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Chai J.,Xian University of Science and Technology | Chai J.,Key Laboratory of Western Mine Exploitation and Hazard Prevention | Qiu B.,Xian University of Science and Technology | Qiu B.,West Virginia University | And 3 more authors.
Caikuang yu Anquan Gongcheng Xuebao/Journal of Mining and Safety Engineering | Year: 2012

To explore the rock deformation in coal mine by the monitoring of embedded fiber Bragg grating (FBG) through deep borehole, an experimental physical simulation model was built for simulating the strata compression and subsidence process. Additionally, a prefabricate concrete bar with three embedded FBG sensors was designed to simulate deep borehole, and was placed in the physical model. The deformation of the prefabricate concrete bar during strata compression and subsidence processes was measured by the wavelength changes of FBG sensors, and was compared to the strain changes monitored by a resistance strain gauge located on the prefabricate concrete bar at the same location. The test results show that the FBG monitoring system has the advantages of high sensitive, reliable and stable, etc, and can realize the real-time monitoring of rock deformation. It is proved that the FBG monitoring system is an efficient method for measuring and understanding deformation of deep rock strata through a surface borehole. Source


Chai J.,Xian University of Science and Technology | Chai J.,Key Laboratory of Western Mine Exploitation and Hazard Prevention | Liu J.-X.,Xian University of Science and Technology | Qiu B.,Xian University of Science and Technology | And 8 more authors.
Tunnelling and Underground Space Technology | Year: 2011

Coalfields based in east China, such as Huaibei, Datun, Xuzhou, Yanzhou, Yongxia and Huainan, have suffered paroxysmal shaft lining fracture and repeated deformation after repair in the last three decades. This phenomenon has required the development of fractured shaft lining repairing technology and a method for detecting rock strata settlement. It is proposed in this paper that, with the method of fiber Bragg grating sensor incorporated into GFRP, a sensing network of fiber Bragg grating wavelength division multiplexing (WDM)/spatial division multiplexing (SDM) mixing array composed of 18 fiber gratings is formed, and it is used for monitoring the settlement of uncompacted hydrous strata. It is the first time that the fiber Bragg grating sensing system is embedded into the 180-m deep uncompacted strata, and the field experiments are conducted at No. 3 Jingning Coal Mine. The layout of optical sensors, the fiber Bragg grating detecting system, the drilling of the borehole and the embedding method of fiber Bragg grating sensors are introduced. The monitoring results of fiber Bragg grating sensors are compared with groundwater level monitoring results. Engineering practice shows that the fiber Bragg grating sensors are working normally and they can be used to detect strain safely and stably. © 2010. Source


Chai J.,Xian University of Science and Technology | Chai J.,Key Laboratory of Western Mine Exploitation and Hazard Prevention | Zhao W.-H.,Xian University of Science and Technology | Zhao W.-H.,Ningxia Coal Mining Company | And 4 more authors.
Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and Technology | Year: 2012

A fiber Bragg grating (FBG) bolt monitoring system was designed and tested to provide long term, continuous monitoring of stresses in the bolt. Stresses that exist in a coal mine tunnel were simulated in the laboratory using a Φ18 metal bolt and a pull out load of 76.44 kN. Three FBG sensors were installed along the bolt to measure strain. An additional sensor was installed at the end of the bolt to monitor the axial stress in the bolt. Three resistance strain gauges were also installed adjacent to the FBG sensors for comparison. The axial stresses and strains were recorded during a pull out test and subsequently analyzed. The results show that axial stresses measured by the FBG sensor at the end of the rod are consistent with both the resistance strain gauges and the other three FBG sensors. The strain transfer function for the FBG sensors along the bolt is 0.879. The FBG sensor is easily installed at the end of the bolt and is reusable. This provides a maintenance advantage. This test method is reliable and effective for real time monitoring of bolts. Source


Deng J.,Xian University of Science and Technology | Deng J.,Key Laboratory of Western Mine Exploitation and Hazard Prevention | Xiao Y.,Xian University of Science and Technology | Xiao Y.,Key Laboratory of Western Mine Exploitation and Hazard Prevention | And 4 more authors.
Fuel | Year: 2015

To study the spontaneous combustion and anaerobic cooling of coal, a 15-t experimental furnace was constructed, and large-scale spontaneous combustion tests were conducted. The coal sample came from No. 3 seam in Dongtan mine in Yanzhou coalfield, Shandong province, China. The variations in temperature, gas ratios, oxygen consumption rate, and heat intensity were studied. The experimental results show that for coal spontaneous combustion below 70 °C, the temperature increases slowly with time and the oxygen consumption rate and heat intensity increase slowly with temperature and accelerate when the temperature exceeds 100 °C. In anaerobic cooling, the cooling rate decreases with the decrease in temperature. When the coal temperature goes from 452.7 to 250.0 °C, the cooling rate decreases rapidly, whereas below 250.0 °C, the cooling rate decreases slowly. The variation trends of the CO2/CO, CH4/C2H6, C2H4/C2H6, and C3H8/C2H6 gas ratios in the spontaneous combustion and anaerobic cooling of coal in a certain range of temperature can be used to predict the temperature of coal. © 2015 Published by Elsevier Ltd. Source


Cheng L.-H.,Xian University of Science and Technology | Cheng L.-H.,Key Laboratory of Western Mine Exploitation and Hazard Prevention | Li S.-G.,Xian University of Science and Technology | Li S.-G.,Key Laboratory of Western Mine Exploitation and Hazard Prevention | And 2 more authors.
Procedia Engineering | Year: 2011

Rationality of assessment index system plays an important role for emergency capability in the coal mine. Combined with the existing results, the primary assessment index system including eight first-level indexes for emergency capability was established based on analysis of influence factor. It was tested with structure equation model (SEM for short) based on some questionnaires and Amos software. And six first-level indexes were determined. The result shows that the assessment index system for emergency capability in the coal mine is objective by structure equation model. © 2011 Published by Elsevier Ltd. Source

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