This study quantifies the benefits of two interlayer systems (steel reinforcing netting and a newly-designed geocomposite membrane) in different pavement applications. Steel reinforcing netting and geocomposite membrane have been installed at the Virginia Smart Road in four different sections. Ground penetrating radar (GPR) surveys and time domain reflectometer (TDR) validated the effectiveness of the geocomposite membrane in preventing water from infiltrating to the underneath layers. In pavement rehabilitation applications, based on finite element (FE) analysis, it was found that the geocomposite membrane would create a protective compressive field around the crack tip and separate the criticality of the stress field in the cracked area from the bottom of the overlay. However, if the crack passes through the interlayer, a faster propagation rate than in a typical pavement is expected. These results emphasize the importance of proper field installation. As to steel reinforcing netting, this study found that this interlayer system would be effective in new pavement systems in both the crack initiation and propagation phases when the cracks start at the bottom of the HMA layers. For the considered pavement structures, steel reinforcing netting was found effective to delay the initiation of the cracks. This delay depends on the stiffness of the hot-mix asphalt (HMA) layers, the reinforcing pattern, and the direction of the strain at the bottom of the HMA layers. After initiation of the crack, steel reinforcement contribute by delaying the rate of crack propagation to the pavement surface. In pavement rehabilitations, however, the crack is already well established in the existing pavement, and steel reinforcement contribution is expected from the time of installation. In this case, steel reinforcement will delay the initiation of the crack in the overlay, and reduce the rate of crack propagation afterwards. Two models, to predict the overlay service life against reflective cracking from existing HMA layers, were developed. / Ph. D.

Several critical issues in the mechanics of the interface between the fibers and matrix in ceramic matrix composites (CMCs) are studied. The first issue is the competition between crack deflection and penetration at the fiber/matrix interface. When a matrix crack, the first fracture mode in a CMC, reaches the interface, two different crack modes are possible; crack deflection along the interface and crack penetration into the fibers. A criterion based on strain energy release rates is developed to determine the crack propagation at the interface. The Axisymmetric Damage Model (ADM), a newly-developed numerical technique, is used to obtain the strain energy in the cracked composite. The results are compared with a commonly-used analytic solution provided by He and Hutchinson (HH), and also with experimental data on a limited basis. The second issue is the stress distribution near the debond/sliding interface. If the interface is weak enough for the main matrix crack to deflect and form a debond/sliding zone, then the stress distribution around the sliding interface is of interest because it provides insight into further cracking modes, i.e. multiple matrix cracking or possibly fiber failure. The stress distributions are obtained by the ADM and compared to a simple shear-lag model in which a constant sliding resistance is assumed. The results show that the matrix axial stress, which is responsible for further matrix cracking, is accurately predicted by the shear-lag model. Finally, the third issue is multiple matrix cracking. We present a theory to predict the stress/strain relations and unload/reload hysteresis behavior during the evolution of multiple matrix cracking. The random spacings between the matrix cracks as well as the crack interactions are taken into account in the model. The procedure to obtain the interfacial sliding resistance, thermal residual stress, and matrix flaw distribution from the experimental stress/strain data is discussed. The results are compared to a commonly-used approach in which uniform crack spacings are assumed. Overall, we have considered various crack modes in the fiber-reinforced CMCs; from a single matrix crack to multiple matrix cracking, and have suggested models to predict the microscopic crack behavior and to evaluate the macroscopic stress/strain relations. The damage tolerance or toughening due to the inelastic strains caused by matrix cracking phenomenon is the key issue of this study, and the interfacial mechanics in conjunction with the crack behavior is the main issue discussed here. The models can be used to interpret experimental data such as micrographs of crack surface or extent of crack damage, and stress/strain curves, and in general the models can be used as guidelines to design tougher composites. / Ph. D.

