基于温变条件下深海管土耦合作用及其破坏机理研究

Most of the deepwater oil recourse is with high wax content in China, and it belongs to the high viscosity of crude oil. To safeguard the subsea pipeline transporting, pipeline working pressure continuously improve. The design temperature is generally reached or exceeded 100 ℃, and may even reach a high temperature of 150℃. Free deformation due to drastic changes in temperature in the long-distance pipeline was constrained by the surrounding soil of pipeline, so that the accumulation of stress in the pipeline will ultimately cause buckling of the pipeline. On the one hand, seriously buckling deformation may lead to increase bending stress in the pipeline, closing to or reaching the yield strength of steel, and cause a threat to the safe operation of the pipeline. On the other hand, it may destroy the heavy layer, insulation layer structures of pipeline, affecting the normal use of the pipeline. Therefore, Studying the interaction between the deepsea pipeline and surrounding soil, inspecting pipelines in the buckling deformation characteristics under temperature stress, revealing the failure mechanism, proposing effective engineering countermeasures to avoid buckling become an important issue to ensure the safe operation of the deep-sea pipeline. The present research will improve the theoretical study of deep-sea pipeline, and provide strong technical support for the safe operation of the deep-sea pipeline. It will provide theoretical and technical support for the realization of deep-sea development strategy.

我国深海油田生产的石油大多含蜡量较高，属于高粘度的原油，为保障其在海底管线中的输送，管线的工作压力不断提高，其设计温度普遍达到或超过100℃，甚至可能达到150℃的高温。长输管道中由于温度变化而产生的自由变形受到周围土体的约束，使管道中的应力的不断累积，最终引起管道的屈曲变形。严重的屈曲变形一方面可能导致管道中的弯曲应力增大，接近或达到钢材的屈服强度，对管道的安全运营造成威胁，另一方面可能导致管道配重层、保温层结构遭到破坏，影响管道的正常使用。因此研究深海管道与周围土体的相互作用，考察管道在温度应力下的屈曲变形特征，探究其变化破坏机理，提出有效避免发生屈曲的工程对策，成为保证深海管道安全运行的重要研究课题。本项目的研究，将完善我国深海管道的理论研究体系，为深海管道的安全运营提供有力的技术支持，为实现我国的深海开发战略提供理论和技术保障。

我国深海油田原油具有温度高、粘度高的特点，输油管道因温度变化会产生形变，受到周围土体的约束，管道中的应力会不断累积，最终引起管道的屈曲变形。严重的屈曲变形一方面可能导致管道中的弯曲应力增大，接近或达到钢材的屈服强度，对管道的安全运营造成威胁，另一方面可能导致管道配重层、保温层结构遭到破坏，影响管道的正常使用。针对以上问题，课题紧密结合南海海域深水油气田开发现状，开展基于温变条件下深海管土耦合作用及其破坏机理研究。通过对深海浅层土体的工程性质进行研究，重点分析了其成因、胶结物、颗粒形态、沉积相作用、抗剪强度、含水量、粘聚力、摩擦角等问题，研究了深海土体在载荷作用下的应力路径及进入塑性状态的判断标准，建立了深海海洋土特征荷载下的时变本构模型，为深海管道与土体的相互作用研究提供了基础。基于深海软土特性研究成果，形成了综合考虑各种不利地基条件变化的海底管道与地基土壤耦合作用的分析方法。最后，提出了控制管道整体屈曲的有效途径。