GEOL 352 Lecture Notes - Lecture 17: Rheology, Compressive Stress, Differential Stress
13 Nov 2020
School
Department
Course
Professor
Document Summary
Elastic - deformation is recoverable when stress is removed. Plastic - deformation is not recoverable, permanent deformation of bonds. Hooke"s law: stress is proportional to strain e=elongation. E =young"s modulus the elastic constant = rock strength different for every rock type determined by experimental means slope of line on stress-strain graph. ~ -10 11 for crustal rocks ( - because want - elongation (shortening) from a + compressive stress. Linear elastic behavior: strain is directly proportional to stress and is recoverable. Brittle behavior: implies failure at the elastic limit. The relationship between the shear strength of a rock (g) and its elastic/tensile strength (e) is governed by its compressibility: Smaller poisson # = larger potential energy--will return to original shape (spring) e perpendicular = e perpendicular to compressive stress. Plastic deformation: deformation due to rearrangement of chemical bonds. Permanent deformation is achieved only after a given threshold or yield differential stress is reached.
