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|Title:||Compaction characteristics of earth-rock mixtures. report 2, blended material|
|Authors:||Donaghe, Robert T.|
Townsend, Frank C.
Earth rock mixtures
|Publisher:||Soils and Pavements Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: Due to limitations of equipment size, compaction characteristics of earth-rock materials are usually determined by laboratory tests on samples contained in small molds and having maximum particle diameters less than those of the full-scale material. 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 objectives of this investigation were to determine the validity of the scalping and replacement procedure and to evaluate two commonly used theoretical methods of computing dry unit weights of full-scale specimens using results from tests performed on minus No. 4 fractions of the total specimen. The objectives were achieved by comparing compaction curves for full-scale specimens (3-in. maximum particle size) and scalped and replaced specimens (3/4-in. maximum particle size); these curves were determined using a mechanical compactor with 18- and 6-in.-diam molds, respectively. Additional comparisons involved compaction curves for scalped and replaced specimens (3/4-in. maximum particle size) determined using a hand-held hammer with the 6-in.-diam mold. Companion compaction curves on the minus No. 4 fractions of the full-scale specimens were determined using a hand-held hammer and 4-in.-diam mold. The materials tested were various combinations of a subrounded to subangular washed gravel having a maximum particle size of 3 in., a subrounded to subangular concrete mortar sand, and a clay (CL). All specimens were compacted in three layers using compaction efforts made approximately equal to standard effort (12,300 ft-lb/ft³) by adjusting the number of blows. The tests indicate that the scalping and replacement procedure results in significantly lower maximum dry unit weight and higher optimum water contents than those obtained for fuli-scale specimens. The use of the theoretical methods provided better approximations of experimental results on full-scale specimens having gravel contents up to 60 percent than the relationships developed using the scalping and replacement procedure. In order to fully define effects due to the scalping and replacement procedure, further testing is needed to determine effects of variations in equipment sizes.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Miscellaneous Paper|
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|MP-S-73-25-Report-2.pdf||17.49 MB||Adobe PDF|