Compaction Problem Research Articles

Effects of stockpiling on selected properties of opencast coal mine soils

Soil stockpiling is a necessary component of opencast coal mining and, because most of the soils involved have arable potential, this involves the possibility of serious soil degradation. A study at four mines on the Highveld of South Africa involved sampling a number of stockpiles of various ages and origins. Samples were also collected from unmined adjacent soils, as well as rehabilitated areas. Results of stockpiling showed a deterioration in all physical and chemical parameters studied. The soil profile texture gradient was disturbed, due to mixing of surface and subsurface materials. Stockpile bulk density rose by 4% from unmined soils and by a further 6% in rehabilitated areas, indicating continuing compaction problems. Cation exchange capacity values did not entirely correspond with the textural changes, suggesting increased leaching, whereas pH values decreased for many stockpiles, requiring post-mining liming to re-establish suitable environments. Organic carbon levels on stockpiles fell by 5%, and by a further 35% to rehabilitated areas. Increasing age of stockpile did not seem to equate to a corresponding increase in degradation, except possibly for pH, which showed a weak correlation. Recommendations from the study include the use of ‘cut and cover’ rehabilitation techniques; continuous soil specialist consultation, and limitations on stockpile height and duration.

Computational Complexity Relationship between Compaction, Vertex-Compaction, and Retraction

In this paper, we show a very close relationship between the compaction, vertex-compaction, and retraction problems for reflexive and bipartite graphs. Similar to a long-standing open problem concerning whether the compaction and retraction problems are polynomially equivalent, the relationships that we present relate to our problems concerning whether the compaction and vertex-compaction problems are polynomially equivalent, and whether the vertex-compaction and retraction problems are polynomially equivalent. The relationships that we present also relate to the constraint satisfaction problem, providing evidence that similar to the compaction and retraction problems, it is also likely to be difficult to give a complete computational complexity classification of the vertex-compaction problem for every fixed reflexive or bipartite graph. In this paper, we however give a complete computational complexity classification of the vertex-compaction problem for all graphs, including even partially reflexive graphs, with four or fewer vertices, by giving proofs based on mostly just knowing the computational complexity classification results of the compaction problem for such graphs determined earlier by the author. Our results show that the compaction, vertex-compaction, and retraction problems are polynomially equivalent for every graph with four or fewer vertices.

On the Parallelization of Stream Compaction on a Low-Cost SDC Cluster

Many highly parallel algorithms usually generate large volumes of data containing both valid and invalid elements, and high-performance solutions to the stream compaction problem reveal extremely important in such scenarios. Although parallel stream compaction has been extensively studied in GPU-based platforms, and more recently, in the Intel Xeon Phi platform, no study has considered yet its parallelization using a low-cost computing cluster, even when general-purpose single-board computing devices are gaining popularity among the scientific community due to their high performance per $ and watt. In this work, we consider the case of an extremely low-cost cluster composed by four Odroid C2 single-board computers (SDCs), showing that stream compaction can also benefit—important speedups can be obtained—from this kind of platforms. To do so, we derive two parallel implementations for the stream compaction problem using MPI. Then, we evaluate them considering varying number of processes and/or SDCs, as well as different input sizes. In general, we see that unless the number of elements in the stream is too small, the best results are obtained when eight MPI processes are distributed among the four SDCs that conform the cluster. To add value to the obtained results, we also consider the execution of the two parallel implementations for the stream compaction problem on a very high-performance but power-hungry 18-core Intel Xeon E5-2695 v4 multicore processor, obtaining that the Odroid C2 SDC cluster constitutes a much more efficient alternative when both resulting execution time and required energy are taken into account. Finally, we also implement and evaluate a parallel version of the stream split problem to store also the invalid elements after the valid ones. Our implementation shows good scalability on the Odroid C2 SDC cluster and more compensated computation/communication ratio when compared to the stream compaction problem.

