Grouting can not only reduce the oxygen supply in the goaf, but also reduce the temperature in the goaf for fire prevention. It can also be used for fire prevention in a wide range of fire zones.

1) Soil to soil ratio

The water-soil ratio is between 2:1 and 4:1, depending on the location of the grouting; the amount of grouting in the goaf can be as good as covering 2 cm of loess in the goaf.

2) Grouting method

It adopts two methods: mining with irrigation and post-harvest grouting. With mining and irrigation: at the same time as the working surface advances, the goaf is grouted. The grouting pipeline is laid on a roadway with a higher elevation in the two sides of the working face. The slurry flows by the self-weight to the goaf in the lower part. The grouting pipeline should be buried in the goaf for about 15-20m, and then grouting is started to prevent the slurry from smearing. The slurry is alternately filled daily. Post-harvest grouting: Grouting after the closed face of the working face is closed, and the grout is filled on the closed wall of the stop-line line until it is filled.

3) Calculation of soil volume for grouting

With the working face with the injection, the amount of soil required for daily grouting is calculated by the following formula:

Qt=K•m•l•H•C

In the formula:

Qt—the amount of soil required for daily grouting, m3/d;

m- layer coal mining height, m;

- working day advancement, m/d;

H—the length of the grouting zone, m;

C—mining recovery rate, %;

K-grouting coefficient, according to the actual situation of the mining area, generally take 0.014--0.03;

4) Selection of grouting process

Commonly used grouting categories include: infusion of loess slurry, "infusion of loess slurry + inhibitor", "infusion of high concentration loess + thickened colloidal slurry", composite colloidal mud and so on.

Under normal circumstances, the “high-concentration loess + inhibitor” grouting process is followed by the injection; when there is a fire sign in the goaf of the working face, the “composite colloidal mud” grouting process is adopted, and the composite colloidal mud is composed of loess and water. , suspension agent, gelling agent composition. The suspending agent is added in proportion to the loess slurry in the ground grouting tank, and after being uniformly stirred, a thickened colloid is formed and transported to the well through the grouting pipeline system.

2 inhibitors fire protection technology

Inhibitors are compounds there are inorganic salts such as calcium chloride (CaCl2.6H2O), magnesium chloride (MgCl2.6 H2O), ammonium chloride (NH4Cl) solution is sprayed on the coal and the like, having a blocking oxide, To prevent the effect of spontaneous combustion, it is called a resisting agent. It can effectively prevent the natural fire of coal seam by spraying and injecting inhibitor in coal mine.

1) Selection of inhibitors and their technical parameters. According to the actual situation of the mine, the use of MgCl2 as a retarding agent can achieve better results and is convenient to obtain. The concentration of the inhibitor solution is preferably controlled between 18 and 20%.

2) Location and time of spraying. Spraying location: two gangs in the lower two lanes on the working face, the floating coal at the rear of the two ends of the brackets, and the gap between the brackets in the rear goaf. Spraying time: After each shift of the working surface.

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