Journal of Pipeline Systems Engineering and Practice

In regards to the development of software for decision support for pipeline renewal, most of the attention to date has been paid to the development of asset management models, which help an owner decide on which portions of a system to prioritize for needed actions. There has not been much work in terms of providing guidance on whether to rehabilitate or replace the pipeline asset and choosing the most appropriate methods for that work. These decisions involve the evaluation of many criteria, which must be considered thoroughly to determine the optimal way of rehabilitating or replacing these systems efficiently and cost effectively. As part of the U.S. EPA Aging Water Infrastructure (AWI) Research Program, one key area of research, conducted in collaboration with wastewater and water utilities, was a study of the current approaches available for making rehabilitation versus replacement decisions. The purpose of this study was to (1) identify the current methodologies and decision support systems (DSS) being used for determining how to rehabilitate or replace underground utilities; (2) identify the critical gaps of these current models through comparison with case history data collected from utilities; and (3) assess the feasibility of substantially improving upon existing approaches. This paper provides a detailed review of DSS and methodologies that have been proposed for use around the world over the past 15 years for renewal decision support and summarizes the findings from visits with eight large utilities in the United States to discuss how each makes their rehabilitation versus replacement decision. Recommendations for the next steps needed to improve upon the existing models to make them more directly useful in terms of decision support are also discussed.

Buried pipelines may be subject to upheaval buckling because of thermally induced compressive stresses. As the buckling load of a strut decreases with increasing out of straightness, not only the maximum available resistance from the soil cover, but also the movement of the pipeline required to mobilize this are important factors in design. This paper will describe the results of 15 full-scale laboratory tests that have been carried out on pipeline uplift in both sandy and rocky backfills. The cover to diameter ratio ranged from 0.1 to 6. The results show that mobilization distance exhibits a linear relationship with $H/D$ ratio and that the postpeak uplift force-displacement response can be accurately modeled using existing models. A tentative design approach is suggested; the maximum available uplift resistance may be reliably predicted from the postpeak response, and the mobilization distance may be predicted using the relationships described in this paper.

An economic design of water distribution system components plays an important role in the water-supplying agency because of the requirement of a large financial investment on construction, operation, and maintenance. Population-based stochastic search algorithms have become a futuristic method for optimal design of water distribution networks. However, the effectiveness of population-based stochastic search algorithms purely depends on several factors, such as population size, degree of randomness involved, penalty function, algorithm operators, and search space size. An analysis of published research shows that a large number of evaluations is required to arrive at the least cost combination of pipe diameters. This paper proposes a new approach, in which flow velocity in a pipe is considered as implicit information for pipe sizing. Three well-known benchmark networks were used to illustrate the applicability of the proposed approach for least-cost pipe sizing of water distribution networks. The result of the model application reveals that the computational effort required to arrive at an economical design is very minimal.

Installation of new buried pipes and culverts, and replacement of existing ones utilizing trenchless technologies, is increasing in popularity because these methods mitigate many of the surface disturbances associated with conventional open-cut placement. Pipe ramming is an efficient technique that allows installation of casings in soils that can present difficulties for other trenchless technologies. Despite increasing usage, little technical guidance is available to owners and engineers who plan installations with pipe ramming. This paper provides an overview of the pipe ramming technique, possible design procedures, and governing mechanics associated with pipe ramming, with the goal of providing a baseline for engineered installations and identifying areas for further research. Methods to estimate soil resistance to ramming, analysis of ground deformations, and ground vibrations are discussed and compared with measurements observed in field installations. Soil resistance predictions based on conventional jacking methods are shown to underpredict measured resistances inferred from dynamic load testing. Empirical Gaussian settlement models commonly employed in tunnel engineering were shown to result in somewhat inaccurate predictions for an observed pipe ramming installation in cohesionless soils. Field measurements of the ground vibrations resulting from ramming are presented and compared with commonly used safe vibration standards developed for residential structures; the frequencies of vibration generally range from 20–100 Hz, are considerably high for small source-to-site distances, and attenuate rapidly with radial distance. In general, the study lays a basis for planning pipe installation projects with the intent of providing technical advancement in pipe ramming.

Submarine pipelines are usually laid unburied. Free spanning may be caused in the line by seabed unevenness, topology changes, scouring, or sand waves. In seismically active areas, the free spannings are prone to severe ground excitations. This article deals with the seismic performance of the submarine pipeline free spanning, and the water/pipeline interaction during the event is its focal point. For this, a numerical finite-element model has been used. Results from a conventional added mass approach have been examined against those from a more elaborate coupled acoustic-structural model. With the coupled system the surrounding seawater, pipe body, seabed, and free spanning have all been incorporated into the model. Both random earthquake and harmonic excitations have been considered. A time domain incremental dynamic analysis (IDA) method has been used to evaluate the pipeline performance. Effects from type, frequency, intensity, and direction of excitation and the free-span length on the pipeline response have been investigated. In most cases, the added mass approach has been found to provide more conservative predictions (in some cases up to 60%) for the free-spanning seismic response in comparison to those obtained from the acoustic method. For the earthquake excitations, the predictions obtained from each of the two methods have been more consistent as compared to the results obtained for harmonic excitations.