Academic literature on the topic 'DEM Soil'
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Journal articles on the topic "DEM Soil"
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Michalopoulou, Maria, Nikolaos Depountis, Konstantinos Nikolakopoulos, and Vasileios Boumpoulis. "The Significance of Digital Elevation Models in the Calculation of LS Factor and Soil Erosion." Land 11, no. 9 (September 16, 2022): 1592. http://dx.doi.org/10.3390/land11091592.
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This study focuses on the role of topography in soil erosion modelling by examining the impact of topographic data from various sources on the calculation of the slope length and slope steepness factor (LS). For this purpose, the Pinios dam drainage basin in the Ilia Regional Unit, Western Greece, was selected as a pilot area of this study. Specifically, six Digital Elevation Models (DEM) from four different sources with various resolutions (5, 30, and 90 m) were compared with ground control point (GCP) values to assess their relative vertical accuracy. These DEM were acquired for the calculation of the LS factor by using two different equations. Then the calculated LS factors were implemented in the RUSLE model for the estimation of soil loss. The current study includes a comparative analysis of the elevation, the slopes, the LS factor, and the soil loss. The results showed that the 5 m resolution DEM had the best vertical accuracy, and thus it is considered to be the most suitable DEM for soil erosion modelling. Moreover, the comparison of the DEM elevation values showed high similarity, in contrast to the slope values. In addition, the comparative assessment of the LS and soil loss values calculated from each DEM with the two LS equations revealed a great divergence. It is noticeable that both LS and soil loss results presented higher values for slopes greater than 20°. It is concluded that the comparison of the LS values calculated with the two examined approaches and the use of different DEM with various resolutions and different sources does not change consistently with the increase of DEM grid size and accuracy. Thus, it is very significant in soil erosion modelling to use an LS equation that imports thresholds in its formula to avoid overestimation in soil loss calculations.
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Aouichaty, Nabil, Yassine Bouslihim, Said Hilali, Abdeljalil Zouhri, and Yahya Koulali. "Influence of DEM resolution on the RUSLE model: Case of abandoned quarries in Settat province (Morocco)." E3S Web of Conferences 314 (2021): 04004. http://dx.doi.org/10.1051/e3sconf/202131404004.
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Topographic slope information is one of the critical variables, which governs soil erosion. This topographic slope can be derived from the Digital Elevation Model (DEM). Significant discrepancies are found in the estimation of soil erosion using different DEMs of different resolutions. In the present study, the Revised Universal Soil Loss Equation (RUSLE) was used for soils in the Settat province (Morocco) to assess the risk of water erosion caused by abandoned quarries. The soil erosion rate was divided into five classes to illustrate the erosion rate variability using two DEMs (30m and 90m). The impact of topography on erosion was determined by calculating the value of the LS factors. In this case, the values obtained vary between 0 - 120.623 for ASTER DEM (30m) and 0 - 10.225 for DEM SRTM (90m). The results also show that most quarries have a soil loss rate that varies between 0 t/ha/year and 8.1 t/ha/year for ASTER DEM (30 m). However, for DEM SRTM (90 m), the soil loss rate is zero. This suggests that RUSLE model users should use high-resolution input data for a close representation of reality and capture the maximum results with reasonable accuracy.
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Wu, Jiaxiong, Yanhua Shen, Shudi Yang, and Zhipeng Feng. "Simulation of Track-Soft Soil Interactions Using a Discrete Element Method." Applied Sciences 12, no. 5 (February 28, 2022): 2524. http://dx.doi.org/10.3390/app12052524.
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With the development of unmanned tracked vehicles, soil model predictions of soft terrains are becoming more essential. In order to accurately simulate the interaction characteristics between soil particles and the track, soil modeling with a discrete element method (DEM) is proposed. Volume-based scaled-up modeling of DEM soil particles and the calibration of DEM input parameters were investigated as a feasible approach to realizing many particle calculations. Calibration of DEM input parameters can solve the distortions between actual and DEM particle sizes. Cohesion and friction parameters of the scaled-up soil particle model were recalibrated by the shape accumulated through the virtual design of the experiment. Soil DEM particles were scaled up to 1 mm spherical particles, and recalibrated DEM parameter values were used to match the actual accumulated soil shape. Three calibrated scaled-up soil models were used for the shear stress–displacement DEM simulation of a track segment, and the mean absolute percentage error (MAPE) was less than 11% compared with the actual shear stress–displacement test. The parameter value of soil traction performance empirical model of a tracked vehicle is modified according to the soil shear stress–displacement DEM simulation. Comparative analysis was performed for travel test results of a tracked vehicle; the relative error of the soil traction prediction results to actuals was less than 16.8%. This showed that the volume-based particle scaling technique is an effective DEM for the mechanical simulation of soil.
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Drover, D. R., C. R. Jackson, M. Bitew, and E. Du. "Effects of DEM scale on the spatial distribution of the TOPMODEL topographic wetness index and its correlations to watershed characteristics." Hydrology and Earth System Sciences Discussions 12, no. 11 (November 12, 2015): 11817–46. http://dx.doi.org/10.5194/hessd-12-11817-2015.
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Abstract. Topographic wetness indices (TWIs) calculated from digital elevation models (DEMs) are meant to predict relative landscape wetness and should have predictive power for soil and vegetation attributes. While previous researchers have shown cumulative TWI distributions shift to larger values as DEM resolution decreases, there has been little work assessing how DEM scales affect TWI spatial distributions and correlations with soil and vegetation properties. We explored how various DEM resolutions (2, 5, 10, 20, 30, and 50 m) subsampled from high definition LiDAR altered the spatial distribution of TWI values and the correlations of these values with soil characteristics determined from point samples, Natural Resources Conservation Service (NRCS) soil units, depths to groundwater, and managed vegetation distributions within a first order basin in the Upper Southeastern Coastal Plain with moderate slopes, flat valleys, and several wetlands. Point-scale soil characteristics were determined by laboratory analysis of point samples collected from riparian transects and hillslope grids. DEM scale affected the spatial distribution of TWI values in ways that affect our interpretation of landscape processes. At the finest DEM resolutions, valleys disappeared as TWI values were driven by local microtopography and not basin position. Spatial distribution of TWI values most closely matched the spatial distribution of soils, depth to groundwater, and vegetation stands for the 10, 20, and 30 m resolutions. DEM resolution affected the shape and direction of relationships between soil nitrogen and carbon contents and TWI values, but TWI values provided poor prediction of soil chemistry at all resolutions.
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Newton, Paul C. D., Gregor W. Yeates, and Des J. Ross. "Response of soil nematode fauna to naturally elevated CO2 levels influenced by soil pattern." Nematology 1, no. 3 (1999): 285–93. http://dx.doi.org/10.1163/156854199508289.
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Abstract As experimental elevation of CO2 in short-term experiments may produce organic matter with decomposition characteristics different from those produced under long-term equilibrated conditions, we sampled the soil nematode fauna near a natural CO2 vent in Northland, New Zealand. Various indices of the nematode fauna showed significant effects, with all being significantly correlated with soil pH, microbial carbon and atmospheric CO2 across the 33 sampling points. There was a general decrease in nematode abundance and diversity, but an increase in dominance and proportion of bacterial-feeding nematodes with increasing atmospheric CO2 concentration. However, when the nematode data from gley and organic soils present at the site were differentiated most of the significant correlations were with soil microbial carbon; they were positive in the organic soil but negative in the gley soil. That these responses can be related to soil carbon and to microbial carbon demonstrates that any general response to long-term CO2 enrichment represents an integration of specific responses by the soil biota in the various soils present. Die Reaktion der Bodennematodenfauna auf durch Bodenbedingungen beeinflusste naturlich erhohte CO2-Werte - Da eine experimentelle Erhohung von CO2 in Kurzzeitversuchen organisches Material erzeugen konnte, das andere Zersetzungseigenschaften hat als das unter ausgeglichenen Langzeitbedingungen entstehende, haben wir die Nematodenfauna in Bodenproben aus der Nahe eines naturlichen CO2-Austrittes in Northland, Neuseeland untersucht. Bei mehreren Kennzeichen der Nematodenfauna zeigten sich deutliche Wirkungen, die alle signifikant korreliert waren mit dem Boden-pH, dem mikrobiellen Kohlenstoff und dem atmospharischen CO2, und zwar quer durch alle 33 Entnahmestellen. Mit steigender Konzentration des atmospharischen CO2 trat eine allgemeine Abnahme der Haufigkeit und der Verschiedenartigkeit der Nematoden ein, aber eine Zunahme der Vorherrschaft und des Anteils bakterienfressender Nematoden. Wenn aber die Nematodenwerte von an einer Entnahmestelle vorhandenen Gley- und organischen Boden vergleichen wurden, bestanden die meisten der signifikanten Beziehungen mit dem mikrobiellen Kohlenstoff. Sie waren positiv im organischen Boden und negativ im Gleyboden. Die Tatsache, dass diese Reaktionen zum Bodenkohlenstoff und dem mikrobiellen Kohlenstoff in Beziehung gebracht werden konnen zeigt, dass jede allgemeine Reaktion auf eine langfristige Anreicherung von CO2 eine Integration spezischer Reaktionen durch die in den verschiedenen Boden vorhandenen biotischen Faktoren darstellt.
