5 Sep 2024

Extending CEMHYD3D to Simulate Hydration of Portland Cement Pastes with High Volumes of Silica Fume

Abstract: Silica fume (SF) influences the hydration rate of Portland cement in differ-ent ways depending on the physical and chemical properties of the SF. This study reports the impact of SiO2 content (%), loss on ignition (%), and Brunauer–Emmett–Teller (BET) specific surface area on the hydration re-action of SF-cement paste mixtures. This study used five types of SFs with varying SiO2 content, loss on ignition (%), and particle morphology. Five SFs were mixed with Class H oil well cement at each of two different re-placement levels (20% or 30% by mass), and the released heat of hydra-tion was measured using isothermal calorimetry. The results were used to improve the pozzolanic reaction simulation feature of the original Virtual Cement and Concrete Testing Laboratory software, which enabled the soft-ware to simulate a higher SF replacement ratio in a cement mixture with higher fidelity. Results showed that a silica fume’s SiO2 content (%), loss on ignition (%), and BET specific surface area significantly influence the heat release rate. The new simulation model agrees well with the measure-ments on all the pastes tested.

5 Sep 2024

Next-Generation Water Quality Monitoring during Dredging Operations: Knowns, Unknowns, and Path Forward

Abstract: Water quality monitoring data are routinely collected during dredging and placement operations to address various state and federal requirements, including water quality standards, with the intention of protecting ecosystem health. However, such efforts may be limited by the lack of a standardized national strategic focus and user-friendly streamlined interfaces to interpret the data. Inconsistencies in how and what data are collected and lack of consensus on scientifically backed biological-effects thresholds make it difficult to quantify potential dredging operations impacts (or lack thereof) both within individual projects over time and across multiple projects of differing characteristics. Summarized herein is an initial effort to define a scientifically backed path forward to improve the value of current and future water quality monitoring and management decisions based on water quality data collected. The provided turbidity data were generally below applicable state thresholds for two case studies but for a third case study did periodically exceed thresholds at depth. This includes providing rationale for strategic focus on the most relevant dredging operations and projects, based on three general site-specific data categorizations: (1) sediment type, (2) dredge type, and (3) ecosystem type.

4 Sep 2024

Comparison of Numerical Simulations of Heat-Induced Stress in Basalt

Abstract: Energy losses due to excessive noise and heat are primary liabilities in traditional mining processes. Some of the currently researched methods to improve these liabilities involve heating the rock to induce internal stress fractures that make it easier to extract or remove rock with traditional mining equipment. Physical experimentation has yielded useful data that have been applied to numerical simulations of the heating and fracturing of rock, and multiple such simulations have been developed in the commercial multiphysics simulator COMSOL. Since COMSOL is not widely available on DoD high-performance computers, the goal of this research is to develop methods of replicating simulations developed in COMSOL as simulations that run in Abaqus FEA, another commercial multiphysics simulator. In this work, a simulated basalt cylinder with a 25 mm radius and a 158 mm height is subjected to a surface heat flux approximating the effects of a laser beam applied to the top of the cylinder. Simulated stress distributions, displacements, and temperatures obtained from both simulators are compared. When comparable results were not obtained using both simulators, the differences in results were investigated using simplified versions of the simulation.

30 Aug 2024

Particle Size Characteristics of Energetic Materials Distributed from Low-Order Functioning Mortar Munitions

Abstract: Particles of explosive filler distributed from low-order (LO) munition functioning are susceptible to dissolution and potential mobilization into groundwater and surface water. We command-initiated three mortar munitions as LO in triplicate using a fuze simulator and recovered particles from an ice surface to constrain LO particle characteristics. Total explosive mass recovery (19–55%) and spatial distribution (0->20 m) varied significantly both between munitions and between replicate LOs of the same munition. The median particle size (0.27–3.99 mm) varied with total mass recovery. In general, LO particles coarsened, and total mass deposition rates decreased logarithmically, with increasing distance from the initiation point.

29 Aug 2024

Experimental Evaluation of Steel Beams with Mechanical Section Reduction Retrofitted with Fiber Polymers

Abstract: Steel elements working in a harsh environment can be exposed to corrosion that degrades their performance and threatens the integrity of the whole structure. Recent studies propose using carbon (CFRP) and basalt (BFRP) fiber–reinforced polymers to repair corroded steel cross sections; however, most of these studies have not explored many of the structural characteristics, including ductility. In this study, we conduct a series of full-scale experimental tests to investigate the impact of corrosion, represented as mechanical section reduction, on steel beams as well as the impact of repairing the beams using CFRP and BFRP in enhancing the beams’ structural performance. Mechanical section reduction, introduced to the flange and web elements, is used to establish a baseline dataset that captures the impact of repairs in the absence of corrosion. Four-point bending loading conditions are utilized for all tested beams. The results show that the reduction of the flange and web section lowers the beams’ yielding load by 10% and 8%, respectively, compared with a beam with a full cross section. Utilizing CFRP and BFRP patches can partially restore the corroded beams’ ductility; however, the BFRP is outperforming the CFRP in improving their ultimate strength by 10% and enhancing their ductility by 10%.

