Strength Behavior of Rocks Under Cyclic Loading

Abstract

In the present study, the strength behavior of the intact rock subjected to cyclic loading has been studied. A series of laboratory tests has been conducted on intact cylindrical specimens of locally available limestone having the diameter of 40 mm and length to diameter ratio of two. Two different of types of cyclic loading tests has been performed under uniaxial condition. First, a series of incremental cyclic test has been conducted at the loading rate of 0.05, 0.1, 0.2 and 0.4 kN/s to study the change in strength and axial deformation of the rock specimen. Tests have also been performed under constant peak and valley stress to study the effect of the number of cycles and peak stresses on uniaxial strength of rock. From the incremental cyclic loading tests, it has been found that the normalized compressive strength reduces logarithmically with the increase in the rate of loading. From the second type of tests, the effect of peak stress has been found to be more significant than the number of cycles of loading. Empirical correlations have also been presented on the basis of the experimental results to estimate the strength under cyclic loading condition. Damage evolution study has also been conducted to quantify the pre-peak damage occurring in rock specimen when it is subjected to incremental cyclic loading.