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Lin, Chunxiu, Chang Xia, Zhen Liu, and Cuiying Zhou. "A Comprehensive Correlation Study of Structured Soils in Coastal Area of South China about Structural Characteristics." Journal of Marine Science and Engineering 10, no. 4 (April 6, 2022): 508. http://dx.doi.org/10.3390/jmse10040508.
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Granite residual soil is a common engineering material, and its mechanical properties are of great importance to engineering safety. This kind of soil presents obvious structural characteristics, and many researchers have emphasized the significance of its structural features. According to previous experiments, from a macroscopic perspective, many researchers have investigated the structural relationship between undisturbed and remolded soils, but few studies have considered it in the mesoscopic aspect. Adopting DEM (a mesomechanical simulation method), we can study how the structure affects the mechanical process between undisturbed and remolded soil. Therefore, this paper combines DEM with laboratory tests to study the structural characteristic correlation between undisturbed and remolded soil. The results indicate that a weak cohesion effect exists in undisturbed soil, and the damage of weak cohesion elements accompanies the failure process. Weak cohesion elements in undisturbed soil cause inhomogeneities in deformation, stress state, and damage accumulation, which ultimately causes differences in strength curves. This paper explains the mechanism of the structural effect on mechanical evolution from a mesomechanical perspective. The DEM simulation method proposed in this paper can be applied to structured soils and better guide engineering practice.
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Zhou, Hao, Tienan Zhou, Xuezhen Wang, Lian Hu, Shengsheng Wang, Xiwen Luo, and Jiangtao Ji. "Determination of Discrete Element Modelling Parameters of a Paddy Soil with a High Moisture Content (>40%)." Agriculture 12, no. 12 (November 24, 2022): 2000. http://dx.doi.org/10.3390/agriculture12122000.
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Discrete element modelling (DEM) parameters are of great importance for the accurate prediction of soil properties and disturbance. This study aimed to provide an efficient method for accurately determining the DEM parameters of a paddy soil with a high moisture content (45.66%). The DEM parameters of the paddy soil modelled using the Hertz–Mindlin with JKR contact model were determined by using the Plackett–Burman (PB), steepest ascent, and central composite tests. The accuracies of the developed DEM models were evaluated using actual slumping tests. Based on the PB test, the surface energy of soil, coefficients of soil–soil rolling friction, and coefficients of soil–steel static friction exerted larger influences on the overall relative error (δZH). The optimization results showed that to achieve a minimum δZH (5.96%), the surface energy of soil, the coefficients of soil–soil rolling friction, and the coefficients of soil–steel static friction should be 0.808 J m−2, 0.11, and 0.6, respectively. The optimized DEM model had an overall relative error of 7.27% with a coefficient of variation of 1.32%, indicating that the DEM parameters of the calibrated paddy soil had good accuracy.
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Chidi, Chhabi Lal, Wei Zhao, Suresh Chaudhary, Donghong Xiong, and Yanhong Wu. "Sensitivity Assessment of Spatial Resolution Difference in DEM for Soil Erosion Estimation Based on UAV Observations: An Experiment on Agriculture Terraces in the Middle Hill of Nepal." ISPRS International Journal of Geo-Information 10, no. 1 (January 13, 2021): 28. http://dx.doi.org/10.3390/ijgi10010028.
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Soil erosion in the agricultural area of a hill slope is a fundamental issue for crop productivity and environmental sustainability. Building terrace is a very popular way to control soil erosion, and accurate assessment of the soil erosion rate is important for sustainable agriculture and environmental management. Currently, many soil erosion estimations are mainly based on the freely available medium or coarse resolution digital elevation model (DEM) data that neglect micro topographic modification of the agriculture terraces. The development of unmanned aerial vehicle (UAV) technology enables the development of high-resolution (centimeter level) DEM to present accurate topographic features. To demonstrate the sensitivity of soil erosion estimates to DEM resolution at this high-resolution level, this study tries to evaluate soil erosion estimation in the Middle Hill agriculture terraces in Nepal based on UAV derived high-resolution (5 × 5 cm) DEM data and make a comparative study for the estimates by using the DEM data aggregated into different spatial resolutions (5 × 5 cm to 10 × 10 m). Firstly, slope gradient, slope length, and topographic factors were calculated at different resolutions. Then, the revised universal soil loss estimation (RUSLE) model was applied to estimate soil erosion rates with the derived LS factor at different resolutions. The results indicated that there was higher change rate in slope gradient, slope length, LS factor, and soil erosion rate when using DEM data with resolution from 5 × 5 cm to 2 × 2 m than using coarser DEM data. A power trend line was effectively used to present the relationship between soil erosion rate and DEM resolution. The findings indicated that soil erosion estimates are highly sensitive to DEM resolution (from 5 × 5 cm to 2 × 2 m), and the changes become relatively stable from 2 × 2 m. The use of DEM data with pixel size larger than 2 × 2 m cannot detect the micro topography. With the insights about the influencing mechanism of DEM resolution on soil erosion estimates, this study provides important suggestions for appropriate DEM data selection that should be investigated first for accurate soil erosion estimation.
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Feng, De Cheng, Wen Xin Zuo, and Peng Cao. "The Prospect and Review of DEM Model Using in Saturated and Unsaturated Soil." Applied Mechanics and Materials 105-107 (September 2011): 1371–75. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1371.
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The saturated and unsaturated soil were widely studied by many researchers nowadays. With the development of calculation mechanics and computer, the discrete element method (DEM), as a powerful technique, has been implemented in saturated soil mechanics. This paper review the development of DEM and its application in saturated soil research. Meanwhile, it also prospect the application of DEM in unsaturated soil research. Besides, it also raised some problems that might be met in the real practice and it also tried to put forward some reasonable methods to solve these problems. In the end, this paper put forward a new DEM contact model based on the surface energy to analysis unsaturated soil.
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Nguyen, Hoang Bao Khoi, Md Mizanur Rahman, and Md Rajibul Karim. "An Investigation of Instability on Constant Shear Drained (CSD) Path under the CSSM Framework: A DEM Study." Geosciences 12, no. 12 (December 6, 2022): 449. http://dx.doi.org/10.3390/geosciences12120449.
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Soil liquefaction or instability, one of the most catastrophic phenomena, has attracted significant research attention in recent years. The main cause of soil liquefaction or instability is the reduction in the effective stress in the soil due to the build-up of pore water pressure. Such a phenomenon has often been thought to be related to the undrained shearing of saturated or nearly saturated sandy soils. Notwithstanding, many researchers also reported soil instability under a drained condition due to the reduction in lateral stress. This condition is often referred to as the constant shear drained (CSD) condition, and it is not uncommon in nature, especially in a soil slope. Even though several catastrophic dam failures have been attributed to CSD failure, the failure mechanisms in CSD conditions are not well understood, e.g., how the volumetric strain or effective stress changes at the triggering of flow deformation. Researchers often consider the soil fabric to be one of the contributors to soil behaviour and use this parameter to explain the failure mechanism of soil. However, the soil fabric is difficult to measure in conventional laboratory tests. Due to that reason, a numerical approach capable of capturing the soil fabric, the discrete element method (DEM), is used to investigate the CSD shearing mechanism. A series of simulations on 3D assemblies of ellipsoid particles was conducted. The DEM specimens exhibited instability behaviour when the effective stress paths nearly reached the critical state line. It can be clearly observed that the axial and volumetric strains changed suddenly when the stress states were close to the critical state line. Alongside these micromechanical observations, the study also presents deeper insights into soil behaviour by relating the macro-observations to the micromechanical aspect of the soil.
Dissertations / Theses on the topic "DEM Soil"
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Fakih, Mahmoud. "Modélisation numérique discrète de la croissance racinaire dans un sol : relation force-forme." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT323/document.
