Atterberg limits
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The document discusses three soil tests: the liquid limit test determines the moisture content needed for a soil pat to close a groove after 25 drops from 10 mm; the plastic limit test finds the moisture content where a 3 mm soil thread will crumble; and the shrinkage limit test measures the volume and mass of wet and dried soil in a dish to determine moisture loss.
Atterberg limits
- 1. ATTERBERG LIMITS Liquid limit test: A soil is place in the grooving tool which consists of a brass cup and a hard rubber base. A groove is cut at the center of the soil pat using a standard grooving tool. The cup is then repeatedly drooped from a height of 10 mm until a groove closure of 12.7 mm. The soil is then removed and its moisture content is determined. The soil is said to be at its liquid limit when exactly 25 drops are required to close the groove for a distance of 12.7 mm ( one half of an inch)
- 2. Plastic limit test: A soil sample is rolled into threads until it becomes thinner and eventually breaks at 3 mm. it is defined as the moisture content in percent at which the soil crumbles when rolled into the threads of 3.0 mm. If it is wet, it breaks at a smaller diameter; if it is dry it breaks at a larger diameter. Shrinkage limit test: It is performed in the laboratory with a porcelain dish approximately 45 mm in diameter and about 12.7 mm high. The dish is completely filled with wet soil. The mass and volume of the wet soil is then recorded. The dish is then oven dried, then the mass and volume of the oven dried soil is also recorded.