Suitability of Bottom Ash for Stowing in Underground Coal Mines with and Without Addition of Settling Agent: Fid-Bau Portal

Suitability of Bottom Ash for Stowing in Underground Coal Mines with and Without Addition of Settling Agent

Roy, Rohit / Chakraborty, Sayantan / Bisai, Rohan / Palaniappan, Sathish Kumar / Pal, Samir Kumar

Stowing is an important aspect for mine stability and surface subsidence. In general, sand is used as a standard stowing material in most of the underground coal mines in India. But now-a-days, sand is being excessively used in construction industry, whereas its replenishment is very slow. Thus, the study's significance is to identify alternate material for stowing which can replace sand. The aim of the study is to find the suitability of bottom ash as stowing material with and without addition of settling agent. Potassium aluminium sulphate [K₂(SO₄).Al₂(SO₄)₃·24H₂O] is used as the settling agent. Different experiments are conducted for physical and drainage characterization of bottom ash. A prototype for simulating stowing operation in the laboratory is fabricated and the efficacy of the bottom ash with and without addition of settling agent is calculated by conducting various experiments. The experiments have been carried out using different percentages (i.e. 2%, 4%, 6%, and 8%) of settling agents. Bottom ash-water slurry at 50% concentration (by weight) with addition of 4% settling agent (by weight of solid) has found to be most effective for stowing operations based on faster percolation, quick settlement and good permeability characteristics. Load-bearing capacity test of the filled solid after stowing is carried out to find the empirical equation to predict the percentage of settlement with respect to in situ stress for particular range of depths. Settlement percentage of the stowed bottom ash is found to be in the range of 10.34–12.71% for the depth of 50–90 m.