Open Access Publications

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Open access publications by faculty, postdocs, and graduate students in the Department of Civil and Environmental Engineering.


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Now showing 1 - 20 of 101
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    Diagnostic load testing and assessment of a corroded corrugated metal pipe culvert before rehabilitation
    (Structure and Infrastructure Engineering, 2023-11-15) Safari, Sajjad; DuBose, Tyler; Head, Monique H.; Shenton, Harry W. III; Tatar, Jovan; Chajes, Michael J.; Karam, Jonathan; Hastings, Jason N.
    Buried culverts are important structures within the civil infrastructure that convey water beneath roadways, bridges, and other systems while also being load bearing. However, many culverts are deteriorating and reaching the end of their design life span, where assessment methods to determine whether replacement or rehabilitation techniques such as spray applied pipe liners (SAPLs) are needed to extend their service life. In this study, mounted sensors and vision-based measurement techniques are used to assess the in situ conditions of a culvert consisting of corrugated metal pipes before being rehabilitated with geopolymer (cementitious-based) SAPLs. Results from diagnostic load tests (variating from static to dynamic) are presented to evaluate maximum deformations, verify the load-carrying effectiveness of the SAPLs, and compare results to design calculations due to the presence of a live load acting on the culvert.
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    pKa prediction of per- and polyfluoroalkyl acids in water using in silico gas phase stretching vibrational frequencies and infrared intensities
    (Physical Chemistry Chemical Physics, 2023-09-01) Murillo-Gelvez, Jimmy; Dmitrenko, Olga; Torralba-Sanchez, Tifany L.; Tratnyek, Paul G.; Di Toro, Dominic M.
    To successfully understand and model the environmental fate of per- and polyfluoroalkyl substances (PFAS), it is necessary to know key physicochemical properties (PChPs) such as pKa; however, measured PChPs of PFAS are scarce and of uncertain reliability. In this study, quantitative structure–activity relationships (QSARs) were developed by correlating calculated (M062-X/aug-cc-pVDZ) vibrational frequencies (VF) and corresponding infrared intensities (IRInt) to the pKa of carboxylic acids, sulfonic acids, phosphonic acids, sulfonamides, betaines, and alcohols. Antisymmetric stretching VF of the anionic species were used for all subclasses except for alcohols where the OH stretching VF performed better. The individual QSARs predicted the pKa for each subclass mostly within 0.5 pKa units from the experimental values. The inclusion of IRInt as a pKa predictor for carboxylic acids improved the results by decreasing the root-mean-square error from 0.35 to 0.25 (n > 100). Application of the developed QSARs to estimate the pKa of PFAS within each subclass revealed that the length of the perfluoroalkyl chain has minimal effect on the pKa, consistent with other models but in stark contrast with the limited experimental data available.
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    Annulus Void Fill Material for Rehabilitated Sliplined Culverts
    (The University of Akron, 2023-03) Patnaik, Anil; Alzlfawi, Abdullah; Das, Shagata
    Sliplining is a method used by transportation agencies to rehabilitate deteriorated culverts. In recent years, ODOT discovered a number of sliplined culverts that did not have their annulus void spaces completely filled. Such culverts experience distortion and settlement as well as reduced structural capacity. Field inspections of several sliplined culverts in Ohio in this study confirmed that the lack of complete annulus void filling is a prevalent problem. Filler grout properties, particularly poor flow characteristics, would prevent the grout from completely filling annulus voids. This led to the investigation of grout properties that are most important to achieve good flow and fillability. New mixture proportions of a controlled low-strength material (CLSM) and cellular grout C40 were developed based on extensive laboratory testing. These improved grouts were also mixed in a batching plant at a larger scale and were pumped over a 200-ft length at an upslope of 2.5% to determine the suitability of these grouts in practical applications. Grouting of the annulus voids of 20-foot-long sections was verified using a 36-inch liner pipe sliplined within a 48-inch host pipe. A suggested basis for changes to the relevant ODOT specifications in SS 837 is recommended.
