Numerical Investigation of the Effects of Internal Friction Angle, Cohe-sion, and Clay Density on the Bearing Capacity of Piled Raft Founda-tions

Piled raft foundations, due to their protrusions along the cross-section, exhibit higher bearing capacity compared to conventional piles and are considered an efficient solution for foundation construc-tion on weak soils, particularly clayey soils. This study investigates the influence of geotechnical parameters, including internal friction angle, cohesion, and clay density, on the compressive bearing capac-ity of a piled raft using PLAXIS 3D finite element software. For this purpose, a concrete piled raft with a length of 10 m and a diameter of 0.7 m was modeled in four different soil types (loose clay, semi-dense clay, dense clay, and alluvial soil of Isfahan). The effects of varying cohesion (30–90 kPa) and internal friction angle (15–45°) were ana-lyzed separately. Results indicate that an increase in clay density sig-nificantly enhances the bearing capacity of the piled raft, such that the bearing capacity in dense clay is more than six times that in loose clay. Additionally, increasing cohesion from 30 to 90 kPa leads to an approximate 62% increase in bearing capacity, while increasing the internal friction angle from 15° to 45° results in about a 59% in-crease. Validation of the numerical results against previous studies shows excellent agreement. Overall, among the parameters investi-gated, soil type has the most pronounced effect, whereas internal fric-tion angle has the least influence on the bearing capacity of piled rafts