In the mining process of high gas mining area, the gas emission from goaf is large, which leads to the gas overrun in the upper corner of the working face, and affects the safe mining of the mine. This paper studies the differential drainage of the upper corner gas by high-level directional long borehole, and then solves the problem of gas control in the upper corner. Taking a fully mechanized mining face as the research object, this paper analyzes the theoretical parameters of the overlying strata failure of the working face, and according to the production practice, the high position directional long drilling layer is arranged differently, and the influence of high position directional drilling on gas drainage effect in different layers is analyzed, and the best location in different distance and height area is obtained to guide the actual production work. The research results show that the differential drainage method of high position directional long borehole can effectively control the gas overrun in upper corner of fully mechanized mining face in thick coal seam.
To prevent coal mine water disasters, the main objective of this study is to predict the water enrichment of the main aquifer in a coal mine of China that has been threatened by water inrush. The prediction is carried out using a geographic information system (GIS) and a coupled analytic hierarchy process (AHP) and entropy model. The flushing fluid consumption, burnt rock distribution, sand–shale ratio, and lithology structure index were determined as the main factors controlling the water enrichment of the aquifer. A thematic map of these main factors was constructed using the spatial data analysis functions of GIS and the data from a total of 146 drilling columns and field investigation. The weights of these controlling factors were calculated using the coupled model. A prediction map of the water enrichment of the aquifer was then developed by overlaying the thematic map with the weights of each controlling factor. The degree of water enrichment was finally divided into four levels for easy interpretation, where Level I denotes the highest water enrichment and poses the greatest threat of water disaster.
Abstract:In the light of more and more urgent hidden fire abnormal detection problem in complex conditions of mine, a method which is used directional drilling technology is put forward. The method can avoid the obstacles in mine, and complete the fire abnormal detection. This paper based on analyzing the trajectory control of directional drilling, measurement while drilling and the characteristic of open branch process, the project of the directional drilling is formulated combination with a complex condition mine, and the detection of fire abnormal is implemented. This method can provide technical support for fire prevention, which also can provide a new way for fire anomaly detection in the similar mine.
Based on the problem of large gas emission and serious gas accumulation in upper corner of the intensive fully mechanized caving face, taking the fully mechanized caving face of Wangjialing Coal Mine in Hedong Mine as the research object, the main gas emission sources of the extremely intensive mining face with low permeability and low gas content were studied. The methods of gas extraction by inserting (burying) pipe in upper corner and directional drilling in upper corner were adopted and carried out. The application of engineering practice and comparative test of effect are carried out. The results show that the maximum extraction purity is 2.8 m³/min, the maximum gas concentration is 0.8% in upper corner, 3.11 m³/min in the high directional borehole and 0.71% in upper corner. After combined extraction, the total extraction purity is 1.33~7.93 m³/min and the fluctuation range of gas concentration in upper corner is reduced to 0.31~0.61% safe point. The effect of gas prevention and control in working face is remarkable.
Underground directional drilling is an important technique to prevent and control water disasters in coalmines. However, the drilling efficiency is generally low in hard rocks, and the conventional hydraulic impactor is not applicable to underground directional drilling.To solve these problems, this paper designs a flexible impact positive displacement motor (PDM) control system, and specified the calculation methods for the relevant hydraulic parameters. Specifically, the hydraulic oscillator and conventional PDM were combined into a PDM with axial impact function. Then, the rolling-in method was introduced to determine the motion law of the disc valve, and compute the time variation of the flow area. The calculation methods were developed for the hydraulic parameters of flexible impact PDM, and adopted to compute the hydraulic parameters of Ф95mm PDM. During the calculation of the axial impact force, the fluctuating pressure difference was preset as per the pump capacity, and the multi-stage piston design was employed to produce a high axial impact force under a small pressure difference; the orifice parameters were calculated based on the fluctuating pressure difference; the impact frequency was derived from mud pump displacement, and the rotation speed and revolution-rotation speed ratio of the rotor. The results show that, when the displacement is 6.5L/s (the normal displacement underground the coalmines), the impact frequency is 12.5Hz, the fluctuating pressure difference is 1.54MPa, the impact force is 15.54kN, the inner diameter of the piston is 35mm, the outer diameter of the piston is 75mm, the offset distance of the disc valve is 4.5mm, and the orifice radius is 9.2m. The calculated results deviated from the prediction of backpropagation neural network (BPNN) by less than 5%, indicating that the structure of the proposed flexible impact PDM is feasible, and that the hydraulic parameters are calculated simply and accurately. To sum up, this research designs a PDM that can theoretically improve the rock-breaking efficiency in hard stratum, providing an important reference for similar research.
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