Key Features Impacting Soil-Conductor Lateral Behaviour as Illustrated by Centrifuge Tests-Paper

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The study investigates how cyclic loading history and pore-pressure dissipation affect the lateral response of subsea well conductors. Centrifuge tests at 40g were conducted on rigid model conductors embedded in reconstituted carbonate silt. The tests applied cyclic displacement sequences with varying amplitudes and cycle counts, including periods of consolidation between loading episodes.<br /><br />Normalised secant stiffness decreased as displacement amplitude and cycling increased. Importantly, stiffness degraded by large-amplitude cycling did not fully recover when subsequent cycles used smaller amplitudes. The degree of this persistent degradation depended on the number of high-amplitude cycles, indicating that response reflects both maximum displacement and accumulated loading history.<br /><br />Excess pore pressure generated during cycling also softened the soil. When pore pressure dissipated between episodes, stiffness increased; under long-term cycling, stiffness initially fell, then partly recovered over time. Thus, cyclic stiffness does not remain at a single steady-state value.<br /><br />The findings suggest that conductor p-y behaviour depends on the conductor’s loading and consolidation history—effects not captured by conventional approaches that use fixed response curves. These changes may influence fatigue-life estimates and shift fatigue hot spots along the conductor as lateral load distribution changes. Similarities between measured conductor stiffness and soil-element shear-modulus behaviour also suggest a possible link for design, though further testing is needed. The research supports developing whole-life soil–conductor models for improved subsea well fatigue assessment.

Keywords

subsea well conductors

cyclic loading history

pore-pressure dissipation

lateral response

centrifuge tests

secant stiffness

carbonate silt

fatigue-life assessment

p-y behaviour

whole-life soil-conductor models