# Axial Load Transfer Mechanism in Fully Grounded Rock Bolting System: A Systematic Review
## 3 Analysis and Results
### Influential Parameters on the Axial Behaviour of FGRBSs
#### 3.3.5 Effects of Bolts Geometry and Surface Profile Configuration on FGRBS Performance  
System splitting is entirely absent with round rebars. Thus, the geometric design of ribs, including their height, width, angle, spacing, and orientation, plays a crucial role in the capacity of FGRBSs (Figure 13).  
The surface profile of the ribs dictates the width of the shear zone and the fracture angle within the encapsulation medium. These factors hold greater significance for FGRBSs compared to conventional steel rebars used in civil engineering applications. This is primarily due to the exposure of FGRBSs to significantly higher dynamic loads [99]. [PERSON], [PERSON] [57] applied discontinuous deformation analysis (DDA) numerical modelling to investigate the effect of rib on the BS. They demonstrated a positive correlation between maximum BS and rib face angle within the range of 30-90\({}^{\circ}\). Conversely, rib face angles below 30\({}^{\circ}\) were found to be ineffective in enhancing BS. It was also stated that larger rib spacing had a possible negative correlation with bond stiffness. Studies conducted by [PERSON] and [PERSON] [63] and [PERSON], [PERSON] [100] demonstrated that BS and axial load capacity increase with the ribs' height and rib spacing. After several pull-out and push tests, [PERSON], [PERSON] [99] found that the axial bearing capacity would be highest where the profile spacing is 37.5 mm. [PERSON], [PERSON] [101] attempted to visualise the failure patterns of rock bolts with different surface profiles using an X-ray CT scanner. The authors concluded that the failure mechanism of FGRBSs is dependent on the specific design of the ribs' shape and the bolt's lugs. [PERSON] et al. [53] highlighted the dependence of the optimal bolt profile configuration in FGRBSs on both the mechanical characteristics of grout and confining stress. [PERSON], [PERSON] [102] performed push and pull-out tests to investigate the influence of rib spacing on transferring the loading mechanism. The study examined the FGRBSs with various spacing of 12, 24, 36, and 48 mm, encapsulated in steel and concrete. The results show a 23.5% increase in the maximum peak loads increased by large rib spacing when confined in the steel. Interestingly, no significant difference in peak loads was observed between large and small rib spacings for FGRBSs encased in concrete. However, in both confinements, energy absorption in large-spacing samples was higher than in the small-spacing samples. [PERSON], [PERSON] [103] attempted to examine the effect of the bolt configuration on the bolt's mechanism by seeking crack initiation and propagation. For this, the FGRBS was simplified as a typical joint. Experiment results revealed that rib angle has little influence on crack initiation and propagation and peak shear strength; however, as the rib angle decreases, shear stiffness slightly increases. [PERSON], [PERSON] [104] studied the influence of various factors of a rock bolt's profile, such as rib angle, mortar thickness, rib space, and rib shape on axial behaviour of rock bolting systems by conducting DDA and experimental methods. After conducting several laboratory pull-out tests, [PERSON], [PERSON] [105] found that the axial bearing capacity of FRGBSs has a positive correlation with the rib spacing.