Contribuição à confiabilidade de estacas tipo raiz através de um estudo de provas de carga estáticas com aplicação da teoria bayesiana.

Abstract

Safety is a subject of great interest in foundation engineering researches, mainly in recent times. Most researchers understand that the simple utilization of safety factor represents an outdated approach for geotechnical designs. The deterministic treatment does not include the uncertainties due to the construction process being the foundation the last step of the design. This aspect has led to the increasing necessity to also verify the risk of the foundation collapse by means of a reliability analysis. The present research aims at contributing to the discussion of the reliability analysis, based on the Brazilian Code rules and the recent developments of predictive methods for pile capacity estimations through a case study using root piles. Two types of uncertainties are studied: that related to soil variability and that from the estimation model. The pile ultimate soil resistance is initially extrapolated by different methods as the maximum likelihood function for using Bayes update. Then the a priori estimation is obtained. Finally, the updating is performed using Bayes method. Two a priori estimation are considered in order to contribute to the open discussions posed by some specialized Brazilian engineers and researchers on risk analysis in foundation engineering. The main idea to consider two distinct a priori estimate was based on two motivations: i) to contribute to the practice in combining information from a documented case as proposed by Vrouwenvelder (1992) and ii) to motivate discussion about the polemic arguments from foundation engineering in Brazil related do the adoption of safety factors below 2 in case of pile tests specified during foundation design.