Uplift Resistance of Buried Pipelines at Low Cover-Diameter Ratios
Uplift Resistance of Buried Pipelines at Low Cover-Diameter Ratios
复制标题
低覆盖径比下埋地管道的抗拔力
DOI：
--
复制
发表时间：
2010
期刊：
影响因子：
--
通讯作者：
S. Mesmar
中科院分区：
文献类型：
--
作者：
Junkan Wang;R. Ahmed;S. Haigh;I. Thusyanthan;S. Mesmar
可靠地估计回填土的最大可用抗拔力对于防止埋地管道的隆起屈曲至关重要。现行设计规范DNV RP F110没有对盖板：管径（H/D）比小于2时如何预测抗拔力给出指导。因此，目前的行业实践是，在H/D比小于1的设计方案中，忽略上拔阻力对剪切的贡献。这种额外保守性的必要性是通过在剑桥大学斯科菲尔德中心进行的一系列全尺寸和离心机试验来评估的，总共进行了21次试验。充填类型包括饱和松散砂、饱和致密砂和干砾石。数据显示，垂直滑移面模型仍然适用于H/D比小于1的松散砂、致密砂和砾石的设计场景，并且没有证据表明在这些低H/D比下剪切的贡献可以忽略。对于砾石中的隆升事件，如果覆盖层大于平均粒径（D50）的1-2倍，则剪切分量似乎是可靠的，目前正在进行更多的研究来验证这一结论。颗粒图像测速（PIV）技术的应变分析证明，垂直滑移面模型能很好地反映松散砂在H/D比为0.5 ~ 3.5时的真实隆升变形机制。在较低的H/D比下（H/D < 0.5），土体的变形机制更倾向于楔形，但土体重量增加的贡献可能被减小的剪切贡献所补偿。因此，基于垂直滑移面模型的设计方程仍然可以很好地估计最大可用抗拔力。通过PIV分析得到的剪切应变场的演化过程，有助于深入了解隆升过程中隆升阻力是如何调动的。版权所有，海洋技术大会。
Reliable estimates for the maximum available uplift resistance from the backfill soil are essential to prevent upheaval buckling of buried pipelines. The current design code DNV RP F110 does not offer guidance on how to predict the uplift resistance when the cover:pipe diameter (H/D) ratio is less than 2. Hence the current industry practice is to discount the shear contribution from uplift resitance for design scenarios with H/D ratios less than 1. The necessity of this extra conservatism is assessed through a series of full-scale and centrifuge tests, 21 in total, at the Schofield Centre, University of Cambridge. Backfill types include saturated loose sand, saturated dense sand and dry gravel. Data revealed that the Vertical Slip Surface Model remains applicable for design scenarios in loose sand, dense sand and gravel with H/D ratios less than 1, and that there is no evidence that the contribution from shear should be ignored at these low H/D ratios. For uplift events in gravel, the shear component seems reliable if the cover is more than 1-2 times the average particle size (D50), and more research effort is currenty being carried out to verify this conclusion. Strain analysis from the Particle Image Velocimetry (PIV) technique proves that the Vertical Slip Surface Model is a good representation of the true uplift deformation mechanism in loose sand at H/D ratios between 0.5 and 3.5. At very low H/D ratios (H/D < 0.5), the deformation mechanism is more wedge-like, but the increased contribution from soil weight is likely to be compensated by the reduced shear contributions. Hence the design equation based on the Vertical Slip Surface Model still produces good estimates for the maximum available uplift resistance. The evolution of shear strain field from PIV analysis provides useful insight into how uplift resistance is mobilized as the uplift event progresses. Copyright 2010, Offshore Technology Conference.