Abstract
Data and information on the cyclic loading behaviour of soft rocks, especially behaviour under irregular cyclic loading, are very limited. This paper shows that the present procedure of estimating residual strain accumulation due to irregular cyclic loading using a fatigue model from uniform amplitude cyclic loading can result in underestimated residual strains. Such underestimation occurs because the present procedure fails to take into account the so-called P2S effect on the softening behaviour of soft rocks under cyclic loading. The parameter P2S is defined as the sum of the magnitudes of the increments in residual strains due to the previous two loading half-cycles. When P2S is large, a large residual strain increment can be expected. This paper also shows that taking the P2S effect into account can improve the simulation of residual strain accumulation due to irregular cyclic loading.