Nickel and iron-based alloys are important structure and cladding materials for modern nuclear reactors due to their high mechanical properties and high corrosion resistance. To understand the radiative and corrosive environment influence on the mechanical strength, computer simulation works are conducted. In particular, this dissertation is focused on multiscale modeling of the effects of radiation-induced solute segregation and oxidation on grain boundary (GB) strength in nickel-based and iron-based alloys. Besides the atomistic scale density functional theory (DFT) based calculations of GB strength, continuum-scale cohesive zone model (CZM) is also used to simulate intergranular fracture at the microstructure scale. First, the effects of solute or impurity segregation at GBs on the GB strength are studied. Thermal annealing or radiation induced segregation of solute and impurity elements to GBs in metallic alloys changes GB chemistry and thus can alter the GB cohesive strength. To understand the underlying mechanisms, first principles based DFT calculations are conducted to study how the segregation of substitutional solute and impurity elements (Al, C, Cr, Cu, P, Si, Ti, Fe, which are present in Ni-based X-750 alloys) influences the cohesive strength of Σ3(111),Σ3(112),Σ5(210) and Σ5(310) GBs in Ni. It is found that C and P show strong embrittlement potencies while Cr and Ti can strengthen GBs in most cases. Other solute elements, including Si, have mixed but insignificant effects on GB strength. In terms of GB character effect, these solute and impurity elements modify the GB strength of the Σ5(210) GB most and that of the Σ3(111) least. Detailed analyses of solute-GB chemical interactions are conducted using electron localization function, charge density map, partial density of states, and Bader charge analysis. The results suggest that the bond type and charge transfer between solutes and Ni atoms at GBs may play important roles on affecting the GB strength. For non-metallic solute elements (C, P, Si), their interstitial forms are also studied but the effects are weaker than their substitutional counterparts. Nickel-base alloys are also susceptible to stress corrosion cracking (SCC), in which the fracture mainly propagates along oxidized grain boundaries (GBs). To understand how oxidation degrades GB strength, the next step is to use density functional theory (DFT) calculations to study three types of oxidized interfaces: partially oxidized GBs, fully oxidized GBs, and oxide/metal interface, using Ni as a model system. For partially oxidized GBs, both substitutional and interstitial oxygen atoms of different concentrations are inserted at three Ni GBs: Σ3(111) coherent twin, Σ3(112) incoherent twin, and Σ5(210). Simulation results show that the GB strength decreases almost linearly with the increasing oxygen coverage at all GBs. Typically, substitutional oxygen causes a stronger embrittlement effect than interstitial oxygen, except at the Σ3(111). In addition, the oxygen-induced mechanical distortion has a much smaller contribution to the embrittlement than its chemical effect, except for oxygen interstitials at the Σ3(111). For the fully oxidized GBs, three NiO GBs of the same types are studied. Although the strengths of Σ3(112) and Σ5(210) NiO GBs are much weaker than the Ni counterparts, the Σ3(111) NiO GB has a higher strength than that in Ni, indicating that Σ3(111) GB may be difficult to fracture during SCC. Finally, the strength of a Ni/NiO interface is found to be the weakest among all interfaces studied, suggesting the metal/oxide interface could be a favorable crack initiation site when the tensile stress is low. Furthermore, the effects of co-segregation of oxygen and solute/impurity elements on GB strength are studied by DFT, using the 5(210) GB in an face-centered-cubic (FCC) Fe as a model system. Four elements (Cr, Ni, P, Si) that are commonly present in stainless steels are selected. Regarding the effects of single elements on GB strength, Ni and Cr are found to the increase the GB strength, while both P and Si have embrittlement effects. When each of them is combined with oxygen at the GB, the synergetic effect can be different from the linear sum of individual contributions. The synergetic effect also depends on the spatial arrangement of solute elements and oxygen. If they are aligned on the same plane at the GB, the synergetic effect is similar to the linear sum, although P and Si show stronger embrittlement potencies when they combine with both interstitial and substitutional oxygen. When they are arranged on a trans-plane structure, only nickel combined with oxygen show larger embrittlement potencies than the linear sum in all cases. Crystal Orbital Hamilton Populations analysis of bonding and anti-bonding states is conducted to interpret how the interaction between solutes and oxygen impacts GB strength. Finally, the continuum-scale CZM method, which is based on the bilinear mixed mode traction separation law, is used to model SCC-induced intergranular fracture in polycrystalline Ni and Fe based alloys in the MOOSE framework. The previous DFT results are used to justify the input parameters for the oxidation-induced GB strength degradation. In this study, it is found that the crack path does not always propagate along