# An Analysis of Rock Bolt Dynamic Responses to Evaluate the Anchoring Degree of Fixation
## 5 Conclusions  
Fully resinated rock bolts exhibit and maintain their anchoring capacity with time if the annulus between the borehole contour and the steel rebar is regularly filled and the curing of the grout has reached its structural standard.  
The connections between the rock bolt and the rock mass along the anchor borehole contour and at the plate significantly influence the measured dynamic strain in the rock bolt. The connections at the interface between the bolt, resin, and rock also impose complicated boundary conditions on the vibrational behavior of the rock bolt.  
Checking the performance of the bolt is essential, and both direct and non-invasive techniques can be adopted. The method discussed in this study allows for certain default conditions because the influencing parameters can lead to a large number of different boundary conditions.  
In summary, the following results and improvements were obtained:  
* We acquired an advanced comprehension of the suitability of modal analyses for the low-cost assessment of the grouting of rock bolts.
* We developed a tool to model the dynamic response of rock bolts in a MATLAB/Live Script environment; this procedure could be adopted for educational and research purposes.
* An analysis of the performance of low-cost sensors for testing the modal and frequency responses of rock bolts was performed. The amplitude and frequency content of the recorded vibration signal were in correlation with the behavior of the resonance frequencies when referring to the quality of the grouting.
* The development of new sensors should be implemented for the adoption of fiber optic technology in mining and tunneling.  
* We provided validation of a non-invasive technique when the controlled conditions of the grout quality and injection process were known; this could be used for the direct pull-out testing of different rock types at different curing and aging times after installation.  
Future work will focus on testing the quality of resins by sacrificing a few resin capsules from each delivery before using the contents underground. The curing of the grouted annulus after installation on site will also be evaluated using the pull-out testing of the anchors and estimations of the grout loss due to leakage along rock joints.  
Conceptualization, J.S. and A.G.; methodology, J.S. and A.G.; software, A.G. and C.O.; validation, A.G., C.O. and J.S.; formal analysis, A.G. and C.O.; investigation, J.S., A.G. and C.O.; resources, J.S. and A.G.; data curation, A.G., C.O. and J.S.; writing--original draft preparation, J.S., A.G. and C.O.; writing--review and editing, J.S., A.G. and C.O.; visualization, J.S., A.G. and C.O.; supervision, J.S., A.G. and C.O.; project administration, J.S.; funding acquisition, J.S. All authors have read and agreed to the published version of the manuscript.  
Funding was provided by the following grants: \"ENERBLAST: Energy in Blasting and Comminution\" BLASTEST, FONDECYT 11200114, the Politecnico di Torino \"Joint Project for the internationalization of Research\" program; the \"Mine-Plant School Project\", IDI 30487869-0, regional government of the VI Region, Chile; \"REMIND: Renewable Energy for Water Treatment and Reuse in Mining Industry\", Horizon 2020 Research and Innovation Staff Exchange (RISE) Project--Marie Sklodowska-Curie Actions, H2020-MSCA-RISE-2018 (GA 823948).  
Not Applicable.  
The authors declare no conflicts of interest.