Abstract
Granite exhibits obvious meso-geometric heterogeneity. To study the influence of grain size and preferred grain orientation on the damage evolution and mechanical properties of granite, as well as to reveal the inner link between grain size‚ preferred orientation, uniaxial tensile strength (UTS) and damage evolution, a series of Brazilian splitting tests were carried out based on the combined finite-discrete element method (FDEM), grain-based model (GBM) and inverse Monte Carlo (IMC) algorithm. The main conclusions are as follows: (1) Mineral grain significantly influences the crack propagation paths, and the GBM can capture the location of fracture section more accurately than the conventional model. (2) Shear cracks occur near the loading area, while tensile and tensile-shear mixed cracks occur far from the loading area. The applied stress must overcome the tensile strength of the grain interface contacts. (3) The UTS and the ratio of the number of intergrain tensile cracks to the number of intragrain tensile cracks are negatively related to the grain size. (4) With the increase of the preferred grain orientation, the UTS presents a “V-shaped” characteristic distribution. (5) During the whole process of splitting simulation, shear microcracks play the dominant role in energy release; particularly, they occur in later stage. This novel framework, which can reveal the control mechanism of brittle rock heterogeneity on continuous-discontinuous trans-scale fracture process and microscopic rock behaviour, provides an effective technology and numerical analysis method for characterizing rock meso-structure. Accordingly, the research results can provide a useful reference for the prediction of heterogeneous rock mechanical properties and the stability control of engineering rock masses.
Highlights
Natural granite is characterized by low permeability, good thermal conductivity, high strength and little deformation
Grain-scale heterogeneity is a combination of several types of heterogeneity, including geometric heterogeneity resulting from grain shape, grain orientation and grain size; material heterogeneity resulting from the mismatch of different grains; and contact heterogeneity resulting from grain boundary anisotropy
finite-discrete element method (FDEM), proposed by Munjiza et al [11], combines the advantages of the finite element method (FEM) and the discrete element method (DEM), continuous mechanical behaviors, such as the elastic deformation of brittle rocks, can be simulated by FEM, while discontinuous deformation behaviors such as damage and fracturing in brittle rocks can be simulated by the cohesive crack element (CCE) and the contact forces of blocks can be calculated by DEM
Summary
Natural granite is characterized by low permeability, good thermal conductivity, high strength and little deformation. This paper used finite-discrete code [15] based on the FDEM to establish a meso-scale numerical model of Beishan granite [16], and analyzed the influence of the grain size and preferred grain orientation on the UTS and damage evolution process. This framework enables the intergranular and transgranular contacts to be modeled explicitly, while taking the actual grain morphology into consideration. The. FDEM-GBM can provide an efficient way to simulate grain breakage and insights into the propagation of grain-scale microcracks, which can elucidate the relationship between the evolution of the UTS and the failure mechanisms of crystalline rocks
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
