###### Abstract  
The disturbance factor (\(D\)) in the Hoek-Brown criterion quantifies excavation-induced rock mass disturbance. Although \(D\) is conceptually defined as a continuous parameter ranging from 0 to 1, the most recent Hoek-Brown guidelines provide descriptions only for boundary conditions related to slopes and tunnels. In slope excavations, the degree of disturbance is governed not only by the excavation method but also by the thickness of the removed overburden, with its influence becoming particularly significant in deep excavations. In recent years, the concept of a transitional disturbance factor, varying with depth from the excavation surface, has gained increasing attention. To address this need, the EXCASS system, an empirical method for selecting appropriate excavation techniques based on the Geological Strength Index (\(GSI\)) and point load strength (\(I_{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{ \text{\text{\  
can be applied. Despite its widespread use, the Hoek-Brown criterion remains an empirical tool, and ongoing revisions aim to improve its applicability to increasingly complex rock mass behaviors encountered in various excavation scenarios. The concept of disturbance, originally introduced by [PERSON] and [PERSON] [4] through two discrete equations representing disturbed and undisturbed conditions, was subsequently refined by [PERSON] and [PERSON] [5]. Their modification transformed the relationship into a continuous function, thereby accommodating varying levels of disturbance between fully disturbed and undisturbed rock mass states. This modification by [PERSON] and [PERSON] [5] marked the first effort to account for different degrees of disturbance, ranging from basic mechanical excavation to uncontrolled blasting, based on the extent of disturbance induced by excavation activities. A similar approach was later incorporated into the Hoek-Brown criterion by [PERSON] et al. [3], wherein a new parameter, the disturbance factor (\(D\)), was introduced. This factor spans a range from 0, which represents an undisturbed rock mass, to 1, corresponding to a completely disturbed rock mass condition. The updated formulation of the Hoek-Brown empirical failure criterion, incorporating the disturbance factor, is presented in Equations (1)-(4). \[\sigma_{1}^{\prime}=\sigma_{3}^{\prime}+\sigma_{ci}\left(m_{b}\frac{\sigma_{ 3}^{\prime}}{\sigma_{ci}}+s\right)^{a} \tag{1}\]  
\[m_{b}=m_{i}exp\left(\frac{GSI-100}{28-14D}\right) \tag{2}\]  
\[s=exp\left(\frac{GSI-100}{9-3D}\right) \tag{3}\]  
\[a=\frac{1}{2}+\frac{1}{6}\left(e^{-c\
icefrac{{GSI}}{{15}}}-e^{-2\
icefrac{{ G}}{{3}}}\right) \tag{4}\]  
where \(GSI\) is the geological strength index, \(\sigma_{ci}\) is the uniaxial strength of the rock material, \(s\) and \(m\) are Hoek-Brown's dimensionless constants, and \(\text{m}_{\text{i}}\) and \(m_{b}\) are \(m_{i}\) parameters of the rock material and rock mass, respectively. Although the disturbance factor was transformed into a continuous form in the equations presented above, there is no widely accepted practical approach for selecting the disturbance factor. On the other hand, [PERSON] et al. [3] proposed a guideline for selecting the disturbance factor for tunnel and slope cases. Despite the addition of the disturbance factor as a continuous parameter ranging from a completely disturbed rock mass (\(D=1\)) to an undisturbed rock mass (\(D=0\)), in order to maintain its practical relevance with the experience of using the probable criterion, [PERSON] et al. [3] included explanations and definitions regarding the lower and upper limits in the guideline for determining the disturbance factor, rather than relying solely on a continuous definition.