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    The Role of Biochar in Regulating the Carbon, Phosphorus, and Nitrogen Cycles Exemplified by Soil Systems
    (Sustainability, 2021-05-18) Pan, Shu-Yuan; Dong, Cheng-Di; Su, Jenn-Fang; Wang, Po-Yen; Chen, Chiu-Wen; Chang, Jo-Shu; Kim, Hyunook; Huang, Chin-Pao; Hung, Chang-Mao
    Biochar is a carbon-rich material prepared from the pyrolysis of biomass under various conditions. Recently, biochar drew great attention due to its promising potential in climate change mitigation, soil amendment, and environmental control. Obviously, biochar can be a beneficial soil amendment in several ways including preventing nutrients loss due to leaching, increasing N and P mineralization, and enabling the microbial mediation of N2O and CO2 emissions. However, there are also conflicting reports on biochar effects, such as water logging and weathering induced change of surface properties that ultimately affects microbial growth and soil fertility. Despite the voluminous reports on soil and biochar properties, few studies have systematically addressed the effects of biochar on the sequestration of carbon, nitrogen, and phosphorus in soils. Information on microbially-mediated transformation of carbon (C), nitrogen (N), and phosphorus (P) species in the soil environment remains relatively uncertain. A systematic documentation of how biochar influences the fate and transport of carbon, phosphorus, and nitrogen in soil is crucial to promoting biochar applications toward environmental sustainability. This report first provides an overview on the adsorption of carbon, phosphorus, and nitrogen species on biochar, particularly in soil systems. Then, the biochar-mediated transformation of organic species, and the transport of carbon, nitrogen, and phosphorus in soil systems are discussed. This review also reports on the weathering process of biochar and implications in the soil environment. Lastly, the current knowledge gaps and priority research directions for the biochar-amended systems in the future are assessed. This review focuses on literatures published in the past decade (2009–2021) on the adsorption, degradation, transport, weathering, and transformation of C, N, and P species in soil systems with respect to biochar applications.
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    Combustion operating conditions for municipal Waste-to-Energy facilities in the U.S.
    (Waste Management, 2021-08-01) Giraud, Robert J.; Taylor, Philip H.; Huang, Chin-pao
    Highlights • Survey of U.S. municipal waste-to-energy (WTE) facilities identified 188 boilers. • These WTE boilers were stratified into nine categories by combustion technology. • WTE boilers typically operate at a gas residence time > 2.4 s above 1160°C. Abstract This paper reports the first known comprehensive survey of combustion operating conditions across the wide range of municipal waste-to-energy facilities in the U.S. The survey was conducted in a step-wise fashion. Once the population of 188 units operating at over 70 facilities was defined, this population was stratified by distinguishing characteristics of combustion technology. Stratum-level estimates for operating conditions were determined from data collected in the survey. These stratum-level values were weighted by corresponding design capacity share and combined to infer national-level operating parameter estimates representative of the overall population. Survey results show that typical municipal waste-to-energy combustion operating conditions in the U.S. are (1) furnace temperature above 1160 °C, (2) gas residence time above 2.4 s, (3) exit gas concentrations of nearly 10% for oxygen (dry basis), and (4) over 16% for moisture. These operating parameter values can serve as benchmarks for laboratory-scale studies representative of municipal waste-to-energy combustion as typically practiced in the U.S. Graphical abstract Available at:
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    Biochar and zero-valent iron sand filtration simultaneously removes contaminants of emerging concern and Escherichia coli from wastewater effluent
    (Biochar, 2023-07-19) Zhu, Linyan; Chattopadhyay, Suhana; Akanbi, Oluwasegun Elijah; Lobo, Steven; Panthi, Suraj; Malayil, Leena; Craddock, Hillary A.; Allard, Sarah M.; Sharma, Manan; Kniel, Kalmia E.; Mongodin, Emmanuel F.; Chiu, Pei C.; Sapkota, Amir; Sapkota, Amy R.
