海底管道掏空与波浪力变化关系试验

THE TEST ON RELATION BETWEEN PIPELINE UNDERCUTTING AND WAVE FORCE CHANGES

鉴于海底油气管道在海洋能源开发中的特殊意义,前人开展了大量管道安全试验研究,特别注重不同底床、不同波浪条件、不同埋置深度等方面的组合试验,本次试验针对危害管道安全的掏空和悬跨开展了波浪水槽试验,探讨黄河三角洲为主的粉土海床上掏空与管道受力关系,弥补这方面研究的不足,结果表明,海底管道受力变化与掏空过程密切相关。连续试验过程表明,海底管道与海床土、波浪水体之间存在密切关系。海底管道在波浪作用下冲刷掏空经历了3个演变阶段:泥沙起动阶段、水流隧道发育阶段、快速掏空阶段和冲刷平衡阶段。水流隧道伴随的管涌对冲刷掏空起重要作用。伴随冲刷掏空,管道波浪力出现规律性转化,从正向作用逐渐过渡到负向作用,也可以分出4个演化阶段:冲刷初始阶段,管道波浪力以正向为主,管道表现为正向力作用下的振动;隧道发育阶段,管道受到的作用力主要是波峰上举力和波谷下拉力,表现为上下振动;管道悬空阶段,波峰负向作用力和波谷正向力交替出现,管道在波浪作用下表现为前后振动;冲刷平衡阶段,管道主要在负向作用力下振动。

Due to the special meanings of submarine oil and gas pipelines in marine energy development,researchers have had a large number of safe experimental studies, and especially pay attention to the com- bined experiments made in different bottoms, different wave conditions and different burying depths. This present gutter test of wave aims at scouring and hanging-up which are dangerous to the pipeline security, in order to understand the relation between wave pressure on pipelines and the undercutting in silty seafloor represented by the Yellow River delta. The test result indicates that the pressure change is closely related with the undercutting course. Our continuous test shows that submarine pipeline is closely correlative with soil of sea bed and waves. The scouring and undercutting of pipeline under wave action experience three developing stages： silt stirring stage, current tunnel developing stage, swift undercutting and scouring equilibrium stage. Flow from the current tunnel plays an important role in scouring and undercutting. With scouring and undercutting, pipeline wave action transforms regularly from positive to negative force gradually, which can be divided into four developing stages：the initial scouring stage during which pipeline wave function is mainly positive,and pipeline shows vibrations under positive force; tunnel development stage during which pipeline vibrates up and down under the wave-crest lifting force and wave-trough downward- pulling force; pipeline hanging-up stage： pipeline vibrates forward and backward according to the negative wave crest and positive wave trough efforts; scouring equilibrium stage： pipeline vibrates mainly under negative force.