Design of backfill and grouting systems used as support in Polish mines
9th International Symposium on Mining with Backfill
In the Polish coal mining industry, the use of mine waste in underground backfill has been the most common means of:
• providing ground support to reduce surface subsidence,
• increasing extraction ratios,
• reducing the quantity of waste for surface disposal,
• reducing the spontaneous combustion of coal.
Waste fill used in Polish coal mines have evolved from early dumped rocks and hydraulically or pneumatically placed crushed rocks up to today’s hydraulically transported, densified and cemented fills with fly ash and flue-gas desulphurization by-products. Over the last decade attention has been focused on the use of different waste as filling material of underground workings and grouting of roof fall rocks in caving area. Grouting the caving area results in reduction of surface subsidence and spontaneous ignitions of coal, in improved ventilation and face conditions in particular the stability of gates.
The paper discusses various criteria to be considered in the preparation of a fill slurry and grout, fill distribution systems, mining geometry and placement methods.
Moreover, in the paper evaluation of the potential of utilizing coarse waste (crushed waste rock, slag and ash) and fine waste (tailings, sludge, fly ash, etc) as a material resource in the production of a backfill slurry and grout for filling and injection in abandoned mines is presented.
The effect of filling and grout injection on current coal mining practice is examined and some implications for future of underground technologies with backfill are predicted.