Zeta potential and electrophoretic mobility for the recovery of a saline soil with organic amendments

ABSTRACT The accumulation of salts in the soil profile produces conditions that affect the growth of crops. The effects of these conditions on crops and the intensity of these effects depend on the quantity and type of salts that predominate and are also influenced by soil characteristics and climate, among other aspects. The salinization of agricultural soils is a serious problem facing agriculture today. The use of organic amendments has increased in recent years, acting on the texture of the soil, correcting compaction or granularity problems, and influencing chemical and/or biological reactions. The objectives of this work were to analyze the use of compost and vermicompost using different analysis techniques to determine the influence of conditions on the remediation of a saline soil. In saturation extracts of soil, compost, and vermicompost, a Zeta potential value 2.34-2.44 times more negative (more-stable colloids) than that in the soil colloids was observed in the amendments. The values of electrophoretic mobility were more negative in the organic amendments compared with the soil. This is the first time that these parameters have been reported for these purposes and for a saline soil. In this study, the soil has low organic matter content (1.65%), so these amendments are expected to improve soil quality and texture, achieving the recovery of saline soils.

More Compact Orthogonal Drawings by Allowing Additional Bends †

Compacting orthogonal drawings is a challenging task. Usually, algorithms try to compute drawings with small area or total edge length while preserving the underlying orthogonal shape. We suggest a moderate relaxation of the orthogonal compaction problem, namely the one-dimensional monotone flexible edge compaction problem with fixed vertex star geometry. We further show that this problem can be solved in polynomial time using a network flow model. An experimental evaluation shows that by allowing additional bends could reduce the total edge length and the drawing area.

Compaction and Physical Attributes of the Soil After the Development of Cover Plants

Compaction problems in heavily tilled soils have been commonly mitigated with the use of cover plants. Aiming to evaluate the effects of compaction on the physical properties of a plyntic Haplic-Alitic Cambisol soil after development of different cover crops, a complete randomized blocks design experiment, with 3 × 3 factorial arrangement and four replications, was conducted. Treatments consisted of cultivation of two legume species, crotalaria (Crotalaria juncea L.) and stylosanthes cv. Campo Grande (Estilosantes capitata + Estilosantes macrocephala) and a grass species, brachiaria (Urochloa brizhantha cv. Marandu), subjected to soil compaction: CM–Conventional soil management (tillage) without additional compaction; CMc4 and CMc8–conventional soil management with additional compaction using a 6 Mg tractor in four and eight wheel passes. Conventional management with additional compaction does not affect significantly the physical attributes at a soil depth of 0.10-0.20 m, and only the soil moisture does not differ according to the soil management, irrespective of the depth and kind of cover plant. Traffic levels in four passes result in an increased soil bulk density and macroporosity in the 0.0-0.05 m, and in soil resistance to penetration and total porosity in the layer up to 0.10 m. Cover crops are important in maintaining soil physical quality to reduce the negative effects of compacting forces, especially to stylosanthes cv. Campo Grande that provided greater soil protection in systems with or without addition of compaction, conditioning the lowest values of bulk density and soil resistance to penetration.

Practical applications analysis and economic efficiency of the method on assessment of the sealing action from the tracked mover on the soil layer

The article describes and evaluates the economic efficiency of applying a modern approach to solving the problem of soil compaction by tracked movers using a new method based on the theory of hereditary creep of elastoviscoplastic materials, taking into account new factors (the time of the impact of movers on the base, rheological properties of the soil, etc.), as well as using a new devices and techniques for determining the physico–mechanical characteristics of the soil layer and modern specialized software products.

A Compact Formulation for the $\ell _{2,1}$ Mixed-Norm Minimization Problem

Parameter estimation from multiple measurement vectors (MMVs) is a fundamental problem in many signal processing applications, e.g., spectral analysis and direction-of-arrival estimation. Recently, this problem has been addressed using prior information in form of a jointly sparse signal structure. A prominent approach for exploiting joint sparsity considers mixed-norm minimization in which, however, the problem size grows with the number of measurements and the desired resolution, respectively. In this work, we derive an equivalent, compact reformulation of the l 2,1 mixed-norm minimization problem that provides new insights on the relation between different existing approaches for jointly sparse signal reconstruction. The reformulation builds upon a compact parameterization, which models the row-norms of the sparse signal representation as parameters of interest, resulting in a significant reduction of the MMV problem size. Given the sparse vector of row-norms, the jointly sparse signal can be computed from the MMVs in closed form. For the special case of uniform linear sampling, we present an extension of the compact formulation for gridless parameter estimation by means of semidefinite programming. Furthermore, we prove in this case the exact equivalence between our compact problem formulation and the atomic-norm minimization. Additionally, for the case of irregular sampling or a large number of samples, we present a low complexity, grid-based implementation based on the coordinate descent method.

