Improvement of Granular Base Course Materials with Portland Cement, Special Report, HR-99

A highway base course may be defined as a layer of granular material which lies immediately below the wearing surface of a pavement and must possess high resistance to deformation in order to withstand pressures imposed by traffic. A material commonly used for base course construction is crushed limestone. Sources of limestone, acceptable for highway bases in the state of Iowa, occur almost entirely in the Pennsylvanian, Mississippian and Devonian strata. Performance records of the latter two have been quite good, while material from the Pennsylvanian stratum has failed on numerous occasions. The study reported herein is one segment of an extensive research program on compacted crushed limestone used for flexible highway base courses. The primary goals of the total study are: 1. Determination of a suitable and realistic laboratory method of compaction. 2. Effect of gradation, and mineralogy of the fines, on shearing strength. 3. Possible improvement of the shear strength with organic and inorganic chemical stabilization additives. Although the study reported herein deals primarily with the third goal, information gathered from work on the first two was required for this investigation. The primary goal of this study was the evaluation of various factors of stability of three crushed limestones when treated with small amounts of type I Portland cement. Investigation of the untreated materials has indicated that shear strength alone is not the controlling factor for stability of crushed stone bases. Thus the following observations were made in addition to shear strength parameters, to more adequately ascertain the stability of the cement treated materials: 1. Volume change during consolidation and shear testing. 2. Pore pressure during shear. The consolidated-undrained triaxial shear test was used for determination of the above factors.

Asymmetric giant magnetoresistance in Co10Cu90 magnetic granular alloys

We have observed a type of giant magnetoresistance (GMR) in magnetic granular Co10Cu90 alloys. The asymmetric GMR depends strongly on the size of magnetic Co particles, which exhibit superparamagnetic behavior at given measured temperature. The asymmetric GMR points to a metastable state that develops when the sample is field-cooled, which is lost after recycling. We propose that high-field cooling produces more effective parallel alignment of small unblocked Co particle moments and interfacial magnetizations, which contributes to the further decrease of the resistance in comparison with the samples zero-field-cooled, and then applied to the same field.

Pilot Construction Project for Granular Shoulder Stabilization, TR-634, 2013

Granular shoulders need to be maintained on a regular basis because edge ruts and potholes develop, posing a safety hazard to motorists. The successful mitigation of edge-rut issues for granular shoulders would increase safety and reduce the number of procedures currently required to maintain granular shoulders in Iowa. In addition, better performance of granular shoulders reduces the urgency to pave granular shoulders. Delaying or permanently avoiding paving shoulders where possible allows more flexibility in making investments in the road network. To stabilize shoulders and reduce the number of maintenance cycles necessary per season, one possible stabilizing agent—acidulated soybean oil soapstock—was investigated in this research. A pilot testing project was conducted for selected problematic shoulders in northern and northeastern Iowa. Soapstock was applied on granular shoulders and monitored during application and pre- and post-application. Application techniques were documented and the percentage of application success was calculated for each treated shoulder section. As a result of this research, it was concluded that soybean oil soapstock can be an effective stabilizer for granular shoulders under certain conditions. The researchers also developed draft specifications that could possibly be used to engage a contractor to perform the work using a maintenance-type construction contract. The documented application techniques from this project could be used as guidance for those who want to apply soapstock for stabilizing granular shoulders but might not be familiar with this technique.

Crushed Stone Granular Surfacing Materials, HR-2046 and MLR-90-07, 1990

This project included the following tasks: (1) Preparation of a questionnaire and survey of all 99 Iowa county engineers for input on current surfacing material practice; (2) County survey data analysis and selection of surfacing materials gradations to be used for test road construction; (3) Solicitation of county engineers and stone producers for project participation; (4) Field inspection and selection of the test road; (5) Construction of test road using varying material gradations from a single source; and (6) Field and laboratory testing and test road monitoring. The results of this research project indicate that crushed stone surfacing material graded on the fine side of Iowa Department of Transportation Class A surfacing specifications provides lower roughness and better rideability; better braking and handling characteristics; and less dust generation than the coarser gradations. It is believed that this material has sufficient fines available to act as a binder for the coarser material, which in turn promotes the formation of tight surface crust. This crust acts to provide a smooth riding surface, reduces dust generation, and improves vehicle braking and handling characteristics.

