Research On Numerical Prediction Of Spudcan Bearing Capacity Of Jack-up Pile Driving Vessel

With the rapid development of offshore wind power engineering,jack-up pile driving vessels are increasingly being applied to the offshore wind turbine installation.The prominent feature of jack-up pile driving vessels is that pile legs are inserted into the seabed soil layer to maintain their stability and carry out construction operations.If the soil strength of the seabed soil layer is too small,the capacity of jack-up pile driving vessels is insufficient,the phenomenon of puncturing to soil layer and even breaking for the pile will occur.These seriously threaten the stability and safety of jack-up pile driving vessels.Moreover jack-up pile driving vessels often suffer from the action of wind,waves and currents during the process of pile insertion,the movement of the pile driving vessel can also have a certain influence on the spudcan bearing capacity.Therefore,the study of the spudcan bearing capacity of the pile driving vessel under the influence of the seabed soil and wind,wave,and current conditions has important engineering practical significance.In this paper,the numerical prediction research on single pile penetration into clay has been carried out by using ABAQUS software,combining the elastic theory of piles with the elastoplastic theory of clay and using the finite element method.In the numerical solution,the dynamic implicit algorithm is used to solve the foundation bearing capacity of the clay layer,and the dynamic explicit algorithm is used to solve the critical height of the clay back-flow.On the basis of verifying the accuracy of the numerical prediction method,the geometric parameters of the legs and shoes of the jack-up pile driving vessel,the hardness and softness of the seabed clay soil,the pile insertion speed of the pile driving vessel,and the influence of the movement of the pile driving vessel on the spudcan bearing capacity were emphatically studied.Furthermore,the stress distribution characteristics of the bottom surface of the pile shoes affected by horizontal and vertical movements of a single pile were studied.The conclusion is obtained in this paper by numerical prediction research.The most influenced factor is the size of the bottom surface of the jack-up pile driving vessel’s pile shoe when the spudcan bearing capacity of the jack-up pile driving vessel is in a single layer homogeneous clay soil.The influence of the width and length of the pile shoe bottom surface on the spudcan bearing capacity is 19% and 11%,respectively.Secondly,it is the effect of the horizontal movement of the jack-up pile driving vessel.The horizontal movement of the pile driving vessel makes the spudcan bearing capacity increase,and the distribution of soil pressure on the bottom of the pile shoe is also changed,as well as the soil pressure on the bottom of the pile shoe is more uneven.Compared to the two states mentioned above,the spudcan bearing capacity is less affected by the undrained shear strength of clay and the vertical movement of the pile driving vessel,both of which are less than 3%.In addition,the spudcan bearing capacity is basically not affected by the radius of the pile leg and the speed of pile insertion.