    Advanced treated municipal wastewater is an important alternative water source for agricultural irrigation. However, the possible persistence of chemical and microbiological contaminants in these waters raise potential safety concerns with regard to reusing treated wastewater for food crop irrigation. Two low-cost and environmentally-friendly filter media, biochar (BC) and zero-valent iron (ZVI), have attracted great interest in terms of treating reused water. Here, we evaluated the efficacy of BC-, nanosilver-amended biochar- (Ag-BC) and ZVI-sand filters, in reducing contaminants of emerging concern (CECs), Escherichia coli (E. coli) and total bacterial diversity from wastewater effluent. Six experiments were conducted with control quartz sand and sand columns containing BC, Ag-BC, ZVI, BC with ZVI, or Ag-BC with ZVI. After filtration, Ag-BC, ZVI, BC with ZVI and Ag-BC with ZVI demonstrated more than 90% (> 1 log) removal of E. coli from wastewater samples, while BC, Ag-BC, BC with ZVI and Ag-BC with ZVI also demonstrated efficient removal of tested CECs. Lower bacterial diversity was also observed after filtration; however, differences were marginally significant. In addition, significantly (p < 0.05) higher bacterial diversity was observed in wastewater samples collected during warmer versus colder months. Leaching of silver ions occurred from Ag-BC columns; however, this was prevented through the addition of ZVI. In conclusion, our data suggest that the BC with ZVI and Ag-BC with ZVI sand filters, which demonstrated more than 99% removal of both CECs and E. coli without silver ion release, may be effective, low-cost options for decentralized treatment of reused wastewater. Graphical Abstract available at: Highlights - The efficacy of BC, Ag-BC, and ZVI sand filtration, and their combinations, in removing contaminants from reused water was evaluated. - Ag-BC, ZVI, BC with ZVI and Ag-BC with ZVI demonstrated > 90% removal of E. coli. - BC, Ag-BC, BC with ZVI and Ag-BC with ZVI demonstrated efficient removal of selected contaminants of emerging concern.
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    Selection of vortex ripple dimensions in sinusoidal oscillatory flows. Part 1. Ripple dimensions and fluid kinematics
    (Journal of Fluid Mechanics, 2023-04-10) Yue, Liangyi; Hsu, Tian-Jian; Horner-Devine, Alexander R.
    Subaqueous vortex ripples in equilibrium are characterized by their unique geometry and dimensions. Motivated by the recent direct numerical simulation study of oscillatory turbulent flow over a wavy bottom by Önder & Yuan (J. Fluid Mech., vol. 858, 2019, pp. 264–314), the objective of this study is to further investigate the fluid dynamical controls that determine the distinctive equilibrium dimensions of vortex ripples. We use direct numerical simulations to investigate the differences in flow kinetics between sinusoidal oscillatory flow over equilibrium and out-of-equilibrium vortex ripples. In comparison with the equilibrium case, the spanwise coherent vortices, the averaged bottom shear stress on overlying flow and the shear stress distribution on the ripple surface are identified as the key fluid dynamical controls on equilibrium dimensions. Based on these controls, we propose mechanisms in the selection of vortex ripple dimensions. We observe that the flow adjusts in such a way that the interaction between overlying flow and vortex ripples tends to generate the strongest coherent vortices while the ripple surface (or overlying flow) experiences the smallest shear stress averaged over ripple wavelength during the selection process. Through a triple decomposition of the flow, the component of the ripple-induced fluctuation is found to dictate these fluid dynamical controls, which implies that this component plays an important role in the evolution of vortex ripples.
