Experimental Study Of Delayed Inflating Hole Sealing Materials

China is a country which is rich in coal. The production of which has been reached3.66billion tons by2012. The coal occupy a large proportion in energy structure, but these coal mining problems that restrict efficient and safety production are focusing on dominating underground mining, complex seam conditions, coal mine accidents occurring frequently and with the gas disaster serious particularly. Gas extraction is a basis measure for gas control, while the quality of gas drainage hole sealing is the key that affects gas drainage rate. In order to improve extraction rates and reduce gas accidents, developing a new type of delaying and expanding material has certain realistic value for plugging the drilling.A solution that microcapsule expansive agent is added in the material is proposed through the research on the sealing mechanism of drilling and the issue that sealing material based mud will effect of the drilling air tightness with the shrinkage deformation producing during plugging. Aluminum powder is selected as a appropriate expansion agent and gelatin (Gel), sodium alginate (SA) are chosen as suitable coating material according to the principle of expansion and microencapsulation technology. A modified expansive agent microcapsule, the ratio of core material to wall material is1.5, is made by Gel/SA mixed solution with Gel condensation method, and the Gel/SA mixed solution is composed of2%Gel solution and2%SA solution thorough the experimental study.Using orthogonal test to determine the dosage of the basic raw materials, in the water cement ratio of0.5, the temperature35℃, dosage of4‰cases effect best, by the expansion of the new type sealing material performance and mechanical performance testing, eventually inflation rate of15%, the compressive strength under the influence of the expansion agent to maintain a certain level, to ensure the strength and expansion coordinated effect.1day compressive strength2.3MPa,3days14.6MPa,7days21.2MPa,28days strength31.7MPa.And sealing material for SEM scanning microscopic observation found that the density of hydration products, structural integrity and through holes, and free of cracks and the control group without adding water slurry and expansive agent directly slurry has cracks and holes.Through these studies, the expansive agent microcapsules in cement base material used in gas drainage hole sealing to hydration in cement base material after a period of time began to swell, delayed the normal expansion agent the phenomenon of the early hydration expansion, invalidate the early expansion into cement hardening under a certain intensity after inflation, to avoid the inflation can effectively compensate the loss of the shrinkage of cement base, can solve the problem of hole leakage, improve the efficiency of gas extraction.