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Les racines des plantes jouent un rôle important dans la croissance et le développement des plantes, et il est bien connu que les interactions mécaniques entre une croissance racinaire et le sol environnant peuvent avoir un impact majeur sur la croissance des racines et par conséquent sur la production de biomasse végétale. Ces interactions mécaniques sont l'un des nombreux facteurs qui peuvent expliquent la variabilité de l'architecture des racines, y compris les facteurs génétiques, environnementaux et l'instabilité du développement. Mais ce facteur a souvent été sous-estimé. Nous supposons que la structure hétérogène du sol à l'échelle des grains, démontrée par la large répartition des forces, peut influencer d'une manière significative sur les trajectoires de croissance des racines. Ce travail de thèse vise à déterminer comment les grains dans les sols granulaires se réorganisent sous l'action de la croissance des racines, et en retour, comment les forces résultantes agissant sur les apex des racines modifient leur développement, y compris la cinématique de leurs trajectoires. Nous avons développé un modèle numérique 2D de la croissance des racines dans un milieu granulaire en utilisant la méthode des éléments discrets (DEM). Le modèle est capable de calculer les forces de contacts grain-grain et racine-grain dans un milieu granulaire. Le système racinaire est modélisé en utilisant des chaînes d'éléments de spheroline connectés. L'orientation de la croissance des racines, à chaque étape de croissance est déterminée par la dynamique de la racine entière sous l'action des forces élastiques internes et des forces de réaction exercées par les grains, ces sont les interactions mécaniques qui contrôlent la croissance numérique dans le modèle.Des études paramétriques ont été réalisées afin (i) d'estimer l'influence de la structure granulaire (distribution de grains de diamètre, la cohésion, la fraction volumique ...) et les propriétés mécaniques des racines (la rigidité à la flexion) sur le signal de force axiale agissant sur la pointe de la racine, et sur les trajectoires et (ii) de définir les lois physiques générales qui peuvent être utilisées en outre pour analyser des données expérimentales. Les courbes de distribution des forces axiales calculées normalisées par leurs moyens au cours d'une période donnée de la croissance, sont caractérisées par une loi de puissance décroissante pour les forces en dessous de la force moyenne, et une décroissance exponentielle pour les forces ci-dessus de la force moyenne, reflétant ainsi la large répartition des forces à l'intérieur d'un matériau granulaire. Une analyse de l'écart-type des déformations locales des trajectoires des racines, résulte deux régimes en fonction la rigidité de la racine. Une première lorsque le sol contrôle les déformations des racines, et une deuxième lorsque la racine est trop rigide, et se déplace plus les grains environnants durant la croissancePlant roots play an important role in the growth and development of plants, and it is well known that the mechanical interactions between a growing root and the surrounding soil can have a major impact on root growth and consequently on plant biomass production. These mechanical interactions are one of numerous factors that explain the variability of root architecture, including genetics, environment and developmental instability. But this factor has often been under-estimated. I hypothesize that the heterogeneous structure of soil at the particle scale, demonstrated by the broad distribution of forces, can significantly influence root growth trajectories. This thesis aims at determining how grains in granular soils are reorganized under the action of growing roots, and in return how the resulting forces acting on root tips modify their development, including the kinematics of their trajectories, in order to develop a general biophysical law of root-soil mechanical interactions. I developed a 2D numerical model of root growth in a granular medium using a Discrete Element Model (DEM). The model is able to compute grain-grain and root-grain contact forces within a granular medium. The root system is modelled using chains of connected spheroline elements. The orientation of root growth at every growth step is determined by the dynamics of the whole root under the action of its internal elastic forces and reaction forces exerted by the grains, which are the mechanical interactions that control numerical growth in the model.Parametric studies were carried out in order to (i) estimate the influence of granular structure (grain diameter distribution, cohesion, volume fraction) and root mechanical properties (root bending stiffness) on the axial force signal acting on the root tip, and on the root trajectories and (ii) define general physical laws that can be used further to analyze experimental data. The distribution curves of computed root tip-grain forces normalized by the mean force during a given period of growth were characterized by a decreasing power law for forces below the mean force, and an exponential fall-off for forces above the mean force, thus reflecting the broad distribution of forces inside the granular material. An analysis of the standard deviation of the local deformations of root trajectories resulted in two different regimes with regard root stiffness. In the first regime, soil controlled the root deformation and in the second, the root trajectory was straighter and displaced more significantly the surrounding grains during growth
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Yue, Peng. "A micro mechanical study of critical state soil mechanics using DEM." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/38060/.
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One of the greatest breakthroughs in soil mechanics was the development of Critical State Soil Mechanics (CSSM) in the 1950s and 1960s and the derivation of a continuum elasto-plastic constitutive model, namely Cam clay, which was the foundation for other continuum models for clays, and much later for sands. However, as yet there has been no micro mechanical analysis which explains the existence of such continuum models; such a micro perspective must take into account the discontinuous nature of soil. Without such insight, the engineer cannot understand which micro parameters affect soil behaviour. This work uses the discrete element method (DEM) to model a silica sand as a sample of discrete particles, with properties which have been calibrated against experimental data in previous work, to build up a micro mechanical picture of the behaviour of sand under different loading conditions. The simplest of loading conditions is the one dimensional or oedometer test and has been modelled to check whether this agrees with previously published research. The simulated sample has then been subjected to isotropic compression to establish a normal compression line in log voids ratio – log stress space, and which turns out to be parallel to the one-dimensional normal compression line, in agreement with CSSM. The evolution of the isotropic normal compression line is due to local shear stresses within the sample, and the origin of the existence of both lines lies in the evolution of a fractal distribution of particles with a fractal dimension of 2.5. The effect of boundary particles has then been minimised by choosing an appropriate aspect ratio and a smaller number of particles in the sample to give a computational time which is acceptable for subsequent shearing to critical states. Isotropically normally compressed samples have been unloaded to different stress levels and sheared to critical states. A unique critical state line (CSL) exists at high stress levels, which is parallel to the normal compression lines, in agreement with CSSM. At low stress levels, the CSL is not linear and is non-unique; that is to say it is a function of preconsolidation pressure because the fractal distribution of sizes has not fully evolved. Samples sheared on the dense side of critical dilate and have a peak strength whilst loose samples exhibit ductile contraction, in agreement with CSSM. At a critical state, the work shows that crushing continues in the formation of ‘fines’, small particles with smaller than 0.1mm dimensions, which plays no part in the mechanical behaviour, which is reflected in the average mechanical co-ordination number and which means that plastic hardening can be assumed to have ceased at a critical state. For the isotropically overconsolidated samples sheared to critical states, a number of different definitions of yield have been used to establish a yield surface in stress space. The work shows that a previously published yield surface for sand (Yu, 1998; McDowell, 2002) gives a good representation of the behaviour, and it has therefore been shown that the sample of discrete particles has been shown to give rise to observed continuum behaviour. The work is, to the author’s knowledge, the first that has shown a DEM soil to show many of the desirable features of sand, in that the sample qualitatively gives normal compression lines and a CSL of the correct slope, which obeys CSSM and which gives a Cam Clay type yield surface in stress space. The work means that the established model can be used in the study of other micro mechanics problems such as particle shape and time effects and the application of DEM to boundary value problems directly.
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Huang, Xin, and 黃昕. "Exploring critical-state behaviour using DEM." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206742.
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The critical state soil mechanics (CSSM) framework originally proposed by Schofield & Wroth (1968) has been shown to capture the mechanical behaviour of soils effectively. The particulate implementation of the discrete element method (DEM) can replicate many of the complex mechanical characteristics associated with sand. This research firstly shows that the CSSM framework is useful to assess whether a DEM simulation gives a response that is representative of a real soil. The research then explores the capacity of DEM to extend understanding of soil behaviour within the CSSM framework.
The influence of sample size on the critical-state response observed in DEM simulations that use rigid-wall boundaries was examined. The observed sensitivity was shown to be caused by higher void ratios and lower contact densities adjacent to the boundaries. When the void ratio (e) and mean stress (p’) of the homogeneous interior regions were considered, the influence of sample size on the position of the critical state line (CSL) in e-log(p’) space diminished.
A parametric study on the influence of the interparticle friction (μ) on the load-deformation response was carried out. The macro-scale stress-deformation characteristics were nonlinearly related to μ and the particle-scale measures (fabric, contact force distribution, etc.) varied systematically with μ. The limited effect of increases in μ on the overall strength at high μ values (μ>0.5) is attributable to transition from sliding-dominant to rolling-dominant contact behaviour. A μ value higher than 0.5 leads to a CSL in e-log(p’) space that does not capture real soil response.
True-triaxial simulations with different intermediate stress ratios (b) were performed. The dependency of strength on b agreed with empirical failure criteria for sands and was related to a change of buckling modes of the strong force chains as b increased. DEM simulations showed that the position of the CSL in e-log(p’) space depends on the intermediate stress ratio b. This sensitivity seems to be related to the dependency of the directional fabric anisotropy on b. The link between the state parameter and both soil strength and dilatancy proposed by Jefferies & Been (2006) was reproduced in DEM simulations.
A new rotational resistance model was proposed and it was shown that the new model can qualitatively capture the influence of particle shape on the mechanical behaviour of sand. However, it was shown that the effect of rotational resistance is limited and to quantitatively compare the DEM simulation results with laboratory testing data, e.g., the critical-state loci, it is necessary to use non-spherical particles.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
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Mok, Benjamin Chit Man. "An investigation of strain localization in cemented sands and mechanisms of stiffness anisotropy using the dem simulations /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202007%20MOK.
