Creep in brittle rock after an increment of uniaxial load

Abstract

An analytical extension of a theory of brittle creep predicts that the form of the creep curve of brittle rock after an increment of uniaxial, compressive load depends on a creep parameter, n, of the rock and the size of the load increment and varies with time.With large load increments and large values of n, creep behaviour quickly loses any trace of creep at the lower load. For smaller increments and smaller values of n, the subsequent creep shows a distinctive mode of approach to normal creep behaviour at the higher load. The early portion of this creep curve can be used to estimate the creep parameters of the material.Experiments on Pennant sandstone are used to show how estimates of the physical parameters controlling the variation of creep with stress and time can be derived, for the first time, from increment creep tests on a single specimen. Keywords: creep, rock, brittle materials, crack, corrosion.