Análise numérica da influência da geometria do contato bloco-solo no comportamento de fundações estaqueadas

Abstract

When design estimates are bigger than the conditions supported by a shallow foundation, it is convenient to add piles to improve its performance, so much in load capacity and in reducing settlements. The combination of different types of foundations such as piled raft up is rarely used due to the complexity involved in the process of transferring loads from the foundation elements to the ground. However, in Brazil it is common to use the pile group joined by a pile cap, however, this system does not consider the contributing portion of the block-soil contact in the load capacity of the foundation. On the other hand, in the pile raft, the block-soil contact contributes to the total load capacity and reduction of settlements. Thus, in this work will analyze the influence of the contact geometry of the block-soil and the spacing between piles on the distribution and transfer of loads in piled raft and pile group, by two-dimensional and three-dimensional finite element analysis (FEM) from the geometric variation of the surface element and spacing (s) between piles, keeping constant the number of piles (L = 5m and d = 30cm) and the liquid contact area for each scenario analyzed (s = 4d, 6d and 8d). For this purpose, nine single blocks will be analyzed, three groups of piles, in the respective spacing "s", and nine piled rafts considering the block-soil contact. It was found that the consideration of this contact caused an increase in the load capacity of the system by up to 84%, when compared to the pile groups. While, in the piled raft, the contact block-soil was responsible for about 15% to 61% of the total load of the foundation. The three-dimensional results reveal that the choice of the block-soil contact geometry does not modify in the total load capacity of the system, although it presents significant changes in the mobilization of lateral friction and transfer of axial load in the piles, which in turn alters the load distribution between the foundation elements. The 3D numerical analysis proved to be able to simulate reliable behavior when properly validated and calibrated, when compared, it is clear that the hybrid analysis presents coherent, however, conservative values.