Avaliação da previsão do comportamento geotécnico de fundações superficiais assentes em subsolos arenosos de baixa compacidade em Fortaleza a partir de ensaios de placa

Abstract

The implementation of a project of shallow foundations requires a prior study of the subsoil. This study includes an allowable stress estimative and prediction of settlements to which the structure will be subjected. To predict the mechanical behavior, investigations are required which can be both field and laboratory. In this context, the plate test is an interesting alternative because, through it, the future behavior of foundation is reproduced in virtually real scale. The present work deals with the study of the behavior of shallow foundations on soils in Fortaleza city, which are sandy low compactness, whose behavior prediction is done currently through the standard penetration test (SPT). The methodology adopted in this study consists of collecting data from plate test and standard penetration test in a local company; collecting disturbed samples in test sites and doing geotechnical characterization of soils in laboratory, previously chosen; performing plate tests with three different diameters (30, 50 and 60 cm), and, finally, analyzing in order to evaluate the performance of sandy soils of low compactness through established methods for predicting the admissible stress, the settlement and coefficient vertical reaction. From there, it was possible to evaluate the performance of several methods commonly used in projects of shallow foundations in practice in Fortaleza city. It was observed that the standard penetration test (SPT) is not an appropriate test for predicting the behavior of sandy soils of low compactness of Fortaleza. In these cases, the prediction of the allowable stress should be made by using more accurate tests like plate tests, cone test (CPT) or even the pressuremeter test (PMT). Moreover, as the coefficient of vertical reaction, the plate test provided superior results to those obtained from correlations with the SPT resistance (N-value). Finally, in relation to the estimation of settlements, the semiempirical method of Décourt (1992) showed the best performance.