Journal of Pipeline Systems Engineering and Practice

Soil resistance to monotonic lateral displacement of buried pipelines has been well studied in the literature, but there is limited information on the interaction between soil and buried pipes subjected to cyclic displacement. A new full-scale testing facility was built to investigate the cyclic interaction behavior between soil and buried pipes for a potential onshore application, in which hydrocarbons can be transported at high pressure and temperature inside large, heavy, steel pipes. A full-scale experimental program was conducted for a 1.2-m-long pipe segment buried under gravel backfills. The pipe segment was subjected to lateral displacement with a series of combined monotonic and cyclic loading protocols. Two parameters were studied in the tests: embedment depths and compaction levels of backfill materials. It was observed that for the gravel backfill, the ultimate displacement could far exceed the expected range specified in the design guideline, and while the ultimate soil resistance to the monotonic loading can be predicted, the ultimate resistance could increase as high as 150% of the value of the monotonic loading case due to the applied cyclic displacement. This increase in the ultimate resistance depended on both the soil compaction and the cyclic loading history.

Protection of the downstream of culvert outlets against scour process, as a water conveyance structure, is a highly significant issue in design of culverts. Frequent field and experimental investigations were carried out to produce a relationship between the scour depth due to the governing variables. However, existing empirical equations do not always provide a precise estimation of the scour depth due to the complexity of the scour phenomena. In this investigation, gene-expression programming (GEP), model tree (MT), and evolutionary polynomial regression (EPR) are utilized to predict the scour depth downstream of culvert outlets. Input variables—considering effective parameters on the scour depth—were defined as sediment size at downstream, geometry of culvert outlets, and flow characteristics in upstream and downstream. Experimental datasets to develop the models were collected from different literature. Performances of the proposed models for the training and testing phases were assessed using several statistical measures. Results of performances indicated that EPR provided the lowest level of precision including index of agreement ($\mathrm{IOA}=0.958$) and root mean squared error ($\mathrm{RMSE}=0.419$) for prediction of local scour depth at culvert outlets than those obtained using MT ($\mathrm{IOA}=0.947$ and $\mathrm{RMSE}=0.471$) and GEP ($\mathrm{IOA}=0.943$ and $\mathrm{RMSE}=0.487$). In terms of accuracy, all proposed equations extracted from artificial intelligence approaches had remarkable superiority to the traditional equations. Ultimately, it has been proven that mathematical expressions given by evolutionary computing tools had sufficient generalization to present an accurate prediction of the local scour depth with respect to preserving physical meaning of results.

The article considers a new approach to oil transportation scheduling in oil pipeline network systems. This new approach is based on a mathematical model that solves the optimization transport problem as a system of objective functions and equality and inequality constraints. The system can be varied depending on the needs of a given pipeline system. The approach allows one to compute oil-flow distribution during a certain time period (e.g., day, week, or month) with a given time sampling (e.g., hour, day, or week) considering pipeline characteristics (e.g., flow capacity and technological regimes, among others), oil properties (e.g., mass sulfur fraction and density, among others), and capacity of tank terminals. In addition, the approach enables one to optimize oil transportation in terms of energy consumption. The possibilities of the proposed approach are shown using a real system of 10 oil pipelines, 9 branches, 4 transitional tank terminals, 3 oil suppliers, and 6 oil consumers. The result of the flow distribution calculation in a branched system, which is the schedule of cargo flows for each pipeline in a whole pipeline system with all constraints satisfied and optimized objective function during a 1-month (744 h) time period with a 1-h time sampling, is shown.

Joints in buried pipelines have diverse configurations and materials, and are subjected to different loading and installation conditions which will influence their performance. Therefore these parameters need to be examined, because joints play an important role in pipeline longevity. This research study developed a numerical model for a buried RC pipeline with a gasketed bell and spigot joint subjected to surface loads representing service conditions. The model was calibrated against experimental data and captured close to 80% of the joint rotation angle and the patterns of hoop strain at the joint components. The model was subsequently used in parametric studies which revealed the locations where a single wheel pair produces the largest shear displacement and rotation of the joints for the burial depth examined. The studies also indicated that a tandem axle configuration produces larger joint rotation than a single axle and single wheel pair configuration. The influence of the soil envelope stiffness and the effect of pavements on the joint performance was also described.

