Research On Pulling Resistance Of Ocean Jack-up Platform Spudcan

Now with the shortage of non-renewable resources,like oil,the world began to ask the ocean for resources.The offshore jack-up drilling platform in the process of oil exploration plays an important role.For the sake of the repeated use of the jack-up platform after the operation,the jack-up drilling platform will pull the spudcan and the leg,and it will then continue its work in the next site.At present,the research of the spudcan mainly focuses on the penetration of spudcan,while there are relatively few studies on the extraction of spudcan.Based on the finite element method,random field theory and Monte Carlo simulation,the random finite element model is established in this paper to study the factors affecting the uplift of spudcan,the composition of uplift resistance,the modification of uplift resistance formula,and the influence of spatial variability on the uplift of spudcan.In this paper,based on ABAQUS,a large finite element software,a finite element model for the uplift of spudcan was established.The change of pore water pressure and effective stress in the uplift of spudcan was considered by using the Cambridge model,and the results were compared and verified with centrifuge experiment results.By the method of programming,we calculate upper resistance,lower resistance,pore water pressure.We carried some parameter studies and analyze the influence of them,such as the compression index ?,swelling index ?,stress ration M,Poisson's ratio v,the initial void ratio e and pulling rate.The backflow of soil,load displacement curve and stress distribution cloud diagram were also studied,and the uplift formula of horizontal anchor was modified to make it applicable to the calculation of spudcan.The model established in this paper was used to verify its reliability.It was found that the excess pore water pressure was the main factor for the increase of the uplift resistance during the uplift of spudcan,and the distribution of the excess pore pressure was not uniform.We used the relationship between the Cambridge model parameters and the plastic index to build the random field of plasticity index,and compared the results of homogeneous soil with random soil.The failure mechanism of extraction were also studied.Some representative nodes were chose to observe the change of excess pore pressure and effective stress and compared the similarities and differences between random phenomenon of soil and the homogeneous soil.Based on Monte Carlo simulation,we carried out on the spatial variability of the spudcan and studied of the influence of the spatial variability by statistical analysis.The reason of maximum and the minimum of pulling resistance were analyzed.We studied the distribution of resistance,upper resistance,lower resistance and tried to find their fitting functions.We did chi-square tests on them with a 95% confidence level.The spatial variability of clay has a great influence on the uplift resistance of spudcan.