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    Development of a Recyclable Flax Fiber Reinforced Polymer Composite
    (Composites in Civil Engineering, 2023-06-28) Das, Shagata; Doshi, Sagar; Millan, Emmanuel; Mendez, Damaris; Luckenbill, Dan; Tatar, Jovan
    This study compared the mechanical properties of a recyclable flax fiber reinforced polymer composite (FFRP) with a covalent adaptable network (CAN) matrix to an FFRP composite with a conventional (unrecyclable) epoxy resin matrix. The results indicated that composites fabricated via vacuum-assisted resin transfer molding (VARTM) exhibited up to 19% higher tensile modulus and strength compared to those fabricated via hand layup, attributed to reduced air void content and more uniform fiber alignment. Microscopy evidence supported by mechanical property tests revealed superior adhesion of the CAN matrix to flax fibers compared to conventional epoxy resin. Additionally, a solvent-based method was demonstrated for separating fibers from the CAN matrix, facilitating reuse or upcycling.
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    Modeling the Partitioning of Anionic Carboxylic and Perfluoroalkyl Carboxylic and Sulfonic Acids to Octanol and Membrane Lipid
    (Environmental Toxicology and Chemistry, 2023-07-13) Torralba-Sanchez, Tifany L.; Di Toro, Dominic M.; Dmitrenko, Olga; Murillo-Gelvez, Jimmy; Tratnyek, Paul G.
    Perfluoroalkyl carboxylic and sulfonic acids (PFCAs and PFSAs, respectively) have low acid dissociation constant values and are, therefore, deprotonated under most experimental and environmental conditions. Hence, the anionic species dominate their partitioning between water and organic phases, including octanol and phospholipid bilayers which are often used as model systems for environmental and biological matrices. However, data for solvent–water (SW) and membrane–water partition coefficients of the anion species are only available for a few per- and polyfluoroalkyl substances (PFAS). In the present study, an equation is derived using a Born-Haber cycle that relates the partition coefficients of the anions to those of the corresponding neutral species. It is shown via a thermodynamic analysis that for carboxylic acids (CAs), PFCAs, and PFSAs, the log of the solvent–water partition coefficient of the anion, log KSW(A−), is linearly related to the log of the solvent–water partition coefficient of the neutral acid, log KSW(HA), with a unity slope and a solvent-dependent but solute-independent intercept within a PFAS (or CA) family. This finding provides a method for estimating the partition coefficients of PFCAs and PFSAs anions using the partition coefficients of the neutral species, which can be reliably predicted using quantum chemical methods. In addition, we have found that the neutral octanol–water partition coefficient, log KOW, is linearly correlated to the neutral membrane–water partition coefficient, log KMW; therefore, log KOW, being a much easier property to estimate and/or measure, can be used to predict the neutral log KMW. Application of this approach to KOW and KMW for PFCAs and PFSAs demonstrates the utility of this methodology for evaluating reported experimental data and extending anion property data for chain lengths that are unavailable. Environ Toxicol Chem 2023;00:1–12. © 2023 SETAC
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    Three-dimensional stress-strain and strength behavior of silt-clay transition soils
    (Canadian Geotechnical Journal, 2023-04-10) Anantanasakul, Pongpipat; Intharachart, Phimmawat; Kaliakin, Victor N.
    The effect of silt content on the mechanical behavior of silt-clay transition soils under three-dimensional stress conditions is presented. Undrained true triaxial tests with constant b values were performed on normally consolidated specimens of silt-clay transition soils created from the same base clay and non-plastic silt, however, with systematically varying gradations. With increasing amount of non-plastic silt, the cohesive soils exhibit less contractive tendencies, stiffer stress-strain response and larger shear strength. The magnitude of intermediate principal stress, as indicated by the b value, also strongly influences the stress-strain relations, pore pressure behavior and both total and effective failure surfaces. Although the transition soils exhibit overall clay-like behavior, more pronounced frictional characteristics, as indicated by the shapes of the failure and plastic potential surfaces, were exhibited with increasing silt content.
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    Physiochemical Controls on the Horizontal Exchange of Blue Carbon Across the Salt Marsh-Tidal Channel Interface
    (Journal of Geophysical Research: Biogeosciences, 2023-06-06) Fettrow, Sean; Jeppi, Virginia; Wozniak, Andrew; Vargas, Rodrigo; Michael, Holly; Seyfferth, Angelia L.
