| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 96 === Taiwan terrain, located at the convergence belt between the Eurasian plate and Pacific plate, has smashed body and many faults overspreading its surface. With the incensement of space required, based on the fact that the tendency living near the fault or surface fracture becomes more popular and the disasters induced from the cracks, extending bring more catastrophic lost in the historic seismic records, it is the more and more important subjects of crack extending for human society today . It can not only be useful for the fault research but also support the cited plans or geotechnical engineering reference for designing, due to aim to reducing the calamity happening and promoting life.
The main fracture spacing distribution studied in this thesis is orthogonal to the body surface, and this research will simplify the three-dimension problem to the two-dimension one basically. The three tools will be applied to examine the behavior for fracture propagation, including physical experiments applying Fracture mechanics, digital image analysis and numerical simulation(Particle Flow Code, PFC2D). It focus on the several phenomenon list as: the fracture propagation, traditional fracture classification, relationship between the different dip angle defined by this study and Fracture toughness, the influence of pre-cracked length to the fracture development, and the investigation for surface displacement field.
As initial experiments showing, the CSTBD tests with variant dip angle will have the diverse fracture prorogations, similar with the former research, compensating the deficit part and the proving the fracture-mode transition. We also execute the single compassed rectangle sample to compare the influence of crack length and dip angle. Owning to the physical test, the crack mode for the dip angle, 30 degree, reveal the mixed mode I-II, but more belong to mode I. On the other hand, the crack mode for the dip angle, 45°degree, more agree with the mixed mode I-II, meaning that the crack tension and shear will appear together. The digital image correlation analysis, with the help through PIV, also adequately show the crack entrenching and spreading during the crack happening. We also observe and compare the rotation-concentrating characteristics with the DIC result during crack formulation and propagation, and we get the similar properties to attest to the applicability for the crack investigation using PIV tool.
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