Uniaxial Compression Experiments And Numerical Simulations of Artificial Rock Samples With Regular Dentate Discontinuity

To study the uniaxial compression performance of artificial rock samples with symmetrical and asymmetrical regular dentate discontinuities, uniaxial compression tests and Particle Flow Code (PFC) numerical simulation are conducted on cement mortar specimens, and the combined effects of dip angle, undulation angle, and number of undulating structures of cracks on the compressive strength, peak strain, elastic modulus, and crack propagation in the specimens are studied. Among these parameters, undulating structure is defined as a single regular dentate structure in the dentate discontinuity; dip angle is the angle between the bottom line of the undulating shape and the horizontal line; undulating angle is the angle between the bottom line of the undulating structure and the left line of the undulating shape; and the number of undulating structures is the number of undulating structures in the dentate discontinuity. The experimental and numerical simulation results show that when the number of the undulating structures and undulating angles remain unchanged, the uniaxial compressive strength of the specimens peak at a dip angle of 90°. In addition, when the dip and undulating angles remain unchanged, the compressive strength, peak strain, and elastic modulus of the specimens decrease with an increase in the number of undulating structures. Moreover, when the number of undulating structures and the dip angle remain unchanged, the compressive strength, peak strain, and elastic modulus of the specimens decrease with an increase in the undulating angle. Further, almost all of the new cracks in the specimens initiate at the tip of the prefabricated cracks.

Investigating the Influences of Indentation Hardness and Brittleness of Rock-Like Material on Its Mechanical Crushing Behaviors

Indentation hardness and brittleness are the important factors to be considered in the study of rock-like materials’ mechanical crushing behaviors. The brittleness of rock-like materials is defined as the ratio of uniaxial compressive strength to tensile strength in this paper. In order to investigate the influences of hardness and brittleness on rock-like materials’ crushing behaviors, quartz sand and high strength α-hemi-hydrated gypsum were used to prepare rock-like materials with different hardness and brittleness through different mass ratios. The artificial rock-like materials can eliminate the effects of natural rock’s weak structure plane on experimental results. The indentation test, Uniaxial compressive test, and Brazilian tensile test were conducted for characterizing the indentation hardness and brittleness of this artificial rock-like materials. The experimental results showed that brittleness increased with the increase of indentation hardness with high correlation coefficient. The confining stress presented a positive impact on the indentation hardness of the rock-like materials. Based on those mechanical properties, the numerical rock models were calculated to study rock crushing behaviors using discrete element method (DEM). A series of rock crushing tests were conducted to investigate the influences of hardness and brittleness of rock-like materials on rock crushing behaviors using a conical pick cutter. The numerical results showed that the normalized specific energy was negatively correlated with indentation hardness index (IHI). The normalized specific energy decreased with the increase of brittleness index (BI) with a high correlation coefficient. This study is beneficial in utilizing IHI and BI to evaluate the mechanical properties, failure patterns, and mechanical crushing efficiency of rock-like materials.