Effects of row deep tillage for the growth base formed by piling up soil in damp lowlands behind coastal sand dunes to construct coastal disaster prevention forest belts on the Kujukuri coastline, Japan

ABSTRACT To successfully afforest coastal forest belts ensuring high disaster prevention, growth bases for them have been constructed by piling up soil in the low wetlands along the Kujukuri coastline. Ground surfaces in such bases are often covered with water because of soil compaction, leaving them susceptible to stagnant water. Water stagnation in soil is problematic, potentially interfering with afforesting coastal forests. Therefore, row deep tillage was conducted for parts of growth bases to combat the poor physical properties of the existing soil. Here, we surveyed soil profiles and measured vertical soil hardness distribution in two forest stands with piling up soil to evaluate the effectiveness of tillage for man-made soil. Soil hardness measurements indicated that the vertical areas with ‘soft’ and ‘hard/consolidated’ soil alternately appeared in growth base profiles. Generally, soil of the dense and very hard layers was apt to be formed by strong compaction of the filled-up soil because of heavy machinery usage during growth base preparation. Such dense and hard soils in the untilled areas of the profiles were also observed in this study. By contrast, it was confirmed that row deep tillage drastically improved soil physical properties, i.e., decreased hardness and increased water permeability, because the sequential hardened subsoil layers were well-broken-up. Moreover, it was observed many thick and large roots penetrated deeper layers with deep tillage areas. These results suggest that row deep tillage of hardened soil is quite effective at securing the areas and providing the physical conditions for deeply penetrated roots into deeper soils, which increases healthy root development. They show the effects of soil hardness reduction and water permeability improvement have been maintained for two decades, at least, after construction. These findings will be useful for alleviating some problems of soil compaction, water stagnation, and tree-growth hindrance that have been encountered on afforestation sites with man-made soil.

Diagnóstico de la compactación en suelos cultivados con maíz en la Región Fraylesca, Chiapas

La compactación del suelo es un problema identificado recientemente como una de las principales limitantes en la superficie maicera del municipio de Villaflores en la región de la Frailesca, Chiapas, debido a ello, requiere ser estudiado con mayor precisión. El objetivo de este estudio fue caracterizar el problema de compactación en la superficie mecanizada cultivada con maíz en el ejido Nuevo México. Se estudiaron 177 predios, en los cuales se determinó la densidad aparente, materia orgánica y textura a las profundidades de 0-20 y de 20-40 cm. Se entrevistaron a los dueños de los predios para obtener información sobre sus prácticas de cultivo y niveles de productividad del maíz. Los resultados muestran que 83.3% del área estudiada presentó compactación superficial y 94.6% compactación en el subsuelo (piso de arado). Los productores señalaron que en años con períodos críticos de sequía los rendimientos se reducen 58%, lo cual esta correlacionado con la disminución de la porosidad a consecuencia de la compactación. Se identificaron como causas principales de la compactación al laboreo intensivo con maquinaria 100% de los sitios, el contenido muy bajo de materia orgánica 100% y el tipo de suelo (luvisoles y acrisoles). La atención del problema de compactación requiere de una estrategia integral de carácter correctivo y preventivo que debe tomar como elemento central la elevación de los contenidos de materia orgánica, para revertir la actual gestión insostenible de la tierra.

A fully implicit and consistent finite element framework for modeling reservoir compaction with large deformation and nonlinear flow model. Part II: verification and numerical example

A fully implicit, fully coupled, and fully consistent finite element framework has been formulated in part I of this work for modeling reservoir compaction through linearizing coupled solid and flow field equations and constructing a local material integrator. In part II of this work, we focus on verification and performance analysis of our numerical formulation and computer implementation using several numerical examples. First, we design a cube problem in triaxial compression to verify our numerical formulation and computer code implementation especially for rock formation in compaction using cap plasticity models. The finite element prediction on stresses is compared with the analytical solution. The second problem we select is a strip footing problem popular in the geotechnical area where the evolution of soil consolidation degrees following the diffusion of pore pressure is the main interest. In this example, we demonstrate a good performance of the proposed numerical formulation on solving different shear and compaction-dominated deformation behaviors by varying the footing length. Importantly, an extremely sharp cap model based on real experimental data for Leda clays, a challenging cap model, is successfully applied in this footing problem. Our focus in this work is to model field reservoirs undergoing serious compaction. A reservoir with complex payzone geometries, multiple horizontal wells, and cap plasticity models with sharp cap surfaces has been successfully solved using our fully implicit formulation. The last example is to model a horizontal wellbore damage problem. Finally, the sensitivity of predicted subsidence to nonlinear flow model, cap hardening parameters, and Lode angles have been systemically investigated and documented in detail, which can provide a constructive guidance on how to successfully model field reservoir compaction problems with cap plasticity models.

