The selection of backfill materials for Barapukuria underground coal mine, Dinajpur, Bangladesh: insight from the assessments of engineering properties of some selective materials

摘要

The study represents an analysis for the selection of backfill materials and backfill process for Barapukuria coal mine which is the only mining industry in the country under production state. Recently, this industry faced massive people protest due to mine-induced subsidence around the mining area. The backfill is the most emerging and developing technology in recent times in mining sectors which can be considered as a prospective option for Barapukuria coal mine in the purposes of increasing the ore recovery and mine stability, consequently reducing the subsidence. For the first time to have a backfill assessment in this underground mine, initially this study searched out the available resources to fill the mined out void as are alluvial sands, power plant fly ash, mine tailing, and Portland cement. In the subsequent steps, these samples were characterized for both cemented and uncemented option under particle size, compressive strength, shear strength, proctor test, and permeability analysis. The particle size analysis evaluates the sands and mine tailing as medium to fine grain uniform and well-graded sample, respectively. In the case of cemented backfill, the compressive strength test on different proportion mixtures of sand, cement, and ash shows compressive strength that is increased with time and cement content. The important finding is the significant influence of ash content, used as Portland cement replacement, in long-term strength. The determined permeability of sand sample is 3.60 x 10(-5) m/s, which is higher than mine tailing valued at 1.11 x 10(-5) m/s. Shear strength of mine tailing with friction angle of 43.19 degrees and cohesion of 5.33 kPa is greater than cohesion less sand sample with friction angle of 37 degrees. Standard proctor test denoted the highest dry density of sand and mine tailing as 1.74 x 10(3) and 2.23 x 10(3) kg/m(3) at 18 and 11 wt% of water content, respectively. After taking into account the findings hydraulic backfill is preferred where the recommended backfill mixture for the mine is sand fill with 5-7 % cement and 8-10 % ash through the consideration of requires volume, materials characterization along with cost consideration.