Investigation on fracture behaviors and damage evolution modeling of freeze-thawed marble subjected to increasing- amplitude cyclic loads

Abstract

Rock is often subjected to fatigue loads in many mining and civil engineering, rock fatigue mechanical behaviors under constant stress amplitude have been widely investigated. Yet the increasing-amplitude fracture mechanical characteristics of rock and the associated damage evolution model are not well understood. In this work, uniaxial increasing-amplitude fatigue loading experiments were conducted using GCTS RTR 2000 rock mechanics system on marble obtained from an open-pit slope with 0, 20, 40 and 60 freeze-thaw (F-T) cycles. Results show that the previous F-T damage of rock affects the fatigue lifetime, secant modulus, Poisson’s ratio, deformation and damage evolution. The damage accumulation and volumetric deformation increase with the increase of F-T cycles. Damage growth rate becomes weaker with increasing fatigue cyclic levels and a two-stage damage accumulation pattern was found, namely, the initial damage and steady damage stage. The sudden increase moment of stress amplitude has obvious effect on rock damage. Based on the experimental data, a damage evolution model was proposed to describe the two-stage fatigue accumulation characteristics. The model is not only suitable for damage description of each fatigue loading level but also the whole loading process. It is found that the applicability of the damage evolution model is not influenced by the initial damage of rock, and will be applied to intact or jointed rock. The studies in this work are expected to improve the understanding the fatigue damage mechanism of rock subjected to multiple level fatigue loading conditions.