Fire Extinguishing Project of Coal Gangue in Gushuyuan Coal Mine
1. Introduction
Some spontaneous combustion areas at the debris heap of Gushuyuan Coal Mine
There is a large-scale spontaneous combustion phenomenon in Gushuyuan Coal Mine of Shanxi Jincheng Anthracite Mining Group Company Limited. The temperature in the spontaneous combustion area can reach 200~600°C, the maximum relative height difference of the terrain in debris heap is 147m, and the slope is in the basically stable state. The continuous burning of gangue may cause landslide disaster, threatening the safety of buildings and roads around. In rainy season, the leachate of gangue pours into the surrounding surface water system, seriously polluting the water source and soil in the surrounding area of the debris heap.
2. Treatment solution
In view of the accumulation characteristics and large-scale spontaneous combustion at the debris heap of Gushuyuan Coal Mine, the drilling and grouting method were adopted for treatment. Class-I boreholes are for realizing grouting fire extinguishing treatment on the shallow fire area, reducing the temperature of the shallow part of the debris heap and improving the on-site construction conditions; Class-II boreholes are for reducing the temperature and extinguishing the fire in the deep part, at the same time filling and strengthening the internal gap at the debris heap, consolidating the loose gangue and improving the slope stability. Finally, cover the slope surface with soil to prevent the waste rock leachate from polluting the surrounding water source and soil in rainy season.
3. Construction situation
Figure Construction site
Six treatment areas are identified by field investigation, drilling and infrared temperature measurement, with a treatment area of about 9000㎡. Firstly, drill the class-I boreholes, pour clay-lime slurry and cement-clay slurry, cool the shallow part and extinguish the fire, inhibit the harmful gas emitted from the surface of the debris heap, and improve the working environment; after the shallow part is cooled and fire is extinguished, drill the class-II boreholes and pour the cement-fly ash slurry; after grouting, cover the surface of the debris heap with soil and plant trees for greening.
4. Achieved accomplishment
(1) Assessment on cooling and fire extinguishing effects at the debris hap
Debris heap with fire extinguished through grouting
After treatment, the maximum temperature in each test hole in the project area is between 40.2°C and 65.8°C, which has dropped below the critical ignition temperature of coal gangue. There is no exposed ignition point on the slope platform and slope surface, and the site has no strong pungent smell. The spontaneous combustion of coal gangue in the area has been treated.
(2) Assessment of the reinforcement effect of the slope at the debris heap
Figure Coring from the Test borehole
After construction, it is found out that the physical and mechanical properties of gangue layer on the slope are significantly enhanced, and it is judged that the overall stability coefficient of slope is greater than 1.35, and the overall stability of waste rock mountain is good.
(3) Assessment of the ecological environment restoration
Figure Rendering of the drainage system and planting on the slope surface
Once grouting is completed, the plants grown on debris heap basically survives through covering soil and landscaping works, and a perfect slope drainage system is established to prevent the rain from washing the gangue to form harmful leachate to pollute the soil, and the damaged ecological environment is well restored.
5. FAQ
(1) What are the obvious advantages in this treatment scheme?
At the same time of reducing temperature and extinguishing fire, the gap between gangues can be effectively blocked to avoid the re-ignition of gangue and ensure the long-term effectiveness of treatment. Innovative grouting method is used to reinforce the high slope of loose accumulation area, and the reinforcement effect is good and meets the design requirements.
(2) How to avoid the hidden danger of landslide when a large amount of grouting is carried out on the platform of the debris heap in thea basically stable state?
Firstly, observe the deformation of slope and the change in slope every day. Secondly, optimize the grouting technology and control the grouting speed, which should not be too large. When a single hole reaches a certain grouting amount, the works should become intermittent in time, and the grouting pressure should not be too large. Stop grouting on time when the abnormal conditions such as surface uplift, crack and grout-taking point occur.
(3) What is the applicable scope in this treatment scheme?
This scheme has a wide range of application, applicable to the shallow and deep coal debris heap with a large area of fire. However, for the fire on the slope surface, the slope should be covered with lime soil by artificial layering after grouting treatment.
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