the weak GBs. As expected, the fracture prefers to occur at the GB orientations perpendicular to the loading direction. In addition, triple junctions can arrest or deflect fracture propagation, which is consistent with experimental observations. Simulation results also indicate that percolated weak GBs will lead to a much lower fracture stress compared to the discontinuous ones. / Doctor of Philosophy / Iron and Nickel based alloys are important structural materials for nuclear reactors due to their good mechanical properties, corrosion resistance, and radiation resistance. Under radiation and corrosive conditions, those alloys are susceptible to radiation induced segregation (RIS) and stress corrosion cracking (SCC). This dissertation is mainly focused on understanding the influence of the two effects on grain boundary (GB) strength. Systematic atomistic scale density functional theory (DFT) simulations are applied for the nickel and iron systems. Based on the DFT results, cohesive zone model is utilized for the continuum scale fracture simulation in nickel and iron polycrystal. First, DFT calculations are conducted for studying the RIS effect on the GB strength in nickel. Al, Cr, Cu, C, Si, P, Fe, and Ti are chosen as segregated element. Σ3(111), Σ3(112), Σ5(210), Σ5(310) four types of GBs are built for GB strength calculations. It is found that substitutional C and P always embrittle the GB, while substitutional Ti and Cr can strengthen the GB in most cases. Partial density of states (PDOS) analysis indicates the formation of C-Ni and P-Ni covalent bonds is the possible reason for their embrittlement effects. Bader charge analysis shows negatively charged elements likely reduce the GB strength. Interstitial element segregation is applied for non-metal elements (C, P, and Si). The results indicate interstitial elements have weaker effects than substitution ones. On the next stage to study the SCC effect, DFT calculations are performed for nickel Σ3(111), Σ3(112), and Σ5(210) GBs with difference oxygen concentration and oxygen incorporation types. Besides partially oxidized GBs, fully oxidized GBs (NiO GBs) and metal-oxide interface are also constructed for comparison. Simulation results show that the GB strength decreases nearly monotonically as oxygen concentration goes up. Typically, substitution oxygen causes a larger embrittlement effect than interstitial oxygen except at Σ3(111). It is found that the large mechanical distortion in this coherent twin GB contributes significantly to the GB strength drop. NiO GBs can be weak (Σ3(112),Σ5(210)) or strong (Σ3(111)). NiO/Ni interface shows lowest strength compared with partially and fully oxidized GBs, indicating the importance of the metal-oxide interface in the SCC process. Furthermore, the combined effects between segregated elements and oxygen are studied in face center cubic (FCC) iron system. In this part only Σ5(210) GB is selected with substitutional Cr, Ni, P, and Si as segregated elements. The results of single element effects show Cr can strength the GB while P has an opposite effect. Other two elements show little effect. For the co-segregation effects, the trans-plane structures have larger embrittlement potencies than in-plane ones for Ni, suggesting the GB strength can also be affected by the spatial arrangement of segregated elements. Finally, cohesive zone model is applied for fracture simulations in polycrystalline nickel and iron under tensile loading condition. It is found that intergranular fracture depends on both GB strength and orientation. GBs perpendicular to the loading direction have higher chances to crack. It is also found the percolated weak GBs induce larger strength drop than the discontinuous ones.

Fracture path transition, from interfacial fracture to a pulled button, in peel tests of spot welds in SAE 1039 steel was evaluated to determine the controlling material properties. Welds were tested in the as welded condition and after tempering at various temperatures to develop a range of hardness and strength in the weld metal. Two transitions were found, from complete interfacial fracture to partial interfacial and from partial interfacial fracture to a pulled button. Samples tempered at less than 350 °C exhibited complete interfacial fracture while those tempered at 500 °C or higher pulled full buttons. Each transition was accompanied by a large increase in the energy absorbed during fracture. Both partial and complete interfacial fracture occurred by intergranular fracture along prior austenite grain boundaries. Optical microscopy utilizing a tint etch indicated that austenite existed as films on prior austenite grain boundaries of samples tempered at less than 500 °C and TEM confirmed that these films were austenite. Weld metal toughness was found to control the fracture path. If fracture initiation was delayed until the applied load caused plastic deformation of the coupons pulled button fracture occurred. Fracture initiation prior to plastic deformation of the coupons resulted in interfacial or partial interfacial fractures. A small secondary hardening peak was observed in samples tempered at 450 °C. Secondary hardening, which normally results from alloy carbide precipitation, was due to AlN precipitation in this aluminum killed plain carbon steel. / Ph. D.