    Tidal channels are biogeochemical hotspots that horizontally exchange carbon (C) with marsh platforms, but the physiochemical drivers controlling these dynamics are poorly understood. We hypothesized that C-bearing iron (Fe) oxides precipitate and immobilize dissolved organic carbon (DOC) during ebb tide as the soils oxygenate, and dissolve into the porewater during flood tide, promoting transport to the channel. The hydraulic gradient physically controls how these solutes are horizontally exchanged across the marsh platform-tidal channel interface; we hypothesized that this gradient alters the concentration and source of C being exchanged. We further hypothesized that trace soil gases (i.e., CO2, CH4, dimethyl sulfide) are pushed out of the channel bank as the groundwater rises. To test these hypotheses, we measured porewater, surface water, and soil trace gases over two 24-hr monitoring campaigns (i.e., summer and spring) in a mesohaline tidal marsh. We found that Fe2+ and DOC were positively related during flood tide but not during ebb tide in spring when soils were more oxidized. This finding shows evidence for the formation and dissolution of C-bearing Fe oxides across a tidal cycle. In addition, the tidal channel contained significantly (p < 0.05) more terrestrial-like DOC when the hydraulic gradient was driving flow toward the channel. In comparison, the channel water was saltier and contained significantly (p < 0.05) more marine-like DOC when the hydraulic gradient reversed direction. Trace gas fluxes increased with rising groundwater levels, particularly dimethyl sulfide. These findings suggest multiple physiochemical mechanisms controlling the horizontal exchange of C at the marsh platform-tidal channel interface. Plain Language Summary Tidal salt marshes store large amounts of carbon belowground in soils, but there is also a significant amount of carbon flowing into and out of these ecosystems via tidal channels. We investigated the carbon flowing between the channel bank and surface water in a salt marsh in Delaware. We found that soil minerals (i.e., iron oxides) control the mobility of carbon as iron oxides retain carbon during ebb tides and release carbon during flood tides as the minerals dissolve. The gradient between the groundwater and surface water elevation (i.e., hydraulic gradient) controls the flow direction for dissolved carbon, altering the concentration and source of carbon found in the tidal channel across tidal cycles. In addition, gases trapped in channel banks are pushed out of the soils as the tide rises. These findings will improve our understanding of carbon cycles in these critical carbon sinks. Key Points - Physiochemical mechanisms control horizontal exchange of carbon across marsh-tidal channel interfaces, affecting lateral carbon flux - Dissolution and reprecipitation of carbon-bearing Fe oxides during flood and ebb tides control the horizontal mobility of carbon - Hydraulic gradients control the carbon character in the tidal channel, and rising tides push greenhouse gases out of the channel bank
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    Hazard assessment framework for statistical analysis of cut slopes using track inspection videos and geospatial information
    (Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2023-06-12) Palese, Michael; Pei, Te; Qiu, Tong; Zarembski, Allan M.; Shen, Chaopeng; Palese, Joseph W.
    Transportation corridors constructed using through- and side-cuts are susceptible to hazardous slope failures, potentially causing infrastructure damage, operational suspensions and loss of life. To monitor the stability of known geohazards at the local scale, geotechnical investigation of each slope is typically performed to calculate a factor of safety. In many corridors, however, this method is labour-intensive due to the quantity of geohazards and statistical methods are instead used to identify hazardous sections. This paper introduces a new slope failure hazard assessment technique, utilising susceptibility mapping of geospatial information and computer vision-based analysis of right-of-way videos recorded by railroad track inspection vehicles, applied to a section of railroad track near Harrisburg, Pennsylvania. Combining these results, an enhanced relative hazard assessment algorithm was formulated. Using the developed framework, geohazards of primary concern were determined which should be prioritised for future geotechnical investigation and remediation efforts.
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    Biophysical flocculation reduces variability of cohesive sediment settling velocity
    (Communications Earth & Environment, 2023-04-24) Ye, L.; Penaloza-Giraldo, J. A.; Manning, A. J.; Holyoke, J.; Hsu, T.-J.
