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Title: Comparisons of vibrated density and standard compaction tests on sands with fines
Authors: Townsend, Frank C.
Keywords: Compaction tests
Soil tests
Soil testing
Soil mechanics
Sandy soils
Soil density
Unit weight determination
Publisher: Soils and Pavements Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Miscellaneous Paper
Abstract: Generally, two laboratory test methods, relative density and standard compaction (impact), are used in establishing density requirements for the placement of embankment materials. The relative density test method is specified for cohesionless soils, generally when fines do not constitute more than 5-12 percent by weight, while the standard compaction test is for cohesive soils. However, for sandy soils containing varying amounts of fines, selection is often based upon the test method considered appropriate to the material. This study was an investigation of various criteria for assisting in compaction test method selection for cohesionless soils with fines. The effects of gradation, percentage and plasticity of fines, and moisture on vibratory and impact compaction of granular soils were evaluated by adding measured percentages (9, 16, and 23 percent) of low plasticity (ML) and medium plasticity (CL) fines to a poorly graded (SP) and a nearly well-graded (SW-SP) sand. Maximum density tests using a vibratory table were made on both oven-dry and saturated soil, minimum density tests were made on oven-dry soil, and standard compaction tests were performed on material at various water contents. Test results indicate that a uniform sand, due to its higher void space, can accommodate more fines and densify more effectively than a well-graded sand with fines. Plasticity of the fines and moisture were found to be interrelated factors affecting the compaction of sand with fines. For low plasticity mixtures, saturation facilitated vibratory compaction. Conversely, for more plastic mixtures, adhesion of the fines to the sand grains restricted vibratory shifting of the grains into a denser structure. The same densities are produced by impact and vibratory compaction at higher percent fines added to the well-graded sand compared to the percent fines added to the uniform sand. Apparently, compaction of a well-graded sand with fines is more affected by water content than a uniform sand with fines. Because moisture and plasticity of fines have such opposing effects on impact and vibratory compaction of sandy soils, guidance for compaction test selection is not clear cut. The current practice of basing compaction test selection on results of relative density tests on ovendry materials and standard compaction densities may not be realistic of field conditions and may lead to the untenable conclusion that vibratory compaction should be used for sands containing in excess of 20 percent fines. It is recommended that the use of the relative density method for compaction control be limited to granular soils with 12 percent or less fines.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Miscellaneous Paper

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