The effects of material parameters on dynamic cone penetrometer results for fine-grained soils and granular materials

Scope of study. A series of tests on fine-grained soil samples were carried out to determine the effects of various factors on Dynamic Cone Penetrometer (DCP) values. The effect of an increase in moisture content (from optimum moisture content to optimum moisture content +20%) on DCP values was analyzed. The effect of an increase in density on the DCP values was evaluated by comparing the values at 100% and 110% maximum dry density. Tests to evaluate the effects of confining pressure and AASHTO soil classification on DCP values were performed at 0, 15, and 30 psi on A-6 and A-7 soils. A relationship was established between DCP values and the resilient modulus at the two moisture states. DCP values of six granular materials were determined at 6, 12, and 18 psi through the use of a modified triaxial cell. Two sources of materials provided three categories of the granular materials (sand, 3/8-in. and 3/4-in. maximum aggregate size). The effects of maximum aggregate size, coefficient of uniformity, and confining pressure were determined.; Findings and conclusions. (A level of significance of 5% is assumed in this discussion.) The investigation found that an increase in moisture content significantly increased DCP values, and an increase in density significantly decreased DCP values in fine-grained soils. AASHTO A-6 and A-7 soils provided significantly different DCP values. Confining pressure was found not to be a significant factor in the determination of DCP values in fine-grained soils. The slope of the simple regression line to predict the resilient modulus from DCP values was found to be significant for soils at optimum moisture content but not significant at optimum moisture content +20%. In the determination of DCP values of granular materials, confining pressure was found to be significant for all materials evaluated. A significant linear trend was observed between DCP values and confining pressure. Maximum aggregate size had no significant effect on DCP values of granular materials. The correlation between coefficient of uniformity with DCP values was found to be significant.