The research presented in this thesis is all based on the impedance method for structural health monitoring. The impedance method is an electro-mechanical technique which utilizes a single piezoelectric transducer as both a sensor and actuator. Due to the high frequencies of excitation used for the method, the sensing area for damage detection can be very localized. Previous work has shown that wave propagation can be added to systems already equipped with hardware for impedance-based structural health monitoring. The work in this thesis shows what happens under varying temperature conditions for a structure being monitored with wave propagation. A technique to compensate for temperature fluctuations is also presented. The work presented here is an initial study to directly correlate the actual amount of damage in a composite specimen with a damage metric indicated by impedance-based structural health monitoring. Two different damage mechanisms are examined: transverse matrix cracking and edge delamination. With both composite defects, a sample is interrogated with the impedance method before and after damage is introduced. The exact amount of damage in each specimen is found using radiography and compared with the health monitoring results. Traditional impedance techniques require the use of a bulky and expensive impedance analyzer. With the trend of structural health monitoring moving towards unobtrusive sensors which can be permanently placed on a structure, an impedance analyzer does not lend itself to these small, low power consuming requirements. In this thesis, an initial attempt to miniaturize the hardware is described. A prototype impedance-based structural health monitoring system, incorporating wireless based communications, is fabricated and validated with experimental testing on a number of different structures. The first steps towards a complete self-contained, robust structural health monitoring sensor are presented. / Master of Science

Yes / Fluidized catalytic cracking (FCC) is regarded one of the most significant operations in the oil refining industries to convert feedstock (mainly vacuum gasoil) to valuable products (namely gasoline and diesel). The behavior of the fluidized catalytic cracking process is playing a main part on the overall benefits of refinery units and improving in process or control of fluidized catalytic cracking plants will result in exciting benefits economically. According to these highlights, this study is aimed to develop a new mathematical model for the FCC process taking into account the complex hydrodynamics of the reactor regenerator system with a new six lumps kinetic model for the riser. The mathematical model, simulation and optimization have done utilizing vacuum gas oil (VGO) as a feedstock and zeolite as a catalyst under the following operating conditions: temperature (733K, 783K, and 813K), weight hourly space velocity (5, 20 and 30hr−1) and catalyst to oil ratio (4, 7 and 10). The best kinetic parameters of the relevant reactions are estimated using the optimization technique based on the experimental results taken from literature. The effect of operating condition (mainly, reaction temp (T), catalyst to oil ratio (CTO) and weight hourly space velocity (WHSV) on the product composition has also been discussed. The optimal kinetic parameters obtained from the pilot plant scale have been employed to develop an industrial FCC process, where optimal operating condition based on maximum conversion of VGO with minimum cost in addition to maximizing the octane number of gasoline (GLN), have been studied. Minimum coke content deposition the catalyst within the regenerator is also investigated here. New results (the highest conversion and octane number, and the lowest coke content) have obtained in comparison with those reported in the literature.

The inverted T-beam bridge system is a bridge construction technique that follows accelerated bridge construction processes. The system was discovered in France and first adopted in the U.S. by the Minnesota Department of Transportation. In 2012 the system was modified and adopted by Virginia, with research being carried out at Virginia Polytechnic Institute and State University (Virginia Tech). The research focused on multiple items involving the system, but the most relevant one is that regarding the transverse bending behavior of the system for different geometries, and joint types between adjacent precast beam members. The study found that using a joint system without any mechanical connection between adjacent beams was most efficient, and gave adequate performance under monotonic loading. The study recommended cyclic load testing be carried out on this joint type, as well as a welded joint similar to those found in decked bulb-T systems. The research contained herein presents the setup and results of this testing. From the work it was found that the no-connection joint behaves adequately under cyclic loading at service loads, however surface roughening between precast and cast-in-place concrete must be adequate. The welded connection behaves well, granted the surfaces to be welded are properly prepared. From these results it is recommended to evaluate different surface roughening techniques, and repeat the cyclic testing using the best. The surface roughening technique chosen should be used to provide guidance on this aspect of construction with inverted T-beams. / Master of Science / The inverted T-beam bridge system is a new type of bridge system intended for use in short to medium length bridges. The system was discovered in France in 2004, where a similar type was being used. It was first modified slightly, and adopted in the in Minnesota. In 2012, the system was again modified to increase its strength and its construction speed, and was then adopted in Virginia. The modifications to the system in Virginia focused on the connections between the individual units making up the bridge, and the geometry of each of these units. The focus of this research was to quantify the long-term performance of two of the connection types currently used on bridges in Virginia. This was achieved by subjecting a test specimen to repeated loads in the laboratory at Virginia Tech. The loading used in the laboratory represented the conditions that a real bridge of this type would be subjected to. The research showed that the two connection types performed well under the repeated loading conditions. However, it was concluded that the concrete surfaces which are in contact with one another must be properly roughened, so that the system maintains its strength. The importance of this research is due to the fact that the large costs associated with maintaining the nation’s bridge infrastructure can be substantially reduced due to this system’s quick and simple construction. In addition to this, road users experience less disruption because of the shortened construction times.

