Experimental evaluation of cemented tailings backfill strength characteristics and acid mine drainage potential

Abstract

Following the research & development of Sustainable Mining by Drilling (SMD) technique in the narrow vein mineral deposits, a conceptual framework for backfilling large-diameter drilled holes has been developed, utilizing a mixture of cemented tailings paste. In the paste mixture, the tailings constitute 75% to 85%, the binder makes up 3% to 9%, and the water content represents 15% to 25% of the total weight of dry materials. This thesis contains a comprehensive assessment of various aspects related to cemented tailings backfill (CTB), including the strength characteristics, measurement of dynamic elastic properties using the ultrasonic method, rheological analysis, and evaluation of acid mine drainage potential. To minimize the cement cost in backfill operation, comparative analysis was conducted in the laboratory for the samples of 6% and 4% cement content by weight along with the concerned proportional mixture of tailings and water to achieve the design strength of 1 MPa. The strength characteristics were evaluated following the compressive strength test, stress-strain behaviour and dynamic elastic properties measurement through ultrasonic wave velocity method. Moreover, on the collected backfilled samples from field location, strength measurement and particle size distribution were conducted to understand the effect of particle gradation on strength development. Then, comparative analysis has been described from lab experimental results to evaluate the acid mine drainage potential. From the static test of tailings, the experimental results shows that the tailings has high potential of acid generation. The long-term kinetic test of cemented tailings mixture with variable cement percentage showing the neutralization behaviour of acid generating tailings for the presence of cement components.