Experimental testing of geomechanical behavior of fiber-reinforced cemented paste backfill (FR-CPB) under warmer curing temperature

Abstract

Backfilling techniques enable improved ore recovery and structural stability to underground mines employing a material to fill the voids after the excavation. Fiber-reinforced cemented paste backfill (FR-CPB) is this material and it consists of mine tailings, cement, mixing, and fibers. After placed into the underground space (called stope), FR-CPB provides sufficient ground support, enables the exploration of larger amounts of ore since no orebody pillars are required to sustain the excavations, and thus enhances mining production. The reinforcement technique has been considered as a promising approach for the backfilling design. However, regarding that mining activities may take place at a depth of more than 1000 meters, the geothermal gradient can not only change the temperature of FR-CPB but also affect its geomechanical behaviors due to its temperature-dependent characteristics. Therefore, the objective of this research is to experimentally investigate compression, tension, shear, triaxial, and fracture behaviors of FR-CPB subjected to different warmer curing temperatures (20°C, 35°C, and 45°C). Moreover, to identify the mechanisms responsible for the evolution of geomechanical behavior, a series of mold-based monitoring programs have been designed and performed to measure changes related to matric suction, electrical conductivity, and temperature in FR-CPB. Additionally, to determine the progress of binder hydration and associated microstructure change, extensive X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) observation have been conducted at the microscale. The obtained results evidenced that warmer curing temperature can significantly affect the fiber-CPB matrix interfacial interaction. Correspondingly, the geomechanical (including tensile, compressive, shear, and fracture) behavior show strong temperature sensitivity from early to advanced ages. Therefore, the obtained results from the present study can not only improve the understanding of the geomechanical behavior of FR-CPB but also contribute to the safe design of backfill structures in underground mines.