Research on technology of gob-side entry retaining under goaf in extremely close distance coal seam
In order to solve the serious deformation problem of surrounding rock of gob-side entry retaining influenced by multiple mining activities under the gobs of extra-close coal seams,taking the 91006 fully mechanized mining face of Shandong Xinchazhuang Mining Co.,Ltd.(hereinafter referred to as"Xinchazhuang Coal Mine")as the engineering background,the structural characteristics and movement rules of the overlying rock roof of the gob-side entry retaining under the gobs were studied and analyzed.By establishing a mechanical structural model of the roof,the calculation method for the entry-side support resistance of the gob-side entry retaining was determined,and the entry-side support resistance was calculated as 3 432 kN.A entry-side composite support system was proposed,mainly consisting of advanced roof breaking hydraulic fracturing and high-strength support with entry-side steel pipe concrete pier columns.The advanced roof breaking and pressure relief technology transformed the entry-side roof from a transmitting rock beam structure to a short cantilever beam structure,greatly reducing the resistance of the entry-side support.Combined with high-strength entry-side support with steel pipe concrete pier columns,the support system was particularly suitable for gob-side entry retaining engineering.The experimental application in the 91006 fully mechanized mining face of Xinchazhuang Coal Mine showed that the entry retaining had achieved good results,with a relatively small overall deformation on the surrounding rock of the roadway,meeting the requirements during mining.
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