Characterisation of rock aggregate breakage properties using realistic texture‐based modelling

Abstract

SUMMARYRealistic texture-based modelling methods, that is microstructural modelling and micromechanical modelling, are developed to simulate the rock aggregate breakage properties on the basis of the rock actual microstructure obtained using microscopic observations and image analysis. The breakage properties of three types of rocks, that is Avja, LEP and Vandle taken from three quarries in Sweden, in single aggregate breakage tests and in inter-aggregate breakage tests are then modelled using the proposed methods. The microstructural modelling directly integrates the microscopic observation, image analysis and numerical simulation together and provides a valuable tool to investigate the mechanical properties of rock aggregates on the basis of their microstructure properties. The micromechanical modelling takes the most important microstructure properties of rock aggregates into consideration and can model the major mechanical properties. Throughout this study, it is concluded that in general, the microstructure properties of rock aggregate work together to affect their mechanical properties, and it is difficult to correlate a single microstructure property with the mechanical properties of rock aggregates. In particular, for the three types of rock Avja, LEP and Vandle in this study, crack size distribution, grain size and grain perimeter (i.e. grain shape and spatial arrangement) show good correlations with the mechanical properties. The crack length and the grain size negatively affect the mechanical properties of Avja, LEP and Vandle, but the perimeter positively influences the mechanical properties. Besides, the modelled rock aggregate breakage properties in both single aggregate and inter-aggregate tests reveal that the aggregate microstructure, aggregate shape and loading conditions influence the breakage process of rock aggregate in service. For the rock aggregate with the same microstructure, the quadratic shape and good packing dramatically improve its mechanical properties. During services, the aggregate is easiest to be fragmented under point-to-point loading condition, and then in the sequence of multiple-point, point-to-plane and plane-to-plane loading conditions. Copyright

Brittleness Evaluation of Glutenite Based On Energy Balance and Damage Evolution

“…The application of brittleness evaluation methods based on stress-strain curves are generally limited to laboratory tests on cores drilled from certain glutenite layers, making it difficult to obtain continuous longitudinal mechanical properties and stress-strain responses of glutenite reservoirs under different in situ stresses. Therefore, to make brittleness models more applicable to fracturing operations and to obtain a continuous longitudinal brittleness index of glutenite throughout the well, it is necessary to integrate geomechanical and petrophysical approaches [51][52][53][54]. There is an intrinsic relationship between geophysical logging data and the physical and mechanical parameters of the reservoir rock mass [2].…”

“…The peak strength and elastic modulus of glutenite specimen remain almost invariant, while the residual strength decreases with an increase in gravel size, which results in an increase in glutenite brittleness. Fracture deflection by gravel can lower the fracture-tip stress intensity and enhance the fracture growth resistance, and the fracture may undergo a "shielding" effect [52][53][54]. When a fracture approaches large-sized gravel, it must accumulate more energy to overcome the resistance.…”

Hybrid Finite‐Discrete Element Modelling of Excavation Damaged Zone Formation Process Induced by Blasts in a Deep Tunnel

“…In addition, Ingraffea, Whittaker et al, and Al-Shayea et al indicated that model-II fracture toughness K IIc is usually larger than mode-I fracture toughness K Ic [32][33][34]. According to Brazilian disc tests for limestone rock, the ratio of K IIc /K Ic is 1.72 [35], while it is 1.64 obtained from numerical modelling of the notched Brazilian disc test for granite materials [36]. Accordingly, the mode-II fracture toughness is assumed to be 1.7 times larger than the mode-I fracture toughness.…”

Hybrid finite-discrete element modelling of asperity degradation and gouge grinding during direct shearing of rough rock joints

“…Further loading causes the three pieces sliding along the formed two shear cracks. Microstructure or statistical methods, such as those proposed by Liu et al (2012), may be introduced based on the actual texture of rock to obtain reasonable failure pattern as observed in experiments. Figure 4 visually illustrates the modelled rock disc splitting failure process in terms of the distributions of the minor principal stress (the compressive stress) and the initiated cracks during the BTS test while the corresponding force and displacement curve is shown in Fig.…”