Research On Influence Of Jack-up Rig Spudcan Installation On Adjacent Pile

As important energy sources,oil and natural gas play a prominent role in our country’s economic development.At present,the storage of our country’s offshore oil and gas resources is much higher than that of mainland oil and gas resources.Vigorously developing offshore oil drilling rigs is the key to ensuring our country’s energy security and improving energy self-sufficiency.Jack-up rigs are widely used in engineering due to their simple structure,less steel required,low cost,strong positioning ability,good operation stability,and ability to adapt to different geological conditions.Jack-up rigs are often employed to perform oil drilling or work-overs for jacket platforms without drilling equipment.During this process,jack-up rigs spudcan installation will have an influence on piles of adjacent jacket platforms.At present,the domestic and foreign research on this problem mainly has the following deficiency: Bending moment of straight piles during spudcan penetration is studied while batter piles widely used in piled jacket platforms is not considered.When adopting a two-stage approach using free-field soil displacements and nonlinear pile-soil spring model to predict bending moment of nearby piles,there are no simplified viable methods available for realistically determining the free-field soil displacements due to the penetrating spudcan.The influence of soil flow and remoulding caused by spudcan penetration on lateral bearing capacity of nearby piles is merely studied.Aiming at above problems,this paper uses the coupled Euler-Lagrangian finite element method to conduct a series of numerical simulation.The main research contents are as follows:The mechanism of batter pile bending moment during spudcan penetration is analyzed and pile head bending moment under the most dangerous azimuthal angle is mainly studied.Then the effect of pile inclination angle,pile bending stiffness,soil elastic modulus,clearance between pile and spudcan and other factors are discussed.A formula is established to predict the maximum pile head bending moment during spudcan penetration.The law of free-field lateral soil displacements during spudcan penetration is studied and the normalized free-field lateral soil displacements is obtained.The effect of soil elastic modulus on free-field lateral soil displacements is analyzed.On this basis,the simplified two-stage approach is established,and the error of the simplified two-stage approach is reduced.Spudcan penetration considering soil remoulding is simulated.The influence of change in soil shear strength field caused by spudcan penetration on pile lateral bearing capacity is studied.Then the effect of clearance,soil elastic modulus,pile diameter,soil softening parameters and other factors are discussed.A method to predict pile lateral bearing capacity after spudcan penetration is proposed.