Volume 17, Issue 3 (September 1994)
Compaction Control of Earth-Rock Mixtures: A New Approach
A new method for compaction control of earth-rock mixtures has been developed which permits the calculation of the maximum dry unit weight and optimum water content of the total material from corresponding values obtained on either the minus 3/4-in. (19.1-mm) or the minus No. 4(4.76-mm) fraction. The new concepts are substantiated by showing their applicability to a wide range of gradations of earth-rock mixtures tested by the U.S. Army Engineer Waterways Experiment Station and other previous investigators. Calculations of maximum dry unit weight and optimum water content of the total material from corresponding values for a fraction are made using a density interference coefficient and optimum water content factor which are shown to be linearly related to gravel content in the material in log-log coordinates. It is also shown that if a sufficient range in gravel content exists in the minus 3/4-in. (19.1-mm) fractions of the total materials, the log-log linear relationships among density interference coefficient, optimum water content factor, and gravel content can usually be obtained without large-scale compaction testing of the parent total materials. In essence, the new method provides project-specific “rock corrections” which accurately track the compaction parameters of the entire family of generically related total materials throughout the range in their gravel contents and maximum particle sizes.