Study on mechanical properties of marble under loading and unloading conditions

It is shown by tests that there are some differences between mechanical properties of rock masses under loading and unloading conditions. A series of tri-axial tests under loading and unloading conditions are done on the marble samples from the slopes of the Jinping Primary Hydropower Project to study the mechanical properties of marble. Then the mechanical parameters are calculated and interpreted, and the complete stress-strain curves are studied and compared. The results of these tests show that there are obvious differences between mechanical properties of marble under loading and unloading conditions. Under the unloading condition, the deformation modulus and the compressive strength decline, and for the shear strength, c declines a great deal, but ψ increases a little. In the failure process, the lateral strain under unloading condition increases much more than that under loading condition with the same confining pressure, the plasticity declines and the brittleness increases. The results show the concrete difference of mechanical properties of marble under loading and unloading conditions and offer important references to engineering problem.