海流作用下海底管道侧向失稳特征的试验研究

Characteristics of Pipeline Losing Lateral Stability under Ocean Currents

对海流载荷下管道在砂质海床上侧向失稳的物理过程进行了试验模拟，分析了管道侧向失稳的典型特征。水动力试验发现，管道侧向失稳经历了三个特征时间：①砂粒起动，②管道轻微侧向位移，③管道侧向失稳。利用机械加载装置分别研究了两端自由和防滚两种端部约束条件下管道在侧向失稳过程中的侧向土阻力及管道沉降特征。实验发现，随着管道水平位移的增加，侧向土阻力逐渐增加并最终达到极限值；而端部约束条件对极限侧向土阻力及其与管道沉降量之间的关系影响较大。两种模型试验结果具有较好的对比性，海流引起的局部冲刷可降低管道侧向稳定性。

The physical process of pipeline losing lateral stability is modeled experimentally with hydrodynamic tests and mechanical-actuator loading tests. Based on the experimental results, the typical characteristics of pipeline losing lateral stability are analyzed. The hydrodynamic experiments indicate that, there usually exist three characteristic times in the process of pipeline losing lateral stability, i.e. （1） onset of local scour around the pipe, （2）slight lateral displacement of the pipe,（3） breakout of the pipe. The lateral soil resistance and the settlement of the pipes with two kinds of constraint conditions are investigated respectively by mechanical-actuator loading method. With the increase of horizontal displacements of the pipe, the lateral soil resistance increases continuously and finally reaches a maximum value. The constraint conditions have much influence on ultimate lateral soil resistance and its relationship with pipe settlements. The comparison between the two types of tests shows that their results are comparable, and the local scour may reduce the pipeline lateral stability in the examined Froude range.