FORECASTING TRAFFICABILITY OF SOILS; REPORT 10: RELATIONS OF STRENGTH TO OTHER PROPERTIES OF FINE-GRAINED SOILS AND SANDS WITH FINES

Attempts were made to establish relations between cone index, rating cone index, and remolding index (penetrometer strength measures commonly used in soil trafficability studies) and moisture content, soil separates contents, Atterberg limits, organic matter content, and dry density. Analyses were based on 6- to 12-in. soil layer data from 95 widely varying soils. In general, the approach followed in analyzing data was to (a) express the relation between a measure of strength and moisture content for each site with one standard equation form, (b) select coefficients that would define the strength-moisture relation for each site, and (c) relate the coefficients to soil properties. Results of the analyses indicate that usually (a) strength decreases with an increase in moisture for a given soil, (b) at a given strength level moisture content increases with a decrease in grain size or an increase in plasticity but is not associated with changes in organic matter content or dry density, (c) at a given moisture content changes in strength are associated primarily with changes in clay and/or sand contents when the U. S. Department of Agriculture soil separates are considered and with plastic and/or liquid limits when the Atterberg limits are considered, and (d) the predictive power of derived strength relations is poor even though the relations are significant (5% level). Appendixes are included in which the basic data and procedures used in obtaining the data are presented.