Buried offshore pipes are prone to upheaval and lateral buckling because of the high temperature and pressure of the materials being transported. An attempt has been made in the present study to evaluate uplift and lateral capacity of buried offshore pipes in a soft clay seabed using finite-element software. The numerical model used in the present study has been validated against results available in the literature. Finite-element analyses are carried out to study the upheaval and lateral buckling behavior of pipes for both the no-tension (NT) condition, i.e., when separation occurs between the pipe and soil, and the full-tension (FT) condition, i.e., when the soil beneath the pipe remains attached to the pipe. The variation of both uplift and lateral normalized capacity factors with soil cover depth ratio is presented for different combinations of soil strength and effective weight. Both uplift and lateral capacity factors have been found to increase and reach a constant peak value with increasing depth of soil cover. A transition from global and local failure mechanisms of a pipe is observed when the capacity factors attain their peak values at a limiting soil cover depth. The critical cases for the design of buried offshore pipe in homogeneous clay are established for both NT and FT conditions.
Screw piles have been used to support a variety of structures due to their ease of installation and high axial capacity. Recently, screw piles have been proposed as an alternative foundation solution for offshore renewable structures due to their quiet or silent installation. Due to their variable geometry, design and prediction of installation requirements and its effect on in-service capacity may be challenging. In this research study, the discrete-element method (DEM) is used to numerically recreate a series of onshore field tests. The aim of the study is to investigate the ability of DEM to be used as a practical design tool for the design and deployment of screw piles. In this case study, the effect of the geometric helix pitch on the installation torque and tensile capacity of screw piles installed into sand is investigated. DEM results show that the geometric pitch of a screw pile appears to have little effect on the installation torque. The results show that DEM has the potential to be used as a practical design procedure for complex foundation installation where the simulation needs to capture installation effects.
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