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- 저자 : Guangan Zhu (검색결과 2 건)
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Changbin Wang,Anye Cao,Guangan Zhu,Guangcheng Jing,Jing Li,Tian Chen 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.3
Rock burst hazards induced by fault slip frequently occur in underground mining and threaten the safety of miners. In this paper, the structures of overlying strata, mechanism of fault slip, and rock burst pre-warning using seismic tomography were investigated in LW7192, a specific island longwall panel in Xuzhuang Colliery. The results show that an asymmetrical “T” structure of overlying strata is formed during LW7192 retreat, and the long hanging length of overlying key strata is maintained due to the short panel width. By analysing a modified fault sliding model, it is found that the time interval between two fault slips has a positive correlation with the energy released therein. The rock burst that occurred in LW7192 has the longest time interval between events compared with other high-energy tremors near the fault, and enormous elastic energies released by fault slip as a form of dynamic load. The superposition of dynamic loads and high stress concentration of the coal-rock mass contributes to the rock burst in LW7192. For forecasting rock burst hazards, seismic tomography was used and the results show that the velocity anomaly regions correspond well with the area of both strong tremors and the rock burst. Ultimately, large-diameter boreholes, directional hydraulic fracturing boreholes, and floor distressing boreholes were taken in the rock burst area, and the pressure relief is proved effective by seismic tomography assessment.
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Passive velocity tomography for mudstone under uniaxial compression using acoustic emission
Anye Cao,Changbin Wang,Guangcheng Jing,Wu Cai,Guangan Zhu,Jing Li 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.1
A passive velocity tomography method using acoustic emission (AE) was used to study characteristics of AE responses and velocity redistributions in mudstone during uniaxial deformation. Two standard cylindrical samples were uniaxially deformed until failure with axial loading rates of 1.00 × 10–3 mm/s and 2.50 × 10–3 mm/s, respectively. AE activities were monitored using eight sensors and every 100 consecutive AE events were used for tomography calculations. For each sample, three typical tomography results were obtained which reflected significant variation of velocity redistributions. From the experimental data, it can be concluded that the stress drop point observed in the stress-strain curves with high energies and AE events indicated coalescence of micro-cracks and formation of the main shear plane. In the initial tomography phase, the velocity difference was low and few AE events were detected. As loading increased, AE events clustered and velocity differences became obvious with high velocities being mainly located near the sample boundary, whereas low velocities begun to propagate from the bottom corner to the core. When approaching failure, velocity anomaly regions further expanded and low velocity regions interconnected with the position being consistent with macro-fractures in the post-failure samples. The positions of the AE events with large energies over 50 μV·s were found to correlate well with high velocity regions in the tomography results whose calculation phase was conducted prior to the occurrence of large energy AE events. This method can be used for the prediction of large energy AE events in rocks under unconfined pressures.
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