Upheaval Buckling Assessment Based on Pipeline Features

Abstract

Upheaval buckling (UHB) is a common design issue for high temperature buried pipelines. This paper highlights some of the key issues affecting out-of-straightness (OOS) assessment of pipelines. The following factors are discussed; uplift resistance soil models, uplift resistance in cohesive soils, uplift mobilisation, ratcheting, uplift resistance at low H/D ratios and the correct methodology for load factor selection. A framework for determining ratcheting mobilisation is proposed. Further research is required to verify and validate this proposed framework. UHB assessment of three different diameter pipelines were carried out using finite element SAGE PROFILE package incorporating pipeline mobilisation and the results are compared with semi-analytical formulation proposed by Palmer et al. 1990. The paper also presents a summary of as-laid pipeline features based on projects over the past 10 years.

Reliability functions for buried submarine pipelines in clay subjected to upheaval buckling

“…Discrepancies between the loading results obtained with Palmer's approach and loading values calculated through finite element modeling (FEM) have been reported in [28]. It was found that these differences are mainly caused by the exclusion of a mobilization displacement (mob).…”

“…This procedure is considered semi-empirical and is appropriate for projects in the stage of FEED, FrontEnd-Engineering-Design (Thusyanthan et al [28]). Analytical expressions presented in [6] followed the beam-column theory and the downward force per unit length (w D ) to keep the pipeline in equilibrium has to satisfy the equation:…”

“…It was found that these differences are mainly caused by the exclusion of a mobilization displacement (mob). Thus, the addition of the mobilization displacement in the original formulation is expressed as [28]:…”

“…Finally, the uncertainty of the vertical loading model [6] is represented in terms of the displacement of mobilization (mob) as defined by [28]. If the Palmer's parameter is equal to the adjusted parameter, then:…”

Uplift Resistance of Buried Pipelines Enhanced by Geogrid

“…Many researchers have investigated the uplift resistance of buried pipelines using mathematical, numerical, and experimental modeling [6][7][8][9][10][11][12][13][14]. Among others, Selvadurai [15] used geogrid to enhance the uplift capacity of buried pipelines in compacted moist cohesionless soils.…”