## 2 Materials and Methods
### Development of a Quantitative Method for Disturbance Factor on the Excavated Slope Face  
As is well known, disturbances in the rock mass during slope excavation operations in a slope come from two primary effects:  
1. The generation of new fractures and an increase in the aperture of discontinuities in rock mass near the excavated slope face. 2. Stress relief due to the removal of the excavation cover, especially in deep slope excavations, which leads to transitional disturbances in the rock mass. The first effect that can be observed on the excavated slope face can be quantified by using the EXCASS system, as it is part of the selection of the excavation method that controls the disturbance on the slope surface. The \(EPI_{opt}\) is calculated using Equation (15) based on the inputs \(GSI\) and \(I_{s50}\). As discussed in the previous section, the \(EPI\) value can be adjusted by applying either a positive or negative \(EPR\) (see Figure 1). However, to eliminate the reliance on the EXCASS system chart and enhance the practical usability of \(EPR\), the variation in \(EPI\) due to \(EPR\)  
Figure 1: Excavation assessment (EXCASS) system chart developed by [PERSON] et al. [9]. can be defined as \(\Delta EPI\). When examining the classification transitions from normal to inapplicable above and below the \(EPI_{opt}\) curve in the EXCASS chart (see Figure 1), it is observed that \(EPI\) typically changes by approximately 5 to 10 units per class transition. To simplify the relationship between \(EPR\) and \(\Delta EPI\), a value of 10 units per class transition was adopted in this study (Figure 2). As illustrated in Figure 2, the \(EPI_{opt}\) value determined for an \(EPR\) of zero can fluctuate by \(\pm\)30 (\(\Delta EPI\)), depending on the EPR value, which ranges between \(-\)100 and +100. The operational excavation power index (\(EPI_{o}\)) can be determined by summing \(EPI_{opt}\) and \(\Delta EPI\), which is considered sufficient for practical applications (Equations (16) and (17)). \[EPI_{o}=EPI_{opt}+\Delta EPI \tag{16}\]  
\[\Delta EPI=0.4 xEPR \tag{17}\]  
As a cost-benefit recommendation for practitioners, \(EPR\) can preferably be used within the range of occasionally (\(-\)) to occasionally (\(+\)). For large-scale slope excavations, such as in open-pit mining, \(EPR\) may be increased to enhance excavation efficiency. Conversely, for sensitive slope excavations where minimizing rock mass disturbance is a priority, \(EPR\) can be reduced to ensure lower disturbance degrees. However, since a negative \(EPR\) value will decrease the \(EPI_{o}\), the use of a negative \(EPR\) value should be approached with caution for large slope excavations that involve significant uncertainties. The limit values of disturbance factors for slope cases, as outlined in the guidelines for estimating the disturbance factor (\(D\)) due to stress relaxation and blasting damage, were used in the development of the relationship between \(EPI_{o}\) and \(D_{f}\). As noted by [PERSON] [16], the notation of \(D\) was replaced with \(D_{f}\) to emphasize that the disturbance pertains only to the slope face. Two descriptions of the rock mass, along with the recommended disturbance factors proposed by [PERSON] and [PERSON] [6], were considered in this analysis, as follows:  
1. Small-scale blasting in civil engineering slopes typically leads to minimal rock mass damage when controlled blasting techniques, such as controlled presplit or smooth wall blasting, are employed (\(D_{f}=0.5\)). In contrast, uncontrolled production blasting can cause considerable damage to the rock face (\(D_{f}=1.0\)). 2. In certain weak rock masses, excavation can be performed using ripping and dozing methods. The damage to the slopes in such cases is primarily attributed to stress relief,  
Figure 2: The relation between \(EPR\) and \(\Delta EPI\). with the mechanical excavation effects of stress reduction resulting in a disturbance factor of \(D_{f}\) = 0.7.