ABSTRACT
The Atterberg Limits are used to describe the phase changes that a fine-grained soil passes through at different Water Contents. At very high Water Content, a mixture of soil and water behaves as a viscous liquid. As the Water Content is reduced, the soil takes on the characteristics of a plastic solid and then a semi-solid, and finally, at a sufficiently low enough Water Content, the soil becomes a brittle solid. The Water Contents where these changes in behavior occur are called the Atterberg Limits, after Albert Atterberg, a Swedish chemist and agricultural scientist, as illustrated in Figure 12.1.
The Liquid Limit is defined as the Water Content that separates liquid behavior from plastic solid behavior. The Plastic Limit is defined as the Water Content that separates plastic solid behavior from semi solid behavior. The Shrinkage Limit is defined as the Water Content that separates semi solid behavior from brittle solid behavior. These are ideal definitions, but we need some simple tests to help us define these boundaries. Over the years, standardized tests have been developed for this and generally seem to provide very good results and are able to separate different soil behavior based on the tests. In this chapter, tests for Liquid Limit and Plastic Limit are described.
