Field Measurements of Ice Scraping Loads on Front Mounted Plow Blades, HR-374, 1997

Removal of ice from roads is of the more challenging task in winter highway maintenance. The best mechanical method is to use a truck with underbody plow blade, but such equipment is not available to all agencies charged with winter maintenance operations. While counties and cities often use motor graders to scrape ice, it would be of great benefit if front mounted plows could be used effectively for ice removal. To reveal and understand the factors that influence the performance of these plows, measurement of the forces experienced by the plow blades during ice scraping is desirable. This study explores the possibility of using accelerometers to determine the forces on a front-mounted plow when scraping ice. The plow was modeled by using a dynamic approach. The forces on the plow were to be determined by the measurement of the accelerations of the plow. Field tests were conducted using an "as is" front-mounted plow instrumented with accelerometers. The results of the field tests indicate that in terms of ice removal, the front-mounted plow is not favorable equipment. The major problem in this study is that the front mounted plow was not able to cut ice, and therefore experienced no significant scraping forces. However, the use of accelerometers seems to be promising for analyzing the vibration problems of the front-mounted plow.

Field Measurements of Plow Loads During Ice Removal Operations, HR-334, 1993

One of the more severe winter hazards is ice or compacted snow on roadways. While three methods are typically used to combat ice (salting, sanding and scraping), relatively little effort has been applied to improve methods of scraping ice from roads. In this project, a new test facility has been developed, comprising a truck with an underbody blade, which has been instrumented such that the forces to scrape ice from a pavement can be measured. A test site has been used, which is not accessible to the public, and ice covers have been sprayed onto the pavement and subsequently scraped from it, while the scraping loads have been recorded. Three different cutting edges have been tested for their ice scraping efficiency. Two of the blades are standard (one with a carbide insert, the other without) while the third blade was designed under the SHRP H-204A project. Results from the tests allowed two parameters to be identified. The first is the scraping efficiency which is the ratio of vertical to horizontal force. The lower this ratio, the more efficiently ice is being removed. The second parameter is the scraping effectiveness, which is related (in some as yet unspecified manner) to the horizontal load. The higher the horizontal load, the more ice is being scraped. The ideal case is thus to have as high a horizontal load as possible, combined with the lowest possible vertical load. Results indicate that the SHRP blade removed ice more effectively than the other two blades under equivalent conditions, and furthermore, did so with greater efficiency and thus more control. Furthermore, blade angles close to 0 deg provide for the most efficient scraping for all three blades. The study has shown that field testing of plow blades is possible in controlled situations, and that blades can be evaluated using this system. The system is available for further tests as are deemed appropriate.

Impacts on Safety of Left-Turn Treatment at High Speed Signalized Intersections, HR-347, 1994

Left-turning traffic is a major source of conflicts at intersections. Though an average of only 10% to 15% of all approach traffic turns left, these vehicles are involved in approximately 45% of all accidents. This report presents the results of research conducted to develop models which estimate approach accident rates at high speed signalized intersections. The objective of the research was to quantify the relationship between traffic and intersection characteristics, and accident potential of different left turn treatments. Geometric, turning movement counts, and traffic signal phasing data were collected at 100 intersections in Iowa using a questionnaire sent to municipalities. Not all questionnaires resulted in complete data and ultimately complete data were derived for 63 intersections providing a database of 248 approaches. Accident data for the same approaches were obtained from the Iowa Department of Transportation Accident Location and Analysis System (ALAS). Regression models were developed for two different dependent variables: 1) the ratio of the number of left turn accidents per approach to million left turning vehicles per approach, and 2) the ratio of accidents per approach to million traffic movements per approach. A number of regression models were developed for both dependent variables. One model using each dependent variable was developed for intersections with low, medium, and high left turning traffic volumes. As expected, the research indicates that protected left turn phasing has a lower accident potential than protected/permitted or permitted phasing. Left turn lanes and multiple lane approaches are beneficial for reducing accident rates, while raised medians increase the likelihood of accidents. Signals that are part of a signal system tend to have lower accident rates than isolated signals. The resulting regression models may be used to determine the likely impact of various left turn treatments on intersection accident rates. When designing an intersection approach, a traffic engineer may use the models to estimate the accident rate reduction as a result of improved lane configurations and left turn treatments. The safety benefits may then be compared to any costs associated with operational effects to the intersection (i.e., increased delay) to determine the benefits and costs of making intersection safety improvements.

