洪水中悬跨管道加装防护索的力学行为及布索方案

Mechanical behaviors of protection cables installed on free-spanning pipelines in floods and its installation program

埋设在河流中的油气管道在洪水的冲刷作用下,容易漂浮于洪水中而形成悬跨,洪水对裸露管道的冲击作用很大,管道易发生显著弯曲变形,其中部分管道由于强烈的洪水冲击而有可能断裂,进而造成严重的后果。为了给悬跨管道在洪水载荷作用下的安全防护提供参考,根据洪水中漂浮管道的受力特点,建立了悬跨管道加装防护索的静力学线性分析模型和非线性有限元模型,通过算例分析了不同管道悬跨长度、洪水流速下防护索的加装角度和位置对管道变形与应力的影响,进而提出了一种临时的水工保护措施:①管道受洪水冲刷作用形成悬跨后,在管道受冲击一侧加装两条对称的临时防护索;②防护索最优的加装位置为管道悬跨长度的1/4处,其方向与管道夹角为60°。最后以API标准X70钢(?)1 016 mm天然气管道悬跨不同跨度为例,探讨了防护索最小许用截面积的影响因素和确定方法。结论认为:悬跨管道加装防护索后显著降低了管道的应力水平,为悬跨管道在洪水载荷作用下的安全防护及现场抢修工程提供了解决方案。

Under the scouring of floods, oil and gas pipelines installed crossing over rivers will often become free spanning in floods. The impact of floods on the exposed pipelines is huge, so the pipelines are susceptible to bending deformation, or even ruptures, which leads to serious environmental and economic consequences. For offering reference for the safety protection of free-spanning pipelines under the effect of flood loads, a static linear analysis model and a nonlinear finite element model were established for the pipelines with protection cables based on mechanical characteristics of the flood floating pipelines. Then, a temporary hydraulic protection measure was proposed, after some examples were adopted to analyze the effect of installation angles and locations of protection cables on pipeline deformation and stress distribution under different spanning lengths and flood rates. First, two temporary protection cables made of wire ropes are installed symmetrically on the impact side of the pipelines, after the pipelines are suspended due to the scouring effect of floods. Second, the optimal installation location is at a quarter of the spanning length with the pipeline cable angle of 60~. And finally, the influential fac- tors and determining methods of the smallest allowable cross-sectional area were explored based on a case study of API X70 line pipes （01016 ram） with various spans and different levels of flood velocity. It is concluded that the stress level of the spanning pipelines are reduced significantly after they are equipped with protection cables. This research result provides a solution for safe protection and field salvaging of free-spanning pipelines under the effect of flood loads.