Performance Evaluation of Concrete Pavement Granular Subbase - Pavement Surface Condition Evaluation, TR-554, 2008

This research project covered a wide range of activities that allowed researchers to understand the relationship between stability, pavement distress, and recycled portland cement concrete (RPCC) subbase aggregate materials. Detailed laboratory and field tests, including pavement distress surveys, were conducted at 26 sites in Iowa. Findings show that specific gravities of RPCC are lower than those of crushed limestone. RPCC aggregate material varies from poorly or well-graded sand to gravel. A modified Micro-Deval test procedure showed that abrasion losses of virgin aggregate materials were within the maximum Micro-Deval abrasion loss of 30% recommended by ASTM D6028-06. Micro-Deval abrasion loss of RPCC aggregate materials, however, was much higher than that of virgin materials and exceeded 30% loss. Modulus of elasticity of RPCC subbase materials is high but variable. RPCC subbase layers normally have low permeability. The pavement surfaces for both virgin and RPCC subbase across Iowa were evaluated to fulfill the objectives of this study related to field evaluation. Visual distress surveys were conducted to gather the detailed current pavement condition information including the type, extent, and severity of the pavement distresses. The historical pavement condition information for the surveyed field sections was extracted from the Iowa DOT's Pavement Management Information System (PMIS). The current surface condition of existing field pavements with RPCC subbase was compared with the virgin aggregate subbase sections using two different approaches. The changes in pavement condition indices (PCI and IRI) with time for both types of pavements (subbases) were compared.

Stabilization Procedures to Mitigate Edge Rutting for Granular Shoulders - Phase II, TR-591, 2011

A multifaceted investigation was undertaken to develop recommendations for methods to stabilize granular road shoulders with the goal of mitigating edge ruts. Included was reconnaissance of problematic shoulder locations, a laboratory study to develop a method to test for changes in granular material stability when stabilizing agents are used, and the construction of three sets of test sections under traffic at locations with problematic granular shoulders. Full results of this investigation are included in this report and its appendices. This report also presents conclusions and recommendations based on the study results.

Motor Grader Operator Maintenance of Granular Surfaced Roads : Tips from Iowa Operators, 1991

This booklet is a compilation of notes taken during motor grader operators workshops held at some 20 different locations throughout Iowa during the last two years. It is also the advice of 16 experienced motor grader operators and maintenance foremen (from 14 different counties around Iowa), who serve as instructors and assistant instructors at the "MoGo" workshops. The instructors have all said that they learn as much from the operators who attend the workshops as they impart. Motor grader operators from throughout Iowa have shown us new, innovative and better ways of maintaining gravel roads. This booklet is an attempt to pass on some of these "tips" that we have gathered from Iowa operators. It will need to be revised, corrected, and added to based on the advice we get from you, the operators who do the work here in Iowa.

Granular Base Materials for Flexible Pavements, HR-131, 1970

The coefficients of relative strength (CORS) of base courses for use in the American association state highway officials (AASHO) interim guide for the design of flexible pavements are determined here. Based on (1) volumetric strain--axial strain relationships at minimum volume, and (2) effective stress ratio-cohesion relationships at maximum effective stress ratio, CORS were determined from the results of laboratory triaxial tests on both asphalt-treated and untreated aggregate base course materials. The researchers conclude that volumetric strain-axial strain at minimum volume appear to be appropriate parameters for determining CORS.

