Avaliação de instalação e desempenho em terreno arenoso de uma estaca helicoidal instrumentada

Abstract

Helical piles are foundation types used to support compressive, tensile, or lateral loading. The capability of being loaded right after installation, the high production rate and the possibility of reutilization in different projects are a few advantages of helical piles. Despite the increasing use of helical pipes, the amount of data collected from field experiments with instrumented helical piles is still relatively small. In this work, the tensile behavior of an instrumented helical pile embedded in a sandy soil deposit is evaluated along the effect of disturbance caused in the ground after installation. The three-plate pile used in this investigation was instrumented with electric resistance strain gages attached to five distinct sections along its shaft. Two sections were used for measuring torque and the other three sections were used for measuring axial load. The performance of the instrumented pile was monitored during installation by measurements of the installation torque. The axial load in the instrumented sections was monitored during two static pullout tests. The disturbance caused by pile installation was evaluated with the results of tests with a dynamic cone penetrometer (DCP) and by radargram renderings from a ground penetration radar (GPR). Results from the instrumented sections showed that the contribution of the top helical plate in the overall bearing capacity is smaller than that of the intermediate and bottom plates. Results from the DCP and the GPR devices suggest that the passage of the helical plates during pile installation reduced soil compaction within a zone of influence from the shaft of approximately three times the diameter of the largest plate.