2025 Volume 81 Issue 15 Article ID: 24-15033
The Architectural Institute of Japan (AIJ) Guidelines for building foundation design propose a formula for calculating the ultimate vertical bearing capacity of spread foundations. In particular, the size effect on sandy ground is thought to be due to the decrease in the angle of shear resistance caused by high confining pressure and progressive failure. Generally, homogeneous and uniform soils are rare, and soil composition is often multi-layered, consisting of sand and clay. Previous studies have examined two-layered clay layers with different strengths, however alternating clay and sand layers taking into account the size effect have not yet been studied. Therefore, in this study, a two-layered soil system of sand and clay was examined using rigid-plastic finite element analysis. A higher-order function is used as a constitutive model for the soil to reproduce the size effect. Simplified formulas are presented for the upper sand layer, the lower clay layer, and the upper clay layer and lower sand layer, and the applicability of the simplified formulas is examined.