Improved attacks on knapsack problem with their variants and a knapsack type ID-scheme

In the present study we consider two variants of Schnorr-Shevchenko method (SS) for solving hard knapsack problems, which are on average faster than the SS method. Furthermore, we study the compact knapsack problem i.e. the solution space is not {0, 1} as in knapsack problem but some larger set, and we present an algorithm to attack this problem. Finally, we provide a three move sound id-scheme based on the compact knapsack problem.

Strength and Permeability of Cultivated Histosols Characterized by Differing Degrees of Decomposition

Core Ideas Cultivated organic soils (Histosols) are highly productive but very sensitive to degradation and compaction. Penetration resistance and saturated hydraulic conductivity are two important parameters related to the degree of decomposition of Histosols. Penetration resistance could be used to assess the depth of the compact layer, as well as the degree of decomposition, of Histosols. Cultivated organic soils (Histosols) are an important part of the agricultural economy in Canada. However, problems of degradation and compaction affect this particular type of soil. The objective of this study was to characterize the soil penetration resistance and the saturated hydraulic conductivity (ksat) in cultivated organic soils that differed in their degree of decomposition. Three fields in the plain of Montreal, in southwestern Quebec, were selected to provide a gradient of degrees of decomposition. Site 1 was classified as a Limnic Fibrisol, Site 2 was classified as a Terric Mesic Humisol, and Site 3 was classified as a Terric Humisol. At each site, penetration resistance and ksat were measured directly in the field. Penetration resistance, particularly at the 25‐cm depth and deeper, was found to increase with increasing soil degradation. An inverse relationship was observed for ksat in the compact layer. The results presented in this study indicate that penetration resistance and ksat are both linked to the degree of soil decomposition. However, the relationship between both parameters is complex, and both parameters are to be measured to achieve a more accurate characterization of organic soils. Further work could assess the depth of the compact layer, as well as the degree of decomposition of organic soils at different spatial scales using penetration resistance. In Histosols, accurately mapping ksat would help in designing field drainage system, as this soil property is difficult to predict from other parameters.

Investigation of the Structural Deformation Behaviour of the Subsoiler and Paraplow Tines by Means of Finitie Element Method

In this study, static stress-deformation analyzes (in terms of material strengths) were presented comparatively through a FEM-based simulation of the subsoiler and paraplow legs designed in a three-dimensional CAD environment. In general, both soil tillage implements with high energy requirements are being used to remove the soil compaction problem on agricultural land. The operating conditions of the implements were simulated using a FEM-based simulation program (Ansys-16). The results of static analysis obtained from the Finite Element Method (FEM) were evaluated on some different materials used in the shank design of both implements and the results were given comparatively. According to the analysis results, the maximum equivalent stress was in paraplow shank foot 122 MPa which is used C-60 material and the maximum vertical dis-placement is 0,00014 mm in the position of shank foot of subsoiler

Characterization and Implementation of Nash Bargaining Solutions with Non-Convexity

We consider bargaining problems with compact star-shaped choice sets arising from a class of economic bargaining environments. Convex or comprehensive (relative to the disagreement point) problems are star-shaped but not conversely. We characterize single-valued solutions satisfying the Nash axioms on the class of compact star-shaped bargaining problems. For the case with two players, we show that there are exactly two solutions with each being a dictatorial (in favor of one player) selection of Nash product maximizers. We provide an extensive form game to implement Nash bargaining solutions. We extend our analysis and results to allow for alternative domains, asymmetries, and more than two players. For the n-player case, Nash solutions are shown to be determined by n-round iterative maximizations of Nash products.

S-visibility problem in VLSI chip design

Abstract: In this paper, a new version of very large scale integration (VLSI) layouts compaction problem is considered. Bar visibility graph (BVG) is a simple geometric model for VLSI chip design and layout problems. In all previous works, vertical bars or other chip components in the plane model gates, as well as edges, are modeled by horizontal visibilities between bars. In this study, for a given set of vertical bars, the edges can be modeled with orthogonal paths known as staircases. Therefore, we consider a new version of bar visibility graphs (BsVG). We then present an algorithm to solve the s-visibility problem of vertical segments, which can be implemented on a VLSI chip. Our algorithm determines all the pairs of segments that are s-visible from each other.

