The penetration and extraction process of the spudcan of jack-up drilling platform may adversely affect the spudcan of the adjacent wellhead platform. The effect of soil strength and the influenced region after the penetration and extraction of spudcan were examined by performing the model tests and the theoretical analysis. A theoretical method for calculating the bearing capacity of an adjacent spudcan within the influenced region of the spudcan penetration and extraction is developed and compared with the model test results. The results demonstrate that

the relative compaction of sand is reduced after spudcan penetration and extraction

and the rate of reduction gradually decreases with increasing distance to the spudcan. The influenced region of the surrounding soil is approximately one times the diameter of the spudcan. The bearing capacity of adjacent spudcan is reduced due to the spudcan penetration and extraction

and the reduction rate of the bearing capacity decreases as the relative distance between two spudcans increases and increases as the relative penetration depth between two spudcans increases. When the relative distance between two spudcans is greater than 2 times the diameter of the spudcan

it can be considered that the spudcan penetration and extraction have no effect on the bearing capacity of the adjacent spudcan foundation.