Study on rheological characteristics of inorganic thixotropic fire extinguishing gel for blocking air leakage of coal mine

In order to effectively block the air leakage in goaf of coal mine, an inorganic thixotropic gel consisting of sodium bentonite, laponite, sodium silicate and composite admixtures was proposed. The gelation time of the gel was tested by the inversion method. The rheological characteristics of the gels under different ratio were conditions studied by using the rotational rheometer. The constitutive equation of the gel was constructed, and the suitable ratio of the gel for blocking the air leakage by grouting was selected. The results show that the rheological characteristics of the gels conform to the Herschel-Bulkley model and the correlation coefficients R² are all greater than 0.99;according to the ratio of S-13 sample, namely, when the mass fractions of sodium bentonite, laponite and portland cement are 4.00%, 3.00% and 0.46% respectively, the inorganic thixotropic gel has excellent fluidity, strong thixotropy and relatively small unrecovered residual stress and yield stress, which is beneficial to transport the gel slurry to goaf and form a stable network gel structure to seal the air leakage and not easy to produce new cracks. The relative pressure between the two ends of the glass cylinder after filling gel can reach -53.9 kPa, which is about 28 times of that without gel filling, indicating good gel sealing performance; in the fire extinguishing experiment, the temperature of coal decreases rapidly and coal is not easy to reignite after injecting gel into the coal piles.