Textural controls on induced polarization and permeability in granular media

The spatial resolution visualized with hydrological models and the conceptualized images of subsurface hydrological processes often exceed resolution of the data collected with classical instrumentation at the field scale. In recent years it was possible to increasingly diminish the inherent gap to information from point like field data through the application of hydrogeophysical methods at field-scale. With regards to all common geophysical exploration techniques, electric and electromagnetic methods have arguably to greatest sensitivity to hydrologically relevant parameters. Of particular interest in this context are induced polarisation (IP) measurements, which essentially constrain the capacity of a probed subsurface region to store an electrical charge. In the absence of metallic conductors the IP- response is largely driven by current conduction along the grain surfaces. This offers the perspective to link such measurements to the characteristics of the solid-fluid-interface and thus, at least in unconsolidated sediments, should allow for first-order estimates of the permeability structure.¦While the IP-effect is well explored through laboratory experiments and in part verified through field data for clay-rich environments, the applicability of IP-based characterizations to clay-poor aquifers is not clear. For example, polarization mechanisms like membrane polarization are not applicable in the rather wide pore-systems of clay free sands, and the direct transposition of Schwarz' theory relating polarization of spheres to the relaxation mechanism of polarized cells to complex natural sediments yields ambiguous results.¦In order to improve our understanding of the structural origins of IP-signals in such environments as well as their correlation with pertinent hydrological parameters, various laboratory measurements have been conducted. We consider saturated quartz samples with a grain size spectrum varying from fine sand to fine gravel, that is grain diameters between 0,09 and 5,6 mm, as well as corresponding pertinent mixtures which can be regarded as proxies for widespread alluvial deposits. The pore space characteristics are altered by changing (i) the grain size spectra, (ii) the degree of compaction, and (iii) the level of sorting. We then examined how these changes affect the SIP response, the hydraulic conductivity, and the specific surface area of the considered samples, while keeping any electrochemical variability during the measurements as small as possible. The results do not follow simple assumptions on relationships to single parameters such as grain size. It was found that the complexity of natural occurring media is not yet sufficiently represented when modelling IP. At the same time simple correlation to permeability was found to be strong and consistent. Hence, adaptations with the aim of better representing the geo-structure of natural porous media were applied to the simplified model space used in Schwarz' IP-effect-theory. The resulting semi- empiric relationship was found to more accurately predict the IP-effect and its relation to the parameters grain size and permeability. If combined with recent findings about the effect of pore fluid electrochemistry together with advanced complex resistivity tomography, these results will allow us to picture diverse aspects of the subsurface with relative certainty. Within the framework of single measurement campaigns, hydrologiste can than collect data with information about the geo-structure and geo-chemistry of the subsurface. However, additional research efforts will be necessary to further improve the understanding of the physical origins of IP-effect and minimize the potential for false interpretations.¦-¦Dans l'étude des processus et caractéristiques hydrologiques des subsurfaces, la résolution spatiale donnée par les modèles hydrologiques dépasse souvent la résolution des données du terrain récoltées avec des méthodes classiques d'hydrologie. Récemment il est possible de réduire de plus en plus cet divergence spatiale entre modèles numériques et données du terrain par l'utilisation de méthodes géophysiques, notamment celles géoélectriques. Parmi les méthodes électriques, la polarisation provoquée (PP) permet de représenter la capacité des roches poreuses et des sols à stocker une charge électrique. En l'absence des métaux dans le sous-sol, cet effet est largement influencé par des caractéristiques de surface des matériaux. En conséquence les mesures PP offrent une information des interfaces entre solides et fluides dans les matériaux poreux que nous pouvons lier à la perméabilité également dirigée par ces mêmes paramètres. L'effet de la polarisation provoquée à été étudié dans différentes études de laboratoire, ainsi que sur le terrain. A cause d'une faible capacité de polarisation des matériaux sableux, comparé aux argiles, leur caractérisation par l'effet-PP reste difficile a interpréter d'une manière cohérente pour les environnements hétérogènes.¦Pour améliorer les connaissances sur l'importance de la structure du sous-sol sableux envers l'effet PP et des paramètres hydrologiques, nous avons fait des mesures de laboratoire variées. En détail, nous avons considéré des échantillons sableux de quartz avec des distributions de taille de grain entre sables fins et graviers fins, en diamètre cela fait entre 0,09 et 5,6 mm. Les caractéristiques de l'espace poreux sont changées en modifiant (i) la distribution de taille des grains, (ii) le degré de compaction, et (iii) le niveau d'hétérogénéité dans la distribution de taille de grains. En suite nous étudions comment ces changements influencent l'effet-PP, la perméabilité et la surface spécifique des échantillons. Les paramètres électrochimiques sont gardés à un minimum pendant les mesures. Les résultats ne montrent pas de relation simple entre les paramètres pétro-physiques comme par exemples la taille des grains. La complexité des media naturels n'est pas encore suffisamment représenté par les modèles des processus PP. Néanmoins, la simple corrélation entre effet PP et perméabilité est fort et consistant. En conséquence la théorie de Schwarz sur l'effet-PP a été adapté de manière semi-empirique pour mieux pouvoir estimer la relation entre les résultats de l'effet-PP et les paramètres taille de graines et perméabilité. Nos résultats concernant l'influence de la texture des matériaux et celles de l'effet de l'électrochimie des fluides dans les pores, permettront de visualiser des divers aspects du sous-sol. Avec des telles mesures géo-électriques, les hydrologues peuvent collectionner des données contenant des informations sur la structure et la chimie des fluides des sous-sols. Néanmoins, plus de recherches sur les origines physiques de l'effet-PP sont nécessaires afin de minimiser le risque potentiel d'une mauvaise interprétation des données.