Lateral Load Resistance of Diaphragms in Prestressed Concrete Girder Bridges, HR-319, 1991

Each year several prestressed concrete girder bridges in Iowa and other states are struck and damaged by vehicles with loads too high to pass under the bridge. Whether or not intermediate diaphragms play a significant role in reducing the effect of these unusual loading conditions has often been a topic of discussion. A study of the effects of the type and location of intermediate diaphragms in prestressed concrete girder bridges when the bridge girder flanges were subjected to various levels of vertical and horizontal loading was undertaken. The purpose of the research was to determine whether steel diaphragms of any conventional configuration can provide adequate protection to minimize the damage to prestressed concrete girders caused by lateral loads, similar to the protection provided by the reinforced concrete intermediate diaphragms presently being used by the Iowa Department of Transportation. The research program conducted and described in this report included the following: A comprehensive literature search and survey questionnaire were undertaken to define the state-of-the-art in the use of intermediate diaphragms in prestressed concrete girder bridges. A full scale, simple span, restressed concrete girder bridge model, containing three beams was constructed and tested with several types of intermediate diaphragms located at the one-third points of the span or at the mid-span. Analytical studies involving a three-dimensional finite element analysis model were used to provide additional information on the behavior of the experimental bridge. The performance of the bridge with no intermediate diaphragms was quite different than that with intermediate diaphragms in place. All intermediate diaphragms tested had some effect in distributing the loads to the slab and other girders, although some diaphragm types performed better than others. The research conducted has indicated that the replacement of the reinforced concrete intermediate diaphragms currently being used in Iowa with structural steel diaphragms may be possible.

Solar Powered Highway Delineator System, HR-367, 1993

Currently, many drivers experience some difficulty in viewing the road ahead of them during times of reduced visibility, such as rain, snow, fog, or the darkness of night- Recent studies done by the National Safety Council provide a detailed contrast between fatal accidents occurring during the day and night. Revealed was that the motor vehicle night death rate (4.41 deaths per 100 million miles driven) was sharply higher than the corresponding death rate during daylight hours (1.21). By providing a delineating system powered by the natural resource of solar power, a constant source of visibility may be maintained throughout the evening. Along with providing enough light to trace the outline of the road, other major goals defined in producing this delineator system are as follows: 1. A strong and durable design that would protect the internal components and survive extreme weather conditions. 2. A low maintenance system where components need few repairs or replacements. 3. A design which makes all components accessible in the event that maintenance is needed, but also prevents vandalism. 4. A design that provides greater visibility to drivers and will not harm a vehicle or its passengers in the event of a collision. This solar powered highway delineator consists of an adjustable solar array, a light fixture, and a standard delineator pole. The solar array houses and protects the solar panels, and can be easily adjusted to obtain a maximum amount of sunlight. The light fixture primarily houses the battery, the circuit and the light assembly. Both components allow for easy accessibility and reduce vandalism using internal connections for bolts and wires. The delineator mounting pole is designed to extensively deform in the event of a collision, therefore reducing any harm caused to the vehicle and/or the passengers. The cost of a single prototype to be produced is approximately $70.00 excluding labor costs. However, these material and labor costs will be greatly reduced if a large number of delineators are produced. It is recommended that the Iowa Department of Transportation take full advantage of the research and development put into this delineator design. The principles used in creating this delineator can be used to provide an outline for drivers to follow, or on a larger scale, provide actual roadway lighting in areas where it was never before possible or economically feasible. In either event, the number of fatal accidents will be decreased due to the improved driver visibility in the evening.

Snow Removal on Iowa's Secondary Roads, HR-267, 1984

Snow removal on the 90,000 mile Iowa secondary road system is a major concern of county engineers. Rural residents rely almost entirely on motor vehicles for travel. They have come to expect passable roads during all types of weather and as most county engineers know, the public is less tolerant of problems in snow removal than in any other highway department function. To avoid snow removal problems, maintenance personnel begin preparation before the winter maintenance season. The slide tape presentation, "Snow Removal on Iowa's Secondary Roads", was developed to assist in training and retraining maintenance personnel each year prior to winter. The program covers preparation for winter, snow and ice removal, and after storm care of equipment.

