Study on the disturbance effect of silty seabed caused by repeated spudcan penetration and extraction

The spudcan penetration and extraction processes of the jack-up drilling rig will seriously disturb the natural seabed. In the present study, the penetration and extraction processes of the jack-up platform in silty seabed were modeled with the help of an indoor physical model experiment, and comparison was made between the model findings and the field CPT repeated penetration results. Based on this, the disturbance effect of silty seabed caused by a single and repeated penetration and extraction of pile was discussed from a qualitative and quantitative perspective, respectively. The results show that compared with the initial spudcan penetration and extraction process, the geometric size of the pile pit caused by the second process was expanded to some extent; the excess pore water pressure caused by the second penetration of pile was lower than that created during the first pile penetration, and the maximum drop could reach 35%; the disturbance degree of seabed caused by the repeated penetration and extraction of pile generally decreased linearly with the increase of the horizontal distance from the center of the pile, and the soil at the middle layer was disturbed more seriously than shallow and deep soils; in comparison with the initial penetration, the tip resistance of pile during the second penetration reduced to some extent, while the corresponding final peak tip resistance was increased, together with the relatively close pulling forces between them; and the development trend of the pile tip resistance monitored from the indoor physical model experiment showed good consistency with the field CPT repeated penetration test results.