GSM ► Soil Mechanics I ► Atterberg Limits
Atterberg Limits
Liquid Limit Test | Plastic Limit Test
Atterberg’s limits tests
A fine-gained soil can exist in any of several states; which state depends on the amount of water in the soil system. When water is added to a dry soil, each particle is covered with a film of adsorbed water. If the addition of water is continued, the thickness of the water film on a particle increases. Increasing the thickness of the water films permits the particles to slide past one another more easily. The behavior of the soil, therefore, is related to the amount of water in the system. Approximately sixty years ago, A. Atterberg defined the boundaries of four states in terms of "limits" as follows:
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Liquid limit: The boundary between the liquid and plastic states;
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Plastic limit: The boundary between the plastic and semi-solid states;
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Shrinkage limit: The boundary between the semi-solid and solid states.
Procedure for Determination of Liquid Limit |
Procedure for Determination of Plastic Limit
These limits have since been more definitely defined by A. Casagrande as the water contents which exist under the following conditions:
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Liquid limit: The water content at which the soil has such a small shear strength that it flows to close a groove of standard width when jarred in a specified manner.
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Plastic limit: The water content at which the soil begins to crumble when rolled into threads of specified size.
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Shrinkage limit: The water content that is just sufficient to fill the pores when the
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