Analysis of Industrial Granular Flow Applications by Using Advanced Collision Models

Granular flow phenomena are frequently encountered in the design of process and industrial plants in the traditional fields of the chemical, nuclear and oil industries as well as in other activities such as food and materials handling. Multi-phase flow is one important branch of the granular flow. Granular materials have unusual kinds of behavior compared to normal materials, either solids or fluids. Although some of the characteristics are still not well-known yet, one thing is confirmed: the particle-particle interaction plays a key role in the dynamics of granular materials, especially for dense granular materials. At the beginning of this thesis, detailed illustration of developing two models for describing the interaction based on the results of finite-element simulation, dimension analysis and numerical simulation is presented. The first model is used to describing the normal collision of viscoelastic particles. Based on some existent models, more parameters are added to this model, which make the model predict the experimental results more accurately. The second model is used for oblique collision, which include the effects from tangential velocity, angular velocity and surface friction based on Coulomb's law. The theoretical predictions of this model are in agreement with those by finite-element simulation. I n the latter chapters of this thesis, the models are used to predict industrial granular flow and the agreement between the simulations and experiments also shows the validation of the new model. The first case presents the simulation of granular flow passing over a circular obstacle. The simulations successfully predict the existence of a parabolic steady layer and show how the characteristics of the particles, such as coefficients of restitution and surface friction affect the separation results. The second case is a spinning container filled with granular material. Employing the previous models, the simulation could also reproduce experimentally observed phenomena, such as a depression in the center of a high frequency rotation. The third application is about gas-solid mixed flow in a vertically vibrated device. Gas phase motion is added to coherence with the particle motion. The governing equations of the gas phase are solved by using the Large eddy simulation (LES) and particle motion is predicted by using the Lagrangian method. The simulation predicted some pattern formation reported by experiment.

The Dynamic Analysis of a Human Skeleton Using the Flexile Multibody Simulation Approach

The human motion study, which relies on mathematical and computational models ingeneral, and multibody dynamic biomechanical models in particular, has become asubject of many recent researches. The human body model can be applied to different physical exercises and many important results such as muscle forces, which are difficult to be measured through practical experiments, can be obtained easily. In the work, human skeletal lower limb model consisting of three bodies in build using the flexible multibody dynamics simulation approach. The floating frame of reference formulation is used to account for the flexibility in the bones of the human lower limb model. The main reason of considering the flexibility inthe human bones is to measure the strains in the bone result from different physical exercises. It has been perceived the bone under strain will become stronger in order to cope with the exercise. On the other hand, the bone strength is considered and important factors in reducing the bone fractures. The simulation approach and model developed in this work are used to measure the bone strain results from applying raising the sole of the foot exercise. The simulation results are compared to the results available in literature. The comparison shows goof agreement. This study sheds the light on the importance of using the flexible multibody dynamic simulation approach to build human biomechanical models, which can be used in developing some exercises to achieve the optimalbone strength.

