波浪下软黏土海床土-泥转换机制及其对管道稳定性影响

在我国大力建设海洋强国这一战略背景下，大量油气采输设施不断兴建于沿海油气田。软黏土是这些油气田的主要沉积物类型，在波浪作用下易转换为流塑状的泥，是管道等海床设施安全服役的极大隐患。本项目针对波浪下软黏土海床土-泥转换机制及其对油气管道稳定性影响展开研究。利用空心圆柱扭剪仪开展单元体试验揭示波浪所引起的主应力轴旋转对土体塑性应变和孔压累积的影响规律；利用离心机机载波浪模拟装置开展模型试验获取波浪下海床地基强度和模量演变规律、海床变形和运动特性以及界面处孔压传递模式。开发反映软黏土海床土-泥转化特性的本构模型，进而建立波浪与自由海床和含管道海床相互作用大变形数值分析模型。最终提出波浪作用下黏土海床土-泥转换评估方法和管道失稳防控措施，以期应用于工程实践。

In the context of China promoting the “maritime power strategy”, a large number of offshore facilities for oil and gas exploitation and transmission are continuously being built in coastal oil and gas fields. Soft clay is the main type of sediment in these fields and prone to transit into mud under wave loadings, which greatly undermines the seaviceability of offshore facilities. This project aims to reveal the mechanism associated with this soil-mud transition process, and to investigate how it affects the pipe-soil interaction of submarine pipelines. Hollow cylinder torsion and shear tests are to be conducted to assess the effect of wave-induced principal stress rotation on soil plastic strain and pore pressure accumulation. Centrifuge model tests will be conducted as well, by means of an in-house designed in-flight wave generator, to obtain the evolution of strength and modulus of the soil, the deformation and motion characteristics of the seabed, and the transmission mode of pore pressure at the water-mud and mud-soil interfaces. Then a constitutive model of marine clay considering the soil-mud transition feature is to be developed, based on which large deformation analysis model of wave-seabed and wave-seabed-pipeline interaction is to be established. Through detailed parametric analyses, methods to assess the soil-mud transition of soft clay seabed under wave action, and measures to prevent pipeline failure, are to be proposed, which are expected to benefit the design of offshore pipelines.