Viabilidade técnico-econômica de fundações superficiais e profundas em solo de alta e baixa capacidade de suporte: estudo de caso de uma residência unifamiliar em concreto armado

Abstract

The choice of the foundation system and of the terrain where a building will be located directly affects both the structural safety and the final cost of the construction, especially in urban areas where lots with different geotechnical conditions prevail. In this context, the present work evaluated the technical and economic feasibility of two foundation solutions applied to the same single-family reinforced concrete house, one shallow, with isolated footings on a lot with natural soil of high bearing capacity, and another deep, with continuous flight auger piles on a lot with fill and soil of low bearing capacity. The object of study comprises a 179 m² house, keeping the same architecture for both scenarios. The structural and foundation design was carried out with the software TQS, and the cost estimation was based on the SINAPI table, complemented by prices from local suppliers. The analysis integrated the execution cost of the foundations with the acquisition value of each lot. It was found that the deep foundation required about 277% more concrete and 131.3% more steel than the shallow one, resulting in a cost 406.8% higher. Although the lot with fill proved to be 39.4% cheaper, this saving was surpassed by the foundation cost, so that the scenario on soil of low bearing capacity turned out to be 38.4% more expensive when lot and foundation were added together. Subsequently, both solutions were optimized to reduce the conservatism of the design, which increased the average utilization of the elements and reduced the foundation cost by 9.9% in the shallow model and 6.5% in the deep one, without altering the cost relationship between the systems. In summary, for the conditions analyzed in this study, the higher bearing capacity of the soil resulted in a lower overall implementation cost, showing that the apparent economy of a cheaper lot may not be confirmed in view of the total cost of the construction. [resumo fornecido pelo autor]