28 Aug 2024

Integrating NOAA’s National Water Model (NWM) into the Antecedent Precipitation Tool (APT) to Support Clean Water Act Decision-Making

Abstract: This study examines the effectiveness of the National Water Model (NWM) in assessing streamflow normalcy under the Clean Water Act, compared to the commonly used Antecedent Precipitation Tool (APT). The APT, used by the Environmental Protection Agency, US Army Corps of Engineers, and environmental consultants, evaluates waterbody conditions based on precipitation data. However, it was found to be less accurate in predicting streamflow normalcy compared to USGS gage data. The NWM, on the other hand, showed promising results in preliminary analyses, outperforming the APT when compared to USGS gage records. This research expands on these initial findings, evaluating the NWM’s performance across the contiguous United States (CONUS) at gage locations indexed to the NHDPlus Version 2.1 stream network. The results suggest that the NWM provides adequate performance for assessing streamflow normalcy where USGS gages are not present, with accuracy ranging from 40% to 60% in the western half of CONUS and 60% to 80% in the eastern half.

28 Aug 2024

Validation of Daily Snow Water Equivalent for a Watershed Statistics Tool

Abstract: The Watershed Statistics tool is a tool currently being developed for the Remote Sensing and Geographic Information Systems Center of Expertise’s (RSGIS) Extreme Cold Weather web portal and will allow users to easily access and visualize snow water equivalent (SWE) data. The SWE data available on this tool are derived from passive microwave signals acquired by satellite through a technique known as enhanced passive microwave SWE. This analysis used available in situ SWE measurements from snow study sites in four watersheds across the United States and Canada to determine the accuracy of the data available on the tool at the watershed scale. In situ measurements of SWE were compared with the Watershed Statistics tool’s SWE data based on watershed, land cover, and elevation to determine causes if discrepancies between the satellite-based estimations on the tool and ground-based measurements. The extent to which the data available on the Watershed Statistics tool agreed with in situ measurements was highly variable. SWE data available on the Watershed Statistics tool agreed the least with ground-based measurements made at higher elevations and in areas with denser vegetation. The findings of this comparison are consistent with known limitations of the enhanced passive microwave SWE technique.

26 Aug 2024

FUNWAVE-TVD Testbed: Analytical, Laboratory, and Field Cases for Validation and Verification of the Phase-Resolving Nearshore Boussinesq-Type Numerical Wave Model

Abstract: Over the last couple of decades, advancements in high-performance computing have allowed phase-resolving, Boussinesq-type numerical wave models to be more practical in addressing nearshore coastal wave processes. As such, the open-source FUNWAVE-TVD numerical wave model has become more ubiquitous across all scientific and engineering-focused R&D organizations, including academic, government, and industry partners. In collaboration with the US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory; the University of Delaware; and HR Wallingford, a robust testbed has been developed to allow users to benchmark their applications against new releases of the model. The testbed presented here includes analytical, laboratory, and field cases, to provide guidance on the operational utility of FUNWAVE-TVD and examines numerical convergence, accuracy, and performance in modeling wave generation, propagation, wave breaking, and moving shorelines in nearshore wind-wave applications. A brief discussion on the efficiency of the model across parallel computing platforms is also provided.

22 Aug 2024

Application of Existing Tools to Systematically Identify Nearshore Placement Sites for Beneficial Use of Navigation Sediments in Lake Michigan

Purpose: The Great Lakes includes 140 federally maintained harbors with an annual dredging program of 2–4 million cubic meters (3–5 million cubic yards)[1] of sediment. Many small harbors are not dredged regularly, and there is an undredged backlog of over 9 million cubic meters (12 million cubic yards) of sediment (USACE-LRD 2021). Current policy (Spellmon 2023) is to maximize the beneficial use (BU) of sediment, with a goal of beneficially reusing 70% of the federal navigation dredging volume by 2030 (that is, the 70/30 goal). In the Great Lakes, clean sands have often been placed on beaches or in the nearshore littoral zone to beneficially nourish the shoreline, but since many harbors are not dredged regularly, no plans exist to beneficially reuse dredged sediments. This lack of existing BU plans is particularly true for harbors with finer grained or mixed sediment. To achieve the 70/30 BU goal and support navigation maintenance and coastal management requires a strategic and systematic approach to identifying BU sites. The purpose of the technical note is to (1) provide an approach to identify potential nearshore placement sites using existing information and models; (2) describe available tools for placement site identification, coastal condition information, and the long-term fate of the sediment; and (3) provide a pertinent case study to describe this approach in practice.

15 Aug 2024

Repair Quality Assessment: Spiral 4

Abstract: The Expedient and Expeditionary Airfield Damage Repair (E-ADR), Joint Capability Technology Demonstration (JCTD) program developed, demonstrated, and transitioned a repeatable capability for rapidly repairing bomb-damaged craters at adaptive base locations using logistically friendly technologies, indigenous materials, and less manpower than traditional crater repair methods. Within the E-ADR JCTD program, quality assessment took a major role to ensure quality repairs were performed while meeting the requirements of “just enough, just in time.” Repair criteria for backfill compaction and surface cap quality were developed through extensive testing. These criteria were incorporated into an easy-to-use and deployable smartphone application, the E-ADR Repair Assessment (ERA) application. This report focuses on the backfill quality assessment criteria development, roughness tolerance of surface caps checking procedure, and the development of the ERA application. The criteria and the ERA application both proved successful in the expedient evaluation of backfill and surface cap materials.