| Driveability of platform foundation piles in offshore engineering is a comprehensive, complex and systemic problem. It involves several subjects such as dynamics, structure mechanics and soil mechanics. In recent years, with the development of offshore oil drilling platforms, the requirement for the pile foundation becomes higher. As the primary type of platform foundation, pile foundations are taking on some new characters, such as larger diameter, longer length and deeper penetration. It is one of the advanced research topics to predict the driveability of such kind of piles more accurately. Based on large amount of pile driving records and several pile driving projects, studies have been performed as follows:(1)The steel piles for deep water jecket have large length, diameter and weight, which makes the level lifting and positioning upright become one of the most important steps of construction. Lifting and positioning upright of super length pile without any bulking is one of the essential problems in the deep water jacket construction. In order to ensure the safety of the pile during construction, the optimum design method of the location of the suspension center was presented and the relationship among stresses, inclination and span length of the pile during overturning was studied.(2)According to Timoshenko's elastic stability theory, a new method of analyzing the stability of pile stick-up was proposed, in which the self weight of pile was considered in the calculation of the critical bulking load. The calculation results for a project calculated with the API code and the proposed method were compared, which prove the applicability of the proposed method in the stability analysis of pile stick-up.(3)Soil plug effect has great influence on the driveability of the pile. Analyzing the soil plug effect accurately and reasonably make great sense in driveability analysis. When applied to piles with super large diameter (about 2m), the existing calculation method of soil plug effect gives untrue results. The static equilibrium method adopting Terzaghi's theory of bearing capacity of deep foundation was introduced, in which the edge load effect was considered and the dynamic effect coefficient was included. The calculation results verified the applicability of the new method in projects with super larger diameter piles. (4)In practice, pile run often occurs when the pile goes into soft clay layer with large thickness. This brings about many inconveniences to construction. Stress wave equation was adopted to modeling the pile run phenomenon in pile driving. The modeling measure was applied to a practical project, and the results agree with the recording data well.(5)Based on the practical project, the causation of pile refusal phenomenon was analyzed by studying the soil strength, the pile design and the construction method. Based on one-dimensional stress wave theory and the driving records, a back analysis method was put forward. The mumber of blow count and the hammer energy for restarting a pile were simulated, and the recovery ratio of soil strength was calculated. The refusal risk analysis of the pile was carried out with the results of back analysis, and the reasonable time or location to break driving was presented.
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