Análise probabilística da estabilidade de taludes em barragens de terra no estado do Ceará

Abstract

The objective of this work is to perform probabilistic analyzes of slope stability in Ceará State earth dams. Carry out the study of slope stability by different methods, compare the values obtained by them, analyze the behavior of the slopes in situations of critical conditions of full reservoir and rapid lowering, perform probabilistic stability analyzes considering the variations in soil characteristics and determine the failure probabilities (PF) of the dam analyzed can be categorized as the specific objectives of this work. Faé Dam and Orós Dam were chosen as study objects and Slide 6.0 software was used to perform the analysis by the Fellenius, Simplified Bishop, Simplified Janbu, Spencer and Morgenstern-Price methods. This study was conducted in four stages. The first consisted of a bibliographic review about earth dams and slope stability analysis and data collection about the studied dams, the second was the dam modeling in Slide 6.0, the third step was the analysis with the software and lastly the review of the results. 1.5 for the full reservoir condition and 1.1 for the fast lowering condition were considered as safety factor limit values. The Janbu and Fellenius methods presented the lowest Safety Factor values and consequently the highest probability of failure. In general the results obtained by the different methods did not show great divergence among themselves. For the full reservoir condition none of the dams had a Probability of Failure greater than 0.000% for the downstream slope. In this condition, based on the Morgenstern-Price method, the probabilistic Safety Factor values were 2,180 for the Fáe Dam and 1,925 for the Orós Dam. At the condition of rapid lowering of the maximum reservoir level in half at a rate of 15 cm/day, the Faé Dam reached a Safety Factor condition of less than 1.1 at the 29th stage, of the 45 stages analyzed, with a Failure Probability of 41.525% and an FSP of 1.091. The Orós dam reached the same condition in the 62nd stage, of the 150 analyzed, with a probability of failure of 21.9% and FSP equal to 1.076. The method chosen to perform the Safety Factor calculations influences the result obtained, both in probabilistic and deterministic analysis, and it is up to the designer to choose between more or less conservative methods.