Fluid-rock interaction during late stages of the Alpine exhumation

Résumé de la thèseLa fracturation des roches au cours de phases compressives ou extensives est un souvent évoquée pour expliquer la circulation de fluide au sein des roches cristallines. Dans le cadre de cette thèse, la circulation des fluides lors de l'exhumation tardive des Alpes a été étudiée en utilisant deux approches différentes: analyses structurales de la déformation fragile d'une part et analyses géochimiques des roches et des minéraux (isotopes stables, datations U/Pb, thermochronologie (U-Th)/He) d'autre part. Cette approche combinée a permis de mieux comprendre l'interaction existante entre les fluides métamorphiques et les fluides météoriques, ainsi que leur interaction avec les roches encaissantes. Le travail a été effectué dans la zone Pennique du Valais suisse.La première partie était focalisée sur la déformation fragile, le but étant de définir les différents types de déformations existantes et de déterminer l'âge relatif des différentes familles de failles. Dans la région d'étude, quatre domaines ont été distingués. Chacun d'eux comportent deux types de structures fragiles, certaines sont minéralisées alors que d'autre non. Au sein de chaque domaine, la direction principale des structures minéralisées correspond à l'orientation des accidents tectoniques majeurs de la région (Aosta- Ranzola Line au Sud, Rhône Line au Nord et Simplon Fault Zone à l'Est), alors que les structures non- minéralisées montrent des orientations plus variables. Ainsi, le premier type de structure est interprété comme résultant d'une dislocation tectonique alors que le deuxième type de structure résulterait d'une dislocation gravitaire locale. Il n'est néanmoins pas possible de classer chronologiquement la formation de ces deux types de structure ni d'attribuer un âge relatif aux changements d'orientation des contraintes majeures.La deuxième étude a été effectuée dans la région de la zone de faille du Simplon. Dans cette zone, la composition isotopique des minéraux ayant cristallisé à l'intérieur des fractures tardives permet de distinguer différents types de circulation de fluide. Les valeurs δ180 du quartz de la roche encaissante ainsi que ceux des veines tardives du bloque inférieur de la faille sont comparables. Ces valeurs indiquent un rééquilibrage et un tamponnage isotopique des fluides tardifs au contact de la roche encaissante lors de la fracturation de cette dernière et de la cristallisation des veines tardives. La même situation est observée dans la partie nord du bloque supérieur ainsi que dans sa partie sud. Ceci n'est néanmoins pas le cas pour la partie centrale du bloque supérieur où les valeurs isotopiques des minéraux dans les veines tardives sont approximativement 3 %o plus basses (avec des valeurs extrêmes négatifs), indiquant une contribution d'eau météorique aux fluides circulant dans les veines. Ces données suggèrent qu'une infiltration d'eau météorique a pu avoir lieu dans le bloque supérieur, où la fracturation des roches est plus intensive car le déplacement relatif le long de la faille y fut plus important, et la température maximale du métamorphisme plus basse. La troisième contribution traite de la géo-thermochronologie de la zone de contact entre la klippe de la Dent Blanche et la nappe de Tsaté. De petits zircons euhédraux ont été trouvés dans un plan de faille minéralisé (parallèle à la Faille du Rhône, voir première partie de l'étude), riche en hématite et quartz, de la zone d'étude. Les analyses U/Pb donnent des âges radiométriques autour de 270 - 280 Ma aux zircons extraits de la minéralisation ainsi que ceux extraits de la roche encaissante, ce qui correspond à l'âge de la nappe de la Dent Blanche et non celui de la nappe du Tsaté qui est elle-même classiquement interprétée comme une ophiolite Jurassique de l'Océan Liguro-Piémontais. Ces données suggèrent que les zircons contenus dans la veine ont été hérités de la roche encaissante. Les résultats (U-Th)/He indiquent un âge de refroidissement différent pour la roche encaissante (25.5 ± 2.0 Ma) que celui de la minéralisation (17.7 ±1.4 Ma). Le thermomètre isotopique quartz-hématite indique une température d'équilibre, et donc de mise en place de la minéralisation, d'environ 170 °C, température très proche de la température de -180 °C de fermeture du zircon pour le système (U-Th)/He. Ceci suggère que l'âge de refroidissement des zircons de la minéralisation correspond aussi à l'âge de formation de la faille.Thesis abstractFluid circulation in fractured rocks is a common process in geology, and it is generally the consequence of faulting and fracturing during both tectonic compression and extension. This thesis is focused on fluid circulation during late stages of the Alpine exhumation. After a structural analysis of the late brittle deformation of the studied samples, several analytical methods (stable isotope investigations, U/Pb radiometric dating, (U-Th)/He thermochronology) have been applied to understand the interaction of metamorphic and meteoric fluids with one another as well as with the host rock. This thesis is articulated around three study directions. All studies were conducted in the Penninic Zone of the Valais, Switzerland. The first study deals with late, brittle deformation and focuses on the different deformation styles and on the relative age of the different families of fractures. In order to do this, late brittle structures observed in four different domains have been subdivided as a function of the existence (or not) and type of mineralization. Comparisons between mineralized and non-mineralized strike directions for all four domains show that mineralized structures follow the strike orientation of major tectonic movements indicated in the Penninic Zone of the Valais (Aosta-Ranzola Line to the S, Rhône Line to the Ν and Simplon Fault Zone to the E), whereas non-mineralized fractures have a more variable strike orientation. This difference could be interpreted as indicative of tectonic-related faulting (mineralized structures) vs. local, collapse-related faulting (non-mineralized fractures), but it is not strong enough to indicate a relative age of the late brittle structures, and/or a change in the orientation of the strain field in post-Miocene times. The second studied area is focused on the Simplon Fault Zone (SFZ). Stable isotope analyses of minerals filling these late fractures indicate that there are two different fluid circulation systems in the footwall and hanging wall of the SFZ. In the footwall, δ180 values of quartz from both the host rock and the late veins range from +10 %o to +12 %o. This is consistent with buffering of circulating fluids by the host rock during fracturing and vein precipitation. In the hanging