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The mechanical properties of a bolting system under cyclic loading were investigated experimentally by pullout tests. Bolts of different diameters were inserted into steel tubes and bonded together by resin or cement to prepare simulated bolting systems for further pullout tests. Uniaxial compression tests showed that cement has a comparatively higher stiffness and peak stress compared with resin...
In order to reveal the stress precursors of the “3.15” rockburst disaster that occurred in the No. 1 working face of Junde coal mine, the combined stress field inversion including static and dynamic stresses was conducted by using P-wave velocity tomography, and the static high-stress concentration regions were further designated. Simultaneously, the evolution of dynamic stress generated by seven...
•Before rockburst, the sudden rise of MS energy and the lower level of event count.•When rockburst, peak value of fault total area, the lower b value, and |Z|>2.•When rockburst, the largest energy ratio in the dominant low-frequency band.•Before rockburst, abnormal cluster of sources and high-energy events congregation.•Prior to rockburst, the sudden drop of EME amplitude indicating macro-fracture.
The mechanism of epoxy-bonded anchor system (EBAS) has been studied by many researchers in the past several decades with different models. However its long-term performance is seldom mentioned and characterized in the literature, which has led to the fatal accident in the Ted Williams Tunnel, Boston in July 2006. This paper suggests a theoretical model to characterize the long-term performance of...
Strong rockburst disaster in deep coal mines is easily triggered by the higher static stress of mining coal seam and the dynamic stress wave disturbance generated by hard and thick roof fall. Revealing the frequency-spectrum evolutionary rule of microseismic (MS) signals before and after roof fall is a very important issue for evaluating and forecasting rockburst danger. By experimental tests for...
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