Volume 35, N. 2, May-August 2012 | DOWNLOAD PDF(8 downloads)
Abstract
Some difficulties of performing an engineering geological mapping task in sites where residual and transported sandy soils are widespread are discussed in this paper. The study area is located in the municipality of Analândia in the southeast of Brazil. In this region landscape evolution is dominated by scarp retreat and relief inversion processes. As transported and residual soils have very similar grain size distributions, the results of geotechnical tests performed on both kinds of soils are very similar. Understanding the regional landscape evolution was essential for performing the mapping task. The method used combined aspects of engineering geological mapping based on synthetic and analytical approaches and it is strongly supported by field observations. The expected engineering behaviors of the mapped units are presented. Some of the units correspond to colluviums that occupy hilltops, a geomorphological position were they would not be expected. Moreover, the “stone lines” are common features in the area and their identification clearly defines the unconsolidated material as allochtonous. However, they are not always located at the bottom of the colluvial deposits, and sometimes they are not present at all or show lateral discontinuity. Some other characteristics are distinctive of these widespread deposits.