wall, δΙ80 values for quartz crystals from the host rock and the late veins are similar in both the northern and southern parts of the detachment that are both affected by the same degree of metamorphism (greenschist to the Ν and amphibolite to the S). This is not the case in the central part of the SFZ, where there is a jump from amphibolite facies in the footwall to greenschist facies in the hanging wall. δ,80 values for quartz from the hanging wall late veins are approximately 3.0 %o lower (down to negative values in some cases) than the values observed in the footwall These data suggest that infiltration of meteoric water may have occurred in the most fractured parts of the hanging wall, where relative displacement on the SFZ was the greatest and the peak temperature lower. In the less fractured footwall the δ180 values reflect a host rock-buffered system.The third study is focused on geo-thermochronology at the contact between the Dent Blanche nappe and the Tsaté nappe where small, euhedral zircons were found in a hematite- and quartz-rich mineralization on a late normal fault plane parallel to the Rhône Line (see first part of the study). U/Pb analysis indicates that the zircons - both in the late mineralization and in the host rock - have absolute radiometric ages clustering around 270 - 280 Ma, which is the accepted age for intrusive rocks from the Austroalpine Dent Blanche units but not for the Tsaté nappe. The latter is classically interpreted as an ophiolitic remnant of the Jurassic Liguro-Piemontais Ocean. U/Pb analyses suggest that zircons in late mineralization are all inherited from the host rock; however, results of (U-Th)/He analyses indicate that cooling ages for the host rocks are different to the cooling ages for the zircons in late mineralization. Indeed, the calculated cooling age for the Arolla gneiss is 25.5 ± 2.0 Ma, whilst the cooling age for the associated mineralized fault plane is 17.7 ±1.4 Ma. Oxygen stable isotope fractionation between quartz and hematite in the same late mineralization corresponds to temperatures of about 170 °C. The proximity of the calculated emplacement temperature for the mineralization and the lower accepted closure temperature for zircon in the (U-Th)/He system (-180 °C) imply that the age of 17.7 ± 1.4 Ma can also be interpreted as the formation age of this late brittle fault.Résumé grand publicLa circulation des fluides dans les roches fracturées est typique de nombreux processus géologiques, et très souvent est la conséquence de la fracturation des roches. Cette thèse aborde la question de la circulation des fluides pendant les dernières phases du soulèvement des Alpes. Après une analyse structurale de la fracturation directement sur le terrain, plusieurs méthodes géochimiques ont été appliquées pour comprendre l'interaction entre les différents fluides circulants, et avec leur propre roche mère. L'étude, concentrée sur trois directions principales, a été conduite dans la zone Pennique du Valais suisse. La première partie traite de la déformation cassante dans le secteur cité. L'analyse détaillée des fractures a permis de les subdiviser en structures minéralisées et non-minéralisées, sur quatre domaines différents. La comparaison entre les directions des structures minéralisées et non-minéralisées a permis de montrer que les premières suivent l'orientation des accidents tectoniques majeurs de la région, alors que les structures non- minéralisées ont une orientation plus variable. Cette différence pourrait être interprétée comme indication d'une dislocation tectonique (structures minéralisées) contre une dislocation gravitaire locale (structures non-minéralisées), mais elle n'est pas assez forte pour indiquer un âge relatif des structures tardives et/ou un changement de l'orientation des contraintes après -20 Ma vers le présent.A partir de ces observations, la deuxième étude est concentrée dans la région de la faille du Simplon. Les analyses géochimiques sur les minéraux remplissant les structures tardives indiquent qu'il y a deux différents systèmes de circulation des fluides dans les deux parties (toit et mur) de la faille. Dans le mur, les valeurs isotopiques des minéraux cristallisés à partir d'un fluide tardif sont les mêmes de ceux de la roche mère, donc il y a eu rééquilibration chimique entre fluide et roche pendant la fracturation de cette dernière et la précipitation des minéraux. Dans le toit, les valeurs isotopiques dans la roche mère et dans les minéraux des veines tardives sont comparables dans les parties Ν et S de la faille, où les roches du toit et du mur ont atteint une température maximale - pendant phase prograde de la formation des Alpes - comparable. Au contraire, dans la partie centrale, où le mur a atteint des températures maximales plus élevées par rapport au toit, les valeurs géochimiques des minéralisations tardives du toit sont parfois plus basses que les valeurs observées dans le mur. Ces données suggèrent que l'infiltration de l'eau de surface aurait pu se produire dans la partie plus fracturée du toit, où le déplacement relatif le long de la faille était majeur et les températures maximales mineures. Au contraire, les données géochimiques du mur de la partie centrale indiquent un système isotopique équilibré par la roche mère.La troisième partie de ce travail se base sur l'étude géochimique intégrée des isotopes stables d'Oxygène et radioactifs du Plomb, Uranium, Thorium et Hélium, auprès d'une faille normale minéralisée et des roches de la région à cheval entre deux nappes, la nappe de la Dent Blanche et la nappe de Tsaté. Ici, des petits zircons ont été trouvés dans la minéralisation citée, riche en hématite et quartz. L'analyse radiométrique Uranium/Plomb a montré que les zircons dans la minéralisation et dans les roches autour ont des âges comparables (autour 280 Ma). Cela signifie que les zircons dans la minéralisation tardive ont été hérités de la roche mère pendant la fracturation et la circulation des fluides tardives. De l'autre coté, les résultats des analyses Uranium-Thorium/Hélium indiquent que les âges de refroidissement pour les roches mères sont différents comparés aux âges de refroidissement pour les zircons dans la minéralisation tardive: ces derniers sont plus jeunes d'environ 8 Ma (autour 25 Ma et autour 17 Ma respectivement). Les analyses des isotopes de l'oxygène sur quartz et hématite dans la même minéralisation donnent une température de mise en place de cette dernière d'environ 170° C. La température de fermeture du système chimique des zircons dans le système (Uranium-Thorium)/Hélium est d'environ 180 °C: la proximité de ces deux températures implique que l'âge de refroidissement de la minéralisation tardive peut également être interprété comme âge de formation de la faille.