Theoretical Analysis and Simulations of Vertically Vibrated Granular Materials

The dynamical properties ofshaken granular materials are important in many industrial applications where the shaking is used to mix, segregate and transport them. In this work asystematic, large scale simulation study has been performed to investigate the rheology of dense granular media, in the presence of gas, in a three dimensional vertical cylinder filled with glass balls. The base wall of the cylinder is subjected to sinusoidal oscillation in the vertical direction. The viscoelastic behavior of glass balls during a collision, have been studied experimentally using a modified Newton's Cradle device. By analyzing the results of the measurements, using numerical model based on finite element method, the viscous damping coefficient was determinedfor the glass balls. To obtain detailed information about the interparticle interactions in a shaker, a simplified model for collision between particles of a granular material was proposed. In order to simulate the flow of surrounding gas, a formulation of the equations for fluid flow in a porous medium including particle forces was proposed. These equations are solved with Large Eddy Simulation (LES) technique using a subgrid-model originally proposed for compressible turbulent flows. For a pentagonal prism-shaped container under vertical vibrations, the results show that oscillon type structures were formed. Oscillons are highly localized particle-like excitations of the granular layer. This self-sustaining state was named by analogy with its closest large-scale analogy, the soliton, which was first documented by J.S. Russell in 1834. The results which has been reportedbyBordbar and Zamankhan(2005b)also show that slightly revised fluctuation-dissipation theorem might apply to shaken sand, which appears to be asystem far from equilibrium and could exhibit strong spatial and temporal variations in quantities such as density and local particle velocity. In this light, hydrodynamic type continuum equations were presented for describing the deformation and flow of dense gas-particle mixtures. The constitutive equation used for the stress tensor provides an effective viscosity with a liquid-like character at low shear rates and a gaseous-like behavior at high shear rates. The numerical solutions were obtained for the aforementioned hydrodynamic equations for predicting the flow dynamics ofdense mixture of gas and particles in vertical cylindrical containers. For a heptagonal prism shaped container under vertical vibrations, the model results were found to predict bubbling behavior analogous to those observed experimentally. This bubbling behavior may be explained by the unusual gas pressure distribution found in the bed. In addition, oscillon type structures were found to be formed using a vertically vibrated, pentagonal prism shaped container in agreement with computer simulation results. These observations suggest that the pressure distribution plays a key rolein deformation and flow of dense mixtures of gas and particles under vertical vibrations. The present models provide greater insight toward the explanation of poorly understood hydrodynamic phenomena in the field of granular flows and dense gas-particle mixtures. The models can be generalized to investigate the granular material-container wall interactions which would be an issue of high interests in the industrial applications. By following this approach ideal processing conditions and powder transport can be created in industrial systems.

Experimental insights into deformation dynamics and intermittency in rapid granular shear flows

This work concerns the experimental study of rapid granular shear flows in annular Couette geometry. The flow is induced by continuous driving of the horizontal plate at the top of the granular bed in an annulus. The compressive pressure, driving torque, instantaneous bed height and rotational speed of the shearing plate are measured. Moreover, local stress fluctuations are measured in a medium made of steel spheres 2 and 3 mm in diameter. Both monodisperse packing and bidisperse packing are investigated to reveal the influence of size diversity in intermittent features of granular materials. Experiments are conducted in an annulus that can contain up to 15 kg of spherical steel balls. The shearing granular medium takes place via the rotation of the upper plate which compresses the material loaded inside the annulus. Fluctuations of compressive force are locally measured at the bottom of the annulus using a piezoelectric sensor. Rapid shear flow experiments are pursued at different compressive forces and shear rates and the sensitivity of fluctuations are then investigated by different means through monodisperse and bidisperse packings. Another important feature of rapid granular shear flows is the formation of ordered structures upon shearing. It requires a certain range for the amount of granular material (uniform size distribution) loaded in the system in order to obtain stable flows. This is studied more deeply in this thesis. The results of the current work bring some new insights into deformation dynamics and intermittency in rapid granular shear flows. The experimental apparatus is modified in comparison to earlier investigations. The measurements produce data for various quantities continuously sampled from the start of shearing to the end. Static failure and dynamic shearing ofa granular medium is investigated. The results of this work revealed some important features of failure dynamics and structure formation in the system. Furthermore, some computer simulations are performed in a 2D annulus to examine the nature of kinetic energy dissipation. It is found that turbulent flow models can statistically represent rapid granular flows with high accuracy. In addition to academic outcomes and scientific publications our results have a number of technological applications associated with grinding, mining and massive grain storages.

