Investigation of Waste Material Properties on Collapse Prevention in Underground Mine under the Backfilling Method

Abstract

Waste material has been selected as an effective backfill in underground mines due to its advantages of collapse prevention, cost-effective, and less surface disposal of mine tailing during mining life. The properties of waste-backfilled materials may significantly support the behavior of the surrounding rock mass. This study aimed to investigate waste material properties on collapse prevention in underground mine under the backfilling method. Waste materials, regarded as valueless and harmless, used in this study were oyster shell, kaolin tailing, stone dust, and low-grade gypsum. Five different mixtures of backfill material made from different ratios of waste materials, cement, water and interface agents were subjected to slump test and uniaxial compressive strength test performed at 3 different curing times including 8, 16 and 28 days. The results showed that all mixtures were within the standard of the slump test except the one with low-grade gypsum as an ingredient. In addition, the overall trend of compressive strength of the mixtures increased as the curing time increased. The mixture with kaolin tailing exhibited the maximum compressive strength of 6 MPa at curing time of 28 days, whereas that with low-grade gypsum exhibited the lowest compressive strength, twice less than the compressive strength of the mixture with kaolin tailing. The presence of kaolin tailing has a significant impact on strength due to its ability to reduce bubbles inside cement mixtures. Furthermore, increasing in curing time leads to an increase in backfill strength.