Research On Numerical Simulation Of Spudcan Penetration For Jack-up Drilling Platform

The jack-up drilling rigs is an important device in the exploration andexploitation of offshore oil and gas resources. In order to ensure the safety of thejack-up drilling rings during the working, it is necessary to evaluate the penetrationresistance of well field. In this thesis, the feasibility of simulating continuouspenetration of spudcan foundation using Coupled Eulerian-Lagrangian technique(CEL) was discussed. The following aspects of the work were carried out and therelevant conclusions were obtained.Firstly, the feasibility of CEL method is analyzed by comparing with centrifugemodel test data and scale model test data. Results are as follows: During the processof spudcan penetration into the homogeneous clay, comparing with the calculationresults of the Skempton ultimate bearing capacity formula, the calculation results ofCEL method are more close to the centrifuge model test results; Using the CELmethod to simulate the scale model test, if the undrained stress-strain relationship ofsoft clay is described by the perfect elastic-plastic model obeying Mohr-Coulombfailure criterion, the elastic modulus is determined using150times of the undrainedshear strength of soil in the conditions of soil and model size in this dissertation. Thepenetration resistance curves of CEL method is close to the results of model test.Secondly, the different influencing factors of penetration resistance data isdiscussed in the process of simulation of spudcan penetration for jack-up drillingplatform using CEL method. The results are as follows: when spudcan is penetratedinto the homogeneous clay, if the truncated boundary of finite element model is4times of the foundation diameter or greater, the influence can be ignored. The settingsfor the different void size have no effect on the calculation results. In the clay soillayer, when spudcan is penetrated in the conditions of0.1m/s penetration rate indisplacement penetration model and0.5MN/s loading rate in force loading model andin the sand soil layer, when spudcan is penetrated in the conditions of0.05m/spenetration rate in displacement penetration model and0.2MN/s loading rate in forceloading model, the penetration process can be seen as a quasi-static process.The applicability of CEL method in practical engineering is evaluated bysimulating the spudcan penetration of jack-up drilling rigs in actual engineering. Theresults show that when using CEL method to simulate the process of spudcanpenetration into the common layered soils, the back-flow of soil can be reflected andthe prediction depth is more accurate and when using CEL method to simulate the process of spudcan penetration into the crusty layered soils, there is a big error withpredicted depth. This needs study in the future.Finally, the influence of spudcan penetration on adjacent pile foundationsplatform is analyzed using CEL method. The results show that with the influence ofover-all platform structure, when spudcan was penetrated to different depth, thedisplacement of pile head arise from spudcan penetration is smaller, but thedisplacement of pile body within a certain range is larger. The position of the positionof the maximum displacement and the maximum bending moment of pile body isconsistent. With the increase of penetration depth, the position of the maximumdisplacement and the maximum bending moment move down.