Journal of Pipeline Systems Engineering and Practice

The process of natural gas transportation through cross-country pipelines, with intermittent repressurization with the help of compressors that use part of the same gas for energy source, is a very interesting optimization problem that has attracted researchers. In the present work, an 18-node network connecting a single source to a single delivery point has been selected for analysis. A steady-state model, incorporating gas flow dynamics, compressor characteristics, and mass balance equations, has been developed. Ant colony optimization, a comparatively new evolutionary technique in pipeline optimization, has been used for minimizing fuel consumption for a fixed throughput. A comparison with a similar optimization tool, a solver of a general algebraic modeling system that extracts the principle of generalized reduced gradient algorithm, indicates an improved solution in terms of fuel consumption minimization.

The performance of segmental pipelines under large ground deformation is strongly influenced by the axial pullout and compressive load capacity of their joints, as well as by the limits on joint rotation during permanent and transient ground deformation. Although ductile iron (DI) pipelines with push-on joints are commonly used in water distribution systems, experimental data and numerical simulation related to their performance under large ground movements are lacking. This paper reports on a series of specially designed four-point bending experiments and finite-element (FE) simulations to characterize 150-mm (6-in.) diameter DI push-on joints. The results were used to develop a relationship between rotation and metal binding as a function of axial pullout, as well as to determine the magnitudes of rotation and moment that initiate joint leakage. FE simulations were performed to investigate the deformation associated with joint leakage. Uniaxial tension and one-dimensional compression tests were performed on the elastomeric gasket and fitted with hyperelastic strain energy approximations to characterize behavior under extreme loading. Numerical models demonstrate joint leakage to be independent of load path, and that a unique pressure boundary predicts leakage for many combinations of deformation.

Joints in gravity flow pipelines can be subjected to internal or external pressure, depending on the conditions. Such conditions will influence the rotational stiffness of the joints and therefore may affect the behavior of the pipeline responding to surface loading. The purpose of this article is to characterize the influence of pressure variations on joint stiffness and assess their effect on pipeline response to live loading. First, rotation tests on a 600-mm-diameter reinforced concrete pipeline with gasketed bell and spigot joints subjected to internal positive and negative pressure are described. Next, numerical analyses are performed to approximate the rotational stiffness of the joint observed during the tests. Subsequently, these results are employed in new numerical analyses to evaluate the influence of the rotational stiffness of the joint on the behavior of a buried pipeline subjected to surface loading. It is shown that variations in pressure affect the rotational stiffness of the joint; however, these variations have little effect on the response of a pipeline when subjected to live loading.

This paper quantifies the impact of model error associated with the burst capacity model on the probability of burst of corroding oil and gas pipelines due to the internal pressure. Three burst pressure models that are widely used in the pipeline industry, namely the B31G Modified, det norske veritas (DNV), and pipeline corrosion failure criterion (PCORRC) models, are considered in the analyses. The time-dependent probabilities of burst of three hypothetical examples, which are representative of the oil and gas transmission pipelines in the United States, are evaluated by using the first-order reliability method (FORM) to carry out the comparative study. The analysis results indicate that the model error has a substantial effect on the burst probability evaluated. The probabilities of burst evaluated by considering the model error can be several orders of magnitude higher than those evaluated by ignoring the model error. The results underscore the critical importance of including the model error associated with the burst capacity model in the reliability analysis of corroding pipelines.

To restrict the thermal expansion displacement of X80 tunnel pipelines, anchor blocks are commonly designed and installed at entrances and exits of tunnels, which makes the anchor block design one of the most important issues. As well known, the key step for anchor block design is to calculate the thrust acting on the anchor block caused by the thermal expansion displacement. In this paper, an analysis method of the thrust is proposed, considering the effects of the vertical earth pressure, transverse horizontal earth pressure, internal pressure, temperature variation, and pipeline–soil friction. Using the condition of deformation compatibility and the hypothesis of stagnation point, the axial force of tunnel pipelines is derived by the unit force method. By combining the compatibility condition between the transition segment length of anchored side pipelines and the displacement of anchor blocks, the thrust acting on anchor block is derived. Using the analytical method and finite-element software, the results of thrust acting on anchor block of the X80 tunnel pipeline for a specific gas pipeline project are calculated and compared. The results show that the analytical results agree well with those determined by finite-element software, and the maximum relative error is only 2.9%. The parameter analysis of the thrust and displacement of anchor blocks is investigated, including the buried depth for anchored pipeline side, the pipeline–soil friction coefficient, the volume of anchor block, the block–soil friction coefficient, the soil reaction coefficient, and the buried depth of anchor block.

