Effects of Brittleness on Crack Behaviors in Rock-Like Materials

Abstract

The principal objective of this work is to understand the effects of brittleness on crack behaviors in rock, rock-like materials, and the underlying fracturing mechanisms. Brittleness, as one of the critical parameters of rock, significantly affects mechanical properties and fracturing behaviors. A better understanding of the effects of the brittleness on fracturing behaviors can lead to a more satisfactory characterization and assessment of the overall behaviors and performances of rock mass. In this study, experiments on rock-like materials with two parallel preexisting flaws are conducted to study the effects of brittleness, as well as the mechanical properties, crack initiation modes, crack coalescence types, and ultimate failure modes, on cracking behaviors of rock-like materials. We find that the content of the adhesive material’s polyamide and epoxy have a significant effect on the brittleness of rock-like materials that consist of sand, barite, epoxy, polyamide, and alcohol at different mass ratios. The brittleness of specimens decreases with increasing content of the cementing agents epoxy and polyamide. Seven types of crack initiation—wing crack, antiwing crack, coplanar secondary crack, oblique secondary crack, out-of-plane tensile crack, out-of-plane shear crack, and far-field crack—are observed in high-speed images of the ultimate failure crack morphology. Four types of crack coalescence are also identified: tension coalescence mode, shear coalescence mode, and the mixed mode including tension-shear coalescence mode and tension-shear-tension coalescence mode. A primary observation was that the ultimate failure mode is a transition from tension failure mode to tension-shear failure mode and shear failure mode, in sequence, and the rupture angle increases gradually with decreasing brittleness. Finally, the effects of the brittleness on the mechanical properties of rock-like materials, including the complete axial stress-strain curves, crack initiation stress ratio, and residual stress, are investigated in detail.

Experimental study on fracture behaviour of three‐flawed sandstone specimens after high‐temperature treatments

“…Furthermore, the brittleness of the rock decreased with the increase in temperature, 52 which affected the fracture behaviour of the rock with pre-existing flaws. 53 Therefore, the transition of the crack coalescence mode at 800 C was primarily due to the thermal cracks and brittleness variation induced by high temperatures.…”

Influence of the nature of the outflow of explosion products from blast holes and boreholes on the efficiency of rock destruction

“…This process depends on the volume of the explosive cavity, total cross-sectional area of the discharge openings (induced and natural cracks, openings in the stemming structure), as well as on the explosive itself and its energy release rate. Figure 1 shows overpressure on the walls of the explosive cavity as a function of EP outflow time [10,11,12]. A similar problem of the dependence of quasistatic pressure on time has been solved in the paper.…”

Creep Experimental Study of Rocks Containing Weak Interlayer Under Multilevel Loading and Unloading Cycles

“…In this study, according to the literature (Fan and Gao 2005;Tsai et al, 2008;Zhao et al, 2017c;Wang C. L. et al, 2018;Wang R. H. et al, 2018;Zheng et al, 2018;Zhao et al, 2019a;Zhao et al, 2019b;Zhou et al, 2019;Zhou et al, 2020), using the cyclic loading and unloading method, the uniaxial compression rheological test under cyclic loading and unloading conditions was carried out on the intact rock and rock containing WI. The influence law of stress level and WI inclination angle on the rheological characteristics of the rock was studied.…”