A Random Finite Element Study On Failure Mechanism And Bearing Capacity Of Spudcan Foundation In Single Layer Clay And Sand Overlying Clay Stratum

As a kind of mobile offshore drilling equipment,the jack up drilling platform can be used for offshore oil and gas exploration and exploitation.As an important part of the jack up drilling platform,the pile leg is attached with a huge inverted cone foundation at the bottom,which is called "spudcan".Its function is to reduce the penetration distance of pile leg in clay.It can bear the supporting force of the sea bottom to the platform,which is convenient to locate or increase the sliding friction between the foundation and the foundation in the sea bed.The effective diameter of the pile shoe foundation is usually10-20 m,and the depth of the pile shoe buried in the sea bed soil is 2-3 times of the diameter of the pile shoe,so as to obtain enough bearing capacity to ensure the safety in the operation process.So far,many scholars have done a lot of research on homogeneous soil and heterogeneous soil,but due to the complex formation process of marine rock and soil,it presents the nature of spatial variation,and its failure mechanism and bearing capacity are quite different from homogeneous soil and heterogeneous soil,although some scholars have explored the pile shoe foundation of single-layer clay soil based on small deformation finite element analysis The bearing capacity of foundation and the influence of failure mechanism,but the small deformation finite element method is difficult to simulate the backflow of soil in the process of continuous penetration of pile shoe foundation,so in this paper,combined with the large deformation stochastic finite element numerical simulation and Monte Carlo method of coupling Euler Lagrange,the failure mechanism of pile shoe foundation is studied when considering the spatial variability of clay foundation and sand covered clay foundation The change of management and bearing capacity.For single-layer clay foundation,when the variation coefficient of undrained shear strength and the relevant length change,there are obvious differences with the airport,which leads to the difference of failure mechanism of pile shoe foundation and the fluctuation of bearing capacity.Therefore,there are obvious differences in the distribution of logarithmic probability density of the excitation shear strength coefficient,but the characteristic value of the excitation shear strength coefficient calculated according to the failure probability But it has certain stability.In this study,the stability of the characteristic value of the excitation shear strength coefficient is not affected by the variation coefficient of the undrained shear strength and the relevant length.Therefore,this value can be used to design in the engineering application to meet the requirements of the target reliability and ensure the economic safety of the project has certain practical significance.For the sand covered clay foundation,the strength of the upper sand layer soil is higher,and the strength of the bottom cohesive soil is lower.When the pile shoe foundation reaches the peak bearing capacity in the sand layer during the penetration process,it is easy to produce puncture damage.When considering the spatial variability of the clay layer,the peak depth is basically the same.The variation of the lower clay strength at this depth has little impact on the internal damage mechanism of the sand,but the underlying pad In this paper,the reliability level of the peak bearing capacity is evaluated according to the logarithmic probability density function of the critical bearing capacity,combined with the failure probability and reliability.