Geophysical for granitic joint patern and subsurface hydrology related to slope instability

Abstract

The groundwater flow in fractured rock is an important process that allows to understand the hydrological dynamics at hillslope scales as well the increase of pore pressure at specific points in the soil-rock contact. Exfiltration from bedrock fractures on the failure surfaces and stability problems related to structural characteristics of rocks are common in the highland region of Rio de Janeiro, which were identified in a landslide scar resulting from a translational shallow landslide at the soil-bedrock interface triggered by the extreme rainfall events in January 2011. Considering the temporary springs from bedrock fractures in fresh landslide scars this research aims to analyze, through Ground Penetration Radar (GPR), the structure of the rock and the pattern of fractures in subsurface to understandand the hole the existence of a network of fractures in the slope hydrogeological dynamics and possible consequences for its stability. GPR results proved the existence of fissural suspended aquifers near the surface and sub-vertical tectonic fractures acting as geological barriers that create saturation zones inducing the formation of suspended discontinuous aquifers. It is possible that the fracture systems are determinant for the deflagration of mass movement in the region, mainly of translational shallow types, on slopes covered by saprolites overlying fractured rocks.