| Some problems, such as the evolvement and fracture pattern of initiation, propagation and coalescence from some primary flaw in rock mass, and the influence on rock strength and seepage property, are always focused by the researchers of geology field, rock mechanics and other corresponding fields. Owing to the complexion of three-dimensional (3D) fractured rock mass, the engineering problems often is simplified to two-dimensional (3D) models in most of the previous studies. But, much 3D fracture information is fully reflected in the simple 2D model. So, recently, some researchers start to focus on the fracture mechanisms and properties of 3D fractured rock mass. These jobs are very important, directive and practical to the design, construction and stability of fractured rock mass, also theoretically significant to earthquake geology science and earth physics fields.Make two brittle materials based on some previous studies. One is a transparent frozen resin, a new type mean material, it's ratio of compressive and tensile strength is about 5; another is a new rock-like material, its components are cement and good sand, the ratio of compressive and tensile strength is up to 23.The flaw effect, dimension effect and basic facture pattern during rock failure is analyzed, first. Several new crack patterns are defined, such as wing crack, anti-wing crack, wrapping wing crack and shell-shaped crack. Then, a series of experiments on the growth and coalescence of 3D flaw in different brittle materials are carried out. The experiments in mean material show that: the wrapping crack is an important pattern for the growth and coalescence 3D flaw; some new growth cracks are observed in the experiments, such as cross crack and petal crack. The cross crack is induced from tensile and tearing stress along the boundary of the flaw plane, it belongs to a mixed mode fracture of Mode I and Moded III. The petal crack is induced from the pure tearing stress, is a fracture of Mode III. The commence of the two types of cracks makes the stress states more complicated near the flaw boundary, and mostly can not be expressed with math equations. For the non-transparent materials, the wrapping wing crack also is observed after splitting the samples. This type of crack belongs to a fully mixed fracture of Mode I, Mode II and Mode III. But, other types of cracks are not observed, directly. Although the internal cracks patterns can not be seen, the flaw configuration in rock mass may be deduced according to the output crack lines on the surface of samples (rock mass), and provide a conference information for the engineering bolted design.For the further study of the fracture of 3D flaw, the acoustic emission (AE) located technique is studied the growth pattern of 3D flaw and AE properties under uniaxial compression, and provide a method to confirm the different stages (initiation, propagation and coalescence) according to the AE properties during the flaw fracture. Then, the strength influence from the spacing and density of 3D flaw are analyzed. For the fractures of surface flaw, the depth ratio d/t (d, flaw depth; t, sample thickness) of the flaw plays an important role on the pattern and growth process of the 3D surface flaw. As d/t<0.6, the facture pattern of 3D surface flaw is very different from 2D through flaw, anti-wing crack is main fracture pattern of surface flaw, wing crack is primary for d/t>0.6. And the same phenomena also are recorded in sandstone and gabbro samples. The results from AE location further supports the new fracture pattern and shows that the anti-wing crack starts to grow within the sample. Furthermorem, the inclined angle of the flaw will main influence the initiation stress of crack.Based on the classical rock fracture theory and elastic theory, the maximum tensile stress flaw is revised. The stress state of any point along the flaw boundary is deduced during uniaxial compression, according to the full mixed fracture mode (Mode I-II-III). The results from the theoretical analysis shows that: the main initiation fracture emerges within a zone near the end tips of the long axis of the flaw, not limited to the tips, the crack almost synchronously initiated in the zone. The bend angle of main crack is very big, the wring angle is small, but not equal to zero. The secondary cracks also synchronously initiated in the middle of the flaw boundary line. At the end tips of the short axis of the flaw, the secondary crack planes only have a bend angles, the wring angle is equal to zero. The results from the above revised maximum tensile stress flaw are the same as that of experiments.The full growth process of 3D flaw is simulated with volume element method with FISH programs in FLAC3D software. The simulation results show that: 2D mode will lose much 3D growth information of cracks, such as the wring action of the crack plane, and the 3D coalescence pattern of cracks. The simulation results provide a new method to further study 3D flaw fracture, and make up some faults of the experimental results.
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