    Biophysical cohesion, introduced predominantly by Extracellular Polymeric Substances (EPS) during mineral flocculation in subaqueous environments, plays important role in morphodynamics, biogeochemical cycles and ecosystem processes. However, the mechanism of how EPS functioning with cohesive particles and affects settling behaviors remain poorly understood. We measure initial flocculation rate, floc size and settling velocity of mineral and artificial EPS (Xanthan gum) mixtures. Combining results from these and previous studies demonstrate coherent intensification of EPS-related flocculation compare with those of pure mineral and oil-mineral mixtures. Importantly, the presence of EPS fundamentally changes floc structure and reduces variability of settling velocity. Measured data shows that ratios of microfloc and macrofloc settling velocity for pure mineral flocs is 3.9 but greatly reduced to a lowest value of 1.6 due to biological EPS addition. The low variability of settling velocity due to EPS participation explains the seemingly inconsistent results previously observed between field and laboratory studies.
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    Aggregated Zero-Knowledge Proof and Blockchain-Empowered Authentication for Autonomous Truck Platooning
    (IEEE Transactions on Intelligent Transportation Systems, 2023-05-10) Li, Wanxin; Meese, Collin; Guo, Hao; Nejad, Mark
    Platooning technologies enable trucks to drive cooperatively and automatically, providing benefits including less fuel consumption, greater road capacity, and safety. To establish trust during dynamic platooning formation, ensure vehicular data integrity, and guard platoons against potential attackers in mixed fleet environments, verifying any given vehicle’s identity information before granting it access to join a platoon is pivotal. Besides, due to privacy concerns, truck owners may be reluctant to disclose private vehicular information, which can reveal their business data to untrusted third parties. To address these issues, this is the first study to propose an aggregated zero-knowledge proof and blockchain-empowered system for privacy-preserving identity verification in truck platooning. We provide the correctness proof and the security analysis of our proposed authentication scheme, highlighting its increased security and fast performance. The platooning formation procedure is re-designed to seamlessly incorporate the proposed authentication scheme, including the 1st catch-up and cooperative driving steps. The blockchain performs the role of verifier within the authentication scheme and stores platooning records on its digital ledger to guarantee data immutability and integrity. In addition, the proposed programmable access control policies enable truck companies to define who is allowed to access their platoon records. We implement the proposed system and perform extensive experiments on the Hyperledger platform. The results show that the blockchain can provide low latency and high throughput, the aggregated approach can offer a constant verification time of 500 milliseconds regardless of the number of proofs, and the platooning formation only takes seconds under different strategies. The experimental results demonstrate the feasibility of our design for use in real-world truck platooning.
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    Mechanical behavior of UV-cured composite stepped lap adhesive joints
    (SAMPE Conference Proceedings 2023, 2023-04-18) Das, Shagata; Gillespie, John W. Jr.; Shenton, Harry W. III; Tatar, Jovan
    Joints often control the design of composite structures because they represent locations of high stress concentrations. Adhesive joints offer several benefits over mechanically fastened connections such as reduced stress concentrations, and higher joint efficiency. This study evaluates the performance of stepped lap adhesive joints. The novelty lies in the implementation of UV-cured vinyl ester resin which allows integration of co-cured stepped lap joints in applications where fast curing at ambient temperatures is required. The experimental program consisted of a series of tensile tests on 20-ply 7781 E-glass laminates integrating UV-cured stepped lap joints, where the primary variables were stepped lap joint angle (ranging from 0.9° to 5.7°) and number of ply drops (ranging from 1 to 10). Physical properties of all the UV-cured joint panels, such as density, void content, fiber volume fraction, and hardness, were also evaluated and compared between the test groups. The preliminary findings indicate that reducing the scarf angle from 5.7° to 0.9° increased the joint strength by a maximum of 115%. The joint strength efficiency approached 100% of the laminate tensile strength for 19-step joints having a scarf angle of 0.9º.
