Abstract:

The deformation features, mechanical parameters and failure characteristics were obtained based on the results of triaxial unloading tests of limestone. It is shown that the evolution of volumetric strain is determined by lateral strain under unloading condition. Failure modes of rock could be classified into three types: primary shear failure, conjugate shear failure and splitting-shear failure. The failure stress difference decreases with unloading velocity increasing under the same initial confining pressure. However, it increases with the initial confining pressure increasing under the same unloading velocity. The rebound value of axial strain increases; while the lateral strain jump decreases with the initial confining pressure increasing at the same unloading velocity. The cohesion of rock increases but the internal friction angle decreases with unloading velocity increasing

Key words: unloading, limestone, mechanical parameters, deformation characteristics