Research On The Mechanism Of Sealing Under Pressure And Material Characteristics Based On Active Support

Coal seam gas seriously affects the safe mining of the working face.Most mines have poor sealing quality and low gas drainage efficiency.To solve these problems,this paper based on the concept of "active support",using orthogonal experiments to develop new cement-based expansion sealing materials.The drilling sealing mechanism under the "active support force" is studied,and the simple and easy-tooperate Sealing device which named two-plugs-and-two-injections bag-type matching sealing technology is selected for field tests.The following research results are mainly obtained:(1)The mix ratio design of the sealing material is based on the orthogonal experiment.We comprehensively investigate 5 factors,such as water-cement ratio,quicklime content,fly ash content,quick-setting admixture,expansive effect on material bleeding rate,fluidity,initial setting time,compressive strength and expansion rate,so as to get the optimal combination of various factors and levels.(2)The stress-strain curve characteristics of sealing materials with different expansion rates were studied by uniaxial and triaxial tests,and the law of their strength characteristics and deformation characteristics with Expansion rate was further analyzed.Combined with the stress-seepage coupling experiment,the permeability evolution law of the sealing material under different expansion rates and the sensitivity of the sealing material to the effective stress are studied.(3)Based on the concept of "active support",this paper studies the radius of the borehole plastic zone,the radius of the broken zone and the displacement around the borehole under the action of the "active support force",and designs the "active support force" test device.The research results show that the greater the active support force provided by the sealing material,the smaller the radius of the plastic zone of the hole,the radius of the broken zone of the hole and the displacement around the hole.Under the same buried depth and the same active supporting force,the larger the rock mechanical parameters,the smaller the radius of the plastic zone of the borehole,the radius of the broken zone of the borehole and the displacement around the borehole.(4)By introducing an energy matching coefficient to characterize the relationship between the deformation specific energy of the plugging grouting body and the energy released by the excavation of the rock mass,the strength design formula of the plugging grouting material required for the rock mass with different buried depths is obtained.When plugging gas drainage boreholes,the plastic zone range of the roadway under creep action must be considered.By introducing the calculation model of the roadway plastic zone considering the creep effect,the maximum plastic zone of the roadway under the creep effect is calculated.The range is 6.65 m,and the plastic zone of the roadway without considering the creep effect is 4.7m.(5)The new expansion sealing material and the supporting "two plugs and two injections" bag-type sealing technology were used for field test.Through the analysis of underground gas drainage data,it is found that the sealing effect of the borehole has been significantly improved.When the gas drainage reaches 90 days,the gas drainage concentration of the "two plugging and two injection" bag-type sealing technology is47.5%.Compared with the old sealing technology on the mine,the gas drainage concentration is increased by 84.8%.The paper has 56 figures,22 tables,and 93 references.