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Preko, Kwasi. "Determination of Volumetric Soil Water Content Using Ground Penetrating Radar Bestimmung des volumetrischen Bodenwassergehaltes mit dem Bodenradar /." [S.l. : s.n.], 2007. http://digbib.ubka.uni-karlsruhe.de/volltexte/1000007396.
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Nishiyama, Kenta. "Analysis of Soil-Tire Interaction Using a Two-Dimensional Finite Element-Discrete Element Method." Kyoto University, 2019. http://hdl.handle.net/2433/245298.
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Li, Jun. "Numerical investigations of the coupled DEM-LBM technique with application to leakage-soil interaction due to a leaking pipe." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4016/.
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This thesis is motivated by developing a numerical tool, FPS-BHAM, in exploring the large-scale fluid-particle system with local interaction behaviours being captured. A blocked partitioning domain decomposition strategy with the philosophies of parallel computing and combination with a large-scale modelling technique is proposed in this thesis. The illustration of detailed implementation of DEM-LBM, with its verification in FPS-BHAM and its validation using a pipe leakage problem, are subsequently conducted. A good parallel behaviour is achieved by applying the blocked partitioning domain decomposition strategy, which is proposed in this thesis. The DEM-DFF technique is also successfully implemented in FPS-BHAM as well. Furthermore, a combination strategy between DEM-LBM and DEM-DFF is proposed in this thesis. A good computational benefit is found to be achieved by adopting the proposed combination strategy. Finally, different behaviours between LBM and DFF during the dynamic propagation to the steady state are investigated by parametric studies.
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Jakob, Christian. "Numerische Modellierung des Verflüssigungsverhaltens von Kippen des Braunkohlenbergbaus beim und nach dem Wiederaufgang von Grundwasser." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-218045.
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Recently observed cumulation of unexpected collapses of slope-distant waste dumps in lignite mining areas of eastern germany re-initiated research of soil liquefaction. Especially it turned the question of internal initials that correspond to water rise. Parallel to laboritory tests and field experiments a micromechanical model should be developed, which can reproduce processes in the soil during saturation.
In first approximation a partly saturated soil consists of two phases: the soil particles and the pore fluid. For micromechanical modeling a coupling of discontinuum particles) and continuum (fluid) is required. The soil particles can be simulated with the Discrete-Element-Method (DEM). For the pore fluid, which is assumed to be a mixture of liquid and gaseous fractions, Pore scale model with Finite Volumes (PFV) is used. At low water content liquid bridges (meniscii) arise between the particles that cause an apparent cohesion. The effect of the meniscii is considered by a correspondingly contact law in the DEM model. During the saturation of a soil both, cohesive effect and fluid bulk modulus, are reduced. In addition buoyancy acts on the particles during the process. The micromechanical modeling approach has the advantage, that just a few model parameters are needed.
The numerical model shows pore fluid pressures during saturation process, that leads to a reduction of effective stress. It is investigated how much the reduction is regarding porosity, degree of saturation, stress conditions and grain shape. Furthermore the influence of model parameters as well as hydromechanics is investigated. The investigations are completed with another series of experiments under special conditions like integration of macropores, horizontal fixed model boundaries and abrupt saturation.
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Bista, Hemanta. "Modeling Hydro-Bio-Chemo-Mechanical Mechanisms in Granular Soils." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1399587419.
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Pelcat, Yann S. "Soil landscape characterization of crop stubble covered fields using Ikonos high resolution panchromatic images." Thesis, Winnipeg : University of Manitoba, 2006. http://www.collectionscanada.ca/obj/s4/f2/dsk3/MWU/TC-MWU-224.pdf.
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Thesis (M.Sc.)--University of Manitoba, 2006.A thesis submitted to the Faculty of Graduate Studies in partial fulfillment of the requirements for the degree of Master of Science, Department of Soil Science. Includes bibliographical references.
Books on the topic "DEM Soil"
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Mense-Stefan, Anna. Standortdifferenzierte Abschätzung von Sickerwasserraten in Hessen: Ein Beitrag zur Ermittlung von Stofffrachten aus dem Boden. Mainz: Geographisches Institut der Johannes Gutenberg Universität, 2005.
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Claassen, Norbert. Nährstoffaufnahme höherer Pflanzen aus dem Boden: Ergebnis von Verfügbarkeit und Aneignungsvermögen. Göttingen: Severin, 1990.
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Teferra, Alemayehu. Formulae, charts and tables in the area of soil mechanics and foundation engineering: Stresses in soils = Formeln, Tafeln und Tabellen aus dem Gebiet Grundbau und Bodenmechanik : Bodenspannungen. Rotterdam: A.A. Balkema, 1988.
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Olivo, Eduardo Felipe Casanova. Introducción a la ciencia del suelo. Caracas: Universidad Central de Venezuela, Facultad de Agronomía, Consejo de Desarrollo Científico y Humanístico, 1991.
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Contaminación del suelo: Estudios, tratamiento y gestión. Madrid: Ediciones Mundi-Prensa, 1999.
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González, Juan Antonio. Valle del Cibao: Ecología, suelos y degradación. 2nd ed. Santo Domingo, República Dominicana: Editora Manatí, 2003.
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Valle del Cibao: Ecología, suelos y degradación. Santo Domingo, República Dominicana: [s.n.], 1999.
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Valarezo, Galo Ramón. Tierras y manos indias: La recuperación del suelo en las comunidades andinas de Chimborazo. Quito, Ecuador: Ediciones Abya-Yala, 1993.
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José Luis de la Horra Ruiz. Estudio de los suelos del Campo de Calatrava (Ciudad Real) y sus condiciones de fertilidad. Madrid: Consejo Superior de Investigaciones Científicas, 2008.
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Italy) Workshop "La percezione del suolo" (2010 Palermo. La percezione del suolo: Atti del workshop : Giornata mondiale del suolo : Workshop "La percezione del suolo", Palermo 2-3 dicembre 2010. Brienza (Potenza): Edizioni Le penseur, 2011.
Find full textBook chapters on the topic "DEM Soil"
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von Schneidemesser, Dirk. "Öffentliche Mobilität und neue Formen der Governance: das Beispiel Volksentscheid Fahrrad." In Öffentliche Mobilität, 139–63. Wiesbaden: Springer Fachmedien Wiesbaden, 2021. http://dx.doi.org/10.1007/978-3-658-32106-2_6.
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ZusammenfassungDer Anstoß für Deutschlands erstes Fahrradgesetz kam aus der Zivilgesellschaft. Der Impuls entstand aus dem weiterhin ungeklärten Konflikt zwischen der Autofixierung der konservativen deutschen Verkehrspolitik und dem progressiven Wunsch nach einer nachhaltigen Mobilität, die sich an den Bedürfnissen der Bürger*innen orientieren soll und eine Umverteilung des Straßenraumes zugunsten des Radverkehrs erforderte. Dass Verkehr nachhaltiger gestaltet werden muss, war Konsens. Über das Wie gingen die Meinungen stark auseinander.
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Vennemann, Christoph. "Kleinstadtforschung des Bundes." In Kleinstadtforschung, 21–28. Bielefeld, Germany: transcript Verlag, 2022. http://dx.doi.org/10.14361/9783839465080-002.
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Christoph Vennemann widmet sich in diesem Beitrag der Kleinstadtforschung des Bundes. Er zeigt auf, welche Forschungsprojekte bereits durchgeführt wurden und welche sich gerade mit den aktuellen Themen der Kleinstadtentwicklung beschäftigen. Dieser Überblick soll die Beweggründe darstellen, die den Bund dazu bewogen haben, sich mit dem Thema der Kleinstadtforschung zu beschäftigen.
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Kirchner, Aljoscha. "Einleitung." In Entwicklung von Methoden zur abstrakten Modellierung von Automotive Systems-on-Chips, 1–5. Wiesbaden: Springer Fachmedien Wiesbaden, 2022. http://dx.doi.org/10.1007/978-3-658-38437-1_1.
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ZusammenfassungEs sind die großen Technologietrends der heutigen Zeit, welche die Automobilbranche nach wie vor zu einem der großen Treiber der Innovationsentwicklung werden lässt. Dabei ist es neben der Digitalisierung und der Elektrifizierung des Automobils insbesondere die Entwicklung des autonomen Fahrens, welche die Komplexität der Anforderungen stetig steigen lässt. Aus den steigenden Anforderungen in der Automobilbranche resultieren steigende Anforderungen bei den Zulieferern. Ziel dieser Arbeit ist die Effizienzsteigerung in der Entwicklung von Automotive System-on-Chips durch die direkte oder indirekte Senkung der entstehenden Aufwände. Hierzu soll eine Methode entwickelt werden, mit dem Ziel, die bestehenden Defizite des aktuellen Entwicklungs-Flows in der Automotive-SoC-Entwicklung zu minimieren. Ein besonderer Fokus der Arbeit liegt dabei auf dem Erstellen und Pflegen der Spezifikationsdokumente.