Long-term and long range migration of radioisotopes in terrestrial systems : mechanisms of radioisotopes (Cs, Sr, Pu, Am) mobilization in soils

Summary Artificial radionuclides were released in the environment during the atmospheric nuclear weapon tests and after accidental events involving nuclear industries. As a primary receptor of the deposition, the soil is a very sensitive compartment and understanding the interaction and migration of radionuclides within soils allows the development of scenario for the contamination risk of the population and of the environment. Most available field studies on radionuclides in soils only concern one or two isotopes, mostly 137Cs, and few physico-chemical soil parameters. The purpose of this study was a broader understanding of the radioecology of an Alpine valley. In a first part, we aimed to describe the depth distribution of 137Cs, 90Sr, 239+240Pu, and 241Am within different alpine soils and to identify some stable elements as indicators for accumulating layers. In the central part of the study, the goal was to investigate the repartition of ^Sr and 239Pu between the truly dissolved fraction and the colloidal fraction of the soil solutions and to identify the nature of colloids involved in the adsorption of ^Sr and 239Pu. These results were integrated in an "advection- sorption" transport model seeking to explain the migration of 239Pu and 90Sr within the soils and to assess the importance of colloidal transport for these two isotopes. A further aspect studied was the role of the competition between the radioisotopes (137Cs and 90Sr) and their stable chemical analogues (K and Ca) with respect to plant uptake by different plant species. The results on the depth distribution within the soils showed that 137Cs was mostly retained in the topsoil, to the exception of an organic-rich soil (Histosol 2) receiving important surface runoff, where migration down to a depth of 30 cm was observed. 137Cs depth distribution within the soils was similar to unsupported 210Pb depth distribution. The plant uptake of 137Cs clearly depended on the concentration of exchangeable potassium in the soils. Moreover, we showed that the 137Cs uptake by certain species of the taxonomic orders Poales and Rosales was more sensitive to the increase in exchangeable Κ compared to other orders. Strontium-90 was much more mobile in the soils than 137Cs and depth migration and accumulation in specific AI- and Fe-rich layers were found down to 30 cm. Copper and Ni showed accumulations in these same layers, indicating their potential to be used as indicators for the migration of ^Sr within the soils. In addition, we observed a 90Sr activity peak in the topsoil that can be attributable to recycling of 90Sr by plant uptake. We demonstrated for the first time that a part of 90Sr (at least 40%) was associated with the colloids in organic-rich soil solutions. Therefore, we predict a significant effect of the colloidal migration of ^Sr in organic-rich soil solutions. The plant uptake results for 90Sr indicated a phylogenetic effect between Non-Eudicot and Eudicots: the order Poales concentrating much less 90Sr than Eudicots do. Moreover, we were able to demonstrate that the sensitivity of the 90Sr uptake by 5 different Alpine plant species to the amount of exchangeable Ca was species-independent. Plutonium and 241Am accumulated in the second layer of all soils and only a slight migration deeper than 20 cm was observed. Plutonium and 241Am showed a similar depth distribution in the soils. The model results suggested that the present day migration of 239Pu was very slow and that the uptake by plants was negligible. 239Pu activities between 0.01 to 0.08 mBq/L were measured in the bulk soil solutions. Migration of 239Pu with the soil solution is dominated by colloidal transport. We reported strong evidences that humic substances were responsible of the sorption of 239Pu to the colloidal fraction of the soil solutions. This was reflected by the strong correlation between 239Pu concentrations and the content of (colloidal) organic matter in the soil solution. Résumé Certains radioéléments artificiels ont été disséminés dans l'environnement suite aux essais atmosphériques de bombes nucléaires et suite à des accidents impliquant les industries nucléaires. En tant que récepteur primaire de la déposition, le sol est un compartiment sensible et des connaissances sur les interactions et la migration des radioéléments dans le sol permettent de développer des modèles pour estimer la contamination de la population et de l'environnement. Actuellement, la plupart des études de terrain sur ce sujet concernent uniquement un ou deux radioéléments, surtout le 137Cs et peu d'études intègrent les paramètres du sol pour expliquer la migration des radioéléments. Le but général de cette étude était une compréhension étendue de la radio-écologie d'une vallée alpine. Notre premier objectif était de décrire la distribution en profondeur de 137Cs, ^Sr, 239+240pu et 241Am dans différents sols alpins en relation avec des éléments stables du sol, dans le but d'identifier des éléments stables qui pourraient servir d'indicateurs pour des horizons accumulateurs. L'objectif de la deuxième partie, qui était la partie centrale de l'étude, était d'estimer le pourcentage d'activité sous forme colloïdale du 239Pu et du 90Sr dans les solutions des sols. De plus nous avons déterminé la nature des colloïdes impliqués dans la fixation du ^Sr et 239Pu. Nous avons ensuite intégré ces résultats dans un modèle de transport développé dans le but de décrire la migration du 239Pu et 90Sr dans le sol. Finalement, nous avons étudié l'absorption de 137Cs et 90Sr par les plantes en fonction de l'espèce et de la compétition avec leur élément analogue stable (K et Ca). Les résultats sur la migration en profondeur du 137Cs ont montré que ce radioélément était généralement retenu en surface, à l'exception d'un sol