Systematic Simplification of CPT-Based Soil Profiles for Assessing the Axial Bearing Capacity of Offshore Piles

Abstract The cone penetration test (CPT) is essential for soil classification and pile bearing capacity assessment. In practice, engineers simplify stratigraphic profiles into representative layers, but this process often depends on subjective judgment, introducing uncertainty. This study proposes an automated CPT-based soil profile simplification framework that preserves key stratigraphic characteristics while minimizing subjectivity. The method determines representative layer thickness based on averaged CPT-derived data and applies systematic merging criteria. Over 50 stratigraphic profiles from Taiwan and Germany were analyzed and compared with results from commercial software. The results show that the axial pile capacity deviations between the simplified and original soil profiles depend strongly on both the T/D ratio and the regional soil conditions. For Taiwanese offshore silty soils, the errors increase with larger T/D values, ranging from 4–42% at T/D=0.25 to as high as 82% at T/D=1.0. In contrast, for German offshore sandy soils, the deviations remain below 20% across all methods and thicknesses. These findings indicate that the proposed simplification approach provides a practical balance between computational efficiency and accuracy, but the acceptable T/D range should be site- and method-dependent.