Offshore natural gas pipelines are critical infrastructures extending for hundreds of kilometers under highly adverse and uncertain conditions. Geohazards, such as debris flows or landslides, consist crucial threats for such pipeline networks, while a serious damage can have devastating financial and environmental consequences. Generally, the assessment of pipe response can be performed via experimental, numerical or analytical models. Currently, the development of analytical models is based on their automated solution utilizing programming languages and mathematical software. Therefore, compared to numerical models, analytical models have the advantage of achieving automatically and fast reliable solutions. Moreover, it is relatively easy to implement them into regulations and to apply them in practice. Under this perspective, the current study presents an advanced analytical methodology to assess the response of offshore natural gas pipelines under the kinematic distress due to landslide or debris flow impact. The methodology focuses on deep water offshore sections (deeper than 200 m) where the pipelines are usually laid directly on the seabed. Extra emphasis is given on the impact of pipe-soil interaction on the pipe response where soil resistance is modeled via a tri-linear manner, according to the regulations of the latest international standards. Firstly, the proposed analytical model is compared with other analytical and numerical models, which are built utilizing the finite element method. Subsequently, an extensive parametric study is carried out for various combinations of soil parameters and loading conditions. It is noted that realistic topographical, geological and mechanical data were used according to the study of the deepest offshore section of the high-pressure natural gas pipeline TAP (Trans Adriatic Pipeline) in the Adriatic Sea. Finally, useful conclusions are drawn regarding the applicability and efficiency of the proposed model.
Simulating the response of offshore gas pipelines subjected to submarine landslides under static and seismic conditions