Practices on Hydraulic Powered Support Selection and Holding Mining Technology Applied to Seam with Extreme Broken Roof and Soft Coal

In order to solve the problems of the coal mining wall spalling and the roof falling at the front of the powered support in the coal mining face in an extrem e broken and soft seam, taking the fully mechanized top coal caving mining in No.9 extreme broken and soft seam as an engineering background, the paper analyzed th e features of the conventional fully mechanized top coal caving mining technique.In combination with the site engineering practices, a study on a holding mining top coa I caving mining technique with non beam distance was conducted. The features would be that with the length expansion of the powered support beam, thus a coal minin g operation could be conducted under the non beam end distance. The expansion beam with a distance of 800 mm could ensure the pilot support.With the spade plate to level the top coal and the powered supports moved forward with pressures, the coal wall spalling could be applied for coal mining .According to the echnioue feafures, the rational three machines matched technology was provided for the coal mining technique and applied to the industrial trial in Luling Mine under the special geological conditions.The coal production of the coal mining face could be reached at 100 000 t per month with good benefits.