Research On Pile-soil Effect Of Jack-up Platform Pile Shoe Insertion-pulling Operation

The jack-up drilling platform has high flexibility,strong maneuverability and low cost,and is widely used in shallow sea exploration and development at home and abroad.The pile boot foundation is usually not designed for specific soil conditions.In soft soil foundations,2 to 3 times the diameter of the pile boot may be penetrated,which is prone to problems such as difficulty in pulling out the pile.At present,the research on the pile boots at home and abroad mainly focuses on the research on the puncture and slippage of the pile boots penetrating into the soil.The pile-pulling and pre-buying method ignores the influence of the pile-insertion process on the soil disturbance,and there is a certain error.Conventional finite element is difficult to reproduce the penetration and uplift of the pile shoe.The CEL or RITSS finite element method can effectively solve the problem of large deformation of rock and soil,but the CEL method cannot establish a special displacement/pore-pressure coupled unit discrete soil model,and the pile up In the process,the adsorption force at the bottom of the pile shoe occupies a large proportion.Based on this,this thesis studies the pile-soil action in plugging-pulling operations through theoretical analysis and numerical simulation,and achieves the following innovative work:(1)Based on the secondary development of ABAQUS,the Python language is used to write scripts to realize the RITSS large deformation finite element method.The soil constitutive model is studied,and the continuous penetration of the pile shoe is completed by using the RITSS large-deformation finite element method.Compared with the existing experimental research on the pile pullout resistance,the accuracy of the numerical method is verified,and the penetration of the pile shoe is analyzed.Soil damage failure mechanism in the process.(2)The existing numerical studies all use the pre-buried method for pile extraction,which is inconsistent with the actual operation process of pile insertion-operation-pile extraction.In this thesis,after the RITSS large deformation finite element method is used to complete the pile insertion,the dissipation of excess pore pressure at the bottom of the pile shoe during the consolidation process will be studied.Based on the secondary development and post-processing of ABAQUS,the excess pore pressure at the bottom of the pile shoe during the pile pulling process is extracted,and according to the excess pore pressure of different nodes and the annular area of the pile shoe bottom corresponding to the node,the adsorption force at the bottom of the pile shoe during the pile pulling process is obtained.The influence of incremental step size,consolida-tion time,depth of pile boot into mud,leg size and slope angle of the top surface of the pile boot on the pile pullout resistance during the pile pulling process was studied,and the soil failure mechanism during the pile pulling process was analyzed.(3)Analyze the existing classical formula of pile pullout resistance,and compare the calculation results of pile pullout resistance formula,numerical simulation results and test results.According to the existing classic pile pullout resistance formula,the calculation program of pile pullout resistance is written in Python language and packaged to generate a visual interface software,which can quickly generate the pile pullout resistance curve according to the soil parameters of the actual working conditions,which can greatly improve the work efficiency.