Interpretação de provas de carga em estacas pelo modelo matemático de Massad contemplando cargas residuais

Abstract

Residual loads arise along driven or jacked piles and on any pile type previously loaded, for example, after conventional load tests. Although the residual loads do not affect the ultimate pile capacity, they change the load transfer and, therefore, the settlement for the service loads. Miscounting of residual loads causes a settlement prediction greater than the actual settlement when residual loads are present after complete unloading. In the case of mixed foundation, the residual loads affect the load partition between the different foundation elements. This research aims to analyze a database of static load tests including driven and excavated, rigid and compressible piles, using the mathematical model of Massad (1992, 1993, 1998, 2004). The model can separate load transferred by lateral friction, tip mobilized resistance and the residual load at the tip based on load test results. Much of the database includes instrumented piles, with the direct measurement of the lateral friction. The total measured friction mobilized resistance is then compared to the total lateral friction obtained by the model. After a detailed study of Massad's contribution, a spreadsheet was developed to automate the calculations and later calibrated with the interpretation of cases documented in the literature. Then, the database was interpreted, separating the piles according to the pile soil relative stiffness and the installation method. The graphical method derived from the original model was also applied in the case of rigid piles. The use of the mathematical model was also compared to the graphic method from Decourt (1991). The tests interpretation is very much in agreement with Massad's previous results and allows a fresh look at relevant aspects of the behavior and performance of pile foundations.