Análise comparativa de soluções de fundações em solos argilo-arenosos para prédios altos em Fortaleza-CE: estudo de caso

Abstract

The verticalization of Brazilian coastal cities poses challenges to foundation design for highrise buildings, particularly in regions with complex geotechnical characteristics. In this context, this study presents a comparative analysis of foundation solutions for a 54-story residential building located on the Fortaleza-CE seafront, founded on sandy-clay soils of the Barreiras Formation. To this end, four alternatives were evaluated: mat foundation (raft), large-diameter bored piles with barrettes, and two piled raft configurations (50 piles Ø2,000 mm and 185 piles Ø1,200 mm). The methodology employed classical analytical methods — Décourt-Quaresma for bearing capacity, Schmertmann and elasticity theory for settlements, and PDR (PoulosDavis-Randolph) method for piled rafts —, which were validated against numerical modeling using ELPLA and RS3 software. Furthermore, the multi-criteria analysis considered technical aspects (bearing capacity, settlements, and angular distortion), economic factors (SINAPI and SEINFRA-CE cost tables), constructability (feasibility and schedule), and environmental aspects. The results indicated that the mat foundation presented average settlements of 10.69 to 10.79 mm and maximum angular distortion of 1/1,343, comfortably meeting the 1/500 limit for high-rise buildings. On the other hand, piled raft Option 1 showed distortion of 1/926, while Option 2 (1/443) did not meet the normative criterion. Field monitoring validation of the mat foundation recorded settlements of approximately 2.00 mm over 64 days, with a settlement rate of 27.17 μm/day, a value consistent with theoretical predictions. Finally, the multi-criteria analysis demonstrated that the mat foundation is the most suitable solution, achieving a score of 4.85, with the lowest estimated cost (R$ 4.09 million), excellent constructability, and minimal environmental impact, showing that shallow foundations can be viable for high-rise buildings when geotechnical conditions are favorable