Characterisation of Shear Creep and Stress Relaxation of Serrate Discontinuity in Rock Mass under Different Loading Paths

In engineering applications, rocks rarely exist in their monolithic form and discontinuities always occur in the rocks. Intuitively there is a considerable difference in rheological properties between monolithic rocks and rocks with discontinuities. The present paper aims to characterise the shear creep and stress relaxation of serrate discontinuity in rock mass under different loading paths. A comprehensive experimental program, including creep tests, stress relaxation tests and unloading tests, on serrate discontinuities, is developed with focus on the effect of the slope angle of the serrated surface of the discontinuity on its creep and stress relaxation. Empirical models for shear creep and stress relaxation are also developed. We found in the paper that the larger the slope angle of a discontinuity is the larger both the creep and stress relaxation are, and the stress-strain relation of discontinuities in rock masses can be different under different loading paths. The significance of the research is that it investigates the simultaneous shear creep and stress relaxation of a serrate discontinuity under various loading paths. The paper concludes that the empirical models for creep and stress relaxation developed in the paper can help geotechnical engineers to analyse and assess the behaviour of rock masses with discontinuities.