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Title: Compaction characteristics of earth-rock mixtures. report 1, Vicksburg silty clay and DeGray Dam clayey sandy gravel
Authors: Donaghe, Robert T.
Townsend, Frank C.
Keywords: Compacting
Compaction equipment
DeGray Dam clayey sandy gravel
Earth rock mixtures
Silty clays
Vicksburg silty clay
Soil consolidation
Soil compaction
Soil mechanics
Publisher: Soils and Pavements Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Miscellaneous Paper
Abstract: Due to limitations of equipment size, compaction characteristics of earth-rock materials are usually determined by laboratory tests of samples contained in small molds and having maximum particle diameters less than those of the in situ soil. Corps of Engineers' laboratories perform such tests on samples from which oversized particles have been scalped and replaced, assuming that test results are comparable to those that would have been obtained on full-scale samples. The purpose of this investigation was to determine effects on compaction characteristics of earth-rock mixtures due to the size of compaction equipment used and the altered gradation resulting from the scalping and replacement procedure. A mechanical compactor equipped with 18-, 12-, and 6-in.-diam molds and 5.5- and 24.7-lb rammers having diameters of 2.0 and 6.0 in., respectively, was utilized for the testing. Comparative tests were performed with a hand-held hammer utilizing standard procedures. Materials tested were Vicksburg silty clay (CL) having LL= 43 and PL= 22 and a clayey sandy gravel (GC) (LL= 37 and PL= 14) with maximum particle size of approximately 3 in. from DeGray Dam in Arkansas. Samples of the CL material were batched using either a commercial kitchen mixer or a pugmi.11, All of the CL specimens were compacted in three layers using compactive efforts approximately equal to the standard effort (12,300 ft-lb/ft³) by adjusting the number of blows. A total of seven compaction curves were developed for the Vicksburg silty clay (CL) and six compaction curves were developed for the clayey sandy gravel. Results of tests performed on the CL material indicate that mold diameters may be varied from 6 to 18 in. without significant effects on maximum dry unit weight and optimum water content. Results of tests on the CL material also show that compaction characteristics are not significantly affected by pugmill versus mixer processing. Results of tests performed on clayey sandy gravel show that significant differences in maximum dry unit weight and optimum water content are obtained in tests performed on samples having a maximum particle size of 3 in. using an 18-in.-diam mold and tests on samples having a maximum particle size of 3/4 in. with replacement of plus 3/4-in. material performed in a 6-in.-diam mold. The maximum dry unit weight was decreased from 127.9 lb per cu ft on the total sample to 123.6 lb per cu ft, and the optimum water content was increased from 8.7 to 10.3 percent. Tests on both materials (CL and GC) indicated that the mechanical compactor consistently gave higher maximum dry unit weights and somewhat lower optimum water contents than the conventional hand-held, sliding-weight rammer. Further testing is required to fully define the effects of scalping and replacing coarse material on the compaction characteristics of earth-rock mixtures.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Miscellaneous Paper

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