## 3 Results Analysis and Discussion
### GeoPIV Analysis Results  
The analysis of pictures taken while the tests were carried out to monitor the deformation at the time of collapse and the formation of the slip band in the unreinforced and reinforced model tests in the soil under different conditions were analyzed using the PIV method. To use this method, GeoPIV-RG, an image analysis module designed for geotechnical research applications running under the MATLAB R2019B program was used (2018). First, the image analysis of the tests carried out on unreinforced soil was made. Afterward, PIV analyses of the experimental groups with 1% and 2% fiber content at 30% relative density were performed, and the PIV analyses of the experimental groups with 1% and 2% fiber content at 50% relative density were performed, respectively. Although the images obtained according to the fiber type are similar, the analysis results obtained from the macromesh fiber-added soils, which have the greatest effect on the bearing capacity in general, are given. The shear strain images resulting from the PIV analyses are shown in Figures 21 and 22.  
Figure 21: _Cont._  
Figure 21: PIV results with Dr = 30%: (**a,b**) Unreinforced; (**c,d**); Fiber content 1%; (**e,f**) Fiber content 2%.  
Figure 22: Cont.  
When the analyses were examined, it was seen that the grain movement in the unreinforced soil was deeper than in the reinforced soil. When the data on reinforced soils were evaluated, it was observed that the displacement decreased as the relative density increased. In general, it can be said that with the increase in the relative density and increasing the fiber reinforcement ratio from 1% to 2%, the displacement decreases and the effect of the loads from the foundation is not transmitted to deeper [45]. In unreinforced model tests, shear surfaces at Dr = 30% relative density were observed to form as punching shear failure, and slip surfaces at Dr = 50% relative density were observed to form as a local shear failure. When reinforcement is added to the unreinforced soil, the slip surfaces of the soil go from a punching shear failure to a local shear failure at Dr = 30% soil. When the percentage of reinforcement was increased from 1% to 2%, the stresses were distributed over a larger area, and a larger area was affected on the right and left sides of the foundation. In general, the addition of reinforcement to the soil transferred the stresses in the soil to a larger area that was observed in the current paper in the case of fiber-reinforced specimens has also been reported before by other researchers such as [PERSON] et al. [71], [PERSON] et al. [72]. In this way, the area over which the stress is distributed has increased and it has been observed that the ultimate bearing capacity is higher in reinforced soils than in unreinforced soils.  
Limitations and Future Work  
Since basalt fiber with a length of 48 mm could not be supplied in the study, the effect of fiber length could not be investigated in the basalt fiber-added experimental groups. In hybrid fiber groups, the fibers were limited by mixing them at the same length and in equal proportions. In the future, the fibers used in the studies to be carried out with random  
Figure 22: PIV results with Dr = 50%: (**a,b**) Unreinforced; (**c,d**); fiber content 1%; (**e,f**) fiber content 2%.  
hybrid fibers can be added to the soil at different percentages, and model tests can be made. The effects of hybrid fibers, which will be prepared by using fibers of different lengths, on soil behavior can be investigated by laboratory and field tests. In addition to the fibers used in the study, the use of different fibers as hybrid reinforcement in the ground can be investigated.