Numerical Analysis Of Driving And Pulling Pile In Jack-up Platform With Skirted Spudcan

Due to the complex soil quality of the seabed,jack-up platforms often suffer from puncture and difficult-to-extract problems during pile insertion and extraction operations.These problems can cause serious accidents to jack-up platforms,cause economic losses,and even casualties.In order to prevent the occurrence of puncture and the difficulty of pulling out piles caused by the spudcan being too deep into the mud,it is necessary to accurately calculate the resistance of the plugging piles to ensure the safety of the plugging and pulling operations of the jack-up platform.Aiming at the hidden safety hazards of traditional spindle-type spudcan in the process of inserting and removing piles,a skirted spudcan structure is proposed.For the skirt structure,the coupled Euler Lagrangian method(CEL)is used to analyze the pile insertion process,pile extraction process and soil flow mechanism of the jack-up platform.(1)Analyze the pile insertion process of skirted spudcan jack-up platform.Firstly,a numerical model for the insertion of spindle-type spudcan in homogeneous layered clay foundation is established,and the resistance of the insertion is calculated.The results are compared with the results calculated by the Brown and Meyerhof formula to verify the correctness of the numerical model.Secondly,based on the verification model,a numerical model of the skirted spudcan insertion pile is established.And compare the pile insertion resistance produced by the skirted spudcan and the spindle-type spudcan.From the analysis results,it can be seen that the use of skirted spudcan can slow down the sudden change of pile insertion resistance and reduce the risk of puncture.Finally,the influence of the skirt length of the skirted spudcan,the strength ratio of the upper and lower soil layers and the thickness of the different upper soil layers on the resistance of the piles is analyzed.It can be seen from the analysis results that when the skirt length is 0.25 D,the pile insertion resistance at this time is the largest and puncture damage is not easy to occur.(2)Analyze the pile pulling process of the skirted spudcan jack-up platform.First,the CEL method is used to establish a numerical model of the pile pulling process,and the numerical calculation of pile pulling resistance is carried out.It is concluded that the maximum resistance of pile pulling occurs when the spudcan is first pulled out.As the pile shoe continues to pull up,the pile pulling resistance decreases slowly.,But basically remain unchanged until the spudcan are pulled out of the soil.Then,quantitative analysis is used to study the influence of skirt pile shoe pulling speed and spudcan foundation depth on pile pulling resistance.From the analysis results,it can be seen that with the increase of the pile pulling speed and the increase of the depth of the spudcan foundation,not only the maximum pulling resistance of the jack-up platform during pile pulling,but also the overall pile pulling resistance will increase significantly.(3)Study the mechanism of soil flow in the process of inserting and pulling out piles on the skirted spudcan jack-up platform.Based on the numerical model of the jack-up platform with skirt-side pile boots,the soil deformation can be calculated.The analysis shows that the soil has four failure modes: surface uplift,cavity formation,wall collapse and backflow.By comparing the soil deformation results with the spindle-type spudcan,it can be seen that a large amount of hard soil will be pressed into the bottom of the skirted spudcan,and a large amount of hard soil will hold underneath,which will make the spudcan insertion resistance smoother and reduce the sudden change in resistance.Circumstances,so the use of skirted spudcan can reduce the harm caused by puncture.Then analyze the soil deformation during the process of pulling out the skirt pile boots.By comparing with the soil deformation results of the spindle-type spudcan,it can be seen that the skirted spudcan have a large side surface area and there is a lot of hard soil in the skirt,and the pile pulling resistance is slightly Larger than spindle-type spudcan.