Analysis on damage evolution of jointed rock masses containing a circular hole under uniaxial compression

Damage evolution of jointed rock masses during the excavation processes may trigger geological engineering disasters. In this study, macroscopic mechanical response (strength, failure characteristics, stress-strain variations, and the process of cracks initiation, propagation and coalescence) were revealed by jointed gypsum samples containing a circular hole under uniaxial compression. The presence of a circular hole prevents the occurrence of axial splitting failure around the hole from penetrating the entire specimen, specimens with low and vertical inclination angles (β = 0°, 30°, and 90°) exhibit more severe damage around the holes, leading to the easier formation of removable rock blocks. Specimens with medium inclination angles (β = 45° and 60°) demonstrate better integrity around the holes but are more prone to instability failure induced by shear slip. In addition, The Oda damage variable is introduced and combined with acoustic emission (AE) characteristic parameters to quantitatively analyze the damage evolution process in jointed rock masses containing a circular hole. It reveals that the first principal invariant (I1) of Oda damage variable and the HPS (hits per second) accumulation have both good consistency and varying degrees of difference with the variation trend of strain. When the variation trend of I1 and HPS accumulation is consistent, it indicates that the surface damage degree of specimens has a good consistency with the internal damage degree of specimens. When the variation trend of I1 and HPS accumulation is different, the difference reflects the anisotropy of the damage degree of the specimen.