Proposta de inclusão da previsão da ocorrência de fissuramento do solo na verificação da segurança de barragens de terra, utilizando análise elástica associada com variação da rigidez – estudo de caso: Barragem de Piaus - Pi

Abstract

During the first filling of a dam, when part of the embankment becomes saturated, the appearance of settlements resulting from the loss of stiffness due to soil wetting is expected, even in very well compacted embankments. Current protocols for designing and verifying the safety of earth dams generally include flow and slope stability analyses, adding the assessment of deformability when the contractor requires it or there is a fear of soil cracking occurring in the field. The general goal of this research is to propose that the prediction of the occurrence of cracking zones, via associated elastic analysis using the stiffness variation technique for unsaturated soils that exhibit deformable behavior when wetted, be integrated into the practices for verifying the safety of earth dams, in the design, first filling, and monitoring phases, in subsequent years of operation. To this end, this research implemented this method of predicting the occurrence of cracks in earth dams, using as a case study Piaus Dam, located in the town of São Julião, in the Southeast region of the State of Piauí. During the first filling, Piaus presented transverse cracks in both abutments, with significant risk to the operational safety of the dam, since the cracks extended to elevations below the water level in the spillway condition. To this end, the simulation of three cross sections of Piaus (maximum section and core-abutment interfaces) was performed, using the softwares Slide2 (two-dimensional transient flow simulation) and UNSTRUCT (stress x strain analysis). The comparison between the results of the associated elastic analysis and observational data of Piaus intended to evaluate the reliability of the proposed modeling. In the simulations, Piaus did indeed present points of greater deformations on the upstream slope and in the crest, close to what was observed in the field. In view of this, a roadmap for performing the associated elastic modeling is presented, with the aim of guiding the geotechnician in the use of this practical and easy-to-implement tool, which requires test parameters that have a consolidated and accessible methodology (characterization and double oedometer), eliminating the need to purchase other expensive software or equipment. The prediction of deformations in dams aims to avoid pathologies that impact the performance and lifespan of the structure, especially when the reservoir volumes fluctuate in response to changes in the rainfall regime resulting from climate changes, such as periods of prolonged drought or heavy rains, which can cause flooding.