Journal of Pipeline Systems Engineering and Practice

Drilling mud (or drilling fluid) is a vital component in a horizontal directional drilling (HDD) crossing project, for which a key function is the removal of the cuttings from the borehole. The rheological properties of drilling mud, including flow index, consistency index, effective viscosity, and flow patterns, are briefly reviewed. A model of the drilling mud behavior in the annular space is thereby established, based upon which the cuttings transport mechanism is analyzed. In this model, the critical factors for the efficient removal of cuttings are considered to be the rheological properties and return velocity of the drilling mud in the annular space surrounding the drill rod within the hole. The rheological properties should therefore be carefully controlled so the cuttings can be suspended or sink very slowly in the mud, and an appropriate return velocity must be selected so the flow pattern is suitable for effectively transporting the cuttings without compromising the stability of the borehole. Finally, a decision procedure is created by which a drilling mud engineer can select the proper mud rheological properties and return velocity. The model and decision process have been applied to a large-diameter HDD river crossing project to demonstrate their practicality.

It is impractical in the dynamic analysis of pipelines to consider the whole length of the pipe in a numerical model. Therefore, a minimum length is desired for the pipe model so that its midpoint responses are not affected by its end conditions. This length can be called the minimum effective length (MEL). In this study, at first, based on extensive nonlinear dynamic analyses, MEL values were determined for various types of soil using the equivalent bilinear springs for consideration of the soil-pipe-interaction. Then, by solving the dynamic equilibrium equation, assuming a linear behavior for the pipe and soil, it was shown that for very long buried straight pipes, the frequencies of all lateral modes are the same, and therefore the participation of higher modes is not negligible in long pipes. To take the higher modes into account, a relation was established between the unburied pipe frequencies and the MEL of the buried pipe. Then, assuming the local buckling of the pipe wall due to axial force and bending moment as the most probable damage of buried pipes subjected to seismic waves, a damage evaluation was performed to determine which conditions led to the reduction of the hollow-section area of the pipe and the loss of its efficiency. Finally, by analyzing various pipes subjected to three-component records, it was shown that the created strain could not lead to local buckling of the pipe. Consequently, other effective factors should be studied more thoroughly in evaluating the damage to buried continuous straight steel pipelines subjected to seismic waves.

Leakage may occur during pressure tests of gas pipelines. Locating the position of leakage followed by immediate repair work becomes very important. On the basis of both the theory of natural gas pipeline transportation and the procedure of pressure test, this paper established a mathematical model of leakage during pressure tests of gas pipelines. Leakage position function and discharge function, as well as the whole numerical simulation process, are studied in this paper by applying numerical inversion to partial differential equations. The theory and methods specified in this paper also can be used for leakage detection in an oil and gas pipeline’s daily operation.

As buried infrastructure in North America and around the world reaches the end of its service life, engineers and infrastructure managers will require an improved understanding of the performance of both deteriorated pipes and repair techniques. To develop this improved understanding, sensing technologies that enable the full pipe behavior to be measured, rather than a small number of localized discrete measurements, are required. A possible solution to this problem is to use distributed fiber optic strain sensors. To this end, a series of buried pipe tests were undertaken on steel, concrete, and high-density polyethylene (HDPE) pipes instrumented with distributed fiber optic strain sensors. The distributed measurements were in agreement with conventional strain gauges, but enabled the full strain distribution around the circumference of the pipe to be measured. This allowed localized behavior that would have been missed with conventional strain gauges to be detected and quantified. In addition, the choice of fiber optic cable proved to be an important consideration due to a trade-off between measurement accuracy and sensor robustness.

Infrastructure systems in the United States are in need of urgent maintenance and rehabilitations. Preservation of culvert networks, a major component of U.S. infrastructure systems, at an acceptable level of serviceability subject to the stringent yearly maintenance and rehabilitation (M&R) budgets is a major challenge for culvert network owners and managers. Decision makers are required to develop an optimum financial plan to minimize the total cost of maintenance and rehabilitation for different expected improvements of the culvert network performance during a given planning horizon. This manuscript presents a discussion on budget planning for maintenance and rehabilitation scheduling and optimization of a culvert network. Any maintenance and rehabilitation expenditure should be justified such that net increase in the asset value should be more than the cost of rehabilitation, where the net worth of an asset should be based on performance rather than on book value. Government standards require owners to maintain or improve the overall condition state of their infrastructure systems with substantial annual investment. In this paper, three methods were proposed to compute the long-term annual investments for culvert networks. They are modified worst first method, network optimization approach, and estimation by the maximum deterioration rate. The performance of a 15-culvert system was simulated using the above methods. Based on the simulation results, the modified worst first method is computationally intensive but provides the optimum budget. The method using maximum deterioration rate provides the lower bound value and should be used as the absolute lowest value that should be allocated. The optimization method uses computer programming and provides an upper bound value for small networks. It is anticipated that for large culvert networks the network optimization approach can be used to provide reasonable long-term annual budgets. Out of the three methods, the modified worst first method provided a minimum long-term annual budget of $9,000 consistent with the government requirements.

