Meitan kexue jishu (Jul 2023)
Research on water leakage control technology of inclined shaft of coal mine based on cement soil curtain of equal thickness
Abstract
The loose layers and shallow weathered bedrock in western China are rich in water, and the inclined shaft crossing the water-rich loose layer is prone to leak at the wellbore construction joints, concrete joints and wall cracks. Leakage will lead to the deterioration of underground working environment, lower working efficiency, increase the burden and cost of underground drainage, and affect the safety of coal mine production. In order to solve the above problems, this paper analyses the characteristics of water seepage in slanting coal mine shafts from the perspective of protecting groundwater resources and safe operation of shafts, and the existing management measures such as drainage, post-wall grouting, rotary pile spraying and curtain grouting. And the principle and structure of soil-cement curtain with equal thickness of water leakage level in inclined shaft, the basis of parameter selection and the method of curtain construction were studied. The effects of formation conditions, comprehensive moisture content, cement content and other factors on the performance of cement curtain were analyzed. The field test application of water leakage control of inclined shaft was carried out in test mining area. The research results shows that the water leakage of inclined shaft in coal mine mostly occurs in the bottom plate, waist wall and the joint of both, and the water inflow was tens of m3/h～ hundreds of m3/h, and some even had water gushing and carrying sand, endangering the safety of the shaft. The equal-thickness soil-cemented curtain forms an equal-thickness wall with uniform thickness, few joints and high water interception rate in the outer stratum of the slanting coal mine shaft through three steps: lateral cutting, retraction cutting and mixing, and slurry mixing to form a wall. It effectively blocks the the hydraulic connection between the inclined shaft, the outside loose layer and the weathered bedrock. The strength of the cement curtain of equal thickness is positively correlated with the cement admixture, and the permeability coefficient is negatively correlated with the cement admixture. The performance of the cement curtain of clay stratum is weaker than that of loess and fine sand stratum. The in-situ core sample of the curtain at the demonstration application site has a compressive strength of 8.62MPa and a permeability coefficient of 2.69×10−8 cm/s. The water influx in the borehole is reduced from 16.8 m3/h to about 1.6 m3/h, which is 90.5% less than before the treatment, and achieved good application results. This method can solve the seepage problem of inlcined shaft in loose layer in western China, ensure the safe operation of the well shaft, and protect the groundwater resources.
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