Abstract
Short-wall block filling mining (SBBM) technology has become an effective way to recover coal resources beneath the aquifer, which are unsuitable, or cannot be used by long-wall mining, such as corner coal pillars, industrial square pillars, and irregular coal blocks as well as the coal beneath buildings, railways, and water bodies. The SBBM method can not only enhance the recovery ratio but also provide a solution for the environment problems associated with gangues on the surface. However, whether the height of water flowing fractures will reach to the aquifer to cause water loss during SBBM has always been a key problem. Therefore, based on the theory of elastic foundation beam and SBBM characteristics, a mechanical model for calculating the height of a water flowing fracture zone in the overlying strata of SBBM was established, and this model calculated that the height of the water flowing fracture zone was 27.0 m in the experimental working face, and the height of the water flowing fracture zone was measured as 26.8 m according to washing fluid loss in the hole, core damage analysis, and drilling TV imaging detection. The comparison results demonstrated that the calculated value almost fit well with the field-measured data, validating the accuracy of the proposed mechanical model, while the predicted value (48.7 m) in the Regulations of coal mining under building, railways and water-bodies deviates greatly from the measured results. This reveals that the prediction formula in Regulations is not effective in predicting the height of the water flowing fracture zone in SBBM. The present research results are of great significance to further enhancing the recovery ratio of coal resources and improving the water-preserved mining theory.
Highlights
During the coal mining process, overlying strata experience significant mining-induced movements and deformation, inevitably causing the collapse and fracturing of strata and forming a lot of fractures [1,2,3]
The height of the water flowing fracture zone was mainly predicted according to the related formula in the Regulations; this prediction formula was concluded in the early 1980s through regression statistics based on limited field measurement data of some mines in China [20]
Because of the specificity of arrangement in the short-wall block backfill mining (SBBM) working face and the filling of gangues in the gob, SBBM differs from long-wall mining in roof management, thereby leading to different rules and mechanisms of mine pressure and fracture development
Summary
During the coal mining process, overlying strata experience significant mining-induced movements and deformation, inevitably causing the collapse and fracturing of strata and forming a lot of fractures [1,2,3]. When this water flowing fracture zone develops towards the aquifer or water-rich regions on the surface, serious water loss can be triggered, thereby leading to the deficiency of water resources and further inducing a series of environmental problems such as land desertification, sparse ground vegetation, and dry-up of streams [4,5,6]. Destruction of the environment and waste of coal resources are facing serious problems that threaten the government’s strategy of sustainable development. To address these problems, an effective environmentally friendly mining
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