冲击荷载作用下有碎石保护结构的海底管线DEM-FEM联合分析研究

Coupled DEM-FEM analysis of submarine pipelines with rock armor berm under impact load

海上平台落物或抛锚对海底的撞击会对海底管线造成一定的损害。通常的防护措施是在管线的上部铺设碎石层形成碎石保护结构,从而耗散部分冲击能量。为了分析该保护结构的防护性能,运用离散元–有限元联合分析的方法,建立冲击荷载作用下有碎石保护结构的海底管线反应分析方法。在该方法中,离散元用于模拟碎石结构,有限元用于模拟其它的连续体。离散元单元和有限元单元通过在它们之间设置接触面的方式进行相互作用。计算得到的碎石保护结构对冲击能量的吸收结果与挪威海洋工程规范中建议的公式一致,且计算得到的海底管线变形规律与模型试验的结果相符。这些结果验证了该方法在评价碎石保护结构下海底管线安全性能方面的适用性。

Submarine pipelines will possibly be damaged by dropped weights from ocean platforms or anchors from ships. The rock armor berm is the method commonly adopted to protect these pipelines by covering them with a layer of gravels, which can dissipate part of the energy of falling objects. In order to estimate the energy dissipating capacity of the rock armor berm, a coupled discrete element method（DEM） and finite element method（FEM） approach is proposed to analyze the dynamic response of pipelines under impact load. In this approach, DEM is used to model discrete gravels and FEM is used to model other continuous objects. The two kinds of elements interact on each other through the contact interface between them. The calculated results of energy absorptions by gravels coincide well with those recommended by the current code of DNV-RP-F107, and the calculated deformation rules of the pipeline are in good agreement with those given by model tests. These results prove the feasibility of using the proposed approach to evaluate the safety of submarine pipelines with rock armor berm.