Fracture experiments on ordered multi-crack body in rock-like materials under uniaxial compression and numerical simulation of wing cracks

In order to study the rules of rock bridge rupture and the influences of occurrence characteristics of intermittent cracks on strength of rock mass, ordered multi-crack bodies are made using cement mortar. Fracture failure experiments on ordered multi-crack body under uniaxial compression are conducted. It is concluded that the transfixion pattern of wing tensile cracks, transfixion pattern of tension-shear cracks between different rows and oblique shear crack transfixion pattern in the same row are the main rapture modes for the ordered multi-crack body. The representative peak strength of specimens decreases with the increasing number of cracks. When the crack angle is small, such as 25°and 45°, the residual strength increases. While the crack angle is large, such as 75°and 90°, the crack density has little effect on the representative peak strength of specimens, and the characteristics of residual strengths are less evident. When the crack density is constant, the representative peak strength of specimens shows an increasing trend when the crack angles change from 25°to 90°. The pattern of main control crack coalescence is proposed. The transfixion of tension-shear cracks between different rows along the clinodiagonal is the pattern of the main control crack coalescence when the angle is 25°. While the crack angle is 45°, the patterns of the main control crack coalescence include two types, which are transfixion of wing cracks and transfixion of coplanar secondary shear cracks along the clinodiagonal. The characteristics of stress-strain concentration in crack tip reveal the fact that the essential reason of initiation of wing cracks is the concentration of tensile strain at crack tip, while the state of biaxial compressive stress-strain concentration near the main