This lecture introduces the concepts of weight volume relationships and phase diagrams. Some tricks for developing a phase diagram are discussed, and a practice problem is provided. Relative density of coarse-grained soil is also defined and discussed.

Download the blank phase diagram here: https://dl.dropboxusercontent.com/u/52858757/Blank%20Phase%20Diagram.pdf

Critical Questions to Consider:
1) Why would geotechnical engineers want to represent the soil as a phase diagram? How would that help us to visualize the contribution of the voids to the behavior of the soil?

2) Which properties of the soil (e.g., air content, water content, void ratio) can be changed and altered? Which properties of the soil are constant?

3) What is the relative density of a soil? Relative to what?