The effect of successive uniaxial and biaxial cyclic loading on the fracture resistance of limestone samples

The results of experiments with two samples of limestone of the Kasimovskoye deposit (Russia) are discussed. The purpose was to compare their resistance to fracture under cyclic quasi-static loadings under compression in one or two directions. Acoustic emission (AE) was recorded during cycles. Between the series, the velocities of longitudinal and transverse elastic waves, and acoustic quality factor Q were measured. The destructive effect was evaluated using the damage parameter ω. The studies showed that deformation of the sample in two directions leads to greater damage, but reduces the strength of the limestone to a lesser extent than the cyclic load in one direction. Cracks formed in the biaxial action of one direction impede the development of cracks in another direction. This mechanism explains the indicated phenomenon. The study was supported by the Russian Foundation for Basic Research, grant No. 17-05-00570.