## 4 Discussion and Conclusions  
During the design analysis phase, the u\({}_{\rm x}\) values were predicted to be 2.22 cm in the 1-1\({}^{\prime}\) Section and 1.53 cm in the 2-2\({}^{\prime}\) section. The ultimate bearing capacity (q\({}_{\rm ult}\)) value of sandstone, as suggested by [PERSON] [35], was accepted as 200 kPa for sandstones, while it was taken to be 75 kPa for weathered sandstone. The inclinometer measurements in Section 1-1\({}^{\prime}\) recorded a field u\({}_{\rm x}\) value of 2.30 mm, whereas in Section 2-2\({}^{\prime}\), the inclinometer measurements indicated a field u\({}_{\rm x}\) value of 3.90 mm. The q\({}_{\rm ult}\) value obtained from the PT1 pull-out test located near Section 1-1\({}^{\prime}\) was determined to be 190 kPa, whereas the PT2 pull-out test yielded 440 kPa. Given that the field measurements were significantly lower than the predicted values, the geotechnical parameters were re-evaluated. Sensitivity analyses were conducted on the Hoek-Brown (HB) constitutive model, commonly used for rock masses, revealing that the geological strength index (GSI) was the most influential parameter. The Rock Mass Rating (RMR) was reassessed based on field performance values to align the rating with the observed results. Using the revised RMR/GSI values, horizontal displacement variations with depth were analyzed for Sections 1-1\({}^{\prime}\) and 2-2\({}^{\prime}\) using the updated HB model parameters (Table 9, Figures 24 and 25). Figure 24: Horizontal displacements in the remodeled Sections 1–1\({}^{\prime}\) and 2–2\({}^{\prime}\). Figure 25: Horizontal displacement values of the inclinometer section in the remodeled Sections 1–1\({}^{\prime}\) and 2–2\({}^{\prime}\). In order to accurately model rock behavior, stress-dependent parameters must be identified, as the failure envelope curvature increases when the GSI decreases and increases. Neglecting non-linear behavior can lead to an overestimation of the stability of nailed slopes [44]. The modified parameters produced analysis results consistent with those reported in previous studies [36; 45]. According to the geometric parameter analysis incorporated in the design of the soil nail wall, the most influential parameters for stability, in descending order, are nail length [17], nail spacing, slope inclination, and nail inclination. Maximum horizontal displacements were observed at approximately 50-70% of the wall's height (Figure 21). These results are also in good agreement with previous studies [36; 45]. As shown in Figure 20, an optimal soil nail inclination of 20\({}^{\circ}\) and a nail spacing of 1.60 m were identified. Although selecting a slope inclination of 75\({}^{\circ}\) or 85\({}^{\circ}\) negatively impacts stability, the results remain within acceptable limits. Soil nail length emerged as the most critical factor for stability. For a 65\({}^{\circ}\) slope inclination, a 4.00 m nail length with a 20\({}^{\circ}\) soil nail angle yielded a factor-of-safety (FoS) value of 2.27. When the slope inclination was increased to 75\({}^{\circ}\), the FoS for a 1.60 m spaced soil-nailed system was 2.22, while at an 85\({}^{\circ}\) inclination, the FoS was 2.16. The high FoS values obtained from the geometric analyses suggest that using 4.00 m nails instead of 6.00 m ones provides adequate stability while offering a more cost-effective solution, even for steeper slopes. This finding is consistent with results from soil-nail test studies [17; 40]. Additionally, as lower forces are recorded away from the head of a soil nail, shortening the nail beyond a certain threshold may have only a minimal effect. Furthermore, nail length has a negligible effect on weathered rock [18]. Reducing the length of the soil nails from 8.00 m to 4.00 m yielded FoS values between 1.9 and 2.10, making it a cost-effective design choice. However, for permanent excavation, a length of 6.00 m is more suitable to ensure greater safety, long-term performance, and environmental stability.