ABSTRACT

The rock massif on which the Castanhão dam is being built is composed of Precambrian metamorphic rocks intruded by igneous rocks. This formation is represented by three stratigraphic units and they are gneissic-migmatitic complex, Ceará Group and alluvial cover. Geostatistical techniques were utilized to analyze and characterize this rocky complex from the data obtained from the samples such as core recovery, RQD, and water loss tests. Variogram modeling of these three variables was carried out considering the values determined through the rotating drill holes. The frequency distribution of the data tend to be skewed. Variographic analysis showed the presence of a good structures. For smaller sample pair distances the variance do not vary much but for higher distances a clear spatial continuity and correlation of the variables can be observed. Geologically variation of the geotechnical properties in gneissic-migmatitc terrains over short distances tend to be minimum.