This brochure provides a summary of the information presented in FEMA P-484, Technical Manual: Conduits through Embankment Dams, including the effects of conduits on embankment dams, internal erosion and backward piping erosion, the factors that can lead to embankment dam failure, and best practices for conduits through embankment dams.
High concentration thickened tailings slurries that appear to be homogeneous mixtures often contain coarse particles that settle in the pipeline under laminar flow conditions. During pipeline transport, these coarse particles may eventually settle to the pipe invert. Frequently, these high concentration suspensions are misclassified as homogeneous slurries, leading to the use of incorrect models for predicting the pressure gradient and flow behaviour. This paper discusses the use of a non-Newtonian two-layer model to predict the pressure gradient of a high concentration suspension with a sliding bed in laminar flow conditions. The success of the model is measured by comparing the results obtained by applying the model to experimental results for a typical iron ore tailings slurry. It was found that the model predicted the laminar flow pressure gradient with less than 10% error for slurries with carrier fluid yield stresses above 10 Pa.
Friction losses is a key parameter in the design of pipeline transportation in paste backfill. A full-scale pipeloop test was conducted in the JCHX Paste Backfilling laboratory to investigate the friction losses of cemented unclassified iron tailings slurry. Friction losses in upward sloping pipe, vertical downward pipe, vertical upward pipe, 90° long radius elbow, horizontal straight pipe and downward sloping pipe were tested simultaneously under different solid fractions. The results indicated that friction losses always increase with flow rate and solid fraction. Friction losses in the elbows are about 1.552.16 times that in the horizontal straight pipe, which is about 2.710.0 kPa·m-1. The pipe-loop test data can be used to analyse the rheological priorities of cemented unclassified tailings slurry. Based on the Buckingham rheological equation, an empirical formula for friction losses was established and applied to a pipe with the optimal diameter of DN 150 mm. It can be concluded that the full-scale pipe-loop test is an effective way to investigate friction losses and the economics of design pipeline transportation.
?There is an increasing trend in iron ore mining in Brazil regarding the disposal and treatment of sandy tailings from concentration processes by reverse cationic flotation techniques. Filtering and later disposal of sandy tailings in piles known as PDR (Tailings Disposal Pile) has been shown to be a rising method to the detriment of known tailings dams. In the case study in question, the tailings thickening operation is too far from the filtration and stacking point, so it was necessary to consider a material transport mode between the two operations (Thickening and Filtration), which was the tailings pipeline. The pipeline is 6.7 km long tail and 52.0 m static lift designed to operate with process variations especially in terms of percent solids and variations in the beneficiation plant rate. The drive consists of five centrifugal pumps with 600 HP motors and the piping follows the ANSI B36.10 dimensional standard and the API 5L Grade B material standard with 16 inch diameter. To support the pipeline sizing a fundamental step was to perform the characterization of the material to be transported. Several tests were performed of granulometry, rheology, abrasiveness, solids density, slurry corrosivity, inclination angle of the pipeline, among others. The results of the tests were used to calibrate the mathematical models. The pipeline was evaluated considering the steady-state and transient flow regime. The results of the steady-state analysis made it possible to specify the quantity and model of the pumps, as well as to evaluate the velocities and pressure losses. The transient analysis, however, was performed to identify the operating scenarios that lead to the highest pressures and thus confirm the characteristics of the pipelines and consider the necessary hydraulic protections.
Today, tens of thousands of conduits through embankment dams in the United States are aging and deteriorating. Many of these conduits were poorly constructed and are not frequently inspected, if at all. With each passing year, deteriorating conduits pose an increasingly greater risk for developing defects that can lead to embankment dam failure. This technical manual provides procedures and guidance for best practices for the design, construction, problem identification and evaluation, inspection, maintenance, renovation, and repair associated with conduits through embankment dams. The technical manual is intended for use by personnel familiar with embankment dams and conduits, such as designers, inspectors, construction oversight personnel, and dam safety engineers. The technical manual includes more than 280 illustrative figures, 34 case histories, and an extensive glossary.
This technical manual provides procedures and guidance for best practices for the design, construction, problem identifcation and evaluation, inspection, maintenance, renovation, and repair associated with conduits through embankment dams. The technical manual is intended for use by personnel familiar with embankment dams and conduits, such as designers, inspectors, construction oversight personnel, and dam safety engineers. The DVD format includes an extensive collection of additional reading references.
This technical manual provides the procedures and guidance for best practices concerning the design, construction, problem identifcation and evaluation, inspection, maintenance, renovation, and repair associated with plastic pipe used in embankment dams. The manual provides in-depth analyses of loading conditions, structural design, and hydraulic design of plastic pipe, and is intended for use by personnel familiar with embankment dams, drains, siphons, and conduits, such as designers, inspectors, construction oversight personnel, and dam safety engineers.