Study on Roof Deposition Characteristics of Coal Seam in High Underground Pressure:A Case Study of the Mengcun Coal Mine
The hard thick roof on the coal mining face has an important influence on the generation of rock burst.The hard thick roof sandstone usually changes in thickness,roof and floor fluctuation and rock mechanical properties in the transverse and longitudinal aspects due to the change of sedimentary facies.The geological condition of Mengcun Coal mine in Binchang Mining area of Shaanxi province is complicated.The roof of the main coal seam is multi-layer thick sandstone,and the mine is threatened by rock burst disaster for a long time.In order to accurately grasp the position and distribution of the hard-and-thick sandstone of coal mining face,and carry out fracturing-weakening to ensure the safe and efficient mining,based on the engineering geological conditions of Mengcun coal mine,this study analyzed the characteristics of petrology,sedimentary facies and petrophysical and mechanical properties by exploring the roof overhanging structure of the coal mining face through the drilling and core-recording of the roadway roof and the drilling TV logging method,and samples the main sandstone bodies of the roof.The main results are as follow:① Five continuous layers of sandstone bodies can be correlated within 100m of the roof of 401103 coal mining face in Mengcun Coal Mine.The variation of sedimentary microfacies in coal mining face leads to the instability of the thickness and elevation of each sandstone body;②In the roof of 401103 coal mining face,the second section of Yan'an Formation,Zhiluo Formation and Anding Formation are all fluvial facies deposits.The rock mechanical strength of fine grained sandstone and siltstone of natural dike facies in fluvial microfacies is relatively the largest.With the gradual increase of rock particle size,the strength of coarse-grained sandstone in the bank facies and riverbed residual facies is relatively reduced.The rock mechanical strength of the same particle size sandstone in different sedimentary environments increases with the increase of quartz content,siliceous cement content and grain support structure.③The present tectonic stress of the mine field and the hard and thick sandstone in the roof are the main causes of mine rockburst disaster.The regional hydraulic-fracturing-weakening of the overlying hard and thick sandstone body can significantly reduce the risk of mine rockburst.
rock bursthard thick sand bodyroof explorationoverburden structuresedimentary faciesmechanical properties of rock