Atterberg limits - The University of Missouri-Columbia...

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The University of Missouri-Columbia MEASUREMENT OF ATTERBERG LIMITS PURPOSE The purpose of this laboratory is to teach you how to measure the liquid and plastic limits of cohesive soils. These limits are perhaps the oldest and most widely accepted of all engineering tests on cohesive soil and are used for a variety of engineering purposes, including soil classification, earthwork specifications, and as an aid in estimating engineering properties of soils. Many engineering companies present plots of liquid limit, plastic limit, and natural water content as a function of depth for practically every site that they investigate. One such plot is shown in Figure 1. In this particular instance, the natural water content is higher than the liquid limit, which suggests that the soil is in essentially a liquid state. Even without further testing, it is evident that this particular soil is soft, very compressible, and not capable of supporting heavy buildings. Figure 1 -- Natural Water Content (W N ) , Liquid Limit (W L ), and Plastic Limit (W P ) Versus Elevation (from Ladd 1972) HISTORICAL DEVELOPMENT The history of the Atterberg limits tests is reviewed by Bauer (1959). Albert Atterberg, a Swedish soil scientist, reported in 1911 on an extensive study of the plasticity of clays. Atterberg experimented with pulverized clays that were mixed with water to form a fluid slurry. When the clays were mixed with lesser amounts of water, the mixture became viscous and, with some drying, even a smeary, sticky mass. With evaporation of further water, this stickiness disappeared and the clay could be shaped as desired. If the clay was dried even more, it became hard, brittle, and incapable of being shaped. To make possible a scientific study of these properties, Atterberg established five limits:
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University of Missouri-Columbia p.2 1. The upper limit of fluidity, which is the limit at which a clay slurry is so fluid that it flows almost like water. 2. The lower limit of fluidity, or flow limit , which is the limit of water content at which two small portions of a clay-water mixture, lying in a dish, will no longer flow together with vigorous blows of the dish. 3. The sticky limit, which is the limit at which the clay is no longer sticky. 4. The roll-out limit, which is the limit at which the moist clay cannot be rolled into threads. 5. The cohesion limit, which is the limit at which damp clay will not allow itself to shrink with further drying. All limits were expressed as water contents by Atterberg. Engineers gradually began to use Atterberg's ideas in the classification of subgrade soils for highway design. However, standard methods of testing were slow to evolve. The limits of most interest to engineers were the lower
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This note was uploaded on 09/23/2011 for the course CIVIL ENGI CE 3400 taught by Professor Rosenblad during the Spring '11 term at Missouri (Mizzou).

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Atterberg limits - The University of Missouri-Columbia...

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