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Kordts-Freudinger, Robert, Diana Bücker, Rebecca Schulte, and Nerea Vöing. "»Ich bin froh darüber, dass das so passiert ist«." In Hochschulbildung: Lehre und Forschung, 263–76. Bielefeld, Germany: transcript Verlag, 2021. http://dx.doi.org/10.14361/9783839456903-017.
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Die explorativ angelegte Studie untersucht die möglichen Chancen des Scholarship of Teaching and Learning (SoTL) bei der Bewältigung des Emergency Remote Teaching (ERT) in Folge der Coronavirus-Pandemie 2020-21. Aufbauend auf Definitionen des SoTL wurden acht Lehrende deutscher Hochschulen zu ihrer Lehre, u.a. zu ihren SoTL-Aktivitäten, ihrer Lehre vor und im ERT sowie zu ihrer künftigen Lehre interviewt; die Transkripte wurden inhaltsanalytisch ausgewertet. Die Ergebnisse deuten auf bestimmte Muster bereits vor dem ERT sowie während des ERT hin: Neben einer stark studierendenorientierten Lehrhaltung und der Einschätzung, dass Reflexion zentral in der Lehre sei, erlebten die Befragten das ERT trotz vorhandener Unsicherheiten und teils größerer Lehrbelastung überwiegend als positive Lerngelegenheit für sich selbst und ihre Studierenden. SoTL diente für viele Befragte als wichtige Ressource auf mehreren Ebenen, sodass die forschende Grundhaltung in der Lehre auch künftig erhalten bleiben soll. Im Ergebnis werden drei Chancen von SoTL für ERT dargestellt.
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Laimer, Simon. "Das Schutzlandprinzip als Grundlage für die Behandlung von grenzüberschreitenden Schadensersatzansprüchen aus der Verletzung geistigen Eigentums." In Italienisches, europäisches und internationales Immaterialgüterrecht, 149–60. Berlin, Heidelberg: Springer Berlin Heidelberg, 2020. http://dx.doi.org/10.1007/978-3-662-62179-0_8.
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ZusammenfassungWeist ein immaterialgüterrechtlicher Sachverhalt grenzüberschreitende Bezüge, mithin Verbindungen zu mehr als einer Rechtsordnung auf, dann ist das darauf anzuwendende nationale Recht nach dem Internationalen Privatrecht des angerufenen Gerichts zu ermitteln. Vom Immaterialgüterrechtsstatut, mithin dem Recht, das den Bestand, Inhalt und Schutz von geistigen Eigentumsrechten regelt, ist allerdings das – aus der Sicht EU-mitgliedstaatlicher Gerichte von der Rom I-Verordnung, in der Schweiz von Art. 122 IPRG erfasste – Statut immaterialgüterrechtlicher Verträge zu unterscheiden, das die schuldrechtlichen Beziehungen zwischen den Vertragsparteien beherrscht. In diesem Beitrag, der das Unions-IPR in den Mittelpunkt stellt und einen vergleichenden Blick auf das schweizerische Kollisionsrecht wirft, soll es allein um die kollisionsrechtliche Anknüpfung von außervertraglichen Schuldverhältnissen gehen, die aus einer Verletzung von Rechten des geistigen Eigentums entstehen (Schutzstatut).
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Klingenberg, Ingo. "Implikationen für die quantitative Studie." In Stressbewältigung durch Pflegekräfte, 151–52. Wiesbaden: Springer Fachmedien Wiesbaden, 2022. http://dx.doi.org/10.1007/978-3-658-37438-9_5.
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ZusammenfassungDer empirische Forschungsprozess der vorliegenden Arbeit setzt sich aus einer qualitativen und einer quantitativen personenzentrierten Analyse zusammen (vgl. 3.2.3). Dieses Kapitel dient zur ersten Evaluation der empirischen Vorüberlegungen, die in den Abschnitten 3.2.1 bis 3.2.3 zusammengentragen wurden, vor dem Hintergrund der Erkenntnisse aus der vorangehenden Analyse in Kapitel 4. Dabei soll der Frage nachgegangen werden, ob und inwiefern Anpassungen des weiteren Forschungsprozesses nötig sind
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Priebs, Axel. "Die geplante Region." In Die Region - eine Begriffserkundung, 115–28. Bielefeld, Germany: transcript Verlag, 2022. http://dx.doi.org/10.14361/9783839460108-011.
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Mit dem Beitrag soll die Bedeutung einer geordneten Entwicklung für die Regionen dargestellt werden, für die die Regionalplanung eine wichtige Aufgabe übernimmt. Dabei sollen sowohl die Entstehung der Regionalplanung in ihrem historischen Kontext vorgestellt als auch das spezifische Planungsverständnis der Regionalplanung (u. a. in Abgrenzung etwa zu Planungsprozessen in der Wirtschaft) erläutert werden. Im Mittelpunkt des Beitrages stehen die wesentlichen Herausforderungen, Aufgaben und Instrumente der Regionalplanung, wobei vertieft auf den sehr wesentlichen Zusammenhang der Siedlungsentwicklung mit dem Verkehr und auf die Bedeutung der Freiräume eingegangen wird. Auch die Möglichkeiten zur Förderung starker Orts- und Stadtkerne werden dargelegt. Von besonderer Bedeutung sind die Möglichkeiten der Regionalplanung, zur Energiewende und zur Bewältigung der Folgen des Klimawandels beizutragen. Abschließend wird dann auf die Abgrenzung der Planungsregionen eingegangen.
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Greiner, Rasmus. "Der Klang der Stille. Filmton und Geschichtlichkeit des Weltraums." In Space Agency - Medien und Poetiken des Weltraums, 159–74. Bielefeld, Germany: transcript Verlag, 2021. http://dx.doi.org/10.14361/9783839439968-009.
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Ausgehend von der Beobachtung, dass zahlreiche filmische Reisen durch den Weltraum nicht nur eine räumliche, sondern auch eine historisierende Dimension aufweisen, schlägt der Beitrag eine Brücke zu Konzepten der filmischen Geschichtsschreibung. Der Weltraum fungiert hierbei als unsichtbares Archiv, in dem Geschichte - in Form von Funksignalen - ,hörbar' ist. Diese vor allem auditive Mediatisierung und Historisierung des Weltraums soll im Folgenden an konkreten Beispielen aus Film und Fernsehen weiter erschlossen werden.
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Genkova, Petia, Verena Fässler, and Henrik Schreiber. "Die Rolle von Erziehungsstilen für den Zusammenhang von Auslandsaufenthalten, Selbstwirksamkeit und interkultureller Kompetenz." In Diversity nutzen und annehmen, 179–97. Wiesbaden: Springer Fachmedien Wiesbaden, 2022. http://dx.doi.org/10.1007/978-3-658-35326-1_9.
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ZusammenfassungAufgrund der zentralen Bedeutung interkultureller Interaktion in der globalisierten Welt ist die Entwicklung der interkulturellen Kompetenz von Studierenden während Auslandsaufenthalten von hoher Bedeutung für Wissenschaft und Praxis. In diesem Kapitel liefern und testen wir einen theoretischen Rahmen, der die Selbstwirksamkeitstheorie des Lernens mit interkulturellem Lernen verbindet. Zu diesem Zweck wurde der Zusammenhang zwischen Auslandsaufenthalt, Selbstwirksamkeit, interkulturelle Kompetenz und dem erinnerten Erziehungsstil als moderierende Variable von deutschen Studierenden (N = 203) mittels einer Querschnittsstudie untersucht. Es konnte gezeigt werden, dass Selbstwirksamkeit den Zusammenhang zwischen der Dauer eines Auslandsaufenthaltes und interkultureller Kompetenz in Abhängigkeit von der Wahrnehmung eines emotional warmen Erziehungsstils der Eltern mediiert. Entgegen unserer Annahmen moderieren die Erziehungsstile Kontrolle und Bestrafung nicht den Zusammenhang von Dauer des Auslandsaufenthalts und Selbstwirksamkeit. Dieses Kapitel soll zum Verständnis des interkulturellen Lernens als Ergebnis der Bewältigung interkultureller Herausforderungen beitragen.
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Genkova, Petia, Edwin Semke, and Henrik Schreiber. "Diversity nutzen und annehmen: Leitfaden." In Diversity nutzen und annehmen, 399–400. Wiesbaden: Springer Fachmedien Wiesbaden, 2022. http://dx.doi.org/10.1007/978-3-658-35326-1_19.
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ZusammenfassungIn der Literatur oder auch unter der Charta der Vielfalt existieren mehrere gute Leitfäden, welche sich mit dem Thema Diversity und der Umsetzung von Diversity in Unternehmen beschäftigen.In der Literatur oder auch unter der Charta der Vielfalt existieren mehrere gute Leitfäden, welche sich mit dem Thema Diversity und der Umsetzung von Diversity in Unternehmen beschäftigen.Aus diesem Grund wollen wir die bereits gut ausgearbeiteten Strukturen an dieser Stelle nicht wiederholen oder kopieren.Wir richten unseren Leitfaden daher an den Fragen aus, die von Führungskräften und Multiplikatorinnen und Multiplikatoren im Laufe des Forschungsprojektes an uns herangetragen wurden. Exemplarisch hierfür steht die Frage „Was soll ich denn machen, wenn ich Probleme im Alltag habe und keiner mich versteht?“.
