NUMERICAL INVESTIGATION ON SUCTION PILE'S HOLDING CAPACITY INSTALLED IN CARBONATE-TYPE SOILS

摘要

Suction piles have not been widely used in carbonate-type soils (i.e., muds/silts) because the pile skin frictions in this type of soils are only about 5% of that in normal clayey soils. The holding capacity of a suction pile installed in these types of soils may be affected by its lower friction. Moreover, pile designers have concerns not only on the development of the Reverse End Bearing (REB) but also on how long the REB can sustain. This paper presents the development of a three-Dimensional Finite Element Analysis (3D FEA) model and the analysis results to investigate the behavior of suction pile for different levels of skin frictions. Firstly, the FEA model is used to investigate the development of the Reverse End Bearing (REB) of a suction pile by assigning two different levels of pile external skin frictions, i.e., 5% and 100% (full skin friction). A vertical load is applied at the center of the pile top. Secondly, the FEA model is used to investigate the behavior of a suction pile for a very low level of pile skin friction (i.e., 5% skin friction). An inclined load with various load angles from horizontal is applied at the padeye (i.e., 16m below seabed). Thirdly, the load carrying (failure) mechanism has been checked by examining the total displacement vectors of soil masses around the pile. Fourthly, a sensitivity study is carried out to investigate the capacity of a suction pile for different usage factors of REB. Finally, suction pile design requirements for carbonate-type soils (i.e., low level of pile skin frictions) are recommended.