Avaliação da capacidade de carga geotécnica em estacas a partir dos métodos semiempíricos e provas de carga estáticas

Abstract

This research presents, in a first step, a study on the behavior of excavated piles of 30 cm in diameter submitted to static load test tests in an experimental field located in the city of Cruz Alta/RS, followed by a study of the reliability of the semi-empirical methods by Aoki-Velloso (1975) and Décourt-Quaresma (1978), with their adaptations, for the stakes tested. To estimate the load capacity, simple reconnaissance soundings carried out on site were used. For the load tests, 3 piles with 30 cm in diameter and 6 meters in length each were submitted to the test. The load versus settlement curve showed a well-defined rupture. The determination of the possible breaking load of the piles was carried out through the average between the values found in the tests and the values found by the Method of Décourt (1998) through the Rigidity Graph. From the results obtained, it is possible to observe that the 3 piles presented results that were relatively consistent with each other. To estimate the strength of the piles, the method proposed by Décourt (2002a) was applied. Based on the results of load tests obtained by Masutti (2020) for piles of 30 cm in diameter and 3.00 m in length in the same experimental field of this study, it was possible to observe that, when doubling the length of the pile, from 3, 00 m to 6 m, its average load capacity increased by 145.27kN, that is, 170.90%. Regarding the semi-empirical methods, the original method proposed by Décourt and Quaresma (1978) was the one that came closest to the results of total load capacity found in the tests, presenting a difference 16.49% lower. However, in relation to the total load capacity, all methods were conservative. In the method by Aoki-Velloso (1975), the correlation between the correction factors that would best adapt to the values found in the PCE tests would be F1 = 3.58F2. The factors α and β of the method by Décourt-Quaresma (1978) would result in α = 0.6749 and β = 1.3417. In a second step, a comparative analysis was carried out between the semi-empirical methods by estimating the load capacity of rotating piles and continuous helix. The estimation of the load capacity of the piles was obtained with the help of the Sisfundações web program, using a database with profiles of SPT tests, most of them carried out in the city of Porto Alegre/RS. The comparison of the results obtained was carried out through the application of statistical tests of Analysis of Variance (ANOVA) and Tukey's test of means comparison. In general, the greatest discrepancy of values between the methods was for the tip resistance in the case of continuous helix piles, and for the lateral resistance in the case of rotating piles. Soils of clayey and silty origin revealed a result of higher geotechnical bearing capacity for the method of Décourt-Quaresma (1978) adapted by Décourt (1996), while the presence of sand resulted in higher values of bearing capacity for the method of Aoki-Velloso (1975).