Evaluation of erosion risk at the base of an electric power transmission line

The Brazilian Federal District is covered by a porous, collapsible tropical soil layer with thickness that can reach 30 meters. Below this layer it can usually be found a stratum of saprolite over slate or metarrythymites strata. Commonly the water table is found at the contact between the porous soil and the saprolite. It is common in this region for the occurrence of gullies and piping. In many cases the piping mechanism is triggered by an increase in surficial water hydraulic gradient in regions of gullies due to the combined action of gradient increase and water table lowering. In view of the regional aspects presented above, this work describes the evaluation of the possibility of a gully reaching an electric power transmission line in its final stage of construction. Studies on the possibility of the gully to move towards the transmission line ii were carried out as well as a surveying on the water table in the area and the direction of the groundwater flow. Laboratory tests were also performed to study the soils in the region, such as soil classification tests and erodibility tests (double-sedimentation, pinhole and Inderbitzen tests). This study indicates that there are no risks for the transmission electric power line being affected by the piping mechanism in the existing erosion process (i.e., gully).