Fatigue Characteristics of Gypsum-Based Mixture Material Used as a Similar Material in Laboratory Experiments under Cyclic Loading

At present, most model experiments of tunnel linings use a gypsum-based mixture material as the similar material for static and dynamic research, but the fatigue characteristics of these materials have not been investigated thoroughly and warrant further research. In this work, a fatigue experiment of a gypsum-based mixture material under cyclic loading was carried out, and the fatigue characteristics at different stress levels were investigated and summarized. The experimental results show that the logarithmic number of cycles to failure exhibit linear variation, and the relationship between the resident strain and cyclic time can be approximated by an exponential function. The strain curve shows that there are obvious three-stage characteristics throughout the loading process and that each stage accounts for 10%, 85%, and 5% of the entire loading time, respectively. The dissipation energy varies over a small range, and its average value demonstrates exponential variation at different stress levels. The accumulated residual deformation due to unrecoverable damage pushes the hysteresis curve in the direction of deformation enlargement over the full cycle process. The evolution law of the fatigue damage curve is related to the inherent parameters of the material only, regardless of the stress conditions, exhibiting exponential nonlinear damage accumulation. This investigation provides an informative reference for the fatigue evaluation of similar materials in indoor experiments.