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Archive: June, 2020
  • PUBLICATION NOTICE: Rapid Screening for Uranium in Soils Using Field Portable X-Ray Fluorescence Spectrometer : A Comparative Study

    Abstract: Depleted uranium armor penetrating munitions are used on testing and training ranges leading to elevated concentrations of U in range soils. To prevent exposure on secure areas contaminated with depleted uranium (DU) hotspots, easy and rapid screening methods are needed. This study explores the feasibility of field portable X-ray fluorescence (FPXRF) spectrometry as a fast screening tool for locating hotspots of DU in the field. Direct comparisons of results were made for U concentrations in soil obtained using a FPXRF spectrometry and measurement of U using ICP-MS after acid digestion. The environmental samples included both field range contaminated soils collected at a munition testing facility and soils spiked with uranium dioxide, uranium trioxide and uranyl nitrate. Using U concentrations measured with ICP-MS from split samples, FPXRF operating procedures and conditions such as analysis time, soil moisture content, sample amount, and sample packing factors were optimized. Results showed that the FPXRF technique yielded similar U concentrations as ICPMS measurements after acid digestion in both standard soil (NIST) samples and DU contaminated range soils. In field contaminated soils, U values with FPXRF were 88.8% of the measurements with ICPMS with a significant correlation (R2: 0.98, n=8). Sample preparation affected the uranium concentration measurements made with FPXRF in the laboratory and in the field. A loose packing of the samples in the sample containers, higher sample occupancy as well as low soil moisture yielded significantly high U concentrations by 4-5%, 15-50% and 43%, respectively. The measured soil U concentrations were not affected by the variation of the sample analysis time. This study suggests that FPXRF is a promising fast screening tool for field DU hotspots as well as detection/location of penetrators in the fields that can increase the ability to rapidly and inexpensively manage DU on ranges and help ensure sustainable use of DU munitions on testing and training ranges.
  • PUBLICATION NOTICE: Characterization of eroded mud aggregates with the Flume Imaging Camera System (FICS) and its added value to sediment management projects

    Abstract: The goal of this technical note (TN) is to describe the functionality and added research value of the Flume Imaging Camera System (FICS), a US Army Engineer Research and Development Center (ERDC)-developed system designed to measure the size of sediment particles immediately following erosion.
  • PUBLICATION NOTICE: Applications of value modeling to USACE Civil Works and beyond

    Abstract: The US Army Corps of Engineers (USACE) Civil Works (CW) portfolio includes $250 billion worth of capital assets. As infrastructure ages and budgets change, new asset management (AM) investment strategies are required to support the maintenance, repair, and replacement (MR&R) of these assets while also providing the greatest value to the USACE and to the Nation. Shrinking budgets and increased scrutiny of government expenditures drive efforts to determine how best to optimize government funds for infrastructure improvement. As a result, USACE-CW AM seeks to create a value model capable of calculating the benefit of MR&R project alternatives regardless of business line. Furthermore, USACE-CW seeks to explore whether such a value model could be used for the generation of defensible budgets that consistently bring high value to the USACE and to the Nation. Thus, this special report reviews past USACE CW efforts to develop a value model for decision analytics. This report also provides an introduction to value modeling while covering applications of value modeling in multiple areas, including AM and portfolio decision analytics.
  • PUBLICATION NOTICE: Hydraulic Analysis and Modeling of Navigation Conditions near the Mississippi River Bridges in Vicksburg, Mississippi

    Abstract: The River and Estuarine Engineering Branch of the Coastal and Hydraulics Laboratory developed a two-dimensional numerical model of the Mississippi River near Vicksburg, MS, using Adaptive Hydraulics to investigate navigation conditions through the Interstate 20 and Old Highway 80 Bridges reach. A focus of the study was determining the Marshall Brown Dikes impact to velocities and navigation through the reach. Proposed dikes, focused on improving currents, were also tested to determine if they are a feasible option to improve navigability through the bridges. A second proposed alternative, a levee to protect the articulated concrete mattress (ACM) field, was also simulated to determine if flood damage to the ACM field could be successfully reduced without negatively impacting navigation. Velocity data from 2008 throughout the reach of concern were used for validation along with water surface elevation data from 2008, 2011, 2016, and 2018. The Marshall Brown Dikes were shown to have a localized impact on velocities near the dikes, but the changes to the velocity downstream near the bridge were negligible for all tested flow rates. Simulations of the proposed dikes did not result in an improvement to navigation conditions, but the proposed levee was successful in decreasing velocities and depths over the ACM field.
  • PUBLICATION NOTICE: Improved Ribbon Bridge Structural Response Validation Testing

    Abstract: vehicles and trucks up to Military Load Capacity 96. The Bridge Supplemental Set (BSS) includes Bridge Erection Boats and an anchorage system to allow for the positioning and securing of the bridge in moving water. Designed to function as either a floating bridge or a raft, the IRB and BSS give military commanders multiple options with regards to the tactical river crossings. The US Army Engineer Research and Development Center (ERDC) was contracted by Product Manager Bridging to provide a structural analysis via high-fidelity numerical modeling of various IRB spans and water flow rates. To this end, a finite element model (FEM) of the IRB was constructed using field measurements of IRB interior bays. To ensure accurate structural response characteristics of the FEM and to build confidence in the simulation results, a validation test series was devised to generate empirical data to correlate against. This report documents the IRB structural response validation testing conducted at ERDC in March 2018. The data contained in this report was used to validate the IRB structural FEM.
  • PUBLICATION NOTICE: Structural Analysis of an Improved Ribbon Bridge Subjected to Hydrodynamic and Vehicular Loading

