Strata-pressure Behavior And Microseismic Detection In Longwall Face Under Old Room And Pillar Mines With Shallow Cover

Shengdong coal area basically utilized room and pillar mining during the first main layer mining process. It build a large area of gob left by room and pillar mining and concentrated coal pillar in the fact of apply room and pillar mining.Due to upper layer coal mining activity, upper roof have experienced a mining stress effect in coal mining; upper seam left pillar increases the elastic potential energy which makes pillar broken in the process of coal seam mining, then dynamic mine strata pressure takes place; Seriously affected the mine safety production.This essay is studied about Shigetai coal shallow buried coal seam coal seam mining in fully mechanized mining face pressure gauge and the micro-seismic monitoring means by introduced a combination of seismic data collected in the field, theoretical analysis, numerical simulations. Got mine pressure regularity and the law of seismic signal and the micro seismic monitoring and prediction method are studied. Earthquake early warning system was developed and verified in engineering field, The main research results are as follows:(1)After mine pressure observation and comprehensive analysis, the first roof weighting pace of 31201 working face is 48.6 meters; the periodic roof weighting pace is 12.7 meters. Before the concentrated coal pillar, the periodic roof weighting pace present at both ends is small, the characteristics of large in the middle. Each region to compressive strength relationships: A large area to compressive strength after across the concentrate pillar> Lower recovery area in seam 2-2 gob left by room and pillar mining>Uphill section across the Liugenggou>Before or after the concentrate pillar.(2)Using numerical simulation study, after the room and pillar coal mining, the residual coal pillar under the upper load, the rock mass in concentrated stress, maximum 40 MPa; and transfer the stress to the floor, seam 3-1 below the vertical stress in coal seam is high and low around the middle of "mountain" form, below the maximum peak stands in the very central of the coal pillar, 8.75 MPa, mining for room before 4.11 times that of the original rock stress in the 31201 working face; there will appear relatively strong phenomenon of underground pressure.(3)Based on the micro seismic monitoring method,distribution and change rule of microseismic events, sums up the law of roof weighting; It is concluded that the micro seismic events ahead of general support peak pressure of energy release cycle 8 ~ 12 h, And periodic weighting of mining face interval corresponding relation; As the number of seismic events, energy and continuous increasing mutations in the 2 ~ 3 d or working face in 8 ~ 12 hours after the roof weighting; The development of the microseismic events height is divided into two areas: 3-1 coal seam of 37 m ~ 67 m above the 2-2 coal low roof strata and 67 m ~ 97 m high 2-2 coal seam roof strata, high cycle contains several low events cycle, consistent with the law of rock breakage, embody the characteristics of the "double roof structure".