## 3 Materials and Methods
### Rock Slope Quality Assessment Using Q-slope  
The Q-index for slopes (or Q-slope) was conceived in 2014, mainly for an immediate application to a hydroelectric power dam in the Dominican Republic. However, the first publication on its application occurred in 2015 [7].  
The equation applied to estimate the value of the Q-slope index shares two-thirds of its content with the original Q-index for underground works [7,27]. The Q-slope is calculated by Equation (2).  
\[Q_{slope}=\frac{RQD}{J_{n}}\cdot\left(\frac{I_{r}}{J_{a}}\right)_{o}\cdot\frac {J_{wice}}{SRF_{slope}} \tag{2}\]  
where:  
RQD: Rock quality designation;  
Jn: Joint set number;  
Jr: Joint roughness number;  
Ja: Joint alteration number;  
O-factor: Orientation factor for the ratio Jr/Ja;  
Jwice: Environmental and geological condition number, which replaces the  
Joint: water reduction factor (Jw) of the original Q-index;  
SRF: Stress reduction factor for the slope. It is the maximum value between SRFa (which addresses physical condition), SRFb (which addresses stress, similarly to the one used in the Q-index); SRFc: (which considers major discontinuity).  
One of the novelties of the Q-slope is the discontinuity orientation factor, known as the O-Factor, which provides an adjustment to the orientation/orientations of the joints present in the studied slope [7]. This parameter is obtained after the joint kinematic analysis establishes the type of failure, considering the orientation of the main joints and the geometry of the slope. The O-Factor is determined from a table in which the only information required is whether the joint (planar failure) or joints (in the case of wedge failure) are very favorably oriented, quite favorable, unfavorable, very unfavorable, or causing failure if unsupported [8]. The information required to identify the O-Factor is easily obtained from the preliminary kinematic analysis of the study cases and field data.  
Another parameter of interest is the strength reduction factor (SRF), which is relevant to consider when the quality of the materials constituting the rocky mass is not high and the heights of the slope increase. These singularities require the appropriate study of the strength state [8]. The strength reduction factor is estimated from the most unfavorable value recorded for subfactors SRFa, physical condition; SRFb, which analyzes various stress-strength ranges; and SRFc, major discontinuity. These subfactors are calculated from data on the type of excavation, blasting, susceptibility to weathering, the physical state of the blocks that constitute the slope, erosion state, unconfined compressive strength, the physical state of the major discontinuity, RQD, and maximum main strength. Depending on available data on sub-parameters a, b, and c, the authors suggest selecting the most unfavorable value or discarding one of the complementary sub-values and only considering the one with the most reliable information that allows for the selection of the best value for SRF.  
For further details about the description and pondering of each factor, the reader is referred to [7; 28].  
The authors of method [7] also proposed the maximum stable angle of the slope (\(\beta\)), expressed in sexagesimal degrees, for a given Q-slope value (Equation (3)).  
\[\beta=20\log_{10}Q_{slope}+65^{\circ} \tag{3}\]  
The geomechanical Q-slope classification requires information on the impact of the construction method on the slope, the state of the surroundings, and effects on exposed slopes, considering the weather, water effects, ice, and evidence of material transportation by gravitational force. Evidence of constructive methods and environmental state was carefully surveyed and compared with the back-analysis of variables--this procedure minimized significant errors in the final evaluation.