Axial response of resin-encapsulated cable bolts in monotonic and cyclic loading

Abstract

The ease of use and the design flexibility of cable bolts have made them a popular choice for rock support. Cable bolts can be encapsulated with cementitious grout or resin. There is a need to better understand the impact of resins on the behaviour of cable bolts under varying load and stress regimes over their long service life. This study reports on 18 large scale resin pull-out tests using a 1000 kN pull-out apparatus. The testing apparatus minimised the rotational movement of the cable at the exit point by using a fully grouted anchor tube. Six cable bolts, ranging from 50 to 100 tonnes in capacity, anchored using a fast-curing urea silica resin, were tested under monotonic and cyclic loading. Each cable type was tested twice in monotonic loading and then the average initial peak load was used to generate a cyclic loading pattern. The study found that the resin product had a relatively low load capacity regardless of the cable type, and that loading type had a minimal impact on the results. The cable diameter had a minor influence on the pull-out results. The resin provided a stiff behaviour and an excellent response to repeated loading.

Coaxial load development along grouted plain strand cable bolts determined by distributed fibre optic strain sensing

“…This was observable from visual post-test inspection of the samples (Figure 9), which showed a conical failure surface at the loaded end of the cable and evidential unscrewing at the unloaded end. This result has also been documented by Rastegarmanesh et al (2023). Referring to Figure 10, this resulted in the highest interfacial shear stress (or resistance to displacement) being generated over the first 0.25 m of the cable, which then dropped to lower and relatively uniform resistance further along the cable.…”