Study On The Pull Capacity Of Bucket Foundation Under Combined Loads

Bucket foundation has been widely used in the development and construction of offshore oil and gas resources such as beach-sea and deep-water offshore platform foundation,as the foundation of seabed facilities such as gravity platform,fixed platform and floating platform.Its application makes up for the shortcomings of traditional marine structure foundation,such as heavy self-weight and high cost,which makes it more suitable for soft soil foundation and complex marine environment.Bucket foundation is subjected to complex loads such as Vertical load(V)and wind wave load(H,M)in the ocean,which brings certain difficulties to the recovery of bucket foundation and the stability of normal work,and has become a hot research topic for the the scholars.The length-to-diameter ratio of the bucket foundation used in the current project is generally less than 10.In this paper,the numerical simulation of ABAQUS software is used to the pull-out bearing characteristics of the bucket foundation under complex loads,with the consideration that the aspect ratio of the bucket foundation is different and the undrained strength of the foundation soil varies with the depth,are studied.The main content,results and innovations of this research are as follows:(1)The bucket foundation subjected to vertical load,horizontal load and bending moment is simulated by finite element software.The effects of the length-diameter ratio of the bucket foundation on the unidirectional ultimate bearing capacity of the bucket foundation are studied,as well as the and the undrained strength of the soil with the depth.The failure mode of the bucket foundation under different load conditions is analyzed systematically,and the ultimate bearing capacity of the bucket foundation under the action of pure vertical pull-up load V,horizontal load H and bending moment load M is obtained.ultimately the calculation formula of ultimate bearing capacity is given according to the finite element calculation result.(2)The more precise fixed displacement ratio method is chosen to adopt,by comparing the fixed displacement ratio method with the calculation principle of the swipe method.The finite element simulation results of the bucket foundation under different displacement ratios is analysed to explore the effects of the aspect ratio of the bucket foundation and the undrained strength of the soil with the depth on the ultimate bearing capacity of the bucket foundation under combined loads VH and VM.The failure mode of the bucket foundation under the combined load is analyzed,and the interaction relationship between the loads under the combined load is studied,in the end the damage envelope is obtained.(3),The calculation formula of the bearing capacity failure envelope of the bucket foundation under the combined load is obtained through the data fitting.The practical example is used to illustrate the application of the calculation formula in the actual engineering.