Deepwater pipelines are susceptible to destructive impacts from submarine debris flows. Understanding the subsea pipeline movement driven by submarine debris flow is critical to the optimization of pipeline routes and mitigation of submarine geohazards. In this paper, a coupling model of submarine debris flow with pipeline interaction is presented to investigate pipeline movement subjected to debris flow impact. The modeling domain of debris flow is represented by a structured grid system with discretized grid nodes. The dynamic properties of debris flow, such as velocities and heights, are calculated at each grid node. The pipeline is discretized into finite elements. Each element consists of two pipe nodes at the ends. The coordinates of each pipe node are determined using a particle tracking algorithm. The velocities of debris flow at the location of each pipe node are interpolated from the debris flow model and then converted to impact forces applied on each pipe node. An empirical formulation is proposed to estimate the displacements of each pipe node from a given Young’s modulus of pipe material and impact force applied by debris flow. The empirical relationship is developed from a series of numerical simulations conducted with the commercial software ABAQUS. The numerical simulations are performed using a simple model configuration subjected to uniformly distributed impact forces. Later, the coupled model is applied to two schematized cases representing continental shelves with a uniform slope and a sinuous canyon. The effects of the Young’s modulus of pipe material, initial failure height of debris flow, and the number of discretized pipe nodes on pipeline movement are investigated through a series of parametric studies.

This paper describes the development and testing of a methodology for continuous detection, size estimation, and location of leaks in pipelines using a closed-loop boundary feedback estimator constructed on a real-time transient model (RTTM). In particular, discussed is an energy-based transient pipeline model that includes effects due to terrain topography and multiple leakage points along the pipeline reach; it admits system interconnections and it is appropriate for a real-time execution. Such model was used in a closed-loop boundary feedback estimator of leaks in pipelines. The resulting system was tested with real-time data obtained from a Supervisory Control and Data Acquisition (SCADA) system protecting an actual buried and branched 60-km length steel pipeline transporting liquefied petroleum gas (LPG).

The need for understanding the performance of district heating pipeline systems has led to the development of a monitoring program. This program includes the design of the connection of an instrumented section of piping within an in-use district heating network. The design complies with the current European district heating recommendations and standards. Monitoring consists of the measurement of earth pressures against the pipes, axial pipe displacements, and temperature of the fluid and soil around the pipes. There are different conditions being tested such as thickness of insulation materials, temperature ranges, and bedding soil type. In particular, there is interest in testing the corner positions. Details of the piping and instrumentation arrangements as well as soil geotechnical characteristics are presented. It was found that when the fluid temperature increased from ambient conditions up to 90°C, pipes were moving all along their length. Moreover, after a fluid temperature drop from 90°C to 20°C over 20 days and subsequent increase to 90°C again, pipe axial displacements did not return to the same values as before.

Diameters and wall thicknesses of flexible pipes are usually designed as per hydraulic requirements, such as flow capacity, internal fluid pressure, and pipe material properties. Proper embedment is then designed to protect the pipe integrity against external loads. This paper considered engineering properties of embedment soils in analysis of flexible pipe–soil system for external load conditions and a new model was developed for the prediction of deflection of flexible steel pipe. Full-scale laboratory tests were performed to develop the new model and finite-element models were analyzed to validate the test results. In this research, the finite-element method was effectively used to model the soil–pipe interaction for five full-scale laboratory tests conducted on a steel pipe. Such models can be used for analysis of flexible pipe embedment design for layered embedment conditions. The results of finite-element analysis showed that the squaring of the pipe occurs when the haunch soil is weak compared to the side column. Another critical observation made during the tests was that the stresses at the bottom of the pipe and the bedding angle are highly dependent on haunch soil strength. It is desirable that the stress due to surcharge load on top of the pipe, weight of the pipe, and water inside the pipe be distributed uniformly across the width of the bedding.

Internal corrosion in carbon steel pipelines is a serious challenge in the oil and gas industry. Conventional rehabilitation techniques used to stop corrosion losses and prolong the life of pipelines use an internal lining system to isolate the corrosive medium from the inner surface of the host pipe. A recent lining technology based on an aramid-reinforced flexible polymer composite liner has been successfully installed in several pipelines. It has been theorized that the added inherent strength of the liner due to the aramid reinforcement can give rise to an increased burst pressure level of the corroded pipeline. Hence, the objective of the study is to investigate, with aid of a nonlinear finite-element (FE) model, the potential structural enhancement, e.g., increase in burst pressure level of the combined liner-carbon steel pipeline system. The mechanical response of the three layers of the liner were determined experimentally and implemented in the FE model. Two different carbon steel pipelines with various internal corrosion defects were considered, and the burst pressure levels before and after installation of the liner were determined with the FE model. The results show that it is possible to achieve an increase in the burst pressure level when this liner is installed. It is concluded that this new liner can serve as a corrosive protective barrier, and in some cases provide structural enhancement to the combined pipe-liner system.

