Pushover Test For Jack-up Platform Considering Spatial Variability Of Clay

Jack-ups are widely used in offshore industry,especially in the exploitation of oil and gas resources.However,the seabed soil layer is complexly distributed,and the Jack-up needs to withstand multiple random loads such as surge hurricane and upper vertical load.Therefore,system bearing capacity,failure mode,failure mechanism of the Jack-up in complex seabed under multiple random loads are necessary to study to ensure its safety.It is very difficult to conduct research on this subject through field test and centrifuge test.Therefore,this paper intends to develop stochastic finite element method to study the stability of jack-up rig under multi-load in complex seabed.In this paper,the finite element numerical simulation method is used to study the influence of system bearing capacity,failure mode,failure mechanism.Combining spatial variability theories with finite element method into numerical simulation analysis,this paper aims to know how combined load and the random soil influence the system capacity,failure mode,failure mechanisms of Jack-ups.In this paper,based on the software of ABAQUS establishing the model of Jack-up(include hull,legs,spudcan foundations)and soil is the foundation.The results obtained in the numerical simulation analysis are compared with the experiment results and theoretical studies.Then,introduce the three-dimensional undrained shear strength field of the soil into the established numerical model.Through the finite element analysis,the vertical,horizontal load,the vertical,horizontal displacement of the spudcan foundations along with applied to hull horizontal load are obtained under the combined load conditions.Comparing with the results of normal consolidated homogeneous soil,combined with the random field contour of undrained shear strength,the soil displacement vector and equivalent plastic strain contour around the spudcans in random soil are analyzed.400 examples of random soil are calculated to study the failure modes of jack-up rigs.It is found that there are many new failure modes exists,such as uneven settlement between the legs,which causes the Jack-up to overturn,the horizontal slip of spudcans,all legs to sink,and the composite failure modes.The distribution law of load between each spudcan is studied.It is found that the horizontal load of the spudcan is closely related to the horizontal displacement.The vertical load will be redistributed between the spudcan foundations alongwith applied to hull horizontal load.