riche en matière organique dans lequel nous avons observé une nette migration en profondeur. Dans tous les sols, la distribution en profondeur du 137Cs était corrélée avec la distribution du 210Pb. L'absorption du 137Cs par les plantes, était dépendante de la concentration en Κ échangeable dans le sol, le potassium étant un compétiteur. De plus, nous avons observé que les espèces ne réagissaient pas de la même manière aux variations de la concentration de Κ échangeable. En effet, les espèces appartenant aux ordres des Poales et des Rosales étaient plus sensibles aux variations de potassium échangeable dans le sol. Dans tous les sols Le 90Sr était beaucoup plus mobile que le 137Cs. En effet, nous avons observé des accumulations de 90Sr dans des horizons riches en Fe et Al jusqu'à 30 cm de profondeur. De plus, le Cu et le Ni montraient des accumulations dans les mêmes horizons que le 90Sr, indiquant qu'il pourrait être possible d'utiliser ces deux éléments comme analogues pour la migration du 90Sr. D'après le modèle développé, le pic de 90Sr dans les premiers centimètres du sol peut être attribué à du recyclage par les plantes. Le 90Sr en solution était principalement sous forme dissoute dans des solutions de sols peu organique (entre 60 et 100% de 90Sr dissous). Par contre, dans des solutions organiques, un important pourcentage de 90Sr (plus de 40%) était associé aux colloïdes. La migration colloïdale du 90Sr peut donc être significative dans des solutions organiques. Comme pour le 137Cs, l'absorption du 90Sr par les plantes dépendait de la concentration de son analogue chimique dans la fraction échangeable du sol. Par contre, les espèces de plantes étudiées avaient la même sensibilité aux variations de la concentration du calcium échangeable. Le plutonium et l'américium étaient accumulés dans le deuxième horizon du sol et nous avons observé seulement une faible migration plus profondément que 20 cm. Selon le modèle, la migration actuelle du plutonium est très lente et l'absorption par les plantes semble négligeable. Nous avons mesuré entre 0.01 et 0.08 mBq/L de 239Pu dans les solutions de sol brutes. La migration du plutonium par la solution du sol est due principalement aux colloïdes, probablement de nature humique. Résumé grand public Dans les années 1950 à 1960, l'environnement a été contaminé par des éléments radioactifs (radioéléments) artificiels provenant des essais des armes atomiques et de l'industrie nucléaire. En effet, durant ces années, les premiers essais de bombes atomiques se faisaient dans l'atmosphère, libérant de grandes quantités d'éléments radioactifs. De plus certains accidents impliquant l'industrie nucléaire civile ont contribué à la dissémination d'éléments radioactifs dans l'environnement. Ce fut par exemple le cas de l'accident de la centrale atomique de Tchernobyl en 1986 qui a causé une importante contamination d'une grande partie de l'Europe par le 137Cs. Lorsqu'ils sont libérés dans l'atmosphère, les radioéléments sont dispersés et transportés par les courants atmosphériques, puis peuvent être déposés dans l'environnement, principalement par les précipitations. Une fois déposés sur le sol, les radioéléments vont interagir avec les composants du sol et migrer plus ou moins vite. La connaissance des interactions des éléments radioactifs avec le sol est donc importante pour prédire les risques de contamination de l'environnement et de l'homme. Le but général de ce travail était d'évaluer la migration de différents éléments radioactifs (césium-137, strontium-90, plutonium et américium-241) à travers le sol. Nous avons choisi un site d'étude en milieu alpin (Val Piora, Tessin, Suisse), contaminé en radioéléments principalement par les retombées de l'accident de Tchernobyl et des essais atmosphériques de bombes atomiques. Dans un premier temps, nous avons caractérisé la distribution en profondeur des éléments radioactifs dans le sol et l'avons comparée à divers éléments stables. Cette comparaison nous a permit de remarquer que le cuivre et le nickel s'accumulaient dans les mêmes horizons du sol que le strontium-90 et pourraient donc être utilisés comme analogue pour la migration du strontium-90 dans les sols. Dans la plupart des sols étudiés, la migration du césium-137, du plutonium et de l'américium-241 était lente et ces radioéléments étaient donc accumulés dans les premiers centimètres du sol. Par contre, le strontium-90 a migré beaucoup plus rapidement que les autres radioéléments si bien qu'on observe des accumulations de strontium-90 à plus de 30 cm de profondeur. Les radioéléments migrent dans la solution du sol soit sous forme dissoute, soit sous forme colloïdale, c'est-à-dire associés à des particules de diamètre < Ιμηι. Cette association avec des colloïdes permet à des radioéléments peu solubles, comme le plutonium, de migrer plus rapidement qu'attendu. Nous avons voulu savoir quelle était la part de strontium-90 et plutonium associés à des colloïdes dans la solution du sol. Les résultats ont montré que le plutonium en solution était principalement associé à des colloïdes de type organique. Quant au strontium-90, ce dernier était en partie associé à des colloïdes dans des solutions de sol riches en matière organique, par contre, il était principalement sous forme dissoute dans les solutions de sol peu organiques. L'absorption de radioéléments par les plantes représente une voie importante pour le transfert vers la chaîne alimentaire, par conséquent pour la contamination de l'homme. Nous avons donc étudié le transfert du césium-137 et du strontium-90 de plusieurs sols vers différentes espèces de plantes. Les résultats ont montré que l'absorption des radioéléments par les plantes était liée à la concentration de leur analogue chimique (calcium pour le strontium-90 et potassium pour le césium- 137) dans la fraction échangeable du sol. De plus certaines espèces de plantes accumulent significativement moins de strontium-90.