Within the EU's railway research program IN2TRACK3, a product known as the 3MB track system (Moulded Multi Modular Block slab track system) has been developed. The new innovative track system can be explained as a hybrid solution between traditional ballast tracks and slab track systems. The project has a primary objective for the 3MB system to reduce life cycle costs, improve reliability and punctuality, and increase capacity. The modular construction system allows for easier maintenance of railway tracks, as damaged parts can be replaced more quickly. In September 2022, a full-scale test was initiated on a 50-meter stretch in Gransjö, north of Boden, situated along the Iron Ore Line (Malmbana). Initially planned for a 2-year testing period, but the track system was dismantled and removed after approximately one year due to the emergence of a recurring severe crack pattern within the blocks. This degree project aims to conduct a thorough damage investigation, focusing on investigation the reasons behind the repeated crack patterns observed in the 3MB system. The analysis will particularly emphasise the design of the reinforcement and assesses whether the chosen concrete type is suitable for the specific conditions of the construction. Various laboratory tests, including compressive strength, tensile strength, and thin section analysis, are employed in this investigation. Additionally, a comprehensive literature study is conducted to ensure its credibility and quality. The results reveal that the aggregate in the sample is porous. This porosity increases the risk of frost damage and cracking in the concrete. The air content was measured at 7.1%, which is somewhat high, together with a high w/c equivalent between 0.50 and 0.55, which has a potentially negative impact on the strength. The study's in-depth analysis of the 3MB system blocks revealed two main problems: the choice of porous limestone as aggregate and insufficient coverage of the reinforcing steel. The porous nature of limestone led to water absorption and frost susceptibility, while inadequate coverage resulted in corrosion and frost cracking. Laboratory experiments also showed low tensile strength and uneven concrete quality. Calculations indicated the need for spalling reinforcement. Workmanship errors, including haphazard concrete pouring and suboptimal rail fastening solutions, exacerbated the situation. The study highlights the need for improvements in the concrete's waterproofing and fatigue strength to meet the system's requirements and avoid similar problems in the future. Despite the challenges, the project presents potential for success with the right adjustments and lessons learned from the initial testing phase. Despite challenges and identified obstacles in the project, the 3MB system can succeed. By fine-tuning the concrete recipe, and optimizing reinforcement and aggregate quality, the problems can be avoided. It is crucial to look beyond these obstacles and stick to the overall goal of the project: to establish the sustainable and efficient railways of the future. These challenges can be overcome through careful measures and ensure the project's positive contribution to the transport sector. / Inom EU:s järnvägsforskningsprogram IN2TRACK3 har en produkt känt som 3MB spårsystem (Moulded Multi Modular Block slab track system) utvecklats. Det nya innovativa spårsystemet kan förklaras som en hybridlösning mellan traditionella ballastbanor och ballastfria banor. Projektet har som primärt mål för 3MB-systemet att minska livscykelkostnaderna, förbättra tillförlitlighet och punktlighet, och öka kapaciteten. Det modulära byggsystemet möjliggör enklare underhåll av järnvägasspår, eftersom skadade delar kan bytas ut på ett snabbare sätt. I september 2022 inleddes ett fullskaleprov på en 50 meter lång sträcka i Gransjö, norr om Boden, belägen längs Malmbanan. Ursprungligen planerad för en 2-årig testperiod, men spårsystemet demonterades och togs bort efter cirka 1 år på grund av uppkomsten av ett återkommande allvarligt sprickmönster inom blocken. Målet med detta examensarbete är att genomföra en grundlig skadeutredning, med fokus på att undersöka orsakerna bakom de upprepade sprickmönster som observerats i 3MB-systemet. Analysen betonar särskilt dimensioneringen av armeringen och bedömning om den valda betongtypen är lämplig för konstruktionens specifika förutsättningar. Olika laboratorietester, inklusive tryckhållfasthet, draghållfasthet och tunnslipsanalys, används i undersökningen. Dessutom genomförs en omfattande litteraturstudie för att säkerställa studiens trovärdighet och kvalitet. Resultaten avslöjar att ballasten i provet är porös. Denna porositet ökar risken för frostskador och sprickbildning i