A full-scale field study was conducted in Kansas to investigate the installation effect on steel-reinforced high-density polyethylene (SRHDPE) pipes. Four 2.13 m-long SRHDPE pipes with a diameter of 0.61 m were connected and buried in a trench with dimensions of 1.52 m wide, 9.15 m long, and 1.40 m deep. Two types of backfill material were used in the trench, namely, Aggregate Base Class 3 (AB3) aggregate and crushed stone. Two pipes were buried in the AB3 aggregate section with an average degree of compaction of 90.4% whereas the other two pipes were installed in the crushed stone section with an average degree of compaction of 89.5%. The soil cover thickness in both the AB3 aggregate and the crushed stone sections was 0.65 m. A vibratory plate compactor was used to compact the backfill material inside the trench. Pipe deflections in the vertical, horizontal, and 45° directions from the pipe crown were monitored during backfilling. Earth pressures around the pipes were measured during the construction. Test results indicate that (1) the peaking deflection of the pipe in the AB3 aggregate section was 1.5 times that in the crushed stone section; however, the vertical diameter change of the pipe in the crushed stone section was 3.5 times that in the AB3 aggregate section after backfilling above the top of the pipe. The pipe diameter change in the crushed stone section in the 45° direction from the pipe crown was greater than that in the AB3 aggregate section. The deflections of the SRHDPE pipe in these two types of backfill material with a soil cover thickness of 0.65 m were much less than the 5% deflection limit suggested for steel and high-density polyethylene (HDPE) pipes by the AASHTO; and (2) the soil arching factors at the top of the pipe in both sections are greater than one (i.e., negative soil arching). The measured lateral earth pressure data verified that the lateral pressure induced by compaction was constant with depth within the pipe range. The measurement of the displacements of ribs at the springlines of pipes in both sections demonstrated that the ribs in the crushed stone section deformed more than those in the AB3 section. A visual inspection of the exhumed pipes did not find any obvious damage to the pipe ribs and liner. Overall, the SRHDPE pipe performed well in these two types of backfill material during installation.

The 2010/2011 Canterbury (New Zealand) earthquakes caused significant damage to buried pipeline infrastructure. Observations of damaged pipes that were made during either repair or replacement were used to define representative examples of the damage to each of the commonly used pipe materials. The different pipe materials that were considered included steel reinforced concrete, polyvinyl chloride, high-density polyethylene, cast iron, asbestos cement, and vitrified clay. Photographs of damaged pipes at the time of repair were collected and analyzed to identify pipe failure modes. It was determined that different pipeline materials exhibited different failure mechanisms during the earthquakes and that each pipe material was found to have a distinct failure signature. In particular, polyvinyl chloride pipes behaved in an unexpected brittle way. The failure mechanisms of each type of pipe are described using engineering nomenclature, and the signature failure modes are categorized and tabulated to facilitate comparison between the differing pipe materials.

Design of reinforced concrete pipes focuses on circumferential bending moment. Analytical or numerical methods can be used to estimate these, but an adequate representation of the soil conditions and pipe properties is necessary. The objective of this research study is to use simple experiments (three-edge bearing tests) along with closed-form solutions to obtain the circumferential flexural rigidity of a 600 mm reinforced concrete pipe for use in calculating moments from experimental measurements of changes in curvature (without knowledge of the soil and loading conditions). The data from the experiments were also used to calculate an elastic modulus that can be used to represent the circumferential flexural rigidity of the specimen in numerical simulations without having to model the reinforcement. An assessment of the methods used in this research study is also presented. Finally, use of the circumferential flexural rigidity in interpretation of buried pipe experiments is illustrated where moments in a reinforced concrete pipeline subjected to live loading are inferred from measured strains, comparing pipes for different burial depths and configurations.

The initial embedment of as-laid offshore pipeline is one of the important design considerations for on-bottom stability analysis. Despite the significant advancement in the use of numerical and analytical methods to predict the as-laid pipe embedment, there is still a lack of understanding about the governing parameters and their influence on the behavior of the pipe-seabed system. In the present paper, a two-dimensional plane strain finite-element model was developed to study the influence of the properties of seabed soil on the pipe load-deformation behavior subject to undrained soil conditions. The model was developed using commercially available finite-element software. The seabed soil was considered to behave as an elastoplastic material following the Mohr-Coulomb yield criterion, while the pipe was modeled as a rigid element. Both continuous and wished-in-place loading were performed up to displacements of 0.5 of the pipe diameter. The influencing parameters, including elastic modulus, shear strength, submerged weight of the seabed soil, pipe diameter, and berm growth, were studied with respect to the vertical collapse load and change in embedment. The results obtained were compared with results reported in the literature, and the parameters that have the most significant influence on the pipe behavior were identified. Results indicated that the heave formation significantly depends on the weight of the soil, and an analytical model was developed to predict the pipe load-displacement behavior, incorporating these factors.