This study investigates the energy savings in the nonisothermal flow of natural gas during its pipeline transportation compared to the isothermal flow. Isothermal and nonisothermal models are adopted while considering the case of the Arab Natural Gas Pipeline. Temperature changes in the natural gas along the pipeline due to heat transfer between the natural gas, the pipeline, and the soil are depicted for different operating conditions. Further, the effects of soil temperature and the inlet feed gas temperature for the different gas flow rates considered are discussed and analyzed. The impact of a nonisothermal steady-state thermal model on the performance characteristics of natural gas in the pipeline is presented showing a resulting reduction in the work required for gas compression at the booster compressor station.

The analytical pretightening force range of flange joints in a pipeline was deduced based on the allowable gasket stress and flange rotation angle considering the nonlinear compression resilience behavior of gaskets. Relationships between pretightening force and working pressure or gasket stress were established. The results show that the corresponding relationship between bolt pretightening stress and gasket stress under different internal pressures is different due to the nonlinear compression resilience performance. Moreover, the region enclosed by the minimum bolt load under initial pretightening, the minimum bolt load under working pressure, and the maximum bolt load corresponding to the limit flange rigidity in the diagram of bolt pretightenting force versus working pressure can be treated as the effective sealing region for flange joints in a pipeline. Additionally, the bolt pretightening range can be defined as [$\max \{S_b^{\mathrm{A}},S_b^{\mathrm{B}}\}$, $S_b^{\mathrm{C}}$] in a diagram of bolt pretightenting stress versus gasket stress. These are simple and effective strategies to define a reasonable pretightening range of flange joints for engineering design and assembly in a pipeline system.

A growing number of large culverts in the national transportation network are in poor condition. Often, aging infrastructures carry heavy traffic through urban corridors. Either after failure or for replacement, reconstruction must occur rapidly to minimize service disruption. In some cases, new materials are used and uncommon construction practice is followed. The I-88 culvert crossing of Carrs Creek in Sidney, New York completely collapsed during record flooding. Rapid construction using expanded polystyrene (EPS) geofoam blocks as lightweight fill enabled partial reopening of I-88 in less than 3 months of closure. Shortly after reopening of the roadway, rapid and continuing settlements became evident. The roadway was again rebuilt using lightweight aggregates as structural fill above the culvert following complete removal of the geofoam blocks. This investigation of the rapid construction failure reexamines the findings and recommendations of a prior study of the failure. Alternative conclusions and suggestions for improving rapid construction practice with geofoam are presented utilizing the I-88 failure as an example in retrospect.

Earthquakes are one of the most devastating natural disasters, annually causing severe damage to underground infrastructures, including unpressurized wastewater and stormwater networks. After intensive seismic damage has been inflicted, especially in municipal regions, application of a trenchless excavation technique is assumed to be an appropriate method for repair and rehabilitation. Trenchless techniques are well known as an appropriate method for new pipe installation, pipe rehabilitation, and pipe repair in populated areas because of their advantages over open-cut methods, although application of these techniques is limited in certain cases of postearthquake restoration of damaged pipelines. Earthquake shocks cause different types of damage to buried pipes, especially those in unpressurized networks where the application of trenchless techniques is very limited. The focus of this study is on these limitations with respect to which trenchless postearthquake techniques are to be applied for repair and rehabilitation of damaged unpressurized networks through a case study. A combination of a case study and direct observations was applied to show that some trenchless techniques like pipe bursting, cured-in-place pipe, and point repair methods cannot be applied to renovation and rehabilitation of damaged underground pipelines in some particular types of damage caused by earthquakes.

Two types of composites, fiberglass/epoxy and fiberglass/polyester, were compared for possible application to natural gas pipelines. The properties of these composites in some corrosive media were estimated using tensile break and weight change tests. These tests were conducted for the composite samples by exposure to hydrochloric acid, sulfuric acid, and sodium chloride chemical solutions as well as ultraviolet (UV) light. Results showed that the corrosion strength of the polyester composite is lower than of the epoxy one in all chemical environments. The resistance of epoxy composite against UV light is higher than that of the polyester type. Generally, the epoxy composite is more resistant than the polyester type in all corrosive environments.