Reasonable Wall Thickness Calculation of Offshore Super-long and Large Diameter Permanent Steel Casing
ZHANG Haishun1, CHEN Ningxian1, TANG Yougang2, HU Ruihai3
1. China Railway Construction Bridge Engineering Bureau Group Co. Ltd, Tianjin 300300, China; 2. Tianjin University, Tianjin 300350, China; 3. China Civil Engineering Construction Corporation, Beijing 100038, China
Abstract:Research purposes: As an auxiliary measure for hole formation of pile foundation, the permanent steel casing of the main bridge of Macao-Taipa Fourth Cross-sea Bridge has a diameter of 2.8 m and a length of nearly 100 m, which is not considered to participate in force. The steel casing of offshore pile foundation is usually constructed by pipe rolling machine or full casing rotary drilling machine. It was very important to ensure reasonable wall thickness of permanent steel casing without deformation when it was not pulled out eventually, which was closely related to construction safety and economic cost. In order to avoid economic waste caused by excessive wall thickness of steel casing, and large deformation caused by insufficient wall thickness in the process of sinking, a 3D model of steel casing and surrounding soil and water was established to simulate the construction process of steel casing subjected to torsion under pressure. Research conclusions: (1) The full-rotary full-casing drilling machine or pipe rolling machine is suitable for sinking of super-long and large-diameter steel casing on the sea. According to the rotary and pressing motion of steel casing, the calculation method of eight loads is given. (2) By means of the research on hoop stress and axial stress, buckling stability of permanent steel casing wall of pile foundation with different pile positions and pile lengths, the steel casing should be in accordance with the permanent structure design on the basis of the bidding documents require. The static calculation and local buckling calculation of safety factor are given, and the reasonable wall thickness of steel casing is determined. (3) The research conclusion can provide a reference for the stability and safety analysis and reasonable wall thickness of permanent steel casing in the drilling pile drilling process using full casing full rotation or pipe rolling machine for super-long and large-diameter offshore pile.
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