Stainless steel liners are being used with increasing frequency for the trenchless rehabilitation of damaged water supply pipelines in China. At present, there is little research on the buckling resistance of stainless steel liners that takes into account the realities of the insertion process into water pipelines after years of service. In this paper, the buckling strength of stainless steel pipe liners has been studied by laboratory testing of lined pipe samples. The results show that the fold-and-form method used with stainless steel liners in practice is difficult to apply and resulted in inadequate installations. Comparing the test results against existing methods for the theoretical prediction of liner buckling strength, it was found that the predictions varied considerably from the test results and they could not be applied directly to the stainless steel liners. In keeping with the results found by previous authors for different liner materials, the gap present between the stainless steel liner and the host pipe is the most significant factor decreasing the critical buckling strength. The results from the Lagrange interpolation method based on strength curves involving the gap between the liner and the host pipes as proposed in the literature were found to fit well with the test data. It is believed that, with proper estimates of the annular gap expected, this approach could be used for the design of stainless steel liners used for water pipe renewal.

Trenchless technology is a group of techniques whose utilization allows for the repair, rehabilitation, and installation of underground infrastructure with minimal excavation. Pilot tube microtunneling (PTMT) is a trenchless technology in which new wastewater pipelines may be installed at precise line and grade over manhole-to-manhole distances. Generally, PTMT is accomplished with the implementation of three distinct phases: (1) jacking of pilot tubes to achieve line and grade, (2) jacking of casing along the pilot bore and rotation of augers to excavate a borehole slightly larger than the product pipe, and (3) jacking of product pipe directly behind the last casing. Understanding the mechanisms affecting PTMT productivity rates and jacking forces is a valuable tool that can assist designers and contractors with risk abatement. This paper outlines the instrumentation and monitoring process used to record jacking frame hydraulic pressures during seven PTMT installations. Cyclic patterns detected in the data enable the productivity rates for each PTMT phase to be determined and critical tasks associated with each phase to be identified. Variations in depth of cover, drive length, pipe diameter, and localized ground conditions allow for trends in jacking forces to be recognized. Jacking force behavior throughout each drive was compared to existing jacking force predictive models developed for the closely related pipe jacking and microtunneling methodologies because there are no currently developed predictive models to represent PTMT installation behavior.

The availability of tools for safety evaluation of a pressure liner is a relevant issue in both structural and hydraulic engineering. Parametric studies for assessing the stability of stiffened steel liners in hydroelectric pressure tunnels, as well as practical design guidelines, are presented in this paper. First, a review of the design methods for steel liners is outlined, with certain key aspects for the critical buckling load assessment of a steel pressure liner being considered. The methodology involves three-dimensional (3D) nonlinear finite element modeling procedures, in which liner constraining and the presence of stiffeners are taken into account. In addition, both large displacements and a surrounding elastic medium are assumed in the model.

The majority of trenchless pipeline projects delivered today use the traditional design-bid-build (DBB) system. Alternative project delivery methods (APDM) have been introduced to increase stakeholder integration and ultimately enhance project performance. The complex nature of trenchless pipeline projects renders them ideal candidates for APDM because of the gap that is often created by an inherent lack of technical knowledge exchange between design engineers and contractors when using DBB delivery. The use of APDM is only beginning to gain acceptance for trenchless pipeline projects. This paper has two objectives: (1) to examine the current usage, comfort level, and stakeholder perception of APDM through a survey of the trenchless industry; and (2) to investigate the published cost performance of completed trenchless projects that employed APDM. The results from the industry survey are threefold: (1) the most used project delivery system in the trenchless industry is DBB; (2) the comfort level of stakeholders in implementing each project delivery method is influenced by the amount each method is used; and (3) the industry respondents perceive APDM to impact certain performance metrics more than others. The initial results from the meta-analysis demonstrate the possible performance impact of APDM on trenchless construction projects, as realized through cost savings ranging from 2 to 44%. This study provides a contribution to the body of knowledge by assisting project stakeholders in better understanding the overall industry perceptions of APDM-related performance improvements. This understanding can guide stakeholders in selecting the most suitable delivery system for their trenchless projects.

