Penetration Performance Analysis And Test Verification Of Egg Shell-snail Shell Shaped Bionic Spudcan

Marine oil and gas resources are the country's important energy sources,its mining equipment are various types of ocean platforms,self-lifting platform is currently the most widely used drilling platform.Typical self-lifting platform is mainly composed of hull,leg structure,lifting system,drilling device and so on.When the platform during operation,the spudcans at the bottom of the leg are in direct contact with the seafloor,which plays a bearing role,but the current spudcans have the problems of low bearing capacity,easy punch through and difficulty in pulling.In order to solve these problems,this paper firstly puts forward a design method of bionic spudcan.By analyzing the geometrical structure of the current spudcan,combining the drag reduction characteristics of the eggshell,the good connection rigidity of the snail shell and the soil,and the functional demand of the spudcan,the blunt end of the eggshell curve is used as the rotary bus in the upper part of the spudcan to reduce the drag of the spudcan,and the bottom of the spudcan is designed as the layered structure like snail shell,and the screw curve is used as the rotary bus of each layer to improve the bearing capacity of spudcan and reduce the risk of punch through,an eggshell-snail shell bionic spudcan with high bearing capacity and low pulling resistance are obtained.Then the influence law of the structure characteristics of bionic spudcan on the penetration resistance is studied.The geometric models of bionic convex spudcan,bionic concave spudcan and ordinary spudcan are established,and the CEL method is used to simulate the penetration process.According to the simulation results,the mechanism of soil flow in the process of penetration under the condition of soft clay under hard clay,and the structural characteristics of spudcan affect the formation of soil plug in the lower part of spudcan,and the size of soil plug formed in the lower part of bionic concave spudcan is the largest.Comparing the ultimate bearing capacity of three kinds of spudcans,it is found that the resistance value of the bionic inner concave spudcan is the smallest in the initial stage of the pile,but in the subsequent stage,the resistance value of the spudcan is the largest,which indicates that the bionic inner concave spudcan is superior to the bionic convex spudcan and the ordinary spudcan in the ultimate bearing capacity.Then the influence law of the size parameters of bionic spudcan on the penetration resistance is studied.A series of numerical models are established by using different valueof the overall height of spudcan and different height ratio of upper and lower part,and the CEL method is used to simulate the penetration process.The results show that when the overall height of spudcan is equal,reducing the height of lower part is beneficial to improve the bearing capacity of spudcan,and can make the spudcan reach the holding layer as early as possible,reduce the depth of the spudcan,and facilitate the pulling of spudcan,and when the soil backflow is seriously,increasing the height of the upper part of the spudcan can reduce the volume of the overburden soil and improve the bearing capacity of the spudcan.When the height ratio of upper and lower part are same,if the depth of spudcan operation before the soil backflow,reduce the overall height of the spudcan,can make the spudcan have a larger bearing capacity,if the depth of the spudcan operation after the soil full backflow,then increase the overall height of the spudcan,it can make the spudcan penetrate into the soil quickly in the initial stage,and provide sufficient bearing capacity in the stabilization stage.Finally,the influence of the structural characteristics of spudcan on the penetration resistance is studied by proportional model test.A simulation test platform for spudcan operation is designed,and a simplified spudcan model is used to carry out penetration test under single clay condition,and the CEL method is used to simulate the penetration process,and the test results are verified with each other.The test and simulation results are in good consistency,and the results show that the structure of the inner concave spudcan has higher ultimate bearing capacity than the convex structure spudcan and ordinary spudcan.