## 1 Introduction  
Soil mechanics has traditionally been focused on the study of sedimentary soils; however, recently, there has been growing interest in residual soils. Granitic residual soils are a type of residual soil originating from the in situ weathering of granitic intrusive rocks exposed at or near the surface. These types of soils are common in numerous parts of the world. The geotechnical characteristics of residual granitic soils have been studied in Brazil [1, 2], China [3, 4], Hong Kong [5], Malaysia [6], Portugal [7], South Korea [8], and Thailand [9], to name a few. A granitic residual soil, locally known as \"maicillo\" is commonly found in Chile. Maicillo is a residual soil resulting from the in situ weathering of granitic rocks formed from intrusive bodies of the Corollaries de la Costa coastal batholith situated parallel to the Pacific coast of Chile. It is one of Chile's most abundant residual soils and can be found between the the Valparaiso Region (33\({}^{\circ}\)00\({}^{\prime}\)S) and the Nhanelbuta mountain range, (40\({}^{\circ}\)00\({}^{\prime}\)S) [10, 11], covering a length of approximately 600 km. Due to the widespread occurrence of this type of soil in Chile and other parts of the world, infrastructure works frequently encounter zones composed of this material, and, therefore, excavations in it are common. Thus, a correct characterization of the materials that make up slopes is necessary for slope stability studies and to guarantee the safety of excavations. The understanding of the influence of each of the factors that determine the stability of a slope in this type of material facilitates its characterization, particularly parameters whose characterizations are much more sensitive. However, the applicability of sophisticated sensitivity analysis methods in geotechnical engineering is normally limited by the amount of available information, both field measurements and information obtained using numerical modeling. Probabilistic and sensitivity analyses are useful tools for studying slope stability in rocks and soils. [PERSON] et al. [12] mentioned that slope designers are interested in understanding which factors influence slope failure in order to implement mitigation, maintenance, and repair measures. Therefore, these probabilistic analyses proved to be interesting research topics. [PERSON] et al. [13] stated that engineers are not completely satisfied with the solutions to given problems provided by traditional approaches, necessitating additional results. They emphasized that, on occasion, knowing the safety factor (SF) or the characterization of the geometry of the failure surface is insufficient. [PERSON] and [PERSON] [14] proposed the inclusion of safety maps as a source of information on parameter changes and how they modify the slope's safety factor and the resulting failure surface. Meanwhile, [PERSON] et al. [15] proposed the inclusion of the influence of human activities on stability. Sensitivity analysis is a powerful method that can be used to derive information on the influence of different parameters on the stability of a slope. For example, [PERSON] et al. [16] carried out a sensitivity analysis for an unreinforced slope composed of a stratum of residual soil over a sandstone stratum located in Kuala Lumpur, Malaysia. The study used [PERSON]'s method [17] and the general limit equilibrium method of slices (GLE) to obtain the safety factor associated with variations in cohesion, friction angle, unit weight, and water table position. The authors found the following order of parameter influence: water table position, followed by the residual soil friction angle, cohesion, and unit weight. They also stated that the underlying sandstone stratum parameters did not influence the analysis, as the failure surface did not reach this material. [PERSON] and [PERSON] [18] used a Monte Carlo simulation to determine the failure probability of a rock slope in Sau Mau Ping, Hong Kong.