Compaction - University of Missouri - Columbia Civil and...

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University of Missouri - Columbia Civil and Environmental Engineering COMPACTION TEST INTRODUCTION Fill materials are used by engineers for a variety of purposes, e.g., to build dams, to construct embankments, to develop low-lying land, to support pavements, and to make sites more suitable for support of foundations. With such fills, it is almost always necessary to improve the engineering properties of the soil by compacting it. The equipment used to compact the soil includes the following types: · Sheepsfoot roller · Rubber-tired roller · Steel-wheeled roller · Vibratory roller The direct consequence of soil compaction is densification of the fill. However, the objective is not so much just to densify the fill as to improve the engineering properties. Some of the improvements that are possible include the following (Head, 1980): Effect of Compaction on Effect of Compaction on Engineering Properties: Performance of the Fill: Higher Strength Greater Stability Lower Compressibility Less Settlement Lower Permeability Less Seepage Less Tendency to Absorb Water Reduced Shrink/Swell Potential In order to investigate the effect of compaction on the engineering properties of fill material, it is necessary to prepare samples, usually in the laboratory, for testing. For example, a number of samples could be prepared over a range in compaction water content or density to study the effect of these parameters on such properties as strength and compressibility of the fill. Based on results of the tests, the proper water content to be used in the field and the minimum acceptable density could be determined.
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University of Missouri – Columbia Civil and Environmental Engineering Compaction Test p.2 A number of techniques have been developed to compact soil in the laboratory --most of the tests fall into four types: 1. "Impact" compaction tests in which a standard weight is repeatedly dropped on the soil sample for a prescribed number of blows. The hammer weight, distance of fall, and number of blows can be adjusted to achieve the desired compactive effort. 2. "Static" compaction tests in which a uniform pressure is applied to the soil and maintained long enough for the soil to compact under the pressure. 3. "Kneading" compaction tests in which a small "foot" is loaded, then unloaded, at various locations on the surface of the sample being compacted; the soil is effectively kneaded with this procedure. 4. "Vibratory" compaction tests in which the soil is vibrated as it is compacted, which is particularly effective in compacting cohesionless soils such as sand and gravel. Ideally, the laboratory compaction tests should simulate the compaction procedures used in the field as closely as possible. Bowles (1978) has compared laboratory methods of soil compaction to field procedures and concludes the following: Laboratory Method Comparable Field Equipment Impact Compaction None Static Compaction Steel or Rubber-Wheeled Roller Kneading Compaction Sheepsfoot Roller Vibratory Compaction
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Compaction - University of Missouri - Columbia Civil and...

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