孤立波作用下海底管道允许悬跨长度简化计算

分析海底管道稳定性时，需要重点考虑管道发生悬空的情况。由于我国油田大多建设在近海地区，因此在考虑管道悬空问题时需考虑浅水区波浪的特点。基于孤立波理论，考虑浅水区波浪的特点，给出浅水区管道悬空段所受的动水作用力。针对常见的悬空形式，从管道最大静弯曲应力不超过材料许用应力的角度出发，推导出浅水区管道允许悬空长度的计算式。最后结合渤海湾某油田海底管道工程，计算出该海区管道的允许悬跨长度，认为该海区有部分管道已超过计算的允许悬跨长度，应进行加固处理。

Simplified calculation of allowable free span length of submarine pipelines under action of solitary waves

It is important to consider the suspension of the submarine pipelines, analyzing the stability of the submarine pipelines. Because of the complex geological conditions of the seabed, the buried pipelines hung on the seabed are affected by waves. Once occurred the suspension of the pipelines, the suspended pipelines would be destroyed under the action of the external environment. The pipelines accidents lead to a great loss of property and bring the pollution of the marine environment. Because most of the oil fields are located in the offshore areas in our country, the characteristics of shallow water waves should be considered.Based on the solitary wave theory, and considering the non-linear effects of the shallow water waves, the hydrodynamic loads on the suspension of the pipelines was calculated in this study.For the common forms of hanging pipelines, considering that the max bending stresses are less than the material's allowable stress, the formula for the allowable free span length is derived. Finally, taking the submarine pipelines works in Bohai bay as a case history, the allowable free span length of the submarine pipelines was calculated.The calculation results show that a part of the pipelines' span lengths exceed the allowable span lengths, and they must be reinforced.