Geological survey and treatment engineering of coal mine goaf
1. Introduction
During the construction of the industrial square of measures well in the north wing of Ningtiaota Coal Mine, there are many cracks and collapse deformation in the site, among which the maximum subsidence of the coal tower is 790mm, and cracks appear in the concrete structure. It is found that the coal 2-2 below the site has a goaf of a small mine, and the site conditions are unstable. As a large industrial site, there is a huge potential safety hazard.
Figure 1 Site cracks Figure 2 Coal tower sinking
2. Treatment solution
According to the characteristics of the goaf, the treatment project adopted the technology of one-time hole forming, full hole intermittent full filling grouting and sand injection. The distance between the boreholes is 10-15m, and the grouting holes are preferentially arranged in the goaf roadway and the building foundation. The grouting material is composed of paste slurry and cement fly ash slurry.
3. Construction situation
The drilling of 12975m / 204 holes was completed, with 14400m3 of sand and 715m3 of grout (50989m3 of cement fly ash slurry and 20726m3 of paste slurry).
Figure3 Paste grouting construction Figure4 Cement fly ash grouting construction
Figure 5 Construction layout plan
4. Achieved accomplishment
After construction, the inspection holes were all free of water leakage and drilling fluid loss. The slurry structure effectively filled the underground goaf area, which plays a better role of reinforcement and support. At present, the industrial site has been completed and put into use
Figure5 Site of coal tower and screening workshop Figure6 Hot blast furnace room and driving machine room
5. FAQ
What are the advantages of paste material grouting and traditional cement fly ash grouting?
A: Paste material filling is a new filling treatment method developed by our institute. In this project, local rich aeolian sand is selected as the main material according to local conditions, which is mixed by the concrete mixing station, and the cost of pulping is low. It is suitable for curtain hole and borehole with a height of more than 0.5m.
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