Water shortages cause intermittent operation of distribution networks in many developing countries. Under limited economic resources and frequent water shortages, the expansion of water supply for municipal use is slow and sometimes infeasible, hence supply management becomes a viable solution for operating water supply networks. One form of demand management is intermittent supply, wherein some parts of the water supply network are cut off from service during certain times and the entire network is in service at other times. Because intermittent water supply causes consumer dissatisfaction and complicates the operation of water supply networks, it is crucial to consider the principles of equanimity and justice in its implementation. This paper develops an optimization model to find the optimal scheduling of intermittent supply that reaches the maximum number of network nodes with desired pressure under various conditions of water shortage and considering the principles of equanimity and justice in a water distribution network. The network operation optimization problem is solved using the honey bee mating optimization (HBMO) algorithm linked to in a hydraulic simulator. The efficiency of the developed scheduling method is demonstrated by implementing it to two distribution networks considering different scenarios of water shortage.

Several statistical models have been proposed to study effects of different covariates in the failure of water pipes. In this paper, three statistical models, the Weibull proportional hazard model (WPHM), the Cox proportional hazard model (Cox-PHM), and the Poisson model (PM), were considered. Curve fitting techniques were proposed for estimation of a baseline hazard function equation for the Cox-PHM to allow for its application in break prediction. The water main failure in the City of Calgary is used for this study. From the statistical models, physical covariates (e.g., pipe diameter, length) compared with environmental covariates (e.g., temperature) were the critical factors impacting the pipe failure rate. Furthermore, WHPM and PM showed the best fit for prediction of metallic and PVC pipes, respectively. Pipe break prediction through estimation of baseline hazard by curve fitting techniques produces good results especially for a young system. This study recommends that a combination of models rather than a single model be used in assessing pipe network condition based on the rate of deterioration and material type of the system.

Horizontal directional drilling (HDD) is a trenchless technology used to install underground utilities. The force required to pull a pipe through the borehole during installation is crucial to design engineers. Various methods have been proposed to estimate the pullback load, each dealing with fluidic drag in a different way. Limitations in fluidic drag estimation by current design procedures have revealed the significance of having a reliable method for calculation. This paper proposes a new method to calculate fluidic drag based on annular flow equations. This method is used to calculate viscous drag for two HDD case studies, and the results are compared to the estimations by current methods, such as PRCI and ASTM F1962. Pullback load estimation based on the new method agrees well with the actual installation loads. This paper also investigates the impact of design factors on fluidic drag by presenting a sensitivity analysis over a practical range of related parameters. The ratio of pipe radius to borehole radius is observed to have the most influence on fluidic drag.

As infrastructure built during the 20th century reaches the end of its service life, engineers and managers are increasingly turning to rehabilitation rather than replacement to potentially reduce costs. For corrugated steel pipes and culverts, one such rehabilitation alternative is to use slip lining where a liner (new pipe) is placed inside the existing deteriorated pipe and the space between them is grouted. The current research seeks to better understand the performance of slip-lined systems by (1) characterizing the properties of a low-strength and a high-strength grout; (2) conducting a series of pipe tests to determine the load-carrying capacity and stiffness of a corrugated steel pipe and pipes that have been rehabilitated with slip liners; (3) understand the impact of grout strength and the liner on pipe stiffness and strength; and (4) determine the level of composite action in the pipe system by using a plasticity approach to estimate the load-carrying capacity of the system. The pipes rehabilitated with low-strength grout had increased strength (three times greater) and stiffness (eight times greater) versus an unrehabilitated pipe, whereas the specimens rehabilitated with high-strength grout showed higher increases in both load-carrying capacity (ten times greater) and stiffness (50 times greater) over the unrehabilitated pipe. The high density polyethylene (HDPE) liner had no impact on the load-carrying capacity of the specimens with high-strength grout and required large diameter changes to enhance the load-carrying capacity of low-strength grout specimens. A plasticity approach was used to estimate the load-carrying capacity of the specimens and indicated that for these tests, composite behavior between the grout and the corrugated steel pipe was developed.