16 Sep 2021

Penetration Modeling of Ultra‐High Performance Concrete using Multiscale Meshfree Methods

Abstract: Terminal ballistics of concrete is of extreme importance to the military and civil communities. Over the past few decades, ultra‐high performance concrete (UHPC) has been developed for various applications in the design of protective structures because UHPC has an enhanced ballistic resistance over conventional strength concrete. Developing predictive numerical models of UHPC subjected to penetration is critical in understanding the material's enhanced performance. This study employs the advanced fundamental concrete (AFC) model, and it runs inside the reproducing kernel particle method (RKPM)‐based code known as the nonlinear meshfree analysis program (NMAP). NMAP is advantageous for modeling impact and penetration problems that exhibit extreme deformation and material fragmentation. A comprehensive experimental study was conducted to characterize the UHPC. The investigation consisted of fracture toughness testing, the utilization of nondestructive microcomputed tomography analysis, and projectile penetration shots on the UHPC targets. To improve the accuracy of the model, a new scaled damage evolution law (SDEL) is employed within the microcrack informed damage model. During the homogenized macroscopic calculation, the corresponding microscopic cell needs to be dimensionally equivalent to the mesh dimension when the partial differential equation becomes ill posed and strain softening ensues. Results of numerical investigations will be compared with results of penetration experiments.

16 Sep 2021

Natural Language Indexing for Pedoinformatics

Abstract: The multiple schema for the classification of soils rely on differing criteria but the major soil science systems, including the United States Department of Agriculture (USDA) and the international harmonized World Reference Base for Soil Resources soil classification systems, are primarily based on inferred pedogenesis. Largely these classifications are compiled from individual observations of soil characteristics within soil profiles, and the vast majority of this pedologic information is contained in non-quantitative text descriptions. We present initial text mining analyses of parsed text in the digitally available USDA soil taxonomy documentation and the Soil Survey Geographic database. Previous research has shown that latent information structure can be extracted from scientific literature using Natural Language Processing techniques, and we show that this latent information can be used to expedite query performance by using syntactic elements and part-of-speech tags as indices. Technical vocabulary often poses a text mining challenge due to the rarity of its diction in the broader context. We introduce an extension to the common English vocabulary that allows for nearly-complete indexing of USDA Soil Series Descriptions.

15 Sep 2021

Field Evaluation of GNSS/GPS Based RTK, RTN, and RTX Correction Systems

Abstract: This Coastal and Hydraulic Engineering Technical Note (CHETN) details an evaluation of three Global Navigation Satellite System (GNSS)/Global Positioning System (GPS) real-time correction methods capable of providing centimeter-level positioning. Internet and satellite-delivered correction systems, Real Time Network (RTN) and Real Time eXtended (RTX), respectively, are compared to a traditional ground-based two-way radio transmission correction system, generally referred to as Local RTK, or simply RTK. Results from this study will provide prospective users background information on each of these positioning systems and comparisons of their respective accuracies during in field operations.

15 Sep 2021

On Enhancing the Mechanical Behavior of Ultra-High Performance Concrete Through Multi-Scale Fiber Reinforcement

Abstract: Steel fibers are typically used in ultra-high performance concretes (UHPC) to impart flexural ductility and increase fracture toughness. However, the mechanical properties of the steel fibers are underutilized in UHPC, as evidenced by the fact that most of the steel fibers pull out of a UHPC matrix largely undamaged during tensile or flexural tests. This research aims to improve the bond between steel fibers and a UHPC matrix by using steel wool. The underlying mechanism for fiber-matrix bond improvement is the reinforcement of the matrix tunnel, surrounding the steel fibers, by steel wool. Single fiber pullout tests were performed to quantify the effect of steel wool content in UHPC on the fiber-matrix bond. Microscopic observations of pulled-out fibers were used to investigate the fiber-matrix interface. Compared to the control UHPC mixture with no steel wool, significant improvement in the flexural behavior was observed in the UHPC mixtures with steel wool. Thus, the addition of steel wool in steel fiber-reinforced UHPC provides multi-scale reinforcement that leads to significant improvement in fiber-matrix bond and mechanical properties of UHPC.

14 Sep 2021

KM Tools: Making Connections

ABSTRACT: Knowledge management is vital to successfully executing research and development programs within the U.S. Army Engineer Research and Development Center (ERDC). Experimental knowledge management initiatives over the years led to discoveries about the best ways to store and access ERDC’s vast knowledge base. This document highlights several of the effective knowledge management tools that evolved from these discoveries, helping you to find and share knowledge!

13 Sep 2021

Photo Degradation Kinetics of Insensitive Munitions Constituents Nitroguanidine, Nitrotriazolone, and Dinitroanisole in Natural Waters

Abstract: Herein the matrix effects on the kinetics of aqueous photolysis for the individual munitions constituents of IMX-101: nitroguanidine (NQ), dinitroanisole (DNAN), and nitrotriazolone (NTO) are reported along with the environmentally relevant kinetics and quantum yields. Photolysis potentially represents a major degradation pathway for these munitions in the environment and further understanding the complex matrices effects on photolytic kinetics was needed. Aqueous systems are of particular interest due to the high solubility of NQ (3,800 ppm) and NTO (16,642 ppm) compared to the traditional munitions trinitrotoluene (TNT, 100.5 ppm) and 1,3,5-trinitro-1,3,5-triazine (RDX, 59.9 ppm). Environmental half-lives (and quantum yields) were found to be 0.44 days, 0.83 days, and 4.4 days for NQ, DNAN, and NTO, respectively, under natural sunlight. In laboratory experiments using nominally 300 nm bulbs in a merry-go-round style reactor in DI water the relative rate of photolysis for the three munitions constituents followed the same order NQ > DNAN > NTO, where DNAN and NTO reacted 57 and 115 times more slowly, respectively, than NQ. In the various environmentally relevant matrices tested in the laboratory experiments NQ was not significantly affected, DNAN showed a faster degradation with increasing ionic strength, and NTO showed a modest salinity and pH dependence on its rate of photolysis.

