Research On The Spudcan Penetration Performance Of Jack-up Platform

In order to meet the growing energy demand,China is actively carrying out jack-up platform research and production.Spudcan is the key bearing structure of jack-up platform.Due to its bad working environment,the platform is easy to punch-through in layered soils comprising hard clay overlying a soft clay layer.It is also easy to slip when the spudcan penetrating near the footprints.In this thesis,in order to solve these problems,the characteristics of layered soils and the structure of the spudcan on the puncture performance are studied;the characteristics of the remaining footprints and the structure of the spudcan on the slip performance are discussed.The main research contents and conclusions are as follows:(1)A finite element numerical model of spudcan penetrating in a hard-soft-hard layered soil is established,the effects of soil characteristics on platform puncture in hard-soft-hard layered foundations are discussed from the aspects of spudcan insertion resistance,puncture speed,and puncture depth.The results show that the platform puncture risk and puncture depth increase with the height of the hard clay layer and the soft clay layer.The total height of hard clay and soft clay remains unchanged,when the relative height ratio is less than 1,the puncture depth increases with the increase of the relative height ratio;when the relative height ratio is greater than 1,the puncture depth decreases on the contrary.The puncture depth increases with the increase of the strength of the hard soil and the strength ratio,decreases with the increase of the strength of the soft clay.(2)Spudcan models with different structural sizes are established,the influence rule and influence degree of spudcan structure on its puncture performance are explored through single variable test and multi-factor orthogonal experiment.The results show that the spudcan diameter has the greatest influence on puncture depth,followed by the spudcan bottom height,and the spudcan bottom shape is the smallest.Increasing the diameter of the spudcan,reducing its bottom height,increasing the height ratio of the spudcan,and adopting a concave bottom shape can effectively reduce the depth of puncture and reduce the risk of puncture.(3)Based on the soil parameter test,the model of the spudcan inserted near the remaining footprints is established,numerical analysis and model test are used to study the influence of the footprints characteristics and spudcan structure on the sliding performance.It shows that when the offset distance is 0.5D,the slip load is the largest,which should be avoided in actual operation,where D is the footprint diameter.The slip force of the spudcan increases with the increase of the footprint depth,the footprint slope and the footprint diameter.The bottom shape,diameter,height ratio and the bottom height of the spudcan have a greater influence on the sliding load: the peak load of the horizontal slip increases with the increase of the spudcan diameter and its bottom height,and decreases with the increase of the height ratio of the spudcan.The concave spudcan can effectively reduce the sliding force and the slipping risk of the platform.