Using distinct element method to analyze fracture propagation behaviors of artificial rock
Date Issued
2010
Date
2010
Author(s)
Huang, Pai-Chin
Abstract
The fracture propagation behavior plays an important role in material cracking. When compressed by external forces, stress concentration usually occurs near the pre-exist cracks. As concentration stress exceeds the strength of the material, local failure near the cracks can induce further extensions and development of the cracks, which could subsequently induce global failure. Due to the strong orogeny, the rock mass in Taiwan is plenty of discontinuities. The discontinuities, which are perceived as the pre-existing cracks in rock mass, can affect the strength of the rock mass. In this research, the pattern of fracture propagation behaviors of artificial rocks with pre-existing cracks under biaxial loading was discussed base on numerical analysis of data collected from lab simulation.
The numerical simulation is executed by the distinct element method (DEM) based software, Particle Flow Code 2D (PFC2D). DEM was preferred to continuous system analysis in simulating the fracture behaviors since the former possesses the advantage of particle separation.
In order to acquire the parameters for PFC2D simulating and verification the PFC2D results, artificial rocks are made to apply the uni-axial compression test, the Brazilian disk test and the Central through Cracked Brazilian Disc test(CCBD). When the verification completed, the parameter is applied in the simulation of the fracture propagation behaviors of pre-existing crack artificial rock sample under biaxial loading. The effect of lateral stress and geometry of pre-existing cracks was discussed. According to the simulation results, the lateral stress caused a great influence on fracture propagation behaviors. The following phenomena were found under high lateral stress level:
1. The development of wing crack was restrained.
2. The direction of secondary crack was veered. The new direction was between the direction of the pre-existing crack and the direction of the wing crack under lower stress level.
3. If the lateral stress were half as large as the uni-axial compression strength, the fracture propagation behaviors along the pre-existing crack was not obvious. The broken zone was bounded in the horizontal direction of the pre-existing cracks.
4. The fracture propagation behavior was not obvious under higher lateral stress level. The broken area was concentrated near the pre-exist cracks and formed broad fracture lines.
Subjects
fracture propagation
fracture coalescence
DEM
biaxial loading
artificial rocks
Type
thesis
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