Metric Training for the Transportation Industry Module V - Motor Vehicle Licensing and Enforcement, HR-376

"Metric Training For The Highway Industry", HR-376 was designed to produce training materials for the various divisions of the Iowa DOT, local government and the highway construction industry. The project materials were to be used to introduce the highway industry in Iowa to metric measurements in their daily activities. Five modules were developed and used in training over 1,000 DOT, county, city, consultant and contractor staff in the use of metric measurements. The training modules developed deal with the planning through operation areas of highway transportation. The materials and selection of modules were developed with the aid of an advisory personnel from the highway industry. Each module is design as a four hour block of instruction and a stand along module for specific types of personnel. Each module is subdivided into four chapters with chapter one and four covering general topics common to all subjects. Chapters two and three are aimed at hands on experience for a specific group and subject. This module includes: Module 5 - Motor Vehicle Enforcement. Examples from Iowa and Federal Motor Vehicle Codes are used as examples for hands on training for the vehicle enforcement type personnel using this module.

Load Ratings for Standard Bridges, HR-239, 1982

The load ratings for these Standard bridges were calculated in compliance with the 1978 AASHTO Manual for Maintenance Inspection of Bridges, using the appropriate allowable stresses for the materials specified by the Standard plans. Distribution of loads is in compliance with the Manual unless otherwise noted. Except for truss spans, all bridges with roadway widths of 18 ft. or less were rated for one lane of traffic. All 18 ft. roadway truss bridges were rated for both one and two lanes of traffic. All bridges with roadway widths exceeding 18 ft. were rated for two lanes of traffic. If the posting rating for two lane bridges was less than legal, then the bridges were rated for traffic restricted to one lane, or to one lane centered in the roadway, as noted on the summary sheet. The ratings are applicable to bridges built in accordance with the standard plans and which exhibit no significant deterioration or damage to the structural members, and which have no added wearing surface material in excess of that noted on the summary sheets and used in the calculations. The inventory and operating ratings were based upon the standard AASHTO HS20-44 loading. The legal load ratings were based upon the three typical Iowa legal vehicles shown on page 5. The legal load ratings were based upon the maximum allowable Operating Rating stresses specified in the Manual. Refer to notations on the summary sheets for additional qualifications on the load ratings for specific standard bridge series. Load ratings for standard bridges with wood floors must be based upon existing conditions of attachment of the wood flooring to the top flanges of longitudinal steel stringers. The ratings must be reevaluated if the existing lateral support conditions are not in accordance with conditions used for the rating and noted on the summary sheets. Details of most of the standard bridges are included in the three books of "Iowa State Highway Commission, Bridge Standards," issued in June, 1972. Copies of plans for those standard bridges that were rated, and that are not included in the original books of standard plans, are being furnished under separate cover with these rating summaries.