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    Bladder expandable robotic system and UV materials for rapid internal pipeline repair
    (SAMPE Conference Proceedings 2023, 2023-04-18) Tierney, John J.; Vanarelli, Alex; Fuessel, Lukas; Abu-Obaid, Ahmad; Sauerbrunn, Steve; Das, Shagata; Deitzel, Joseph; Tatar, Jovan; Heider, Dirk; Shenton, Harry W. III; Kloxin, Christopher J.; Sung, Dae Han; Thostenson, Erik; Gillespie, John W. Jr.
    This paper describes a novel composite placement process to fabricate stand-alone structural pipe within existing legacy pipelines—with no disruption in gas service. The process utilizes low-cost, UV-curable, glass fiber reinforced plastics (GFRP) for discrete preforms made from continuous fiber fabrics. These sections are designed to meet 50-year service life by addressing the unique loading conditions of the pipe repair allowing for the design customization of the preforms to accommodate the state of pipe corrosion, access points or other local features that may vary along the length of the pipe. The approach offers maximum design flexibility and customization while minimizing installation time and cost. The preforms are fabricated above ground using rapid automated manufacturing methods for quality control. The preforms are transported by a tethering system to the robot. The robot is comprised of a self-propelled dual inflation expandable bladder system that places, consolidates, and cures standard or custom composite sections along the entire pipe length in a continuous co-cure process. This system is designed to adapt to pipe features that include lateral tees, service connections, joints, gaps, and irregular cross sections. In addition, variable thickness composite sections can be placed along the pipe where exposed to high external loads under railroads, highways, airports or where soil erosion and movement occurs. This paper presents the robot design, assessment of UV curable resins, embedded sensing methods, and fabrication of pipe sections with this system.
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    Predicting Subsurface Architecture From Surface Channel Networks in the Bengal Delta
    (Journal of Geophysical Research: Earth Surface, 2023-03-19) Xu, Zhongyuan; Khan, Mahfuzur R.; Ahmed, Kazi Matin; Zahid, Anwar; Hariharan, Jayaram; Passalacqua, Paola; Steel, Elisabeth; Chadwick, Austin; Paola, Chris; Goodbred, Steven L. Jr.; Paldor, Anner; Michael, Holly A.
    Groundwater is the primary source of water in the Bengal Delta but contamination threatens this vital resource. In deltaic environments, heterogeneous sedimentary architecture controls groundwater flow; therefore, characterizing subsurface structure is a critical step in predicting groundwater contamination. Here, we show that surface information can improve the characterization of the nature and geometry of subsurface features, thus improving the predictions of groundwater flow. We selected three locations in the Bengal Delta with distinct surface river network characteristics—the lower delta with straighter tidal channels, the mid-delta with meandering and braided channels, and the inactive delta with transitional sinuous channels. We used surface information, including channel widths, depths, and sinuosity, to create models of the subsurface with object-based geostatistical simulations. We collected an extensive set of lithologic data and filled in gaps with newly drilled boreholes. Our results show that densely distributed lithologic data from active lower and mid-delta are consistent with the object-based models generated from surface information. In the inactive delta, metrics from object-based models derived from surface geometries are not consistent with subsurface data. We further simulated groundwater flow and solute transport through the object-based models and compared these with simulated flow through lithologic models based only on variograms. Substantial differences in flow and transport through the different geologic models show that geometric structure derived from surface information strongly influences groundwater flow and solute transport. Land surface features in active deltas are therefore a valuable source of information for improving the evaluation of groundwater vulnerability to contamination. Key Points: - We demonstrate a novel approach that harnesses land surface characteristics to inform groundwater modeling in deltas - The subsurface lithologic data of an active delta is more consistent with surface features than that of an inactive delta - Incorporation of surface information can improve the prediction of contaminant transport in aquifers Plain Language Summary: The structure of groundwater aquifers affects how groundwater and contaminants move through them. In deltas, dynamic river networks are responsible for depositing sediments that ultimately form subsurface aquifers. Therefore, the characteristics of the surface river channel network should provide information about the structure of the subsurface. We tested this idea using a large set of sedimentary data from the Bengal Basin. We created models of the subsurface based on the surface network and showed that the subsurface data reflect the model characteristics in deltas that are actively depositing sediment. Using these subsurface models as input for groundwater flow models, we showed that incorporating this surface information is important for being able to predict how contaminants move in groundwater.
