## 4 Discussion and Conclusions  
This study addresses the long-standing challenge in the literature concerning the selection of the disturbance factor, a critical parameter in slope stability analyses, particularly as excavation depth increases. For over two decades, the disturbance factor, defined as a continuous value between 0 and 1, has largely been determined based on user experience since its introduction in the Hoek-Brown failure criterion. The definition proposed by [PERSON] and [PERSON] [6] serves as the primary guideline, offering boundary values for disturbance factors for slopes and tunnels, rather than a continuous functional relationship. However, the use of the disturbance factor between the lower limits (\(D\) = 0.5 and \(D\) = 0.7 for small-scale and large-scale slopes, respectively) and the upper limit (\(D\) = 1) is completely left to the user's discretion. Two notable key studies by [PERSON] et al. [7] and [PERSON] et al. [8] aimed to overcome the subjectivity in applying this experience-based guide. However, the relations derived by [PERSON] et al. [7] and [PERSON] et al. [8] are based on empirical equations that incorporate other empirical relationships. Due to the nature of such equations, there is a potential for errors from each component to compound in the final derived \(D\) relationship. While these two studies provide a continuous variation for the disturbance factor between 0 and 1, both rely on wave velocity measurements (\(V_{p}\) and \(C_{p}\)), which must be taken before and after the disturbance. In other words, in a disturbed rock mass condition, measuring both wave velocities with depth is only possible once the slope excavation has reached that depth of the excavation stage. In addition, the compatibility of this relation with the lower limit values of \(D\) = 0.5 and \(D\) = 0.7 for small and large-scale slopes, respectively, as suggested by the developers of the Hoek-Brown failure criterion for slope excavations, is also open to discussion. However, the two mentioned seismic-based studies have the potential to be considered in field verification and potential improvement efforts of the practical quantitative tool proposed in this study. Rock mass disturbance due to the excavation operations in a slope mainly occurs due to two effects. The first is the generation of new fractures and the widening of discontinuity apertures in the rock mass close to the excavated slope face. The second is stress relief caused by the removal of the overburden, especially in deep slope excavations, which results in a transitional disturbance within the rock mass. The first effect is mainly related to the excavation method, such as diggers, rippers, hammers, and blasting. Therefore, the first effect, which can be observed on the excavated slope surface, can be quantified using the EXCASS system developed by [PERSON] et al. [9], which aids in the selection of appropriate excavation methods. Based on this concept, the EXCASS system has been incorporated into [PERSON]'s [6] qualitative guideline for determining the disturbance factor of an excavated slope face. Moreover, the compatibility of this relationship with the lower limit values of \(D\) = 0.5 and \(D\) = 0.7 for small and large-scale slopes, respectively, is satisfied. It is very important in successful engineering designs such as slopes, tunnels, and dam construction to minimize disturbance to the rock mass during the excavation process. However, a stronger excavation method, which may increase the degree of rock mass disturbance, might be preferred to reduce the completion time for deep slope excavations. Conversely, in critical slope excavations, a weaker excavation method may be chosen to minimize rock mass disturbance. For this purpose, \(\Delta EPI\), which is determined as positive (stronger) or negative (weaker) depending on the \(EPR\), provides flexibility to the proposed tool. It allows the user to determine the level of disturbance based on the user's experience, while also considering the importance of the degree of excavation.