Effect of Soil Variability on Strain Demand Associated With Moving Slopes

Assessment of strain demand is a critical component in strain-based design. The strain demand associated with moving slopes is influenced by a number of factors related to the properties of the pipeline, the surrounding soil, and the general slope characteristics. Available empirical models for assessing strain demand are limited to special cases of slope movements, and detailed finite element analyses are often performed in order to accurately assess the strain demand for specific slopes. Soil properties and slope movements are acknowledged to be highly uncertain, with the uncertainty stemming in part from the lack of site-specific data and in part from the inherent variability in soils. The sensitivity of strain demand to the effect of soil variability is an important consideration when establishing the safety margin that must be employed when using the strain-based method for pipeline design or assessment. In this paper, a finite element analysis of pipe-soil interaction is employed to assess the influence of soil variability on strain demand. Strain demand is shown to be highly influenced by variability in slope movement parameters and soil properties. Strategies to reduce the variability in the strain demand either through increased data collection or through pipeline design are discussed.