Fracture behavior of fiber-reinforced cemented paste backfill under curing pressure

Abstract

Due to the rapid strength acquisition rate, relatively high solid content, and sustainable reuse of waste tailings, cement paste backfill (CPB) technology has gradually become a standard practice in underground mining operations. To improve the engineering behavior and performance of CPB materials, fiber-reinforced CPB (FR-CPB) has attracted increasing interest over the past decade. The application of fiber reinforcement can improve the mechanical properties, including the material strength and ductility, and enhance post-peak resistance. However, the successful implementation of fiber reinforcement requires the full consideration of field curing conditions. After placement into underground mined-out voids (called stopes), the massive backfill structure (with a backfilling height of tens to hundreds of meters) yields a high-level curing pressure under the gravity effect, which accompanies the development of microstructure and macroscale mechanical properties of backfill materials from early to advanced ages. Therefore, to accurately assess the development of mechanical properties and behaviors of FR-CPB, it is essential to fully consider the effect of curing pressure. Moreover, the previous studies focus mainly on the conventional geomechanical behaviors, including compressive, tensile, and shear behaviors, of FR-CPB materials based on the elastoplastic theory. As a result, the previous studies aim to correlate the permanent deformation and material degradation and thus evaluate and design backfill materials for their engineering applications. However, as a type of cementitious material, the brittle response and the associated catastrophic failure of the CPB matrix are governed by the crack growth. Through crack propagation and coalescence, the degradation of mechanical properties occurs and may lead to material failure at the macroscale. [...]