Estudo de estabilidade de uma encosta em Faxinal do Soturno – RS

Abstract

In Rio Grande do Sul, are not uncommon records of landslides that affect the structure of highways, especially during rainy seasons. On the RS 149 highway, between the cities of Faxinal do Soturno and Nova Palma, there was a failure in the runway structure associated with a landslide. The affected junction is located at the base of a steep slope near the left bank of the river Soturno. The slope is covered by colluvial material with evidence of older rotational landslides and rising water at its base. Its substrate consists of sandstones of the Botucatu formation. The main objective of this research is to understand the process that originated the rupture of the highway characterizing the mass movement and the involved materials; laboratory tests were performed to classify the material, as well as shear strength tests, to obtain the resistance parameters. From the results, stability analyzes were performed using the Slide software. Mass movements, such as landslides and creep, were detected in the region. These movements modify the topography, greatly influencing the surface drainage of the waters. The highway drainage system today is completely inefficient. The accumulation of water at the side of the highway causes uncalculated pressure on the structure of the landfill and there is also soil saturation, reducing the stability of the massif, which can lead the mass of soil to slip. In the stability analysis, with the Slide software, when the shear strength parameters were used for the condition of large deformations, SF values ranging from 0,94 to 1,23 were obtained. The shear strength parameters that lead the slope to failure are between the peak condition and that of large deformations, indicating that the initial failure already involved a considerable decrease of resistance due to the accumulation of deformations. It seems that the failure occurred due to the sum of several factors. It is believed that soil under the landfill today has a residual resistance where there is already an orientation of the particles, causing new movements to occur easily. Another important factor is the inadequate drainage of the highway, contributing to the instability of this site.