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Unformatted text preview: The University of Iowa Department of Civil & Environmental Engineering Fall Semester, 2002 53:030 Soil Mechanics Lab Experiment No. 3: Liquid and Plastic Limits of Fine-Grained Soils Equipment: liquid limit device, grooving tool, porcelain evaporating dish, spatula, 5 water content tins, mass balance, oven, plastic squeeze bottle, glass rolling plate and paper towels. A. Background The liquid limit (LL) of a soil is defined as the water content at which a trapezoidal groove of a specified shape, cut in a moist soil in a special cup, is closed after 25 taps on a hard rubber plate. The plastic limit (PL) is the water content at which the soil begins to break apart and crumble when rolled into threads 3mm ( 1 8 in) in diameter. The shrinkage limit (SL) is the water content at which soil reaches its minimum volume as it dries out from a saturated condition. These limits, customarily expressed as whole numbers of water content percentage, are the so-called Atterberg Limits of a soil. In this laboratory assignment, we will measure the liquid and plastic limits of a given soil. In and of themselves, the Atterberg limits mean little. But as indices to the significant properties of a fine- grained soil, they are quite useful. The liquid limit has, for example, been found to be directly proportional to the compressibility of a soil whereas the plasticity index or (LL - PL) represents the range in water content through which the soil is plastic. The liquid and plastic limits are further used in both the AASHTO and UCS classification schemes.the soil is plastic....
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- Fall '09
- Environmental Engineering