An Experimental Study on the Effects of Bearing Pressure on the Friction Angle for Spudcan Penetration Analysis

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4. An Experimental Study on the Effects of Bearing Pressure on the Friction Angle for Spudcan Penetration Analysis

Prediction of the penetration of spudcans into sand involves using bearing capacity calculations, which are dependent on the chosen friction angle. This has led to discussions on which value of the friction angle should be used for spudcan penetration analysis. The mobilised friction angle during spudcan penetration is influenced by the relative density of the soil and the size of the spudcan, and, consequently, the stress level in the failing soil. In fact, the bearing pressure under spudcans can be very high, causing a decrease in the peak friction angle, due to lower dilation caused by high confining stresses. Therefore, as stated by ISO 19905-1 (2023), using the peak friction angle directly for design may not be appropriate, as it may lead to an overestimation of soil resistance. The main goal of this study was to demonstrate the widely reported effects of high confining stresses on the peak friction angle, by conducting a series of drained triaxial tests on sand at different relative densities with increasing values of mean effective stress. The values of the friction angle derived from laboratory testing were then compared with values estimated using a strength-dilatancy relationship. Finally, the results obtained from the laboratory were used to assess the differences between existing guidelines for spudcan penetration analysis, taking into account the typical bearing pressure values encountered in the field.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

14 - Spudcans: penetration, extraction, interactions