ABSTRACT

Backfill mining is a lucrative method for extracting coal buried under buildings, and water bodies, which can substantially increase the resource usage efficiency by mitigating the strata movement and surface subsidence. Its effectiveness depends on the mechanical properties of granular backfill materials. A permeability test was performed on gangue and fly ash samples under different stress levels using an original seepage test system. The variation patterns of the broken rock’s internal pressure and permeability were determined. The test results indicate the weakening of the seepage effect on granular materials and a gradual reduction of washed away fly ash. The permeability values fall into the range of 3.2 × 10⁻¹⁵ ~ 3.2 × 10⁻¹³m⁻², and non-Darcy factor is between 3.2 × 10¹⁰ and 3.2 × 10¹² m⁻¹. This phenomenon was more pronounced in samples with smaller particle sizes. As the axial stress increased, the backfill material showed a decline in permeability and an increase in the non-Darcy flow coefficient. As the content of fly ash increased, the mass loss grew sharply, which occurred mainly at the early seepage stage. The results are considered instrumental in the characterization of water and sand inrush.

摘要

回填开采是开采埋在建筑物和水体下的煤炭的一种有利可图的方法，可通过减轻地层运动和地表沉陷来显着提高资源利用效率。其有效性取决于颗粒回填材料的机械性能。使用原始的渗漏测试系统对脉石和粉煤灰样品在不同应力水平下进行了渗透性测试。确定了碎石内部压力和渗透率的变化规律。试验结果表明，对粒状材料的渗透作用减弱，并且冲走的粉煤灰逐渐减少。渗透率值在3.2×10 ^-15〜3.2  ×10 ^-13 m ^{-2的范围内}，并且非达西系数在3.2×10 ¹⁰和3.2×10 ¹² m ^-1之间。这种现象在粒径较小的样品中更为明显。随着轴向应力的增加，回填材料的渗透性下降，非达西流动系数增加。随着粉煤灰含量的增加，质量损失急剧增加，这主要发生在渗流初期。该结果被认为有助于表征水和沙的涌入。