Abstracts Earth and Environmental Sciences

Estudo experimental de parâmetros geotécnicos da barragem de terra da margem esquerda de Itaipu: Experimental study of geotechnical parameters of Itaipu left earth dam

by Júlia Bosso de Mello

Itaipu Binacional is a hydroelectric plant located on the Paraná River, between Brazil and Paraguay, and consists of a series of dams, made of concrete, rockfill and earth. Since 1984, when the initial filling of its reservoir was completed, the water level presented small variations. However, dry periods have caused the water level to remain longer at lower heights, subjecting the foundation and the dam soil to more intense cycles of drying and wetting. This research aims to experimentally study geotechnical parameters of the foundation and massif soil of the left earth dam under saturated and unsaturated conditions. Hydraulic conductivity and eodometer and triaxial compression tests were conducted to update the geotechnical parameters according to the Unsaturated Soil Mechanics, and water retention curve and soil volumetric shrinkage tests were performed to determine parameters that allow predicting the behavior of the dam considering variations in the water level. The results indicate that the water retention curves have typical plastic clays characteristics and that both the natural and the compacted soils presented high shear strength. It was also possible to prove the influence of higher suctions on the mechanical behavior of the soil, increasing the strength shear and decreasing the volume change. Finally, the results highlight that the deformation by volumetric shrinkage of the compacted soil during drying conditions was higher than the deformation by oedometric consolidation, demonstrating that the compacted soil is more susceptible to volumetric change due to drying effects than to external loads applied, as long as there are favorable conditions to such occurrences.