Optimization of Settlement and Bearing Capacity in Clayey Soils Using the Taguchi Method in Düzce

In geotechnical foundation engineering, the bearing capacity and settlement behaviour of clay soils are key parameters governing foundation performance. Insufficient bearing capacity and excessive settlements limit economical foundation design and may lead to increased structural deformations. This study investigates the physical and mechanical properties of low-plasticity (CL) and high-plasticity (CH) clay soils obtained from boreholes drilled in Düzce Province, Türkiye, where bearing capacity, settlement, and relevant soil parameters were determined through field and laboratory testing and subsequently evaluated using statistical analyses. The calculated bearing capacity values ranged from 192 to 556 kPa, while settlement values varied between 0.88 cm and 5.83 cm. The corresponding maximum-to-minimum ratios were approximately 2.89 for bearing capacity and 6.62 for settlement. The effects of unit weight, water content, particle size distribution, groundwater level, internal friction angle, and cohesion on the bearing capacity and settlement behaviour of the examined clay soils were systematically assessed. The results indicate that unit weight is the most influential parameter for increasing bearing capacity and reducing settlement in CL-type soils, whereas the cohesion coefficient is the dominant parameter in CH-type soils. The results indicate that variations in shear strength and moisture-related parameters exert a significant influence on foundation performance. The findings provide quantitative insight into the relative impact of key soil parameters and offer practical implications for the design of building foundations in clayey soils under similar geological and geotechnical conditions. From a practical perspective, the findings support foundation design, especially in earthquake-prone areas, by accounting for soil bearing capacity and ensuring that settlements remain within permissible limits to maintain long-term structural performance.