Comparative Evaluation of Cone Penetration Test Data for Estimating the Bearing Capacity of Pile Foundations in Sandy Soils of Sanur, Bali

Accurate estimation of foundation bearing capacity is a fundamental aspect of geotechnical engineering design, directly influencing the safety, serviceability, and cost-efficiency of structural systems. Among various in-situ testing methods, the Cone Penetration Test (CPT) has gained widespread application due to its efficiency, reliability, and ability to provide continuous soil profiling. However, despite its advantages, CPT data may exhibit considerable variability even within relatively small areas, especially in sandy soil conditions commonly found in coastal regions. Such variability can lead to significant differences in estimated bearing capacities, posing challenges in foundation design decision-making. This study presents a comparative analysis of CPT data collected from several locations within the Sanur area of Denpasar, Bali, Indonesia. The selected sites are geologically characterized by predominantly sandy deposits with minimal cohesive content. The ultimate bearing capacity of shallow foundations was estimated using Terzaghi’s classical bearing capacity theory, assuming a foundation depth of 6 meters for consistency across all test points. The results reveal that the calculated single pile bearing capacity ranges from 10.22 to 13.42 kN with 0.30-meter diameter and 6-meter depth. Coefficient of Variation (CoV) values support this finding, with qc​ exhibiting moderate to high variability (15%–62%) and fs​ showing lower variability (7%–17%). These CoV values are consistent with established ranges for sandy coastal soils and align with findings from previous studies. This moderate degree of variation reflects the influence of local subsurface heterogeneity, even in seemingly uniform sandy strata. The study highlights the necessity of integrating statistical evaluation of geotechnical parameters into design procedures, especially in environments where small-scale soil variability can affect structural performance. The findings provide practical insights for geotechnical engineers and practitioners, emphasizing the importance of multiple CPT soundings and spatial analysis when developing foundation design criteria in similar coastal environments.