Cantilever piles or well foundations in supporting temporary deep excavations: comparison of performance, safety and cost

Due to the increasing population in the metropolitans, the construction of the high-rise buildings and shopping malls etc. has rapidly increased for last three decades. Therefore, especially in the city centers, the area of the construction sites has become very limited. Moreover, the requirements such as high bearing capacity of the soils beneath the skyscrapers and the parking area for the vehicles makes the application of the deep excavations essential. It is well-known that designing both safe and economical retaining structures in cohessionless soils such as sands and gravels or silty-clayey mixtures of them is still a challenging issue in geotechnical engineering discipline. Under that circumstances, the construction of two types of the retaining structures frequently comes into the minds: cantilever piles and well foundations. These retaining systems should be designed not only to be resist against failure but also to meet safety requirements for existing buildings and infrastructures near the site until the active forces, which are induced by the soil mass, are supported by the structural elements of the superstructures. In addition to this, the horizontal deformations along the retaining structures should be less than the limits defined by the specifications and the structural codes. In this study, the performances and costs of the both cantilever piles and well foundations in different excavation heights are compared parametrically. For this purpose, a benchmark sandy soil profile given in the literature and the retaining systems are modeled in 2D by using finite elements method. Furthermore, in order to determine the internal forces based reinforced concrete design and the unit costs; a well-known commercial software is used. The promising results of this study could guide to the design engineers in practice for selecting safer and more economical systems within engineering judgment.