2D and 3D numerical analysis of pile length variation on piled raft foundations

As technology advances rapidly, the construction of high-rise and heavy structures is becoming increasingly important. In cases where a project must be constructed on soils with low strength, where soil parameters are not suitable, either raft foundations or piled raft foundations must be used. In geotechnical engineering, it is crucial to select a foundation type that is both capable of meeting the existing adverse conditions and cost-effective. The utilization of piled raft foundation systems, which consist of the total load-bearing capacity of both rafts and piles, is on the rise. The construction of piled foundations is quite expensive compared to shallow foundations. For this reason, optimum economic costs should be considered in the design of piled foundations. By using different combinations of parameters affecting the design, analyses can be performed with the help of computer software to save time and labor. The obtained numerical analysis results should be compared with each other. After these comparisons, more realistic and economical designs can be modelled. In this study, 2D and 3D numerical analyses were conducted separately for three different relative soil densities (Dr=10%, Dr=40%, and Dr=65%) for piled raft foundations with various lengths of edge piles (10 cm, 15 cm, 25 cm, and 30 cm). As a result of the numerical analyses performed with PLAXIS 2D and 3D CONNECT Edition V21 package programs, the bearing capacity and settlement values of piled raft foundations in response to the load from the structure were investigated. As a result of the numerical analyses, it was observed that the bearing capacity values increased by 150-200% and the settlement values under certain loads decreased by 15-40% when the length of the edge piles increased from 10 cm to 30 cm. In addition to that, it has been observed that the bearing capacity increases by 250-380% as the relative density (Dr) of the soil increases from 10% to 65%. When the bearing capacity and settlement values obtained from changing the length of edge piles and relative density are analyzed, it is observed that these values are within acceptable safe limits. Considering all these issues, it is concluded that more economical designs can be made by reducing the edge pile lengths within the specified limits.