Pipe ramming installations generally induce high levels of ground vibrations that may affect the structural integrity of nearby buildings and utilities. This paper investigates the ground vibrations associated with pipe ramming installations and develops reliable models for estimating the ground vibration levels in an effort to avoid the undesirable effects of the vibrations. The study presents field observations of ground vibrations in which an open-ended steel casing 1,070 mm in diameter and 37 m long was driven into granular soils using two pneumatic hammers of varying energy. The ground vibrations observed during the installation are presented as a function of magnitude of peak particle velocity, frequency content, and direction of propagation. Observations indicate that a wide range of amplitudes and frequencies is possible, ranging from 1 to $100\mathrm{mm}/\mathrm{s}$ and 20 to 100 Hz, respectively, for the case of forward and laterally propagating vibrations. The forward-propagating vibrations were observed to exceed the safe limit vibration criteria for a proposed pipe alignment for close source-to-sensor distances, indicating a potential for damage caused by pipe ramming-induced vibrations. The attenuation characteristics of the pipe ramming-induced vibrations were assessed by adopting and calibrating the existing scaled-distance empirical model and compared to those for a number of common construction operations.

High-density polyethylene (HDPE) pipes are widely used throughout the world due to their significant advantages. Most of the previous studies have focused on the behavior of the pipe-soil system under live loading and the development of theories and design methods. However, studies on the effect of construction on the response of HDPE pipes buried in fine-grained soils have not been well understood. In this study, a full-scale field test was conducted to investigate the earth pressure and deflection of three profile-wall corrugated HDPE pipes during installation in fine-grained soils. Pipes with diameters of 300 and 600 mm were buried in trenches with a width of 2.0 m. The test results demonstrate that the pipes deformed into a vertical ellipse before the backfilling reached the top of the pipe level and then gradually rerounded afterwards. The measured vertical earth pressure above the top of the pipe was lower than the overburden stress and pressure calculated using the Marston load theory, which is attributable to the positive soil arching developed in the backfill and the effect of compaction. When the backfilling level was above the top of the pipe, the lateral earth pressure at the pipe springline was approximately two times the corresponding geostatic pressure, which was attributed to the soil arching developed in the soil cover. Linear functions were proposed to correlate the measured pipe deflections both in the vertical and horizontal directions with the soil cover thickness. The proposed vertical deflection-soil cover thickness relationship was validated using the data reported in a previous study. An empirical equation was also developed to quantify the unique relationship between the ratio of vertical deflection to horizontal deflection and the soil cover thickness.

In oil transportation stations, the plunger motion exhibited by positive displacement pumps can cause a great deal of vibration that can influence the secure operations of the equipment and pipelines. If resonance between the equipment and pipelines occurs, their integrity can be compromised, resulting in catastrophic damage. Therefore, both stress analysis and vibration analysis are necessary before a pipeline is formally put into operation. For this study, mechanical models of pipelines and constraints in positive displacement pump pipeline systems, based on theories of stress and vibration in pipelines, were created. Numerical simulations, including stress, modal, and vibration analyses were performed on-site at an oil transportation station in west China. The data were collected, reported, calibrated according to published standards, and then analyzed. The results revealed that the models created were reliable for stress and vibration analyses of pipelines in practical applications and that resonance between pipelines and equipment can be avoided by enhancing the pipeline’s support and increasing its natural frequency. This research also provides engineering design suggestions for positive displacement pump pipeline systems.

In this study, the neurofuzzy-based group method of data handling (NF-GMDH) as an adaptive learning network was utilized to predict the maximum scour depth at equilibrium downstream of culvert outlet structures. The NF-GMDH network was developed using particle swarm optimization (PSO). Effective variables on the maximum scour depth at equilibrium included those of sediment size downstream of culvert outlets, the geometry of culvert outlets, and the flow characteristics upstream and downstream of the culvert. Training and testing performances of the NF-GMDH-PSO network were carried out using nondimensional data sets that were collected from the literature. The testing results of the NF-GMDH-PSO model were compared with the gene-expression programming (GEP) and traditional equations. The NF-GMDH-PSO network produced a lower error of maximum scour depth at equilibrium prediction than those obtained using the other models. Also, the most effective parameter on the maximum scour depth at equilibrium was determined using a sensitivity analysis approach.

The vertical uplift resistance of interfering pipelines buried in sands has been computed using the lower-bound limit analysis in conjunction with finite elements and nonlinear optimization. The soil mass is assumed to follow the Mohr-Coulomb failure criterion and an associated flow rule. It is specified that all the pipes fail simultaneously at the same magnitude of the failure load. For different clear spacing ($S$) between the pipes, the magnitude of the efficiency factor (${\xi }_{\gamma }$) is determined. Because of pipes’ interference, with a reduction in the spacing between the pipelines, the magnitude of ${\xi }_{\gamma }$ is found to decrease continuously. The results were found to compare quite well with the available data from literature for horizontal strip anchors.