    Abstract: Structural modeling and simulations were performed to determine limit states of an Improved Ribbon Bridge (IRB) subjected to hydraulic and vehicle loadings. Measurements of as-built IRB bays were used to construct a three-dimensional, computer-aided design model. The model was used to create a computational finite element model (FEM) that was validated through correlations of simulation results and empirical data. The validated FEM was used to establish limit states (i.e., maximum current and vehicular loading conditions for 110 and 210 m IRB crossings). Analyses revealed that the primary structural failure mode was yielding in the steel pins that link IRB bays. Assuming the IRB is adequately restrained at the shores, a 110 m IRB can withstand currents up to 11 ft/s with no vehicle traffic; a 210 m IRB can endure up to 7 ft/s under the same conditions. For risk crossings, one Military Load Classification-70 vehicle on the bridge, 110 and 210 m IRBs can tolerate currents up to 9 and 7 ft/s, respectively. Under normal crossing conditions vehicle spaced 100 ft apart, a 110 m IRB has the structural capacity to endure currents up to 9 ft/s; the maximum current for a 210 m IRB is 5 ft/s.
  • PUBLICATION NOTIFICATION: Effect of Tropical Storms and Precipitation on Dredging Volumes: Houston-Galveston, TX, and Mayport, FL

    Abstract: This study characterizes infilling responses within dredged navigation channels to rainfall from tropical storms and hurricanes. This project created a web tool based on the methods described in this report. This report discusses the different analysis methods considered to relate storm and rainfall to dredging volumes at two pilot sites, Galveston, TX, and Mayport, FL. A comprehensive storm Impact Factor for hurricanes was developed to quantify the impact at a site based on proximity, duration, and wind speed. The methods vary based on the length and timing of periods of storms and rainfall prior to a dredge event. At Galveston, TX, when 2-year dredging volume totals were compared to hurricane activity occurring in the previous 2 years, the maximum dredging volume removed was higher after higher hurricane activity when compared to low activity periods. The average amount dredged was higher following periods of high hurricane activity. At Mayport, FL, dredging volumes were compared to hurricane activity occurring since the last dredging action took place. Similarly to Galveston, TX, the maximum dredging volume removed was higher after higher hurricane activity periods when compared to low activity periods. The average amount dredged was higher following periods of high hurricane activity.
  • PUBLICATION NOTICE: Quantification of the Flow Field around a Draghead Using a Physical Model

    Abstract: This study quantifies the hydraulic flow field around a draghead using a 1:7 scaled California and general type draghead. The flow field velocity measurements were taken with each draghead stationary and moving with a prototype speed of 2 knots. The measured velocities increased proportionally with the pumping flow rate. Measured velocities were found to be inversely proportional to the distance from the draghead. As a result, the greatest entrainment velocities for the California draghead were measured between the two visors and below the visors. The entrainment velocities laterally of the dragheads were found to increase by a factor of 2 with the addition of either a concrete or sand bed below the draghead. The measured velocities changed dramatically when the draghead was moving with a prototype speed of 2 knots. The measurement locations to the side of the dragheads did not show the presence of fluid entrainment; instead, the velocities were dominated by the forward motion and subsequent generation of a shear layer around the draghead. The velocities behind the draghead indicated the presence of a wake behind the draghead, with the fluid moving forward at velocity equivalent to or greater than the forward translation speed.
  • PUBLICATION NOTICE: Rapid Watershed Assessment Tools Based on High-Resolution Terrain Data

    Abstract: The goal of this project was to develop rapid watershed assessment methods to estimate channel stability and sediment transport potential using high resolution terrain data (Light Detection and Ranging-LiDAR) to support US Army Corps of Engineers (USACE) watershed planning. This project developed a suite of tools based on advanced remote sensing technologies (LiDAR) that use off-the-shelf, high-resolution terrain data to rapidly assess watershed condition at the channel, floodplain, valley, and watershed scales. The widespread availability of high-resolution terrain data provides an opportunity to assess watershed conditions in great detail over large spatial extents. For this project, a channel assessment method was developed using a new LiDAR Hydraulic Geometry Relationships (HGR)-based approach for developing regional curves.
  • PUBLICATION NOTICE: A Generalized Approach for Modeling Creep of Snow Foundations

    ABSTRACT:  When an external load is applied, snow will continue to deform in time, or creep, until the load is removed. When using snow as a foundation material, one must consider the time-dependent nature of snow mechanics to understand its long-term structural performance. In this work, we develop a general approach for predicting the creep behavior of snow. This new approach spans the primary (nonlinear) to secondary (linear) creep regimes. Our method is based on a uniaxial rheological Burgers model and is extended to three dimensions. We parameterize the model with density- and temperature-dependent constants that we calculate from experimental snow creep data. A finite element implementation of the multiaxial snow creep model is derived, and its inclusion in an ABAQUS user material model is discussed. We verified the user material model against our analytical snow creep model and validated our model against additional experimental data sets. The results show that the model captures the creep behavior of snow over various time scales, temperatures, densities, and external loads. By furthering our ability to more accurately predict snow foundation movement, we can help prevent unexpected failures and extend the useful lifespan of structures that are constructed on snow.