Mass transfer and particleinteractions in granular systems and suspension flows

The purpose of this study was to investigate some important features of granular flows and suspension flows by computational simulation methods. Granular materials have been considered as an independent state ofmatter because of their complex behaviors. They sometimes behave like a solid, sometimes like a fluid, and sometimes can contain both phases in equilibrium. The computer simulation of dense shear granular flows of monodisperse, spherical particles shows that the collisional model of contacts yields the coexistence of solid and fluid phases while the frictional model represents a uniform flow of fluid phase. However, a comparison between the stress signals from the simulations and experiments revealed that the collisional model would result a proper match with the experimental evidences. Although the effect of gravity is found to beimportant in sedimentation of solid part, the stick-slip behavior associated with the collisional model looks more similar to that of experiments. The mathematical formulations based on the kinetic theory have been derived for the moderatesolid volume fractions with the assumption of the homogeneity of flow. In orderto make some simulations which can provide such an ideal flow, the simulation of unbounded granular shear flows was performed. Therefore, the homogeneous flow properties could be achieved in the moderate solid volume fractions. A new algorithm, namely the nonequilibrium approach was introduced to show the features of self-diffusion in the granular flows. Using this algorithm a one way flow can beextracted from the entire flow, which not only provides a straightforward calculation of self-diffusion coefficient but also can qualitatively determine the deviation of self-diffusion from the linear law at some regions nearby the wall inbounded flows. Anyhow, the average lateral self-diffusion coefficient, which was calculated by the aforementioned method, showed a desirable agreement with thepredictions of kinetic theory formulation. In the continuation of computer simulation of shear granular flows, some numerical and theoretical investigations were carried out on mass transfer and particle interactions in particulate flows. In this context, the boundary element method and its combination with the spectral method using the special capabilities of wavelets have been introduced as theefficient numerical methods to solve the governing equations of mass transfer in particulate flows. A theoretical formulation of fluid dispersivity in suspension flows revealed that the fluid dispersivity depends upon the fluid properties and particle parameters as well as the fluid-particle and particle-particle interactions.

Aspereza equivalente de ríos con contorno granular grueso

El concepto de aspereza equivalente (ks) permite relacionar la resistencia al flujo de cauces de contorno granular con el tamaño de las partículas que lo conforman, mediante la ley logarítmica de distribución vertical de velocidad de la corriente. En este artículo se revisa el estado del conocimiento acerca de los criterios para la predicción de dicha relación con el objetivo de brindar una guía para la selección de los mismos. Pese a que el análisis de las experiencias compiladas desvela la dispersión de resultados, a efectos prácticos se recomienda para ríos de grava y de montaña: ks 3•d90; ks 3,4•d84 y ks 7•d50. Dicha dispersión y el hecho de que ks sea varias veces superior al diámetro medio del sedimento puede atribuirse en diferente grado: a la heterogeneidad del sedimento en lechos naturales, a las formas de fondo, al transporte sólido de fondo,así como a las limitaciones del modelo logarítmico de distribución de velocidad bajo ciertas condiciones de flujo. La predicción de ks en función de variables estadísticas del campo de elevaciones del lecho se ha revelado como una alternativa con una elevada capacidad explicativa, por lo que en la medida que avancen las técnicas microtopográficas se consolidará esta vía como el método del futuro.