Mine Pressure Behavior During The Combined Mining Of Thin Coal Seams In Close Distance In Baoxin Coal Mine

Based on the project background of close distance thin coal seams in Lanhua Baoxin coal mine, the ground pressure rule of combined mining with thin coal seams was studied through field research, theory analysis, numerical simulation and in situ measurement. The mechanical model of mine pressure behavior in combined mining with thin coal seams was builded up, and the ground pressure rules of No.2101 and No.3101 working faces were forecasted. The concept of dynamic and reasonable distance in combined mining was offered. The ground pressure rule of No.3101 working face was analysed by field measurement. The arrangement form and location of roadways in 2101 and 3101 working face were ensured.The supporting mechanics, supporting scheme and parameters of roadways in No. 2 and No.3 coal seams were offered in the thesis based on the background of Lanhua Baoxin coal mine. The main research work and result were shown as follows:(1) The background of Lanhua Baoxin coal mine was analysed, and the based conditions of combined mining between No.2 and No.3 coal seams was affirmed. The mechanical model of mine pressure behavior in combined mining with thin coal seams was builded up, and the ground pressure rules of No.2101 and No.3101 working faces were forecasted.(2) The computing method of reasonable distance between working faces during the combined mining was offered, and rhe results shown that the reasonable distance relates to the coal seam thickness, coal body strength, roof and floor characters, and mining strength. When there were more coal seams or coal mining slicing, the reasonable distance would be changing along with the strata moving angle.(3) The numerical simulation results showed that, the working face in No.3 coal seam had influenced the working face and goaf in No.2 coal seam. The incorporate shows that, the goaf floor of working face in No.2 coal seam sinked, and the arrangement area of vertical stress were increased, so as the vertical displacement of surrounding rock. The pressure behaviour of combined mining was more than single coal seam mining, even the plastical distribution was increased not very much.(4) The difference of overlying rock moving rules between combined mining and single coal seam mining was verify in further during the physical simulation research. The final caving form of overlying rock in combined mining was similar to the overlap of two trapezoid goafs, and the strata moving angle of botoom goaf in No.3 coal seam was smaller than the upper one in the No.2 coal seam.(5) During the research work, the mining method, main equipment and parameters of combined mining between close distance and thin coal seams were ensured, based on the producing conditions of coal mine. The insitu observed result shown that, during the mining of 3101 working face in No.3 coal seam, the influence range of bearing stress ahead was further than 40 m. However, the height of bearing stress was not very big because of the great strength of strata between No. 2 and No.3 coal seams. The height of stress influence range was almost 4 m when the test point were 40 m away from working face, which was good to the application of combined mining.(6) The measurement method of ground pressure was confirmed. After a large number of measurement data of hydraulic supports, the the first time pressure step was 21.4 m, when the periodic weighting step was 10.4 m. The character of No.3101 working face was similar with theoretical analysis, such as the periodic weighting is out of sync, the press in left is bigger than right hand, middle part is bigger than two sides, and so on.(7) During the thesis research, the characters of surrounding rock in tunnelling roadways was grasped through drill coring and lab test on mechanical parameters in No. 2 and No.3 coal seam and roof strata. The results were shown that, the roof strata of coal seams were very hard, plentiful jointing, strength anisotropy and great compressive strength in vertical joint direction. In result, the roof strata of coal seams were general stable.(8) During the research work, the store condition of No. 2 and No.3 coal seams, the production capacity, and the mining intensity were considered overall. The arrangement form and location of roadways in 2101 and 3101 working face were ensured.The supporting mechanics, supporting scheme and parameters of roadways in No. 2 and No.3 coal seams were offered in the thesis based on the background of Lanhua Baoxin coal mine.The results of this study have great guiding significance on pressure controlling in Lanhua Baoxin coal mine, and have reference value to similar conditions as close distance thin coal seams mining. In the beginning of 2015, the combined mining method of close thin coal seams in Lanhua Baoxin coal mine was tested through practice, and the application result was very well. The coal mine contribution was completion acceptance, which shown that the research work in this thesis was truthfulness, workable, and in theory and practice.