## 2 Study Sites  
The Andes is a mountain range spanning from southern Chile to Colombia, in the heart of the South American continent. It is characterized by young high elevations, high plateaus, and significant slopes with deep valleys, only surpassed by the Himalayas. The roads and railways of rugged countries such as Bolivia, Peru, and Ecuador are often affected by slope failure problems. These risks entail high maintenance costs, long delays and disruptions in services, and hazards and disasters across the network of national road routes. Ecuador is located in the northwestern corner of South America, bordering Colombia to the north, Peru to the south, and the Pacific Ocean to the west (Figure 1). The insular region of Ecuador is represented by the Galapagos Islands, named by UNESCO as a World Heritage Site, which are part of the Ecuadorian territory and the Biosphere Reserve and Ramsar Sites [23]. The present study focuses on continental Ecuador, historically marked by strong seismic events that have shaped the regional geology, dividing the country into three geological regions: (i) coast or littoral; (ii) Sierra or Interandina; and (iii) Oriente or Amazonia (Figure 1). Figure 1: Geographic location of the study and geological regions of Ecuador. The coast is subdivided into three sub-regions, south, central, and north, in which mainly sedimentary rocks are found, such as conglomerate, claystone, shale, and limestone. The Sierra is divided into north-central, central-south, and south-southwest. The predominant geology of the Sierra includes volcanic and intrusive rocks of the andesitic lavas, pyroclastic rocks, tuffs, and greywackes. The Amazon, also known as the Ecuadorian East, is divided into north, central, and south (west), with mainly sedimentary rocks such as conglomerate, sandstone, shale, claystone, gypsum, slate, and limestone. Geological materials originate from hot spots in the Galapagos Islands, with basaltic lavas dominating [24]. This section briefly lists the areas in which the studied slopes are located (Figure 1). The thirty study sites are located in seven different provinces of the three regions that constitute continental Ecuador: (i) Bellavista neighborhood, via Las Aguas and Faculty of Natural Sciences of the University of Guayaquil (Guayas province), (ii) Coaque-Santa Teresa highway (Manabi province), (iii) Vias Cahuaji-Cotalo, San Juan--Guaranda and Cascada Ojo del fantasma (Chimborazo province), (iv) Papallacta road from Quito to the east (Napo province), (v) El Cajas (Azuay province), (vi) Cantera Mesa, vias Pache-Pinas and Pacha-Ayapamba (El Oro province), and (vii) via Ambato-Guaranda, zones Cashisagua and Gallo Rumi (Bolivar province). Guayaquil (Guayas province) is the most important city on the coast of Ecuador. Guayaquil is nestled chiefly on the banks of the Guayas River, on soft sedimentary terrain with little relief. However, to the west of Guayaquil, there is a series of hills with maximum altitudes of 300 m a.s.l., formed by folded sedimentary rocks. In this province, seven slopes (aslope no. 1, 2, 3, 4, 5, 6, and 7) were studied on byways, courts, streets, and quarries. The heights of these slopes range from 4 to 18 m and include wedge, planar, and toppling stability failure types. The Spondylus route follows the coast of Ecuador. Slope no. 8 is located in the coastal province of Manabi, on a highway called Coaque-Santa Teresa. The 12-m height slope is unstable and presents a wedge-type fault in Andesite Basalts. The province of Chimborazo is placed in the south-central part of Ecuador and includes the Chimborazo, Tungurahua, and Altar volcanoes as the most critical topographic features. The geology of Chimborazo is mainly composed of andesites, rhydites, granites, lavas, volcanic tuffs, and laharite floors. In this Andean province, five unstable and very steep Quasi-Stable slopes (slope no. 9, 10, 11, 12, and 13) are located in avenues and fairways, with heights ranging from 55 to 70 m and presenting wedge, toppling, and planar failures.