Conference papers on the topic "DEM Soil"
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Guo Xu, Du Mingyi, and Kang Yanyan. "Soil erosion analysis based on DEM." In 2010 2nd International Conference on Information Science and Engineering (ICISE). IEEE, 2010. http://dx.doi.org/10.1109/icise.2010.5691270.
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Farzi Sizkow, Saman, and Usama El Shamy. "A Comparison between Coupled SPH-DEM and LBM-DEM Approaches for Soil Liquefaction." In International Foundations Congress and Equipment Expo 2021. Reston, VA: American Society of Civil Engineers, 2021. http://dx.doi.org/10.1061/9780784483428.006.
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Guo, Yuan, and Xiong (Bill) Yu. "Coupled DEM and CFD Simulations of Soil Erosion." In Geo-Chicago 2016. Reston, VA: American Society of Civil Engineers, 2016. http://dx.doi.org/10.1061/9780784480151.065.
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Ivanovs, Janis, Toms Stals, and Santa Kaleja. "Impact of the use of existing ditch vector data on soil moisture predictions." In Research for Rural Development 2020. Latvia University of Life Sciences and Technologies, 2020. http://dx.doi.org/10.22616/rrd.26.2020.036.
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Wet soils play an important role in hydrological, biological and chemical processes, and knowledge on their spatial distribution is essential in forestry, agriculture and similar fields. Digital elevation models (DEM) and various hydrological indexes are used to perform water runoff and accumulation processes. The prerequisite for the calculation of the hydrological indexes is the most accurate representation of the Earth’s surface in the DEM, which must be corrected as necessary to remove surface artifacts that create a dam effect. In addition, different resolutions for DEM give different results, so it is necessary to evaluate what resolution data is needed for a particular study. The aim of this study is to evaluate the feasibility of using existing ditch vector data for DEM correction and the resulting implications for soil moisture prediction. Applied methodology uses a network of available ditch vectors and creates gaps in the overlapping parts of the DEM. The data were processed using open source GIS software QGIS, GRASS GIS and Whitebox GAT. Ditch vector data were obtained from JSC Latvian State Forests and the Latvian Geospatial Information Agency. The results show that by applying the bottomless ditch approach in forest lands on moraine deposits, depending on the accuracy of the ditch vector data, the values of the prediction of the soil wetness both increase and decrease. On the other hand, in forest lands on graciolimnic sediments it is visible that predicted soil wetness values increase in the close proximity of ditches. For forest lands on glaciofluvial and eolitic sediments there were no visible changes because of lack of ditches.
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Zhao, Deming, Xuyan Hou, Dewei Tang, Jingfen Yuan, Shengyuan Jiang, and Zongquan Deng. "DEM parameter matching of high-dense lunar soil simulant." In 2015 IEEE International Conference on Information and Automation (ICIA). IEEE, 2015. http://dx.doi.org/10.1109/icinfa.2015.7279602.
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Jiang, M. J., B. L. Xi, Z. F. Shen, and Y. S. Dai. "DEM Analyses of Soil Cutting Test in Lunar Ground." In Earth and Space 2014. Reston, VA: American Society of Civil Engineers, 2015. http://dx.doi.org/10.1061/9780784479179.012.
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El Shamy, U. "DEM Simulation of the Seismic Response of Shallow Foundation on Liquefiable Soil." In Geotechnical Earthquake Engineering and Soil Dynamics Congress IV. Reston, VA: American Society of Civil Engineers, 2008. http://dx.doi.org/10.1061/40975(318)119.
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Jayakumar, Paramsothy, Dave Mechergui, and Tamer M. Wasfy. "Understanding the Effects of Soil Characteristics on Mobility." In ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/detc2017-68314.
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The Army’s mission is to develop, integrate, and sustain the right technology solutions for all manned and unmanned ground vehicles, and mobility is a key requirement for all ground vehicles. Mobility focuses on ground vehicles’ capabilities that enable them to be deployable worldwide, operationally mobile in all environments, and protected from symmetrical and asymmetrical threats. In order for military ground vehicles to operate in any combat zone, mobility on off-road terrains should be extensively investigated. Mobility on off-road terrains is poorly understood because of the empirical and semi-empirical methods used in predicting the mobility map. These methods do not capture the soil deformation as well as its non-linear behavior. The discrete element method (DEM) was identified as a high-fidelity method that can capture the deformation of the soil and its non-linear behavior. The DEM method allows to simulate the vehicle on any off-road terrain and to generate an accurate mobility map. In this paper, a simulation study was undertaken to understand the influence of soil characteristics on mobility parameters such as wheel sinkage, wheel slip, vehicle speed, and tractive force. The interaction of the vehicle wheels with soft soil is poorly understood, this study helps understand this interaction. A nominal wheeled vehicle model was built in the DIS/IVRESS software and simulated over different cohesive and non-cohesive soils modeled using DEM. Some characteristics of these soils were varied namely, the soil inter-particle cohesion, the soil inter-particle friction, the soil particle size, and the soil density. The mobility parameters were measured and correlated to the soil characteristics. This study showed that the vehicle speed increased with cohesion, friction, soil density, and particle size, while wheel sinkage and wheel slip decreased with those parameters. The influence of these characteristics combined is more complex; extensive studies of other soil characteristics need to be carried out in the future to understand their effect on vehicle mobility.
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Peña, Andrés A., Ramon García-Rojo, Fernando Alonso-Marroquín, Hans J. Herrmann, Masami Nakagawa, and Stefan Luding. "Investigation of the Critical State in Soil Mechanics Using DEM." In POWDERS AND GRAINS 2009: PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON MICROMECHANICS OF GRANULAR MEDIA. AIP, 2009. http://dx.doi.org/10.1063/1.3179884.
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Sadek, Mohammad A., Mehari Tekeste, and Mojtaba Naderi. "Calibration of soil compaction behavior using Discrete Element Method (DEM)." In 2017 Spokane, Washington July 16 - July 19, 2017. St. Joseph, MI: American Society of Agricultural and Biological Engineers, 2017. http://dx.doi.org/10.13031/aim.201700777.
Full textReports on the topic "DEM Soil"
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Shmulevich, Itzhak, Shrini Upadhyaya, Dror Rubinstein, Zvika Asaf, and Jeffrey P. Mitchell. Developing Simulation Tool for the Prediction of Cohesive Behavior Agricultural Materials Using Discrete Element Modeling. United States Department of Agriculture, October 2011. http://dx.doi.org/10.32747/2011.7697108.bard.
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The underlying similarity between soils, grains, fertilizers, concentrated animal feed, pellets, and mixtures is that they are all granular materials used in agriculture. Modeling such materials is a complex process due to the spatial variability of such media, the origin of the material (natural or biological), the nonlinearity of these materials, the contact phenomenon and flow that occur at the interface zone and between these granular materials, as well as the dynamic effect of the interaction process. The lack of a tool for studying such materials has limited the understanding of the phenomena relevant to them, which in turn has led to energy loss and poor quality products. The objective of this study was to develop a reliable prediction simulation tool for cohesive agricultural particle materials using Discrete Element Modeling (DEM). The specific objectives of this study were (1) to develop and verify a 3D cohesionless agricultural soil-tillage tool interaction model that enables the prediction of displacement and flow in the soil media, as well as forces acting on various tillage tools, using the discrete element method; (2) to develop a micro model for the DEM formulation by creating a cohesive contact model based on liquid bridge forces for various agriculture materials; (3) to extend the model to include both plastic and cohesive behavior of various materials, such as grain and soil structures (e.g., compaction level), textures (e.g., clay, loam, several grains), and moisture contents; (4) to develop a method to obtain the parameters for the cohesion contact model to represent specific materials. A DEM model was developed that can represent both plastic and cohesive behavior of soil. Soil cohesive behavior was achieved by considering tensile force between elements. The developed DEM model well represented the effect of wedge shape on soil behavior and reaction force. Laboratory test results showed that wedge penetration resistance in highly compacted soil was two times greater than that in low compacted soil, whereas DEM simulation with parameters obtained from the test of low compacted soil could not simply be extended to that of high compacted soil. The modified model took into account soil failure strength that could be changed with soil compaction. A three dimensional representation composed of normal displacement, shear failure strength and tensile failure strength was proposed to design mechanical properties between elements. The model based on the liquid bridge theory. An inter particle tension force measurement tool was developed and calibrated A comprehensive study of the parameters of the contact model for the DEM taking into account the cohesive/water-bridge was performed on various agricultural grains using this measurement tool. The modified DEM model was compared and validated against the test results. With the newly developed model and procedure for determination of DEM parameters, we could reproduce the high compacted soil behavior and reaction forces both qualitatively and quantitatively for the soil conditions and wedge shapes used in this study. Moreover, the effect of wedge shape on soil behavior and reaction force was well represented with the same parameters. During the research we made use of the commercial PFC3D to analyze soil tillage implements. An investigation was made of three different head drillers. A comparison of three commonly used soil tillage systems was completed, such as moldboard plow, disc plow and chisel plow. It can be concluded that the soil condition after plowing by the specific implement can be predicted by the DEM model. The chisel plow is the most economic tool for increasing soil porosity. The moldboard is the best tool for soil manipulation. It can be concluded that the discrete element simulation can be used as a reliable engineering tool for soil-implement interaction quantitatively and qualitatively.
