Name and describe the limits and indexes that are important to the understanding of soil classification.

Question

What will be an ideal response?

Answer 1

Important to understanding soil classification are the liquid limit, plastic limit, plasticity index, and the shrinkage limit of soils. These states of soil consistency are indicated in terms of water content. The liquid limit (LL) of a soil is the water content expressed as a percentage of the dry weight at which the soil will start to flow when subjected to a shaking test. The plastic limit (PL) of a soil is the moisture content percentage at which the soil begins to crumble when it is rolled into a thread 1.8 in. (3 mm) in diameter. The plasticity index (PI) is the difference between the liquid limit and the plastic limit and indicates the range in moisture content over which the soil will remain in a plastic condition. The shrinkage limit (SL) is the water content at which soil volume is at its minimum.