Study On The Anomaly Mechanism Of Strata Behavior Of Fully Mechanized Faces With Super-Large Mining Height In Shallow Coal Seam

The coal seams in shendong area were buried shallow with large thickness and great mining conditions. In recent years, some mines have mined seams in deep layer,for example, the working faces of 5-2 coal seam in daliuta coal mine with distance of 145 meters in maxmum from the upper coal seam. Compare with former shallow seam, the strata behavior differed significantly in spite of the same mining height and similar supporting intensity which pullzed the roof control and selection of hydraulic in working faces. Based on this,the paper studied on the anomaly mechanism of strata behavior of fully mechanized faces with super-large mining height in shendong area by means of field measurement,physical simulation and numerical simulation.By the measurement in No.12106 working face and No.52303 working face,the paper reached the weighing characteristic of strata behavior of fully mechanized faces with super-large mining height, Especially some indexes,such as periodic weighting length, dynamic factor. Through the analysis,the paper put forward the effects of key strata structure on strata behavior in working faces with different burial depths.The physical simulation showed that key strata may break synchronously from the range of whole columnar in condition of fully mechanized faces with super-large mining height which may intensify the ground pressure. Compare with No.12106 face,during the period of pressure in No.52303 working face,the fracture of upper key strata may lead to the synchronous break of below key strata and the increase of burial depth resulted in the increase of load act on key strata. These two factor meaned that the destruction height of the cover rocks and load act on hydraulic support were much larger. Based on the physical simulation,the paper study on the extreme layer of key stratum which can affect the strata behavior. The result showed that the support resistence increased at first then decreased and finally became steady as the rise of primary key stratum when below key stratum remained unchanged. According to simulation results,the support resistence reached the maximum in the distance of 115 meters between coal seam and primary key stratum and became steady after 135 meters. Then the paper put forward that,in shendong central mining area, the max distance between coal seam and key stratum which can affect the strata behavior was 135 meters.The research results guide the safety and efficient mining of fully mechanized faces with super-large mining height in shendong area, and enriche the academic system of the interaction relationship between supports and surrounding rock.