Research On The Gas Migration Mechanism Of Steep Thick Seam In Fully Mechanized Top-coal Caving

There are plentiful coal resources in our country, and the problems from gas hazards alsotook place frequently. The reserves of steep coal seam in Urumqi Xinjiang mining areaoccupy more than a quarter of the total of China’s steep seam. The occurrence conditions,coal seam structure and the stress environment are different from the other types of coal seam.In the process of the fully-mechanized caving mining, the gas migration mechanism of theworking face and goaf are more complicated than the other condition of coal seam. Theamount of gas gushed from the working face resulted in gas overrun frequently, especially onthe upper corner of working face. That brings about a serious threat on the safety of workingface and efficient production. In addition, due to the uneven distribution of gas, the explosionaccidents would happen easily and result in heavy casualties and huge economic losses.Therefore, the research on gas migration mechanism in the process of coal mining has animportant scientific significance and economic value.Papers mainly research on the gas migration mechanism of steep thick seam in fullymechanized top-coal caving. On the basis of summarizing the predecessors’ research results,and we systematic investigate the production technology conditions of the Wudong coal mine,the geological characteristics of coal seam and the mechanism to cause disasters. At the sametime, using the theory analysis, the physical simulation experiments, the numerical calculationand other technical methods, we researched on the gas migration mechanism of steep thickseam in fully mechanized top-coal caving. In addition, combined with locate productionpractice, we improved technical conditions of mining and guaranteed the safety and efficiencyof mining. The main contents and conclusions are summarized as follows:With the45#coal seam of+620level of the Wudong mine as the example, we built astope model on a similar scale of1:100and did the physical simulation experiments in the laboratory. Experiments show that the gas concentration in the condition of water flooding ishigher than not under the condition of water injection. Besides, on the stage of the top-coalcaving, the increasing trend and the rate of gas concentration in the condition of waterflooding is more obvious under the condition of less water injection. On the stage of the roofcaving, gas concentration in the condition of water flooding and less water injection appearreduce in gradient type.Combined with locate working face’s parameters of45#coal seam, we established thecorresponding physical model and carried out the numerical simulation experiments. Theexperiments show that the gas concentration is increasing from working face to deep goaf inthe goaf towards direction. On the tilt direction, the gas concentration is increasing from thedown corner to the upper corner. It needs to be taken out because the gas concentration of theupper corner exceeded standard. Meanwhile, the gas concentration shows a trend of increasefrom goaf floor to the old roof in the vertical direction.Aimed at the realistic problems of the45#coal seam of+620level, we had carried on theapplication of geological radar detection technology, and taken the optimized design of theventilation system and the gas drainage practices. The results show that the productionconditions and the production efficiency of the45#coal seam of+620level are improved afterthe ventilation system optimization and implementation of gas pre-drainage engineering.