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Case studies of pipeline repairs following extreme ground movement events demonstrate how the displacement accommodating mechanisms of hybrid-segmented pipelines perform favorably (requiring less repairs to maintain serviceability) compared with traditional pipeline systems. Hybrid-segmented pipelines utilize a joint-locking mechanism that allows a pipe segment to move a prescribed displacement before engaging the next segment of pipe. Given the recent emergence of these technologies, there is a need to understand how these systems respond to relative movement between the pipeline system and soil because this interaction directly impacts the soil resistance accumulated along the joint and at the connections. Frictional resistance along a pipe barrel and the passive resistance developed at the face of an enlarged connection can be quantified for a single pipe segment; however, the development of these forces along a pipeline system, composed of multiple segments, is dependent on how the pipeline accommodates induced displacements. This study establishes an analytical framework that captures the displacement accommodation mechanisms of hybrid-segmented pipelines under axial ground movement and estimates the subsequent accumulations of resistance (frictional and passive) along the system. The proposed framework determines how a series of pipe segments engage and the subsequent total resistance developed based on inputs for pipe, connection, and soil properties. The proposed framework is validated with established numerical models and previous analytical approaches, demonstrating favorable comparisons. Although previous analytical models can estimate the total geotechnical demands on a pipeline system for various levels of ground movement, the proposed analytical framework is able to capture the allowable displacement and joint-locking mechanisms that uniquely differentiate hybrid-segmented systems from traditional pipelines. The analytical framework presented in this study can be used by designed engineers to make informed decisions on which pipeline systems are best suited for various conditions and ground movement scenarios. [ABSTRACT FROM AUTHOR]

Buried pipelines subjected to permanent ground deformations (through, e.g., earthquake-induced liquefaction or fault rupture) often experience widespread damage. Regardless of the direction of ground movement, pipelines tend to respond and experience damage axially due to their directional stiffness characteristics. In addition, case studies and previous testing have shown that damage is concentrated at the pipe joints due to their lower strength compared with a pipe barrel. Previous testing has also shown that axial forces increase significantly when pipe connections have jointing mechanisms, such as coupling restraints, with larger diameters than the pipe barrel alone. These enlarged joints act as anchors along the pipe, increasing the soil resistance at these locations. Current methods for predicting the axial force along a pipe underpredict the force demands and oversimplify the mechanics of soil resistance on the joint face. This study conducts a series of 12 pipe-pull tests in a centrifuge, varying joint diameter and burial depth, to quantify the axial forces developed. A strong linear correlation was observed between the soil resistance on a joint face and the joint surface area and burial depth. The study also proposes an analytical solution based on pullout capacity design equations for vertical anchor plates as a function of soil and pipe joint properties. The proposed solution to calculate joint resistance is in good agreement with the centrifuge tests performed for this study and previous full- and model-scale experiments. The proposed prediction equation is anticipated to have future applications to other buried structures because it is based on mechanisms of passive resistance commonly encountered in underground structures and lifelines. [ABSTRACT FROM AUTHOR]