The Floor Water Bursting Machnism Analysis Of Floor Water Bursting In Coal Mines And Research On Floor Water Bursting Monitoring Technique

The carboniferous and Permian coal field is a important coal field in china .The substrate coal bed is on the top of the Ordovician and carboniferous limestone aquifers .the a quatard between the aquifer and the coal is about 30-60meters thick .So floor water bursting occurs usually.The floor water bursting is a geology hazard in coal mines in the east of china .But the water bursting can be predicted ,because the physical mechanism of water bursting can be studied . So the research on the water bursting mechanism and forecasting technique become the key technique of coal mining on top of the high pressure aquifer . In the dissertation the water bursting mechanism, water bursting theory and predicting technique are researched .In the first part of the dissertation, the rock -hydraulic experiment is devised according to water bursting essence, and the stress-permeability under triaxial compression is studied , which indicates that the permeability coefficient is inversely proportional to the virtual direct stress ,and the permeability coefficient changes suddenly on some conditions .The phenomenon is explained according to the fracture mechanism ,which indicates the rock crevice stretches and spreads under the rock stress and hydraulic pressure .So the rock crevice permeability increases suddenly .The shearing spreading along the crevice which destruct the microstucture and increase the permeability is subordinate .It is pointed that analyzing the floor water bursting according to the fracture mechanism is adaptable when the geology condition and the fracture mechanic criterion of water bursting is decided .The influence of the tectonic stress field .engineering stress and groundwater to the crevice stress intensity factors are analyzed. The phenomenon of the lagging water bursting is explained applying crevice inferior critical spreading .The mechanic capability of the crevice clay filling falls because the physiology and chemistry of the groundwater,which lags the crevice spreading and leads to the lagging floor water bursting.On the basis of explaining hydraulic fracture technique applying fracture mechanics theory ,the computation equation of the critical stress intensity factor is deduced .So the testing method is obtained according to the theory, which lay a foundation of theory and experiments for distinguishing water bursting applying fracture theory.The Kirchhoff and Reissner board bending fracture theory is introduced in the dissertation .The board endure transverse load ,which produce inner and outer displacement .The stress and strain in the board changes in the direction of thickness .Not only the board transverse shearing distortion but also the thickness is considered in Reissner board bending fracture theory .So Reissner theory is adapted to simulate the mining face floor .the computation of the crevice stress intensity factor is studied. The influence of the board width ,thickness and sustaining condition to the stress intensity factor is analyzed by ordinary model computation .the computation indicates the board thickness ,water pressure exert a tremendous influence to the stress intensity factor. In the second part of the dissertation, the delimiting method of the stope width mining on high pressure aquifer is decided for the example of 9103 stope in Dong Pang Coal Mine .The critical stress intensity factor is tested applying the hydraulic fracture technique .The technique of monitoring face floor water bursting indications is researched on the basis of studying the practical hydrogeology and engineering geology condition .The 9103 stope is monitored for 21 days .The monitoring data is analyzed applying the Reissner board bending fracture theory ,and the floor stress intensity factor is computed .Applying the floor water bursting criterion of fracture mechanics , it is concluded that the stope water bursting will not arise .The mining practice of the stope proves the conclusion right.