Monitoring of in-situ properties for cemented tailings backfill that under drainage condition

Cemented tailings backfill technology is commonly applied to fill mined-out areas generated by mining activities. Understanding the evolution of physical and mechanical properties of tailings backfill is important for the design of a safe and high-efficient backfill system. The in-situ performance monitoring experiments in the real stope and the in-situ similarity simulation monitoring experiments (under the drainage and undrainage conditions) are conducted. The evolution mechanisms of in-situ properties such as bleeding rate, sedimentation rate, temperature, pore water pressure, total stresses, and effective stress during the curing of tailings backfill are analyzed. The results indicate that the sedimentation rates for the tailings backfill under drainage and undrainage conditions are 6.07% and 3.99%. The average maximum temperatures are 37.5 and 33.9 degrees C. The setting times under the two conditions are 7.1 and 355.2 h. Comparatively, the setting time measured in the stope where one filter pipe is installed is 22.6 h, indicating that the drainage condition significantly affects the sedimentation, temperature, and setting in the field tailings backfill. As the height of the tailings backfill increases, the deviation between the theoretical value and measured data for the total stresses in the field tailing backfill gradually enlarges. This phenomenon suggests that the arching of pressure formed at lower tailings backfill could reduce the load, and contribute to the stability of stopes. In addition, the effects of filling speed and backfill height on the evolution of the total stresses are discussed.