betongen. Lufthalten uppmättes till 7,1%, Vilket är något högt, och tillsammans med ett högt vatten-cement-tal mellan 0,50 och 0,55, ger de en potentiellt negativ påverkan på hållfastheten. Studiens djupgående analys av 3MB-systemet block avslöjade två huvudproblem: valet av porös kalksten som aggregat och otillräcklig täckning av armeringsstålet. Kalkstenens porösa natur ledde till vattenabsorption och frostkänslighet, medan otillräcklig täckning resulterade i korrosion och frostsprickor. Laboratorieexperiment visade också på låg draghållfasthet och ojämn betongkvalitet. Beräkningar indikerade behovet av spjälkningsarmering. Utförandefel, inklusive ej fullgod betonggjutning och suboptimala rälbefästnings-lösningar, förvärrade situationen. Studien framhåller behovet av förbättringar i betongens vattentäthet och utmattninghållfasthet för att möta systemets krav och undvika liknande problem i framtiden. Trots dessa utmaningar har projektet en potential att bli framgångsrikt med rätt justeringar och lärdomar från den initiala testfasen. Trots utmaningar och identifierade hinder i projektet kan 3MB-systemet lyckas. Genom att finjustera betongreceptet, optimera armeringen och ballastkvaliteten bör uppkomna problemen undvikas. Det är avgörande att se bortom dessa hinder och hålla fast vid projektets övergripande mål: att etablera framtidens hållbara och effektiva järnvägar. Genom noggranna åtgärder kan dessa utmaningar övervinnas och säkerställa projektets positiva bidrag till transportsektorn.

In this study, a progressive failure analysis is used to investigate leakage in internally pressurized non-circular composite cylinders. This type of approach accounts for the localized loss of stiffness when material failure occurs at some location in a structure by degrading the local material elastic properties by a certain factor. The manner in which this degradation of material properties takes place depends on the failure modes, which are determined by the application of a failure criterion. The finite-element code STAGS, which has the capability to perform progressive failure analysis using different degradation schemes and failure criteria, is utilized to analyze laboratory scale, graphite-epoxy, elliptical cylinders with quasi-isotropic, circumferentially-stiff, and axially-stiff material orthotropies. The results are divided into two parts. The first part shows that leakage, which is assumed to develop if there is material failure in every layer at some axial and circumferential location within the cylinder, does not occur without failure of fibers. Moreover before fibers begin to fail, only matrix tensile failures, or matrix cracking, takes place, and at least one layer in all three cylinders studied remain uncracked, preventing the formation of a leakage path. That determination is corroborated by the use of different degradation schemes and various failure criteria. Among the degradation schemes investigated are the degradation of different engineering properties, the use of various degradation factors, the recursive or non-recursive degradation of the engineering properties, and the degradation of material properties using different computational approaches. The failure criteria used in the analysis include the noninteractive maximum stress criterion and the interactive Hashin and Tsai-Wu criteria. The second part of the results shows that leakage occurs due to a combination of matrix tensile and compressive, fiber tensile and compressive, and inplane shear failure modes in all three cylinders. Leakage develops after a relatively low amount of fiber damage, at about the same pressure for three material orthotropies, and at approximately the same location. / Master of Science

The majority of soils in the Mississippi Delta are vertisols, which are prone to waterlogging and can negatively affect crop production. Thus, our goal was to investigate whether widening the spacing of irrigated furrows will relieve waterlogging and improve corn productivity. The effects of furrow irrigation spacing on corn grain yield and quality were investigated for three years at a research station and a commercial farm. Widening furrow irrigation spacing up to 8 m never decreased corn grain yield, and higher corn yields were documented in 8 m furrow spacing compared to narrower irrigation spacing. Irrigation water was found to spread underground at least 4 m perpendicular to the irrigated furrow and refill the soil from the bottom up. As irrigation spacing widened, water flow accelerated through the field and infiltration was reduced, especially for the soil away from the irrigated furrow. This suggests irrigation water savings of up to 30 % from adopting wide-spaced furrow irrigation in vertisols.