Assessing Cold Temperature Effects on Fully Grouted Rock Bolts Using Distributed Fiber Optic Sensors

Fully grouted rock bolts are one of the most employed ground support systems in underground mining and civil engineering projects. Industrial demands have pushed underground projects deeper and into more extreme environments, such as in Canada’s Northern regions, increasing their complexity and potential hazards. Permafrost temperature conditions can potentially affect the performance of the FGRB systems, however, the existing research into these effects is limited. A series of laboratory pull-out tests were conducted on 1300 mm embedment length specimens in order to observe behaviour changes and study the capacity development of FGRBs in two curing conditions (− 20 and − 5 °C). The study utilized distributed fiber optic technology leveraging Rayleigh Optical Frequency Domain Reflectometry to provide continuous strain profile monitoring (at a spatial resolution of 0.65 mm) along the embedment length during pull-out testing. The cold temperatures proved to be a challenge in grouting FGRBs, and affected the grout strength and the strains experienced by the FGRB specimens. The support systems’ capacity development were observed to have stabilized at 35 days in both conditions, however, the ultimate capacity of specimens cured at − 20 °C remained 10% lower than that of the specimens cured at − 5 °C in the long-term (i.e. 90 days). Understanding these effects and further analysis of FGRB specimen behaviours overtime insights into the composite support systems’ performance at extreme temperatures. This paper highlights the results of this study and aims to bridge selected gaps in existing literature.