TRAFFIC CONTROL WITH AUTOPILOT AS AN ALTERNATIVE TO DECREASE SOIL COMPACTION IN SUGARCANE AREAS

<p>Control the machinery traffic through autopilot and use the combined spacing of two rows are possible solutions to mitigate soil compaction problems. The objective of this study was to evaluate traffic control using autopilot in order to soften the problem of soil compaction in mechanically-harvested sugarcane areas. The study was conducted in two experimental areas belonging to Usina Santa Fe, in New Europe, São Paulo, Brazil. The design was a randomized block design, with 3 treatments: T1 = sugarcane planted in single spacing and without autopilot (1.50 m); T2 = sugarcane planted in single line spacing and managed on autopilot; T3 = sugarcane planted under combined spacing of two rows (1.50 × 0.90 m) and managed with autopilot, with 4 replications. Was collected samples in the wheel row (WR) and the seedbed (SB), which was located next to the plant row to, in layers from 0.00 to 0.15 and 0.15-0.30 m. It was observed that the seed bed area showed higher porosity in the treatments with autopilot in the second year of evaluation. There were no differences in pore sizes and shapes between the treatments in the two years studied. The large and complex pores were observed to be reduced in the second evaluation year. </p>

Interpretation and Use of Penetrometer Data to describe Soil Compaction in Vineyards.

A portable recording penetrometer was used for in situ field measurements of soil strengths in existing experiments with known profile characteristics. The data reported include effects of soil preparation methods, tractor wheel compaction and soil moisture on soil strength, as well as a case study in a productioll'vineyard. The penetrometer proved to be a useful instrument in identifying and quantifying soil compaction problems and the effects of soil management systems in vineyards. The data revealed that serious subsoil compaction can exist which may result in very poor vine performance and even death of the vines.

Long‐Term Soil Structure Observatory for Monitoring Post‐Compaction Evolution of Soil Structure

Core Ideas We provide long‐term data on soil structure evolution following compaction. Treatments with and without plants and with and without tillage are included. Monitoring includes soil physical and biological properties and crop measures. Compaction decreased fluid transport capability and increased mechanical impedance. The projected intensification of agriculture to meet food targets of a rapidly growing world population are likely to accentuate already acute problems of soil compaction and deteriorating soil structure in many regions of the world. The key role of soil structure for soil functions, the sensitivity of soil structure to agronomic management practices, and the lack of reliable observations and metrics for soil structure recovery rates after compaction motivated the establishment of a long‐term Soil Structure Observatory (SSO) at the Agroscope research institute in Zürich, Switzerland. The primary objective of the SSO is to provide long‐term observation data on soil structure evolution after disturbance by compaction, enabling quantification of compaction recovery rates and times. The SSO was designed to provide information on recovery of compacted soil under different post‐compaction soil management regimes, including natural recovery of bare and vegetated soil as well as recovery with and without soil tillage. This study focused on the design of the SSO and the characterization of the pre‐ and post‐compaction state of the field. We deployed a monitoring network for continuous observation of soil state variables related to hydrologic and biophysical functions (soil water content, matric potential, temperature, soil air O2 and CO2 concentrations, O2 diffusion rates, and redox states) as well as periodic sampling and in situ measurements of infiltration, mechanical impedance, soil porosity, gas and water transport properties, crop yields, earthworm populations, and plot‐scale geophysical measurements. Besides enabling quantification of recovery rates of compacted soil, we expect that data provided by the SSO will help improve our general understanding of soil structure dynamics.

Simulation of Industrial Wastewater Treatment from the Suspended Impurities into the Flooded Waste Mining Workings

The paper is dedicated to the mathematical model of slurry wastewater treatment and disposal in a flooded mine working. The goal of the research is to develop and analyze the mathematical model of suspended impurities flow and distribution. Impurity sedimentation model is under consideration. Due to the sediment compaction problem solution domain can be modified. The model allows making a forecast whether volley emission is possible. Numerical simulation results for “Kolchuginskaya” coal mine presented. Impurity concentration diagrams in outflow corresponding to the real full-scale data obtained. Safely operation time mine workings like a wastewater treatment facility are estimated. The carried out calculations demonstrate that the method of industrial wastewater treatment in flooded waste mine workings can be put into practice but it is very important to observe all the processes going on to avoid volley emission of accumulated impurities.