An Experimental Study of the Effect of Temperature and Stress on the Creep of Rocks

Abstract

Measurements have been made of the creep of a number of different rocks (anhydrite, dolomite, sandstone, marble, micrograndiorite and peri‐dotite) at temperatures up to 750°C under conditions of constant compressive or torsional stress. The apparatus is described in the paper. The results show that at temperatures below about 0–2 Tm (where Tm is the absolute temperature of melting) the creep strain is proportional to the logarithm of the time under load, and is approximately proportional to the stress and to the temperature. At higher temperatures the creep rate falls off less rapidly with time, and the creep strain is proportional to a fractional power of the time, with the exponent increasing as the temperature increases and reaching a value of ∼1/3 at temperatures of about 05 Tm. At these temperatures the creep increases with stress according to a power greater than unity and possibly exponentially and it increases with temperature as exp(‐ U/kT), where U is an activation energy and k is Boltzmann's constant. These results are strikingly similar to those obtained in measurements on metals, and it is thought that they can be explained in an exactly similar way in terms of competing processes of strain‐hardening and thermal recovery. A discussion of this hypothesis is given, and it is shown to be in quite good agreement with the results, both qualitatively and quantitatively, bearing in mind the specific features of mineral crystals. On this basis an estimate is made of the rate of steady state creep of peridotite. Copyright © 1965, Wiley Blackwell. All rights reserved