Development of elastic cemented material for consolidating cracks around drilling holes in gas drainage in soft coal seams

In order to consolidate the cracks around the borehole in the coal seam,an elastic cemented material for fracture consolidation of coal and rock was prepared by using polydimethylsiloxane, PMHS, polypropylene fiber and straw fiber as raw materials. The micro morphology of polypropylene fiber and straw fiber in the elastic cemented material was observed by scanning electron microscope and particle analyzer.The effects of different contents of polypropylene fiber and straw fiber on the mechanical properties of elastic cementitious materials were studied by universal testing machine The results show that: adding a certain amount of polypropylene fiber and straw fiber can enhance the mechanical properties of elastic cemented material;With the increase of content of polypropylene fiber and straw fiber, the mechanical properties of elastic cemented material became worse;The optimal content of polypropylene fiber-straw fiber was 0.6%-1%.Polypropylene fiber can be used as a connecting material to bridge the internal discontinuous area of elastic cemented material. At the same time, the surface of polypropylene fiber is rough, which can bond more colloids and increase the resistance of polypropylene fiber degumming. When the content of straw fiber is 0.5% and 1%, the straw fiber dispersion in the material is better, and when the content is 1.5%, the straw fiber in the material begins to appear agglomeration.When the content is 2%, the agglomeration was serious.The elastic cemented material had good cohesiveness with the coal, which can bond the loose coal together to form a whole, with a certain mechanical strength.The reinforced coal module gradually deformed in the process of force loading, but the reinforced coal is not crushed, and still maintains good integrity.The field test showed that the gas mixed flow decreased slowly with the increased of the extraction time, and there was no sharp fluctuation or decrease of gas mixing flow, which proved that there was no instability problem in the borehole during the extraction process, and the borehole wall remained intact.