Study On Phenomena Of Underground Pressure At Fully Mechanized Caving Face In Zaoquan Coal Mining

The steeply dipping seam is defined by coal seam which pitch is35°~55°.When coalseam pitch is more than35°,the movement of surrounding rocks is different from coal seamwhich pith is less than35°.Researching and controlling the roof movement law andcharacteristics of strata behaviors in the process of mining of steeply dipping seam,takingeffective measures for safe mining,have great practical significance to reduce the roofaccidents, improve resource recovery, reducing consumption, increasing the economic benefitof the mine.In this text,studying on the120210fully-mechanized caving working-face in Zaoquancoal mining variable angle-critical steeply dipping seam and using the existed theory ofsteeply dipping seam,and then analysing regulations of coal-pressure manifestation throughsite test,the physical simulation experiment and numerical simulation．Research conclusing that:(1) The overlying strata collapse showed obvious asymmetricarch from the horizontal and vertical displacement,the arch peakis located in the upperworking face,key roof caving is not synchronized with immediate roof,but coordinated withthe up deformation.From the overlying rock displacement characteristic,variable angle-criticalsteeply dipping seam can thought to be combination of Steeply dipping seam and inclinedcoal seam.(2)Because of overlying strata have sub critical key layer resulting from the size ofthe periodic pressure phenomenon.The initial weighting step is67m,the cycle weighting stepis19.8m， the rock caving angle is45°.When weighting average stress concentrationcoefficient of support pressure is2.1,the peak pressure is generally located at the front side10~20m,the abutment pressure influence scope is75~110m.(3)The mechanical characteristicsof surrounding rock in working-face are asymmetrical arch. As the inclination angleincreases,the lower end of the stress concentration zone and the maximum stress value increases,the upper end of the stress concentration zone decreases.At the same time,theasymmetric of the roof and floor stress releasing zone is more obvious.The top peak walue ofabutment pressure closes to the wall,the below far away from the wall,but the supportingpressure reduced.The research obtained phenomena of underground pressure at fully mechanized cavingface through site test and simulation experiment,has great significance for actual productionand rock control and has draw lessons from a meaning.for the safe and efficient mining ofsimilar condition face.