Abstract
In solid backfill coal mining (SBCM), loose gangue backfill material (LGBM) is used to backfill the goaf after coal resources are exploited from the underground mines. Under certain geological conditions, LGBM with a certain height may be soaked in the water, and then becomes saturated, significantly altering its mechanical properties. The confined compression experiments were used in this paper to analyze the deformation and the crushing characteristics of LGBM with varying water soaked heights in coal mines. The results showed that a large number of small holes that were distributed in the gangue blocks were the main reason why the material absorbed water and was softened. The crushing ratio and the maximum axial strain of LGBM samples gradually increased with the water soaked heights of the samples. In addition, there was a strong linear correlation between the crushing ratio and the maximum axial strain. When LGBM was used as a solid backfill material in SBCM, its deformation resistance would significantly decrease after it was soaked in the water. Higher water soaked height of LGBM led to lower deformation resistance and greater influence on the quality of backfilling. This research has great significance in getting a deep and better understanding of the mechanical properties of LGBM, as well as guiding engineering practice.
Highlights
Solid backfill coal mining (SBCM) is a green mining technology that can meet the challenges of gangue dumps on the surface and the coal mining under buildings, railways, and water bodies.This technology is aimed at using the solid waste material, such as loose gangue and fly ash, to backfill the goaf and to support the overburden strata after the coal resources are exploited from the underground
loose gangue backfill material (LGBM) is backfilled into the goaf, the roof experiences rapid subsidence, with a sagging rate of greater than 0.075 m/month
Field monitoring datas from a number of mines (e.g., Pingdingshan twelfth coal mine [22], Zhai zhen coal mine [23], and Jining 3# coal mine [24]) have consistently shown that after LGBM is backfilled into the goaf, the roof experiences rapid subsidence, with a sagging rate of greater than 0.075 m/month
Summary
Solid backfill coal mining (SBCM) is a green mining technology that can meet the challenges of gangue dumps on the surface and the coal mining under buildings, railways, and water bodies This technology is aimed at using the solid waste material, such as loose gangue and fly ash, to backfill the goaf and to support the overburden strata after the coal resources are exploited from the underground. In the process of SBCM, there were many factors that would have influence on the filling quality, including the types and the mechanical properties of solid backfill materials, mining geological conditions, backfilling process design, etc. Materials were soaked in the mine water and their mechanical properties would change significantly, which would affect the filling quality. Materials are soaked in the mine water, and their mechanical properties will change dramatically, affecting the filling quality. It is of great significance to guide the engineering practice of SBCM and to ensure the filling quality
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