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Pomp, Caron. Evaluation des Angebots für den Wissens- und Technologietransfer in der Lausitz. Technische Hochschule Wildau, 2022. http://dx.doi.org/10.15771/innohub_7.
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Die Lausitz durchläuft einen durch den Ausstieg aus der Braunkohleverstromung bedingten Strukturwandel. Dieser soll durch eine Vielzahl von Aktivitäten, Fördermitteln und neue Institutionen proaktiv gestaltet werden. Man erhofft sich neue wirtschaftliche Impulse und verstärkte Innovationsaktivitäten in der Region. Für die Schaffung von Innovationen fällt dem Wissens- und Technologietransfer (WTT) eine wichtige Rolle zu. Gerade in dieser bewegten Phase eines großen Transformationsprozesses stellt sich die Frage, wie es um das Angebot des WTT bestellt ist. Gibt es ausreichend und passende Impulse aus der Wissenschaft für Wirtschaft und Gesellschaft, werden diese bedarfsgerecht vermittelt? Für ein „gutes“ WTT-Angebot gibt es einige Anforderungen. Diese werden im vorliegenden Arbeitspapier dargestellt. Anschließend wird überprüft, ob das aktuelle Angebot in der Lausitz diesen Anforderungen genügt, basierend auf einer Expert:innenbefragung verschiedener im WTT aktiver Organisationen der Region.
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Zhang, Xingyu, Matteo Ciantia, Jonathan Knappett, and Anthony Leung. Micromechanical study of potential scale effects in small-scale modelling of sinker tree roots. University of Dundee, December 2021. http://dx.doi.org/10.20933/100001235.
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When testing an 1:N geotechnical structure in the centrifuge, it is desirable to choose a large scale factor (N) that can fit the small-scale model in a model container and avoid unwanted boundary effects, however, this in turn may cause scale effects when the structure is overscaled. This is more significant when it comes to small-scale modelling of sinker root-soil interaction, where root-particle size ratio is much lower. In this study the Distinct Element Method (DEM) is used to investigate this problem. The sinker root of a model root system under axial loading was analysed, with both upward and downward behaviour compared with the Finite Element Method (FEM), where the soil is modelled as a continuum in which case particle-size effects are not taken into consideration. Based on the scaling law, with the same prototype scale and particle size distribution, different scale factors/g-levels were applied to quantify effects of the ratio of root diameter (𝑑𝑟) to mean particle size (𝐷50) on the root rootsoil interaction.
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Avnimelech, Yoram, Richard C. Stehouwer, and Jon Chorover. Use of Composted Waste Materials for Enhanced Ca Migration and Exchange in Sodic Soils and Acidic Minespoils. United States Department of Agriculture, June 2001. http://dx.doi.org/10.32747/2001.7575291.bard.
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Restoration of degraded lands and the development of beneficial uses for waste products are important challenges facing our society. In addition there is a need to find useful and environmentally friendly applications for the organic fractions of municipal and other solid waste. Recent studies have shown that composted wastes combined with gypsum or gypsum-containing flue gas desulfurization by-products enhance restoration of sodic soils and acidic minespoils. The mechanism by which this synergistic effect occurs in systems at opposite pH extremes appears to involve enhanced Ca migration and exchange. Our original research objectives were to (1) identify and quantify the active compost components involved in Ca transport, (2) determine the relative affinity of the compost components for Ca and competing metals in the two soil/spoil systems, (3) determine the efficacy of the compost components in Ca transport to subjacent soil and subsequent exchange with native soil cations, and (4) assess the impacts of compost enhanced Ca transport on soil properties and plant growth. Acidic mine spoils: During the course of the project the focus for objective (1) and (2) shifted more towards developing and evaluating methods to appropriately quantify Ca2+ and Al3+ binding to compost derived dissolved organic matter (DOM). It could be shown that calcium complexation by sewage sludge compost derived DOM did not significantly change during the composting process. A method for studying Al3+ binding to DOM was successfully developed and should allow future insight into DOM-Al3+ interactions in general. Laboratory column experiments as well as greenhouse experiments showed that in very acidic mine spoil material mineral dissolution controls solution Al3+ concentration as opposed to exchange with Ca2+. Therefore compost appeared to have no effect on Al3+ and Ca2+ mobility and did not affect subsoil acidity. Sodic alkaline soils: Batch experiments with Na+ saturated cation exchange resins as a model for sodic soils showed that compost home cations exchanged readily with Na+. Unlike filtered compost extracts, unfiltered compost suspensions also significantly increased Ca2+ release from CaCO3. Soil lysimeter experiments demonstrated a clear impact of compost on structural improvement in sodic alkaline soils. Young compost had faster, clearer and longer lasting effects on soil physical and chemical properties than mature compost. Even after 2 growing seasons differences could still be observed. Compost increased Ca2+ concentration in soil solution and solubility of pedogenic CaCO3 that is highly insoluble under alkaline conditions. The solubilized Ca2+ efficiently exchanged Na+ in the compost treated soils and thus greatly improved the soil structure.
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Spiwoks, Markus, Johannes Scheier, and Oliver Hein. Zur Beurteilung von Konjunkturprognosen - Eine Auswertung von Prognosen zur Entwicklung des BIP, der Industrieproduktion und der privaten Konsumausgaben in zwölf Industrienationen. Sonderforschungsgruppe Institutionenanalyse, 2011. http://dx.doi.org/10.46850/sofia.9783941672031.
Full textAbstract:
Die vorliegende Studie verfolgt vier Ziele. Sie soll einen kurzen Überblick über die wichtigsten Verfahren der Prognosegütemessung bei makroökonomischen Prognosen geben. Es sollen zwei neue Verfahren zur Beurteilung makroökonomischer Prognosen vorgestellt werden: Der Test auf Informationszuwachs und der GOVA-Koeffizient. Die Autoren denken, dabei handelt es sich um besonders geeignete Ansätze, weil sie realistische Anforderungen an die Prognostiker stellen. Außerdem soll gezeigt werden, dass Prognoseerfolge und Prognosemisserfolge mit dem Test auf Unverzerrtheit nicht angemessen differenziert werden können. Darüber hinaus soll die Studie einen Überblick über den Erfolg von Konjunkturprognosen in zwölf Industrienationen geben. Im Einzelnen handelt es sich um Konsensprognosen zur Entwicklung des BIP, der Industrieproduktion und der privaten Konsumausgaben in den USA, Japan, Deutschland, Frankreich, Großbritannien, Italien, Spanien, Kanada, Niederlande, Schweiz, Schweden und Norwegen.
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Chefetz, Benny, and Jon Chorover. Sorption and Mobility of Pharmaceutical Compounds in Soils Irrigated with Treated Wastewater. United States Department of Agriculture, 2006. http://dx.doi.org/10.32747/2006.7592117.bard.
Full textAbstract:
Research into the fate of pharmaceutical compounds (PCs) in the environment has focused on aspects of removal efficiency during sewage treatment, degradation in surface water and accumulation in soils and sediments. However, very little information is available on the binding interactions of pharmaceuticals with dissolved organic matter (DOM) originating from wastewater treatment. Such interactions can significantly affect the transport potential of PCs in soils by altering compound affinity for soil particle surfaces. Our primary hypothesis is that the transport potential of PCs in soils is strongly impacted by the type and strength of interaction with DOM and the stability of resulting DOM-PC complexes. The overarching goal of the proposed work is to develop a better understanding of the risk associated with introduction of PCs into the environment with treated wastewater. This goal has been achieved by elucidating the mechanisms of the interaction of selected pharmaceuticals (that have shown to be widespread wastewater contaminants) with DOM constituents; by determining the stability and fate of DOM-PC complexes introduced to soils and soil constituents; and by evaluating the potential uptake of these compounds by plants. Based on the results obtained in this study (column and batch sorption-desorption experiments), we suggest that PCs can be classified as slow-mobile compounds in SOM-rich soil layers. When these compounds pass this layer and/or are introduced into SOM-poor soils, their mobility increases significantly. Our data suggest that in semiarid soils (consisting of low SOM), PCs can potentially be transported to the groundwater in fields irrigated with reclaimed wastewater. Moreover, the higher mobility of the acid PCs (i.e., naproxen and diclofenac) in freshwater column systems suggests that their residues in soils irrigated with reclaimed wastewater can leach from the root zone and be transported to the groundwater after rain events. Our data obtained from the binding experiments of PCs with DOM demonstrate that the hydrophobic DOM fractions were more efficient at sorbing PCs than the more polar hydrophilic fractions at a pH near the pKa of the analytes. At the pH of natural semiarid water and soil systems, including that of reclaimed wastewater and biosolids, the role of the hydrophobic fractions as sorption domains is less important than the contribution of the hydrophilic fractions. We also hypothesize that the DOM fractions interact with each other at the molecular level and do not act as independent sorption domains. In summary, our data collected in the BARD project demonstrate that the sorption abilities of the DOM fractions can also significantly affect the mobility of pharmaceutical compounds in soils influenced by intensive irrigation with treated wastewater or amended with biosolids.
