Creep of Rocks

"Creep" is the name applied to the slow deformation of solids under small loads acting over long periods of time. Two types of apparatus have been developed for the purpose of investigating the creep of rocks in response to stresses below the "elastic limit," as ordinarily defined. The present paper describes results obtained with these instruments during runs of various duration, up to 550 days. It is found that in many cases there is measurable flow at stresses below the "elastic limit." An empirical law has been derived which resolves this deformation into two types of flow, termed "elastic flow" and "pseudoviscous flow." The creep characteristics of several materials at room temperature and atmospheric confining pressure are described. Preliminary experiments on creep at high pressure and on creep by recrystallization are reported.