Soil-Pipeline Interaction Modeling and Assessment in Unstable Slopes

Abstract

Due to their length, oil and gas pipelines usually face different geotechnical problems along their routes (fast or slow, shallow or deep landslides) that impact the pipe integrity. In the current state of practice, this problems are analyzed considering the system as a beam on elastic foundation (Winkler type models), in which the loads on the pipe (e.g. internal pipe pressure and geostatic loads) are studied independently. A more realistic description of the soil-pipe interaction phenomenon that allows the prediction and explanation of the pipe failures found in the practice requires more advanced methodologies, involving the constitutive behavior of soil and pipe and the combined effect of different types of loads. In order to assess in a better way the soil-pipe interaction problem in landslides, this paper presents a 3D numerical model of the system, including the combined effect of different loads (such as landslide loads, geostatic loads and pipe internal pressure). The results obtained with the model were validated against real field measures in the OCENSA pipeline system and are expressed as soil displacement versus pipe strain relations. These relations are being used successfully in the evaluation of the behavior of the pipeline in unstable slopes, resulting in an important tool in the OCENSA pipeline integrity program.