Mechanical Behavior and Damage Modeling of Dolomite Under Drying–Wetting Cycles and Variable Lower Bound Cyclic Loading

Abstract

To investigate the long-term stability of open-pit mine slopes under the coupled effects of seasonal rainfall-induced drying–wetting (D-W) cycles and mining-related transportation machinery loads, variable lower limit cyclic loading tests were conducted under a confining pressure of 1 MPa on intact dolomite specimens subjected to 0, 1, 5, 10, and 30 D-W cycles. The evolution of physical and mechanical properties, energy dissipation behavior, and failure modes was systematically investigated. Results show that water absorption increased significantly from 0.48% to 1.56% with an increasing number of D-W cycles, whereas the peak strength gradually decreased. Specifically, peak strain increased markedly in the early stage and then tended to stabilize. As the lower stress limit increased, the peak strength exhibited a quadratic trend. Moreover, when the lower stress limit was ≤ 15 MPa, cyclic loading produced a strengthening effect, with the peak strength increasing by up to 10.2%. The dissipated energy density increased significantly with the number of D-W cycles, and a damage constitutive model—derived primarily from theoretical analysis and refined through empirical correction—was established. Moreover, increasing the lower stress limit promoted a transition in the macroscopic failure mode from tensile to shear failure, which was further intensified by D-W cycling.