The effect of the mobile jack-up spudcan penetration and extraction on adjacent platform piles is an important issue in ocean engineering. Residual moments along piles will exist due to strata plastic deformation after spudcan extraction. If the residual response is large, the combination of the residual load and extreme environmental load may become the controlling load case for the piled structure. In order to understand the variation of the pile responses during spudcan penetration and after extraction, adjacent pile responses are calculated using the Coupled Eulerian Lagrangian (CEL) finite element method. Two kinds of typical seabed, clay and fine sand, are considered during calculation. The effects of the spudcan penetration depth, the spudcan-pile clearance, the shear strength of strata and the pile head constraint on adjacent pile responses are analyzed during spudcan penetration and after extraction. Calculated results show that residual responses of adjacent piles depend on the penetration depth, the clearance, the shear strength and the pile head constraint. The residual response of piles in soft clays is different from that in sands. For piles in soft clays, the residual response of adjacent piles will increase with decrease of the shear strength and the maximum residual pile shaft moment is larger than that during spudcan penetration. For piles in sands, the maximum residual pile shaft moment is about 70-80% of that during spudcan penetration. Therefore, the residual response of piles should be considered when the effect of spudcan penetration on adjacent platform piles is evaluated.
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