Control of Concrete Deterioration Due to Trace Compounds in Deicers, Phase II, HR-299, 1989

This report presents results of research on ways to reduce the detrimental effects of sulfate-tainted rock salt deicers on portland cement concrete used for highway pavements. Repetitious experiments on the influence of fly ash on the mortar phase of concrete showed significant improvement in resistance to deicing brines is possible. Fifteen to twenty percent by weight of fly ash replacement for portland cement was found to provide optimum improvement. Fly ashes from five sources were evaluated and all were found to be equally beneficial. Preliminary results indicate the type of coarse aggregate also plays an important role in terms of concrete resistance to freeze-thaw in deicing brines. This was particularly true for a porous ferroan dolomite thought to be capable of reaction with the brine. In this case fly ash improved the concrete, but not enough for satisfactory performance. An intermediate response was with a porous limestone where undesirable results were observed without fly ash and adequate performance was realized when 15% fly ash was added. The best combination for making deicer-resistant concrete was found to be with a non-porous limestone. Performance in brines was found to be adequate without fly ash, but better when fly ash was included. Consideration was given to treating existing hardened concrete made with poor aggregate and no fly ash to extend pavement life in the presence of deicers, particularly at joints. Sodium silicate was found to improve freeze-thaw resistance of mortar and is a good candidate for field usage because of its low cost and ease of handling.

Correlation Studies BPR Type Roughometer vs. PCE Type Road Meter, MLR-68-2, 1968

The BPR type Roughometer has been used by the Iowa State Highway Commission since 1955 for the evaluation of the relative roughness of the various Iowa road surfaces. Since the commencement of this program, standardized information about the roughness of the various Iowa roads with respect to their type, construction, location and usage has been obtained. The Roughometer has also served to improve the economics and quality of road construction by making the roughness results of various practices available to all who are interested. In 1965, the Portland Cement Association developed a device known as the PCA Road Meter for measuring road roughness. Mounted in a regular passenger car, the Road Meter is a simple electromechanical device of durable construction which can perform consistently with extremely low maintenance. In 1967, the Iowa State Highway Commission's Laboratory constructed a P.C.A. type Road Meter in order to provide an efficient and reliable method for measuring the Present Serviceability Index for the state's highways. Another possibility was that after considerable testing the Road Meter might eventually replace the Roughometer. Some advantages of the Road Meter over the Roughometer are: (1) Road Meter tests are made by the automobile driver and one assistant without the need of traffic protection. The Roughometer has a crew of four men; two operating the roughometer and two driving safety vehicles. (2) The Road Meter is able to do more miles of testing because of its faster testing speed and the fa.ct that it is the only vehicle involved in the testing. (3) Because of the faster testing speed, the Road Meter gives a better indication of how the road actually rides to the average highway traveler. (4) The cost of operating a Road Meter is less than that of a Roughometer because of the fewer number of vehicles and men needed in testing.

Deicing Salt Corrosion with and without Inhibitors, MLR-87-8, 1989

Chloride ion penetration through concrete to reinforcing steel is causing the premature deterioration of numerous bridge decks in Iowa. The purpose of the research reported in this paper was to determine whether any of several additives or alternative deicing chemicals could inhibit corrosion of reinforcing steel. The deicers tested were calcium magnesium acetate (CMA), CMA plus NaCl (NaCl: sodium chloride), Quicksalt plus PCI, and CG-90, a polyphosphate solution being developed by Cargill. Two tests were established. First, steel coupons were placed in a 15% solution of a deicer and distilled water to determine which alternative deicer would cause the least amount of corrosion in solution. The coupons were weighed periodically to determine each coupon's weight loss from corrosion. The second test involved ponding a 15% solution of each material on reinforced concrete blocks. Weekly copper-copper sulfate electrical half-cell (CSE) potential readings were taken on each block to determine whether corrosive activity was occurring at the steel surface. When the ponding research was concluded, concrete samples were taken from one of the three blocks ponded with each deicer. The samples were used to determine the chloride ion content at the level of the steel. Results show that all the deicers were less corrosive than NaCl. Only pure CMA, however, significantly inhibited the corrosion of steel embedded in concrete.

Variations of Tine Texturing of PCC Pavement, MLR-93-4, 1996

Seven experimental texture sections were constructed on the Polk-Jasper RP-163-1(50)--16--77 project just east of Des Moines. The experimental sections included two groove depths for a longitudinal tine texture and 13 mm (1/2 in.), 19 mm (1 in.) and variable spaced transverse tine textures. An artificial turf textured section was also included. Friction values and a rating of objectionable noise were determined for all sections. All transverse tine textures generated a high level of objectionable noise. The longitudinal tine texture was rated very good in regard to objectionable noise. At this time, all tined textures are providing satisfactory friction values.