Jack up drilling platform has been widely used for its superior performance. However, due to the increase of various problems in service, it has also attracted more and more attention from the offshore oil industry. In particular, the complex soil conditions on the sea floor bring certain difficulties to the field staff. In the same sea area, with the increase of the number of operations, the situation of jack up offshore drilling platform carrying out secondary or multiple jack-up leg embedment operations in the vicinity, or even in the same location will increase year by year. Therefore, this phenomenon is called "step on the footprints". The problems become more and more frequent, and have a significant impact on the operation safety of offshore platforms. In the process of "step on the footprints" of jack-up drilling platform, the spudcan will slide transversely along the direction of footprints to varying degrees. If the sliding distance is too large, the leg or platform structure will be damaged. Therefore, the influence of spudcan slip on the platform structure and the determination of critical slip distance in different directions of spudcan are of great significance for the safe operation and running of jack up drilling platform. Based on the symmetrical structure of the three-leg jack-up offshore platform, in this paper, the influence of the footprints of spudcan on CJ50 jack up drilling platform is studied and analyzed by finite element method, and the critical slip distance in different directions of spudcan on jack up drilling platform is calculated. At the same time, the stress of the key parts of the hull and leg under the critical slip distance of the spudcan is calculated. The structural stress method is used to calculate the structural stress and equivalent structural stress of the K-joint weld of the key part of the truss leg. It is of great significance for designers and operators of jack up offshore platforms.

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