Research On The Structure And Support Load Analysis Of Full-mechanized Mining Face In Close Distance Coal Seam Under Goaf

The distance coal seam is widely distributed in our country, but most of them are difficult to mining. The reserves of most of superior mine seam conditions and the service life of mine are decrease with the popularization and application of the fully mechanized mining equipment and the technique of caving coal and high production and efficient large mining height technology. Thus, the mining problem of distance coal seam is urgently necessary to solve and it has been highly emphasized.The mutual influence of adjacent coal seam mining is increase with the interlayer distance of coal decrease. The roof complete degree of lower coal seam has been damage influenced by the mining of upper coal seam before it is be mined when the adjacent distance of coal decrease to certain extent, which lead to the change of roof structure and stress environment in lower coal seam. The mining of lower coal seam must induce a lot of new underground pressure behavior such as the accident of roof emitting and leakage and support pressure comparing with the mining of single seam. But the achievements of mining of close distance coal seam under goaf are very few in world. So the problem of close distance coal seam mining must be research to maintain high production and efficient development of mining area.The existing achievements of mining of close distance coal seam under goaf are about the analysis of mining face pressure behavior law in lower coal seam mining, the reasonable roadway location choice of lower coal seam to avoid concentration stress of pillar and the control of surrounding rock. There is still no a system research on the structure and support load of full-mechanized mining face in close distance coal seam under goaf leading to the difficulty of maintain mining face, the alternation of extraction and the lose of coal.Regarding the mining of close distance coal seam under goaf as research object, the article do a system research on the structure of cover rock, caving characteristics, the load-bearing characteristics and determination of the reasonable load support of full-mechanized working face in close distance coal seam under goaf through the theoretical analysis, UDEC numerical simulation,field observation and so on. Research contents are as follows:(1) According to bearing overlying strata, the overlying strata, which is on the full-mechanized working face in close distance coal seam under goaf, is divided into four kinds of structure forms through the theoretical analysis and UDEC numerical simulation:one kind of structure form is composed by the immediate roof rock and caving zone of rock; one kind of structure form is composed by the immediate roof rock, caving zone of rock and fracture rock; one kind of structure form is composed by the immediate roof rock, basic roof and caving zone of rock; one kind of structure form is composed by the immediate roof rock, basic roof and caving zone of rock and fracture rock. In addition to, the caving characteristics and the load-bearing characteristics of these four kinds of structure forms are analysed, at the same time, the determination method of load immediate roof, natural equilibrium arch load, the height of caving zone and the height of fracture zone are pointed out.(2) A analysis of static load and dynamic load on these structures of direct roof rock and caving zone of rock; immediate roof rock, caving zone of rock and fracture rock; immediate roof rock, basic roof and caving zone of rock; immediate roof rock, basic roof and caving zone of rock and fracture rock is done. And the determination method of reasonable load support of four structures is pointed out.(3) Field engineering application. Based on the actual geology condition of Jialequan coal mine, the overlying strata is regarded as a structure of immediate roof rock, basic roof and caving zone of rock. The working resistance of support under theoretical calculations is between3893.9and4264.8kN per support, and the support of ZY4000-13/28is selected in actual production. The working resistance of support under theoretical calculations by field test data is3676.3-4026.5kN per support. The maximum working resistance of support is4626kN per support and the average working resistance of support is3605kN per support during the period of the pressure change of9101working face. The industrial test results indicate that the rated working resistance of ZY4000-13/28support is fessible to Jialequan coal mine.