Monitoring the failure process of cemented paste backfill at different curing times by using a digital image correlation technique

Abstract

• Volumetric water content (VWC) was used to quantify hardening process of cemented paste backfill (CPB). • Fracture development in CPB having different curing times was visualized by using the DIC technique. • Fracture process was divided into four stages, i.e., the gestation, initiation, propagation and coalescence of fractures. Understanding the mechanical properties and failure process of cemented paste backfill (CPB) is fundamental for the backfill design in underground mining. In this research, physical and mechanical tests were conducted on CPB having different hardening times. The volumetric water content (VWC) was used to reflect the CPB hardening process because it is a confirmed controlling variable that strongly correlated with the peak strength, brittleness index and maximum strain at fracture initiation. Moreover, the deformation behavior, fracture development and failure pattern of CPB having different curing times were observed by using a digital image correlation (DIC) technique. The experimental results suggest that the fracture development can be divided into four stages, the gestation, initiation, propagation and coalescence of fractures. The failure pattern changed from shear to tensile-shear composite and finally to tensile failure as the water content decreased. The results contribute to better understanding the time-dependent mechanical behavior of CPB after it is back-filled into underground stopes.