lists of Abbreviations, of Symbols and of Terms currently included in geotechnical reports.