Abstract
In this study, the continuum-discontinuum element method (CDEM) was used to investigate the tensile fracture mechanism of rock materials. An isotropic rock disk model and models considering different foliation inclinations were established, and three schemes were used to simulate the rock fracturing in Brazilian test. Then, the influences of the rock matrix and foliation strengths on anisotropy rock fracturing were investigated. Furtherly, simulation results were verified, and the rock fracture mechanisms were discussed. The results show that the rock fracturing in Brazilian test can be accurately simulated by CDEM, which is in accordance with the experimental results. For isotropic and horizontal foliation rock, the stress concentration in loading positions causes a local fracture of rock sample, and application of a local strengthening scheme can simulate the integral tension fracture of sample middle. As the foliation angle varies from 15° to 45°, the rock fracturing is affected by the stress concentration and foliation distribution. In splitting simulation, a strengthening scheme should be adopted to overcome this influence. As a result, the rock sample generates the sliding and compression-shear fracture. As the foliation angle changes from 45° to 75°, the foliation, rather than the matrix, dominates the fracture behavior of rock sample. For vertical foliations’ rock, as the middle foliation thickness is appropriately broadened, the simulation results are reasonable. In general, the tensile strength of anisotropic rock entirely decreases with an increase of foliation angle, and the effect of foliation strength on the tensile strength rock sample is larger than that of the rock matrix.
Highlights
Because the fracture resistance of rock material is weaker under tension than under compression, so the investigation of rock tensile fracturing is important. e Brazilian disk testing method is usually used to obtain the tensile strength of rock material [1,2,3]
During the stiff wire loading, the stress concentration near the loading positions causes a local failure of rock sample as shown in model I, and the tensile strength obtained by Brazilian test is smaller than the actual tension strength of rock materials
For the fracturing simulation of anisotropic rock in the Brazilian test, the splitting process of horizontal foliation rock can be well simulated by a strengthening scheme. e strengthening scheme is suitable for investigating the fracturing of rock samples with the smaller foliation angle; simulations without a strengthening scheme are more suitable for investigating the fracturing of rock samples with the larger foliation angle
Summary
Because the fracture resistance of rock material is weaker under tension than under compression, so the investigation of rock tensile fracturing is important. e Brazilian disk testing method is usually used to obtain the tensile strength of rock material [1,2,3]. E Brazilian disk testing method is usually used to obtain the tensile strength of rock material [1,2,3] Rock anisotropy such as fissuring, jointing, and foliation are the important factors in studying the situ stress measurements, displacement control in rock, and excavation damage development. Due to the interaction of intact rock fracture and joint face sliding, the failure mechanism of rock mass has been discussed by certain studies using the discrete element method (DEM) [17, 18]. E failure characteristics of phyllite specimens under Brazilian tests are investigated by the particle discrete element method, and the influence of rock foliation strength and matrix microstructure was studied numerically [21]. A continuum-discontinuum element method (CDEM) combines the advantages of the finite element method and the discrete element method, which has gradually become an effective simulation method to study the failure mechanisms of rock materials [27,28,29,30,31,32,33]
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