Optimising spudcan shape for mitigating horizontal and moment loads induced on a spudcan penetrating near a conical footprint

Abstract

The horizontal force and moment induced on a spudcan as it penetrates next to an existing seabed footprint have been identified as one of the key challenges in the offshore oil and gas industry. This paper assesses the potential of changing and then optimising the spudcan foundation shape to mitigate the spudcan-footprint interaction. Large-deformation finiteelement (LDFE) analyses are performed using the Coupled Eulerian-Lagrangian (CEL) approach with the simple elastic-perfectly plastic Tresca soil model modified to enable strain softening and to incorporate strain-rate dependency of the shear strength. The spudcan shape was optimised by parametric analyses varying the spudcan's skirt length, underside profile, and number of holes through the spudcan periphery. A spudcan with a flatter (or even concave) underside profile and with holes was shown to significantly reduce the induced horizontal force and moment during reinstallation next to an existing footprint. However, use of skirts has an adverse influence. Based on the results, an optimised spudcan shape is proposed.

Finite Element Analysis and Parametric Study of Spudcan Footing Geometries Penetrating Clay Near Existing Footprints

“…Their research showed that the soil is obviously disturbed during the initial penetration and will recover with time. To simplify the problem, many of the following studies assumed an artificial footprint, such as Kong [13], Zhang et al [15], Jun et al [16][17][18][19]. The assumption of an artificial reverse cone footprint may respond to a fully recovered 'real' footprint after a long period from the initial penetration.…”

Mitigation Effect of Perforation Drilling on the Sliding Risk during Spudcan Installation Close to Footprints

“…For the first category, Hossian et al [16] laid a foundation by experimental studies of the effect of spudcan's shape on spudcan-footprint interaction. Jun et al [17][18][19] proposed some novel spudcan shapes for easing spudcan-footprint interaction and optimized the shapes through experimental and numerical investigations. For the other category, the "perforation drilling" technique was proposed as a measure of seabed reconstruction, by weakening the bearing capacity of the soil outside the footprint which reduces the eccentricity of the soil under the spudcan.…”