10 Sep 2021

Variability in Weed Biological Control: Effects of Foliar Nitrogen on Larval Development and Dispersal of the Alligatorweed Flea Beetle, Agasicles hygrophila

Abstract: Host quality can have dramatic effects on performance of biological control agents but its importance is understudied. We used a combination of field measurements and laboratory experiments to determine the range of foliar nitrogen (FN) that larvae of the alligatorweed flea beetle (Agasicles hygrophila) are exposed to in the field and its importance to larval development and dispersal. Seasonal variability in FN was assessed at field sites spanning southern to northern Louisiana every 2–3 weeks during the growing season for four years. In a series of laboratory experiments, alligatorweed FN was manipulated to examine its influence on larval development and survival (under different temperature regimes), adult biomass, and dispersal of the biological control agent, A. hygrophila. Foliar nitrogen and rearing temperature had strong independent effects on larval development rate. We demonstrated that increasing nitrogen in leaf tissues shortens larval A. hygrophila developmental time and increases survival to adulthood, regardless of exposure temperature during development. It also suggests that foliar nitrogen may have important effects on biological control of alligatorweed, particularly as a result of seasonal variation in temperature and plant nutrition at field sites, and could contribute to observed variation in A. hygrophila efficacy in the field.

9 Sep 2021

Shear and Tensile Delamination of Ice from Surfaces: The Ice Adhesion Peel Test (IAPT)

ABSTRACT: For decades, researchers have sought to understand the adhesion of ice to surfaces so that low-cost ice mitigation strategies can be developed. Presently, the field of ice adhesion is still without formal standards for performing ice adhesion tests. The U.S. Army Corps Engineers’ Research and Development Center’s Cold Regions Research and Engineering Laboratory (ERDC-CRREL) has a longstanding history as an independent third party for ice adhesion testing services. Most notably, CRREL’s Zero-Degree Cone Test (ZDCT) has been an industry favorite for more than 30 years. Despite its wide acceptance, the ZDCT contains some shortcomings, namely that freshwater ice is formed on the surface of interest within the confines of an annular gap. To address this limitation, CRREL developed and uses the Ice Adhesion Peel Test (IAPT) for testing ice adhesion. This test employs an open planar substrate from which the ice can be removed under either tensile or shear loading, thereby allowing ice to be grown directly on the target substrate without the use of molds. The IAPT configuration is therefore amenable to different ice types and geometries and will provide utility to research studies that aim to develop surface treatments to mitigate ice in a wide range of environments. This report describes the IAPT and its use for characterizing the ice adhesion properties of materials.

9 Sep 2021

Mat Sinking Unit Supply Study: Mississippi River Revetment

Abstract: The Mississippi Valley Division (MVD) has maintained the Mississippi River banks for over 80 years. The Mat Sinking Unit (MSU), built in 1946, was considered state-of-the-art at the time. This system is still in operation today and has placed over 1,000 miles of Articulated Concrete Mats along the Mississippi River from Head of Passes, LA, to Cairo, IL. A new MSU has been designed and is expected to be fully mission capable and operational by the 2023 season, which is expected to increase the productivity from 2,000 squares/day up to 8,000 squares/day with double shifts and optimal conditions. This MSU supply study identifies and optimizes the supply chain logistics for increased production rates from the mat fields to the MSU. The production rates investigated for this effort are 2,000 squares/day, 4,000 squares/day, and 6,000 squares/day. RiskyProject® software, which utilizes a Monte Carlo method to determine a range of durations, manpower, and supplies based on logical sequencing is used for this study. The study identifies several potential supply and demand issues with the increased daily production rates. Distance to casting fields, number of barges, and square availability are the major issues to supply increased placement rates identified by this study.

9 Sep 2021

Geophysical Investigation to Assess Condition of Grouted Scour Hole: Old River Control Complex—Low Sill Concordia Parish, Louisiana

Abstract: Geophysical surveys, both land-based and water-borne, were conducted at the Old River Control Complex‒Low Sill, Concordia Parish, LA. The purpose of the surveys was to assess the condition of the grout within the scour region resulting from the 1973 flood event, including identification of potential voids within the grout. Information from the ground studies will also be used for calibration of subsequent marine geophysical data and used in stability analysis studies. The water-borne survey consisted of towed low frequency (16-80 MHz) ground penetrating radar (GPR), whereas the land-based surveys used electrical resistivity and seismic refraction. The GPR survey was conducted in the Old River Channel on the upstream side of the Low Sill structure. The high electrical conductivity of the water (~50 mS/m) precluded penetration of the GPR signal; thus, no useful data were obtained. The land-based surveys were performed on both northeast and southeast sides of the Low Sill structure. Both resistivity and seismic surveys identify a layered subsurface stratigraphy that corresponds, in general, with available borehole data and constructed geologic profiles. In addition, an anomalous area on the southeast side was identified that warrants future investigation and monitoring.