Recycling of waste rock as a filler to prevent ground subsidence

In this study, we investigate to use waste rock as a filler for filling the cavity of abandoned mines. We discuss that waste rock can be used as a filler in the side of environmental and structural stability. Waste rocks from four mines, such as Samgi, second Yeonwha, Dongwon and Dogye, are used. Leaching tests are conducted to check the environmental stability by four methods of Soil Leaching Test, MALT, TCLP and KSLT. According to the results, Cu, Cd, Cr and As were not detected and other metals leached below 0.5 ppm. Compressive strength of waste rock and crushed waste rock are measured to evaluate the structural stability. Mixtures of crushed waste rock are used to evaluate the possibility of enhancing compressive strength. Mixture 1 is composed of 11.1% of above 13.2mm, 22.2% of 9.5-13.2mm, 33.3% of 6.7-9.5mm, 22.2% of 3.5-6.7mm and 11.1% of 2.0-3.5mm. And mixture 2 is composed of 50% of above 13.2mm and 50% of 9.5-13.2mm. Compressive of the latter was more than that of the former. Waste rock can be probably used as a filler, considering the compressive strength of commercialized filler, or 40 Kg/cm(2).