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Chefetz, Benny, and Jon Chorover. Sorption and Mobility of Pharmaceutical Compounds in Soils Irrigated with Treated Wastewater. United States Department of Agriculture, 2006. http://dx.doi.org/10.32747/2006.7709883.bard.
Full textAbstract:
Research into the fate of pharmaceutical compounds (PCs) in the environment has focused on aspects of removal efficiency during sewage treatment, degradation in surface water and accumulation in soils and sediments. However, very little information is available on the binding interactions of pharmaceuticals with dissolved organic matter (DOM) originating from wastewater treatment. Such interactions can significantly affect the transport potential of PCs in soils by altering compound affinity for soil particle surfaces. Our primary hypothesis is that the transport potential of PCs in soils is strongly impacted by the type and strength of interaction with DOM and the stability of resulting DOM-PC complexes. The overarching goal of the proposed work is to develop a better understanding of the risk associated with introduction of PCs into the environment with treated wastewater. This goal has been achieved by elucidating the mechanisms of the interaction of selected pharmaceuticals (that have shown to be widespread wastewater contaminants) with DOM constituents; by determining the stability and fate of DOM-PC complexes introduced to soils and soil constituents; and by evaluating the potential uptake of these compounds by plants. Based on the results obtained in this study (column and batch sorption-desorption experiments), we suggest that PCs can be classified as slow-mobile compounds in SOM-rich soil layers. When these compounds pass this layer and/or are introduced into SOM-poor soils, their mobility increases significantly. Our data suggest that in semiarid soils (consisting of low SOM), PCs can potentially be transported to the groundwater in fields irrigated with reclaimed wastewater. Moreover, the higher mobility of the acid PCs (i.e., naproxen and diclofenac) in freshwater column systems suggests that their residues in soils irrigated with reclaimed wastewater can leach from the root zone and be transported to the groundwater after rain events. Our data obtained from the binding experiments of PCs with DOM demonstrate that the hydrophobic DOM fractions were more efficient at sorbing PCs than the more polar hydrophilic fractions at a pH near the pKa of the analytes. At the pH of natural semiarid water and soil systems, including that of reclaimed wastewater and biosolids, the role of the hydrophobic fractions as sorption domains is less important than the contribution of the hydrophilic fractions. We also hypothesize that the DOM fractions interact with each other at the molecular level and do not act as independent sorption domains. In summary, our data collected in the BARD project demonstrate that the sorption abilities of the DOM fractions can also significantly affect the mobility of pharmaceutical compounds in soils influenced by intensive irrigation with treated wastewater or amended with biosolids.
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Imhof, Agnes. Der Sang, den keiner erfasste : zur Entschlüsselung von Stefan Georges Geheimsprache. Universitätsbibliothek Johann Christian Senckenberg, November 2019. http://dx.doi.org/10.21248/gups.51756.
Full textAbstract:
Diverse Quellen zu Stefan George (1868-1933) berichten von einer Geheimsprache, die der exzentrische Dichter noch in seiner Schulzeit erfunden und über Jahre hinweg weiterentwickelt haben soll. Zweck war neben dem poetischen Aspekt vor allem die Verschlüsselung von Informationen. Ich werde im Folgenden anhand des einzig erhaltenen Fragments, zweier Verse am Ende des Gedichts "Ursprünge" von 1904, zeigen, dass das Vokabular vor allem altgriechisch mit romanischen Elementen ist. Weiterhin lässt sich nachweisen, dass die Grammatik an das damals beliebte Esperanto, eine Kunstsprache auf der Basis v.a. romanischer Sprachen (Latein) mit vereinfachter Grammatik, angelehnt ist.
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Döring, Thomas, and Lorenz Blume. Einbindung der neuen Länder in den bundesstaatlichen Finanzausgleich - Eine empirische Schätzung der Einheitslasten der westdeutschen Länder. Sonderforschungsgruppe Institutionenanalyse, 2012. http://dx.doi.org/10.46850/sofia.9783941627215.
Full textAbstract:
Sowohl in der finanzwissenschaftlichen als auch der rechtswissenschaftlichen Diskussion in Deutschland besteht Einigkeit darüber, dass die fiskalischen Folgen der Wiedervereinigung von Bund, Ländern und Kommunen gemeinsam zu tragen sind. Mit diesem Verständnis der Deutschen Einheit als „Gemeinschaftsaufgabe“ aller drei Gebietskörperschaftsebenen des föderalen Bundesstaates ist die Vorstellung verknüpft, dass es diesbezüglich zu einer angemessenen Lastenverteilung zwischen Bund, Ländern und Kommunen kommt. Eine vollständige Kosten-Nutzen-Analyse des deutschen Vereinigungsprozesses und seiner Auswirkungen auf die Haushalte von Bund, Ländern und Kommunen, die die verschiedenen Haben- und Soll-Positionen in aller Breite und Differenziertheit erfasst, ist dabei aus ökonomischer Sicht aufgrund der schieren Quantität der zu berücksichtigenden Nutzen- und Kosteneffekte kaum zu bewältigen. Diese Komplexität reduziert sich zwar, wenn nur die finanzwirtschaftlichen Effekte des deutschen Vereinigungsprozesses betrachtet werden, aber auch eine solche Analyse muss eine Vielzahl entsprechender Lasten in den Blick nehmen. Vor diesem Hintergrund sind die nachfolgenden Überlegungen auf zwei zentrale Punkte ausgerichtet: Zum einen bedarf der Begriff der „Einheitslasten“ einer grundlegenden Klärung (Abschnitt 2). Dabei steht die Frage im Zentrum, ob das ökonomische Lastenverständnis sich in der Erfassung reiner Zahlungsströme erschöpft oder auch darüber hinausgehende Tatbestände zu berücksichtigen sind. Zum anderen wird in diesem Beitrag ein methodischer Ansatz entwickelt, mit dem die Einheitslasten, die aus dem unmittelbar horizontalen Länderfinanzausgleich resultieren, empirisch quantifiziert werden können (Abschnitt 3). In Abhängigkeit von den verfügbaren Daten sowie zur Gewährleistung einer hinreichenden Zahl an statistisch verwertbaren Datenpunkten werden hierzu die Jahre von 1969 bis 2009 als Betrachtungszeitraum für einen ökonometrischen Strukturbruchtest gewählt. Auf dieser Grundlage lassen sich sowohl die durchschnittliche Belastung aller westdeutschen Länder insgesamt als auch die individuelle Belastung einzelner Länder aus der Einbeziehung der ostdeutschen Länder in den horizontalen Finanzausgleich näher bestimmen.
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Anderson, Andrew, and Mark Yacucci. Inventory and Statistical Characterization of Inorganic Soil Constituents in Illinois. Illinois Center for Transportation, June 2021. http://dx.doi.org/10.36501/0197-9191/21-006.
Full textAbstract:
This report presents a statistical analysis of the Regulated Substances Library (RSL) developed by the Illinois Department of Transportation. The RSL is comprised of surficial soil chemistry data obtained from rights-of-way subsurface soil sampling conducted for routine preliminary site investigations. The 3.7-million-record RSL database is compared with four independent studies of inorganic soil constituents of naturally occurring soils in Illinois. A selection of 22 inorganic soil analytes are examined in this study: Al, Sb, As, Ba, Be, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Hg, Ni, K, Se, Na, Tl, V, and Zn. RSL database summary statistics, mean, median, minimum, maximum, 5th percentile, and 95th percentile, are determined for Illinois counties and for recognized environmental concern, non-recognized environmental concern, and de minimis site contamination classifications. The RSL database at a 95% confidence level is compared with current and proposed thresholds for defining naturally occurring soil concentrations for the selected analytes. The revised thresholds proposed by Cahill in 2017 are predominantly larger than the current standards found in the Tiered Approach to Corrective Action Objectives rules and are in better agreement with observed distributions of soil concentrations for both naturally occurring and RSL soils. A notable exception is antimony (Sb), for which Cahill proposed a reduced threshold similar in magnitude to the median for many Illinois Department of Transportation districts.