The instability of rock slopes along highways is a major concern as it may result in economic losses, increase in maintenance cost and even fatalities. The BR-471 Highway is one of the most important roads in Rio Grande do Sul, Brazil. It connects the main agricultural areas of the State and the port of Rio Grande, one of the largest ports in the country. This highway intercepts the city of Canguçu in a section with an extensive rock slope. In this context, the present paper provides a preliminary study on the stability of this slope based on the Slope Mass Rating (SMR) system. The slope is ranked as class III/IV. Localized wire mesh and removal of prominent blocks in conjunction with deep drainage are suggested as supports.
The BR-471 Highway is one of the most important roads in Rio Grande do Sul, Brazil. It connects the main agricultural areas of the State and the port of Rio Grande, one of the largest ports in the country. This highway intersects the city of Canguçu, which is located on an elevated rocky region. The most prominent rock slope observed in the region has a length of approximately 400 m. Although there is a ditch at the slope base, this segment presents a considerable pedestrian flow due to its location in the urban zone. In addition, it is common to observe small flows of water on the slope's face in humid periods. Therefore, investigating the stability conditions of this slope is of great importance to the local community.
The geomechanical classification SMR - Slope Mass Rating (Romana 1985) allows a preliminary low-cost assessment of susceptibility of rock slopes to failure. It consists of an adaptation of the RMR - Rock Mass Rating (Bieniawski 1989), which was first introduced as a geomechanical classification applied to underground excavation. Over the past thirty years the use of the SMR system has been extended to many countries, confirming its usefulness by the international technological community (Romana et al. 2015). According to Pantelidis (2009) it is the most commonly used classification system for slopes. Brazil lacks of research involving this type of approach to slope stability analysis. Regarding specifically the use of SMR system, there are no published papers in the State of Rio Grande do Sul on the subject. In the light of the foregoing, this paper aims to present the results of SMR application on the section of the BR-471 which traverses the city of Canguçu, as well as provide suggestions of support methods. This study is part of a larger research aimed at analyzing slope stability along BR-471 Highway between the cities of Canguçu and Pelotas - RS.