Numerical Study Of The Penetration And Extraction And The Reinstallation Of Spudcans Of Jack-ups

The foundations of Jack-up will form depressions with a diameter of over ten meters in the seabed after being installed and retrieved,which are also called ?footprints?.If the platform is reinstalled near the footprint,the spudcan may slide into the footprint,causing bending damage of the legs or even the danger of overturning the platform,which is called ?step in footprint?.Since the existing numerical simulations on the problem of the footprint are calculated and analyzed based on the artificial footprint without considering the disturbance of soil of the footprint,there is some distance to the real footprint.Therefore,this paper uses the ABAQUS/CEL large deformation finite element method to simulate the process of forming a natural footprint through the installing and retrieving of a spudcan with considering the different strain softening conditions,and based on this kind of natural footprint to analyze the dynamic response of reintallation,considering flat footing,spudcan and skirted footing.Mainly content and conclusions are as follows:(1)This paper mainly analyzes the mechanism of the formation of natural footprint by three kinds of spudcans under different strain softening conditions,and the geometry of the footprint and the distribution of the soil shearing strength in the footprint.The geometry of the "depression zone","disturbance zone","?-shaped core disturbance zone",and "unperturbed zone below the footprint" are used to quantitatively describe the formed footprint.The degree of disturbance of footprint formed by skirted footing being installed and retrived are larger than that of the other two kinds of spudcans.(2)This paper discusses the response of eccentricity to the reinstallation of spudcans based on natural footprint,and compares them with the calculation results of artificial footprint.The results show that there are obvious differences in horizontal reaction force and bending moment during reinstallation of spudcans,especially for the latter.When spudcan is eccentrically reinstalled near the natural footprint,the bending moment will produce double peaks.In the case of artificial footprint,the bending moment will only produce single peak.