This lesson combines a few unrelated (but important!) topics from geotechnical engineering. First, the basic concept of PQ diagrams (or stress paths) are introduced. You are shown how to compute Mohr-Coulomb strength parameters (i.e., c and phi) from a PQ diagram. Second, the topic of sensitivity in shear strength is introduced. Quick clays are discussed and their formation is summarized. Finally, the topic of thixotropy is briefly summarized.

Here is the link to the Rissa Landslide video (...an old video produced by the Norwegian Geotechnical Institute): https://www.youtube.com/watch?v=3q-qfNlEP4A&t=4s

Learning Objectives:

1) Transform a series of Mohr-circles to PQ space and calculate modified strength parameters;
2) Use the modified strength parameters to compute Mohr-Coulomb shear strength parameters c and phi;
3) Compute the sensitivity of a soil;
4) Describe what a quick clay is and how it is formed; and
5) Explain what thixotropy is