Coalface Stability Of Longwall Large Mining Height Fully-Mechanized Panel In Steeply Dipping Coal Seam

Ewirgol 2130 mine 25221 face dip angle is large, mining is difficult, which has lots of factors affecting the coal wall, coal wall repeatedly spalling restricted face safe and efficient mining during mining, the related theory and control technology are needed to guide field production. Through studying the coal wall mechanics and instability characters and failure mechanism, providing such condition coal wall instability control measures, it is of great significance for enriching mining technology theory of longwall large mining height face in steeply dipping coal seam.Thesis combined with field test, numerical analysis(FLAC3D, 3DEC) and theoretical analysis method to study failure characteristics, the factors affecting the coal wall, failure mechanism and control measures of stability of large mining height in steeply dipping seam,the chief contents and results are shown as follows:(1) Coal wall mechanics, migration asymmetric, high frequency instability, instability region will be gradually expanded, different coal wall instability forms and extent in different regions of face, when instability extent is serious broken coal wall will slide down to press the lower part coal and make it happen rotary spalling.(2) The main influence factors of coalface stability include mining height, face dip,support resistance, advance speed, coal tensile strength, et., and the coal wall instability rate and extent increase when pseudo oblique angle increases in a certain range(face dip decrease),mining height increases, advance speed slows down, support unloading, low coal strength will aggravate the coal wall stability state.(3) The coal wall instability of large mining height face in steeply dipping seam is caused by the superposition effect composite factors which decided by working face internal and external problems. External problems—support frequent unloading, long time empty roof,variable mining height and pseudo-angle(make the top pressure loading and unloading leavingthe coal wall fatigue damage), lead to the roof pressure strength increased and prolonged,internal problems—25221 coal wall strength is low, with partings, large height, leading to coal wall poor self-stability, and composite mechanical action(pre-blasting vibration, mechanical vibration, gas pressure, the coal wall weight) perturbations, the interaction of internal and external factors causes coal wall instability. The inclination condition will lead to force tendency decomposition, oblique component will enable the formation of broken coal slip.According to production practices and experimental research, the measures such as timely adjustment of mining height(pseudo oblique) and strengthening coal wall are recommended,the field has been well applied, which provide scientific guidance for such coal mining.