Papers by Author: Zhe Ming Zhu

Abstract: Coal usually contains many cracks which affect the stability of mining zone. In order to research the fracture mechanism of cracked coal, a special case of three collinear cracks filling with gas is considered. A set of complex stress functions which satisfy all the required conditions are first derived, based on Muskelishvili’s results. The least square boundary collocation method is used to enforce the external boundaries approximately, and the stress intensity factors (SIF) can then be computed according to the related formulae. The value of SIFs for different crack orientations, different crack distance under different loading are calculated. The results shows that the most unfavorable crack orientation is in the 45° angle and the confining stress and the distance between cracks have a considerable effect on the SIF value.

Abstract: Rock bursts are a main geologic hazard in underground engineering processes, such as mining engineering and tunnel excavation, so it has become an important subject for many researchers and engineers. Photoelasticity, which is a nondestructive, whole-field and graphic stress-analysis experimental technique, is widely used for 2-D and 3-D analysis for getting the information of principal stress difference and principal stress direction of samples. In this paper, the effect of the position and orientation of cracks, which is situating inside the surrounding rock mass of a tunnel, on stress intensity factor (SIF) is analyzed. The results show that crack orientations and the load conditions of tunnel affect stress intensity factors significantly.

Abstract: In order to investigate the effect of defects on rock fracturing under dynamic loads, blasting experiments using PMMA specimens with pre-existing defects were conducted. The defects include holes, pores and small open joints, etc., and they are randomly distributed. In order to verify the experimental results, numerical simulation was implemented. It is shown that under blasting loads, most cracks initiate at pre-existing defect tips, and near free boundary, many cracks developed near defect tips are parallel the free boundary. The numerical results qualitatively agree with experimental results

Abstract: In order to extract the mineral resources existing at great depths, the mining industry is facing new serious challenges to safe and productive mine operation, and such challenges arise largely as a result of the high pressures imposed on deep mine excavations. In order to investigate the effect of confinement on rock fracturing under dynamic loads, blasting experiments by using cement mortar plates, which are square with a single centralized borehole, have been carried out. Two kinds of confinement, i.e. uniaxial and biaxial, are applied to the square plates. In the study of defect effect, circular cement mortar plates with randomly distributed defects are employed, the results show that confinement and defects affect rock fracturing significantly.