Research On Several Issues Of CEL Numerical Simulation Of Spudcan Penetration And Its Effects On Adjacent Piles

Spudcan penetration resistance and its effects on adjacent piles have drawn much attention among researchers when considering jack-up drilling rigs.On the basis of previous research,simulations of free-field spudcan penetration and that with an adjacent pile are carried out using Coupled Eulerian-Lagrangian(CEL)method.Through a series of research as follows,relevant conclusions are obtained.Firstly,five typical seabed profiles commonly encountered in the field are considered: clay,sand,clay overlying sand,sand overlying clay,and layered soils.Simulation of spudcan penetration using Coupled Eulerian-Lagrangian(CEL)FEM is conducted,and numerical results with centrifuge test results are compared.It is shown that:(1)The setting of the range of Eulerian domain has no effect on the calculation results for various soil profiles.(2)Fine mesh is selected near the spudcan while coarse mesh far away in CEL models.For various soil profiles,the research confirms that decreasing the size of fine mesh or increasing the range of fine mesh can ease the vibration of the penetration resistance curves.By comparison,the conclusion provides references that the size of fine mesh is proposed to be set as 0.05 times the diameter of the spudcan,meanwhile,the range of fine mesh is proposed to be set as 2 times the diameter of spudcan for various soil profiles.(3)When the displacement-controlled loading is adopted,the penetration rate has a little effect on the profile of clay,while a great effect on the profile of sand overlying clay,and it has a certain influence on the layered soils.By comparison,a penetration rate of 0.2m/s is selected in FEM when investigating the calculated penetration resistance in various soil profiles.On the basis of above work,the simulation of spudcan penetration in the model test of 1g based on CEL method is conducted.Different grid sizes in the model are selected and the vibration of several penetration resistance curves is compared.It can be found that the conclusion is feasible for the simulation of the 1g model test.Secondly,effects of the spudcan penetration on the adjacent pile are analyzed by CEL method to seek a rational setting method of Eulerian domain depth.By comparison of the numerical results with different pile lengths,different clearances between the spudcan and the adjacent pile and different soil conditions further on the founda-tion of previous work,the influence of Eulerian domain depth on the numerical results is discussed.It is shown that when a depth from the mudline to the 0.5 times the diameter of spudcan below the penetration depth is selected for the Eulerian domain in the CEL finite element model,the calculated results are comparatively rational.Finally,the distribution of the stress during spudcan penetration on the adjacent pile is analyzed based on Non-linear Foundation Model with p-y soil springs.Then,the control equation is established and solved.It is found that the calculated results are consistent with the centrifuge test results approximately.Afterwards,the lateral soil pressure on the adjacent pile in the model test is analyzed preliminarily and distribution curves of the stress on the pile shaft are provided.