## 4 Conclusions  
A robust laboratory investigation was conducted in order to better understand the effects of ribs, rib spacing and grout annulus on rebar rock bolt performance, as well as complementary modelling development and analysis. This was achieved through the development and employment of an advanced strain-sensing methodology using fiber optics. This research investigated the effect of rib spacing on the activation length, stress attenuation pattern and general behaviour of fully grouted rock bolts for ground support purposes. From the strain data that were produced and collected by the DOS and other supporting instrumentation, it was seen that rib spacing and ribs had a large effect on the general behaviour of the grouted rock bolt systems. Selected investigations concerning themselves with rib spacing presented in literature have shown that with increased rib spacing, better bond strength can be achieved. However, it should be noted that this research was only done on small embedment lengths and generally in very stiff confining mediums. Findings from this current research program highlight that such trends may not extend to less stiff rock or longer embedment lengths. In agreement with the literature, it was determined that stiffness decreased with increased rib spacing. Strain profiles generally showed the following with increase rib spacing: strain was attenuated less effectively, suggesting a reduction of bond performance, with increased rib spacing strain attenuation appeared more linearly suggesting weaker mechanical interlock and, more variance along the strain profile as was observed. These considerations should be explored further prior to in situ implementation by industry. Design engineers should carefully study the predicted loading applied to their support systems that consider grouted rock bolts. They should also pre-determine the amount of displacement that is expected to occur based on the ground conditions in order to make appropriate design decisions. This will allow for informed decisions on the specifications associated with the bolts chosen for a particular project. The implementation of the DOS technique highlighted within this research can also provide geo-professionals with insight into the performance and behaviour of the support elements in situ in a true observation approach. Despite the wide range of annuli tested, no continuous trends were seen across rib spacings. Although limited, selected support was seen that may support the hypothesis that a grout annulus of 9 to 12 times rib height is optimal. The large negative effects found in some of the cited literature were not observed in the testing that was presented herein. Other researchers speculated that these effects were caused by installation methods and not material behaviour. The findings of this research support this theory. This research looked to generate nominally identical (to the laboratory experiments) numerical models that are capable of representing the behaviour of full-length specimens, and compare the model results against experimental results. It was found that modelling using a contact analysis provided a better representation of observed laboratory behaviour of longer embedment length specimens and was able to reproduce a similar effect with increased rib spacings. Specifically, the numerical model was able to capture exponential strain decay, as is seen in experimental results. This is significant as this was not captured in the previous models which used model interactions as joints. This investigation provided further proof of concept of using such methodology for quality control purposes. This novel methodology was also leveraged to provide greater insights into factors which define the performance and behaviour of fully grouted rebar rock bolts. In this research, we continue to investigate and refine the monitoring of ground support and ground support parameters, with the goal of supporting long-term monitoring, numerical representation, and optimization.