Treatment project of underground fire of the coal seams at Lijiapan Kindergarten in Shenmu County
1. Introduction
Lijiapan kindergarten is located at the edge of coal outcrop 2-2, and there was spontaneous combustion of coal seams nearby. There were surface cracks and collapses at the edge of the playground in the southwest of the kindergarten, and the gas with sulfur odor continued to gush out of the surface, as shown in Figure 1 and Figure 2. According to the survey results, the fire area spreaded from the southwest to the southeast of the kindergarten, which was close to the teaching building, and there was a major potential safety hazard.
Figure 1 Collapse of the fence at the southwest corner of the site | Figure 2 Collapse of road inside the site |
2. Treatment Solution
The ground borehole grouting method was used to cool and extinguish the fire in the burning coal seam, and the formed underground cavity was filled and reinforced at the same time. The grouting slurry was mainly divided into clay lime slurry and cement fly ash slurry, the first sequence hole used clay lime slurry for firefighting and cooling, and the second sequence hole used cement fly ash slurry for site reinforcement. In the southwest corner of the site, two or three rows of grouting holes were constructed to form a fire-isolating wall to isolate the surrounding fire sources.
3. Construction situation
1245m / 83 holes were drilled, and a total of 6722m3 grout was injected(clay lime slurry 5736 m3, cement fly ash slurry 986 m3).
Figure 3 Construction plan
4. Achieved accomplishment
The construction of the inspection hole and temperature measurement hole was carried out, the CO content in the gas in the boreholes within the control area is less than 100ppm, which meets the extinction standard of coal field fire area. The grouting solid isolated the peripheral burning area and hindered the burning of the coal seam in the control area, at the same time the cement fly ash slurry fills the holes caused by the fire, which plays a reinforcing role in the control area and improves the stability of the site.
5. FAQ
What is the reliability of the fire barrier? Will the fire of the coal seam pass through the bottom of the barrier?
A: according to the survey results and dynamic construction exploration on site, it was basically determined that there was no residual bottom coal near the construction isolation zone. In order to ensure the reliability of the isolation zone, the construction at the isolation zone should reduce the drilling spacing, adopted 2~3 rows of grouting holes, increase the width of the isolation zone, and then arrange temperature measurement holes outside and inside the isolation zone for long-term temperature observation.
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