Research On Advanced Support Segment Stability For Gob-side Entry Of The Soft Floor In Extra Thick Seam

Taking the soft floor in gob-side entry of fully mechanized caving faces in Shuiliandong Min e as engineering background, the thickness of reserve roadway bottom coal was the key factor to affect bottom pressure and influence the stability of advanced hydraulic support bearing capacity. Based on the detailed analysis on the basis of predecessors’ research results, laboratory experiments, theoretical analysis, numerical simulation and field practice were combined together to doing a research for motion law of roof and floor specific pressure testing mechanism. Since stability of forepoling was influenced by bottom coal thickness, and the stability of forepole section was directly affected by forepoling stability. Therefore, forepole section was indirectly detemiined by surrounding rock of roadway. Reasonable bottom coal thickness in gob-side entry was calculated in theory, the numerical simulation was used to study bottom coal thickness’s influence on the stability of surrounding rock, and the reliability of research results are verified through engineering practice.Based on the theory of mining pressure, roof motion law was studied in detail, and the dynamic pressure was analyzed; Through establishing of mechanical model of support-surrounding rock, reasonable forepoling supporting strength was calculated.Finally, the reasonable forepoling supporting strength is not less than0.73MPa and no more than0.93MPaUsing theoretical analysis, field test these research methods, statistical regularity on different thickness of bottom coal with bottom pressure was concluded and the "S" type curve distribution was presented; By theoretically calculating advanced hydraulic support structural mechanics characteristics, bottom pressure distribution was concluded and the maximum base contact pressure is6.81MPa.FLAC3D software is used to simulating bottom coal thickness0.5m、1.0m......3.5m,and different location of roof stress nephogram and roof stress curve roof from working face is obtained. After comparison and analysis,from the front and rear30m range of the working face roof stress nephogram, and the whole roadway surrounding rock stress is lesser with bottom coal thickness not less than2.5m,and the peak distance of abutment pressure is farther from the gob-side entry, and it is the most stable with a long distance of abutment pressure peak.Through field practice and theoretical research, a set of recycling bottom coal technology was summarized and successfully carried out in Shuiliandong Mine, as a result, roadway height and coal recovery rate were both increased. Industrial experiments show that when the roadway bottom coal thickness is greater than or equal to2.5m, surrounding rock was stable with less roof to floor convergence, two sides deformation amount and bottom drilling amount, forepoling can move smoothly;-when the roadway bottom coal thickness is less than2.5m, two times serious bottom drilling of forepoling was taken place, and the above problems were solved through forepoling undercover, bottom grouting and adding to wood crip. Considering economic factors, the thickness of bottom coal in gob-side entry of fully mechanized caving faces3802is2.5m.