Numerical Analyses On Effects Of The Spudcan Penetration On Piles Of Adjacent Platform

Jack-up drilling rigs is widely used in offshore oil and gas exploration. The penetration of a spudcan of jack-up drilling rigs beside a pile of jacket platform may causes adverse effects to the pile stability Inevitably. So it's necessary to make analysis and evaluation on effects of the spudcan penetration on the pile of adjacent offshore platform.In this article, the problem of effects of the spudcan penetration on an adjacent pile is researched.First, the feasibility of using Coupled Eulerian-Lagrangian(CEL) method to simulate the process of penetration of spudcan is analyzed by comparing the penetration resistance of the spudcan with the theoretical solution of SNAME standard. The results show that the calculation result of CEL method are close to the theoretical solution and CEL method can reflect the actual phenomenon of soil such as soil uplift on the mud surface and soil siltation.Second, the different parameters of penetration resistance data is discussed in the process of simulation of spudcan penetration of jack-up drilling rigs using CEL method. The results are as follows: different values of Eulerian stratum depth and the coefficient of friction of spudcan and soils had small effect on the result of CEL method; different values of penetration rate of spudcan had small effect on the result of CEL method; gravity of soil should be considered during the penettation process.Then effects of the spudcan penetration on the adjacent pile of different pile head condition is analyzed by CEL method, The feasibility of this method were verified by centrifuge model test. The selection of Eulerian stratum depth has a significant effect on the calculation results. research shows that:(1)In the CEL FEM analysis of effects of spudcan penentration on pile of fixed pile-head condition, If the penetration depth is less than 0.75 times the diameter of the spudcan,the Eulerian stratum depth can be selected as 1-1.25 times the diameter of the spudcan; If the penetration depth is more than 0.75 times the diameter of the spudcan, the Eulerian stratum depth can be selected as 0.5 times the diameter of the spudcan below the penetration depth.(2) In the CEL FEM analysis of effects of spudcan penentration on pile of free pile-head condition, If the penetration depth is less than 0.5 times the diameter of the spudcan,the Eulerian stratum depth can be selected as 1.5-2.5 times the diameter of the spudcan; If the penetration depth is more than 0.5 times the diameter of the spudcan, the Eulerian stratum depth can be selected as 0.5-1 times the diameter of the spudcan below the penetration depth.At last, The effects of the spudcan penetration on the adjacent pile is analyzed by the modifie strain path method and winkler foundation method, it shows that the calculation results of the soil displacements and pile displicements are more conservative than the centrifuge model test results. The simplified theoretical analysis can only be used in the qualitative analysis.