In this video, I introduce several soils mechanics concepts related to the shear strength of clays. I discuss drained strengths of clays, including peak strengths, softened strengths, and residual strengths. I briefly discuss undrained strengths of clays, and I compare/contrast UU triaxial results with CU triaxial results. My recommendation: do a CU triaxial test instead of a UU triaxial test whenever possible.