The Occurrence Characteristics Of Coal Seam And Soft Roof With Forecast In Anshan Minefield

The main coal seam of Miaohagu mining are in Anshan well field buried shallow,thesurface valleys cut severely and fracture developed.To study the occurrence characteristics ofthe coal seam and distribution range of the weak and difficult to supporting roof has importantguiding significance for the layout of the working face,roadway support and roof managementof the main coal seam in this mining area.This text from the aspects of regional tectonic evolution illustrated the control functionof the characteristics of the tectonic movement and the evolutionary process of sedimentarystructures before and after the coal accumulating period for the occurrence of Yanan coalmeasure strata of Jurassic coal field in northern Shaanxi.According to two indicators of theadmissibility index （Km） and the coefficient of variation of the coal seam’s thickness （S） toevaluate the stability of the main working bed in quantitative.On the base of drawing coalthickness contour map and the seam’s floor contour map,analyzed and summarized the changecharacteristics of the thickness,distribution and occurrence depth variation of the main coalseam.In accordance with the combination characteristics of lithology which revealed bydrilling histogram,the main working bed structure type is roughly divided into four typesincluding normal bedrock roof, The normal bedrock add the roof of the weathered bedrock,weathering bedrock roof roof and loose bed roof, and on the basis to compile the coal bedroof strata structure map.According to the characteristic of the main coal seam’s thickness variation and itsdevelopment of immediate roof rock, the ancient action of the main seam roof in depositionwere analyzed. The result indicates that the thickness of No.4^-2 coal seam in the northeast ofmine field is less than0.8m due to the ancient fluvial of the seam roof in deposition; the non-mining area of No.5^-2 coal seam in the east of the mine field may exist a northeasternancient fluvial zone. The of coal-bearing strata in the mine field affected by normal fault F1,F2and F3, because of its influence the coal-bearing strata in Yan’an formation in north grabenzone is still relatively intact and the upthrown of south fault only reserve the first part in thelower part of the Yan’an formation coal mine segment. The normal fault in the study area maybe formed during Eocene in Paleogene to Miocene by tectonic evolution analysis. The paperexplores the control of weathering and erosion on occurrence of main coal seam and thinksthat Yan’an formation strata is mainly affected by weathering and denudation prior to andafter the deposition of the Jingle formation in Cenozoic, leading to coal seam saves morelayers but distributing discontinuously in general in north graben area and less layers anddistributing discontinuously in south monoclinic area.Through to analysis the drilling site for various types of coal seam roof strata structureand to predict the no drilling site for thickness of normal bedrock above the coal seam invalleys zone comprehensive analysis of the preparation of soft coal seam roof withdistribution forecast map,provides reference basis for layout of mining engineering.