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This paper presents an approach for probabilistic analysis of pipelines buried through geohazard-prone areas that induce permanent ground movements potentially. In this approach, an easy-to-implement response prediction tool based on the finite-difference method is integrated with simple but robust Monte Carlo simulation methods. The probability of strain capacity exceedance is calculated when a pipeline is subjected to the ground movement of different magnitudes. In the strain-based limit state function, the strain capacity is determined using existing equations in the literature, and the strain demand is calculated using an accurate and efficient tool based on the finite-difference method. After obtaining the conditional probabilities of failure of pipes at given magnitudes of ground movement, the probability of failure of pipes as a function of time is also calculated considering the probability of ground movement initiation. The proposed approach is demonstrated through a case study of pipelines subjected to landslides. Pipelines are crucial components of lifeline infrastructure systems that facilitate the transportation of diverse gas and fluid substances. The vulnerability of pipelines buried in geohazard-prone areas necessitates a proactive approach to risk mitigation. This study introduces a methodology for assessing pipeline safety through probabilistic analysis. The methodology considers the probability of the pipeline's resistance to ground movements, as well as the likelihood of potential geohazards like slope creep and landslides. An innovative approach is employed to calculate the probability of the pipeline's resistance to ground movement, providing relatively accurate results while minimizing time requirements. The probability of slope creep and landslide events is derived from relevant guidelines and engineering reports. The final result, represented by the probability of failure, serves as a quantifiable measure to determine the safety level of the pipeline. This study can be referenced during decision-making processes related to pipeline design and maintenance, ultimately enhancing pipeline system safety. [ABSTRACT FROM AUTHOR]

The structural integrity of buried pipelines is often threatened by permanent ground deformation (PGD) within the pipeline route. Oil and gas transmission steel pipelines, which usually traverse several kilometers, are mostly buried. Inevitably, they can cross over areas with considerable geohazard concerns due to different soil types or extreme topographies. PGD usually occurs with various patterns, magnitudes, and directions relative to the pipeline axis with varying influences on the structural performance of buried pipelines. This paper discusses a comprehensive investigation of the effect of PGD patterns on the strain demand of pressurized buried continuous steel pipelines subjected to ground movement. The maximum strains induced in buried pipelines by longitudinal and transverse ground displacements of different patterns are presented. A three-dimensional nonlinear beam-Winkler spring finite-element (FE) analysis is used. The FE model accounts for the elastic-plastic behavior of pipe and nonlinear pipe-soil interaction. A straight NPS 42 Grade X70 steel pipeline with a wall thickness of 14.3 mm was considered and assumed to be fully embedded in two different soil types (stiff clay and dense sand). The pressurized pipeline was subjected to six different PGD patterns (i.e., sinusoidal, trapezoidal, ridge, ramp, block, and step) of three different magnitudes (1.0, 2.0, and 3.0 m). Each pattern was applied in the transverse (vertical and lateral) and longitudinal directions. The results show a significant variation in the strain demand of buried pipelines subjected to the various PGD patterns. The longitudinal strain induced in a pipeline due to PGD of the same magnitude but different patterns varies by up to 752%. Moreover, stiff clay is found to impose more strain on buried pipelines than dense sand. The results presented in this paper can be a useful reference in the safety assessment of straight sections of a similar buried pipeline under PGD. [ABSTRACT FROM AUTHOR]

This paper proposes a novel mitigation approach to improve the safety and structural integrity of buried steel transmission pipelines subjected to ground deformation. This method involves altering the boundary condition of buried pipelines with adjacently installed special geomaterial blocks (SGBs) consisting of a set of expanded polystyrene geofoam and polypropylene squared plastic boxes. The proposed SGB allows accommodating ground deformation while significantly reducing the ground-induced forces in the pipe. The mitigation technique is first presented, followed by the experimental test program developed to evaluate the beneficial effects of SGB on the pipe response when subjected to lateral and oblique displacements. Furthermore, a simplified spring-based analytical modeling approach is proposed for predicting the force-displacement response of the pipe–SGB–soil assembly with emphasis on the interaction between the pipe and soil under the new boundary condition. The analytical model is validated using experimental test data. The results of the experimental tests confirm the efficiency of the proposed remediation and feature the relationship between the applied displacement and the force developed in the pipe. Furthermore, it is found that the proposed simplified analytical model can appropriately predict the expected reaction of the pipe equipped with the SGB. [ABSTRACT FROM AUTHOR]

A novel mitigation technique is proposed in this paper to effectively improve the safety and integrity of buried pipelines subjected to ground deformation and to mitigate the detrimental effects of ground deformation on the pipe. This technique involves the installation of special geomaterial blocks (SGBs) adjacent to the pipe. The SGB consisting of multiple layers of hollow plastic boxes placed between layers of high-density expanded polystyrene (EPS) geofoam blocks forms a thick sandwich panel structure, which is oriented such that its orthotropic mechanical property allows the pipe to move laterally without developing significant reactions against the soil. A summary of past mitigation techniques and the method proposed in this study are first presented. Large-scale experimental testing used to assess the beneficial effects of the SGB on the pipe response when subjected to lateral and oblique displacements is then presented, followed by a simplified finite element model proposed to numerically simulate the pipe-SGB-soil interaction under lateral soil displacement. The results confirm that the proposed remediation method can significantly reduce the soil-pipe interaction force. Furthermore, the proposed beam-based numerical model that can be used in engineering design predicts well the lateral load-deformation response of the system. [ABSTRACT FROM AUTHOR]

The assessment of reliability levels associated with the design and safety factors (DFs and SFs) is important for modern pipeline engineering to achieve probabilistic design using a conventional deterministic format. To this end, this paper evaluates the probabilities of failure (POFs) for different pipe configurations, corrosion defects, and DF/SFs. Two limit states are considered: the yielding of intact pipes based on Barlow's equation and the failure of corroded pipes based on the RSTRENG model under internal pressure. The uncertainties of all the important variables are considered, including the RSTRENG model error. The POFs associated with different DF/SFs are calculated and discussed; the safety levels (e.g., safety class) of pipes based on the different DF/SFs are also determined. The DFs commonly used for the yielding of intact pipes are found to be in the highest safety class. The SFs used for corroded pipes based on the RSTRENG model are also found to be in the highest safety class for long corrosion defects but in the lowest safety class for short corrosion defects. [ABSTRACT FROM AUTHOR]

The integrity assessment of dents in liquid pipelines, as regulated by codes and standards, is based mostly on depth and threat integration, with strain analysis incorporated as a nonmandatory recommendation for gas pipelines. There have been incidents in which the current regulatory criteria have not successfully predicted imminent failures of dents, leading to operators using noncodified, more conservative approaches to maintain safety, typically resulting in poor dig efficiency. The dent assessment methods currently available in the industry do not account for the sequences of loading by which a dent may have formed. In this paper, the effects of different load sequences on the remaining life of plain dents in liquid pipelines are demonstrated using a validated finite-element analysis. A parametric study is carried out to confirm that the findings hold true for a range of pipe geometries, materials, and dent depths. The findings indicate that the severity and/or remaining life of a dent cannot be fully assessed based on its depth alone. The restraint condition, indenter shape, loading sequence, and pressure-cycling history should be considered for a reasonable assessment of the remaining life of plain dents. [ABSTRACT FROM AUTHOR]