Centrifugal model tests on influences of anchor dropping on offshore pipelines

Anchoring is one of the important factors affecting the safe operation of submarine pipelines. The centrifugal model tests are carried out by using the TK-C500 geotechnical centrifuge and the newly developed anchor dropping test devices. The force changes of the submarine pipelines are measured, and the influences of the anchor dropping operation on the shallowly buried submarine pipelines are analyzed. The test results show that the dropping distance has a universal influence on the change of the bending moment of the pipelines, and the increment of the bending moment of the pipelines has obvious nonlinear characteristics with the horizontal distance of the dropping point and the buried depth of the pipelines. When the Hall anchor of 12.3 t falls directly above the pipelines with ϕ630, the bending moment increment of the pipelines is much larger than its plastic yield bending moment regardless of the different dropping distance or the buried depth of the pipelines, and the safe operation of the pipelines is seriously threatened. When the dropping distance is less than 3.5 m and the horizontal distance is greater than 1.4 m, and the dropping distance increases to 7 m and the horizontal distance is greater than 2.8 m, the increment of bending moment of the pipelines will not exceed the plastic yield bending moment. As the dropping distance continues to increase, when the anchor falls within a certain range of the pipelines, it will pose a serious threat to the safe operation of the pipelines.