Mining of Mineral Deposits

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Numerical modeling analysis of floor stress distribution under coal pillars and roadway stability in close-distance coal seams

Quang Phuc Le1,2, Trung Tien Vu1,2

1Hanoi University of Mining and Geology, Hanoi, Vietnam

2Research Group: Sustainable Development of Mining Science, Technology and Environment, Hanoi University of Mining and Geology, Hanoi, Vietnam


Min. miner. depos. 2025, 19(4):1-11


https://doi.org/10.33271/mining19.04.001

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      ABSTRACT

      Purpose. The stability of the lower coal seam roadway under the condition of close coal seams is a key issue in underground mining, mainly when the roadway is located under the coal pillar of the upper seam. This paper analyzes the stress distribution rule under the coal pillar to determine the reasonable location of the roadway in the lower seam at Thong Nhat Coal Mine, Vietnam.

      Methods. Numerical simulation model using FLAC3D software was conducted to investigate the distribution and redistribution of stress under the coal pillar and the goaf area, considering vertical-horizontal stress, physical parameters of rock and actual boundary conditions.

      Findings. Four different roadway layout locations were assumed for comparison: Under the center of the pillar (A), under the edge of the pillar (B, C) and in the floor area under the goaf (D). The results showed that the highest stress concentration was at location A, with a concentration coefficient of 2.4-2.7 times the initial stress, creating a high risk of instability. Locations B and C had lower stresses but were still strongly affected by the pillar load. In contrast, location D showed a significantly lower and uniform stress distribution, and a small plastic zone development range, which was favorable for maintaining roadway stability.

      Originality. The choice of roadway location is decisive for the safety and longevity of the project. In the geological conditions at Thong Nhat Coal Mine, arranging the roadway in the floor area under the goaf outside the coal pillar with a horizontal distance of 5m (location D) is the most reasonable and safest. At the same time, it is necessary to avoid arranging the roadway directly under the coal pillar.

      Practical implications. The research results provide a scientific and practical basis for design work, improving stability, reducing maintenance costs and ensuring safety in underground mines with close coal seams.

      Keywords: coal pillar, coal seams, floor stress distribution, mining-induced pressure, roadway stability, Thong Nhat Coal Mine


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