Contribution to the Engineering Soil Classification of Cohesionless Soils.

This report is a state-of-the-art examination of existing soil classification systems with emphasis on classification of cohesionless soils. The purpose of the report is to note and suggest possible improvements to the Unified Soil Classification System currently used by the Corps of Engineers. Characteristics of soil types pertaining to roads and airfields and soil stabilization are also considered. Criteria for differentiating between coarse-grained soil groups which have diverse engineering properties, but which are not fully described in other classification systems, are also proposed. Boundaries between clean gravels or sands, gravels or sands with some fines, gravels or sands with fines, and fine-grained soils are suggested as 5, 20, and 50 percent fines, respectively. Coarse-grained soils are also classified with respect to their coefficient of uniformity and coefficient of curvature as well graded and poorly graded, with the poorly graded further separated into narrow i. e. uniform and gap gradations. Criteria to separate each group are presented.