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    Numerical modeling of revetment and sill in reducing shore erosion
    (Coastal and Offshore Science and Engineering, 2022) Yuksel, Z. T.; Kobayashi, N.
    Interactions among waves, sand beaches, and rubble mound structures are difficult to investigate experimentally, because of the differences between the model and prototype, and to predict numerically, because of complex sediment dynamics inside porous structures. A small-scale experiment in a wave flume was conducted by Yuksel and Kobayashi (2019) in order to compare sand beach profile evolution and wave overtopping of a sand berm for the three cases of no structure (N), a stone revetment protecting a steep sand berm (R), and a stone sill reducing wave action on the berm (S). An existing numerical model verified with the small-scale N, R, and S tests was used to predict what may happen to prototype revetments and sills. Froude similitude with a length ratio of 1/16 (model/prototype) was used to scale up the incident waves, beach profile, and stones in the prototype. The sand was kept the same in hypothetical prototype PN (No structure), PR (Revetment), and PS (Sill) tests. The computed wave transformation and stone damage were predicted reasonably well. The beach profile changes were larger in the prototype because the fine sand was exposed to much larger waves.
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    Coastal topography and hydrogeology control critical groundwater gradients and potential beach surface instability during storm surges
    (Hydrology and Earth System Sciences, 2022-12-02) Paldor, Anner; Stark, Nina; Florence, Matthew; Raubenheimer, Britt; Elgar, Steve; Housego, Rachel; Frederiks, Ryan S.; Michael, Holly A.
    Ocean surges pose a global threat for coastal stability. These hazardous events alter flow conditions and pore pressures in flooded beach areas during both inundation and subsequent retreat stages, which can mobilize beach material, potentially enhancing erosion significantly. In this study, the evolution of surge-induced pore-pressure gradients is studied through numerical hydrologic simulations of storm surges. The spatiotemporal variability of critically high gradients is analyzed in three dimensions. The analysis is based on a threshold value obtained for quicksand formation of beach materials under groundwater seepage. Simulations of surge events show that, during the run-up stage, head gradients can rise to the calculated critical level landward of the advancing inundation line. During the receding stage, critical gradients were simulated seaward of the retreating inundation line. These gradients reach maximum magnitudes just as sea level returns to pre-surge levels and are most accentuated beneath the still-water shoreline, where the model surface changes slope. The gradients vary along the shore owing to variable beach morphology, with the largest gradients seaward of intermediate-scale (1–3 m elevation) topographic elements (dunes) in the flood zone. These findings suggest that the common practices in monitoring and mitigating surge-induced failures and erosion, which typically focus on the flattest areas of beaches, might need to be revised to include other topographic features.
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    Critical facility accessibility and road criticality assessment considering flood-induced partial failure
    (Sustainable and Resilient Infrastructure, 2022-11-25) Gangwal, Utkarsh; Siders, A. R.; Horney, Jennifer; Michael, Holly A.; Dong, Shangjia
    This paper examines communities’ accessibility to critical facilities such as hospitals, emergency medical services, and emergency shelters when facing flooding. We use travel speed reduction to account for flood-induced partial road failure. A modified betweenness centrality metric is also introduced to calculate the criticality of roads for connecting communities to critical facilities. The proposed model and metric are applied to the Delaware road network under 100-year floods. This model highlights the severe critical facility access loss risk due to flood isolation of facilities. The mapped post-flooding accessibility suggests a significant travel time increase to critical facilities and reveals disparities among communities, especially for vulnerable groups such as long-term care facility residents. We also identified critical roads that are vital for post-flooding access to critical facilities. The results of this research can help inform targeted infrastructure investment decisions and hazard mitigation strategies that contribute to equitable community resilience enhancement.
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