Different Degrees Of Compaction Research Articles

Suffusion response of well graded gravels in roadbed of non-ballasted high speed railway

The suffusion mechanism of well graded gravels in the application of high speed railway roadbed is still not fully understood. Field inspections of high speed railway show that suffusion of well graded gravels can result in mud pumping and affect the normal operation of high speed trains. This paper reports a total of 12 laboratory suffusion tests on well graded gravels typically used in Chinese high speed railway roadbed under three different degrees of compaction (93%, 95% and 97%). The influence of degree of compaction and initial fines content on the critical hydraulic gradient of roadbed materials and the characteristics of suffusion is systematically investigated. The results show that well graded gravels suggested by the design code can experience suffusion once the hydraulic gradient reaches a critical value. The critical hydraulic gradient generally increases with the degree of compaction and the initial fines content. An empirical equation is proposed to predict the eroded mass of fine particles, which can reasonably reproduce the experimental measurements for well graded gravels under different failure hydraulic gradient.

Oct4 Pioneers Genomic Nucleosomes in Motion

Gene regulation programs rely on dynamic changes in the structural packaging of genomic DNA. The DNA is stored in chromatin, a structure of arrays of nucleosomes with different degree of compaction and length of inter-nucleosomal linker DNA. In the nucleosome, 4 histone proteins form an octamer which wraps 147 basepairs of DNA around. Each histone is present twice and has a structured cores and intrinsically disordered terminal tails. Changes in chromatin structure are controlled by the DNA sequence, the conformational dynamics and post-translational modifications of histone tails, and by the binding of proteins to the nucleosomes.

Experimental study on dynamic stress dynamic strain relationship and dynamic modulus of reinforced expansive soil

Dynamic triaxial tests are carried out on saturated expansive soil of Qinchong Road, Guangxi at different compaction degrees, numbers of reinforced layers, confining pressure, dynamic stress dynamic strain relationship, and dynamic modulus attenuation law under frequency combination to study the dynamic characteristics of reinforced saturated expansive soil under different influencing factors. Results show that the dynamic constitutive relationship of the saturated expansive soil when the loaded waveform is a half-sine wave conforms to the R. L. Kondner hyperbolic model; the dynamic elastic modulus decreases with the increase of dynamic strain, and the relevant fitting parameters are given. A dynamic elastic modulus attenuation model considering different degrees of compaction, numbers of reinforced layers, confining pressure, and frequency is proposed through regression analysis of the test results.

Effect of compaction on the relationship between electrical resistivity and soil water content in Oxisol

Geophysical methods that allow determination of soil electrical resistivity (ρ) make estimates of the space-time variation of soil water content (θ) viable, as well as of other important physical properties and soil structure. The aims of this study were to test models for the θ-ρ relationship in a Typic Hapludox with clay texture under tropical conditions, and to determine the effect of the degree of compaction on this relationship. Undisturbed samples were collected and, in the laboratory, after saturation, they were artificially compacted to obtain different degrees of compaction (DC): 76 % (control), 84 %, 90 %, and 94 %. Readings of resistivity were made simultaneously to weighing of the samples for determination of θ. The power (θ = aρb), exponential (θ = cexp(ρd)), and logarithmic (θ = e + flog10(ρ)) models were tested. The power model (“Archie’s Law”) best described the θ-ρ relationship (R2 = 0.77; p < 0.05), differing from what was expected from the literature for clay soils. The coefficients were different from those reported for temperate climate soils, resulting in lower ρ values as the soil dries. Furthermore, the θ-ρ relationships were affected by the DC of the soil; however, the logarithmic model allowed the best differentiation of these effects. The logarithmic model showed that the θ-ρ relationship has two patterns, depending on θ: pattern A when θ > 0.20 m3 m−3 and pattern B for θ < 0.20 m3 m−3. Pattern A showed that compaction led to higher values of θ for the same value of ρ; and in pattern B, the opposite occurred. Simultaneously modelling ρ in accordance with the DC and with the degree of saturation (DS) showed that θ has a greater effect on ρ than soil compaction does. Thus, measurement of ρ proved to be a tool of good accuracy for estimation of θ under weathered tropical soil conditions after calibration. However, we suggest that diagnosis of soil compaction be performed under drier soil conditions to eliminate the preponderant effect of θ on ρ.

Permanent deformation analysis of base layers with recycled material: Effect of density and stress level

Full-depth reclamation techniques present numerous advantages for pavement rehabilitation strategies. The recycling process produces a thick layer of stabilized or unstabilized reclaimed materials, which is used as a new base layer of RAP aggregates. The compaction of the unstabilized thick layer is critical for adequate permanent deformation behaviour of the reclaimed layer. In some agencies, the smooth drum compaction is often used directly after the recycling process to compact the reclaimed materials. Previous studies demonstrated the challenges associated with adequate densification of the thick reclaimed layer through its whole thickness, leaving among other a material with a vertical density gradient. In that context, this study was designed to quantify the effect of the degree of compaction on the permanent deformation behaviour using cyclic triaxial tests. Granite and limestone aggregates were mixed with RAP in order to obtain mixes with 50% RAP, and each blend was tested using a permanent deformation test procedure at four different degree of compaction. One of the tested degree of compaction was a varying compacted density over the sample height. It was found that the analysis of this particular sample performance could be done on the basis of the average dry density of the sample. The shakedown ranges of each sample were analyzed with respect to stress ratio and degree of compaction. The behaviour for each type of mix was also similar. A generalized model was therefore proposed allowing to predict the range of permanent deformation behaviour knowing stress level and the degree of compaction. The general model between shakedown range and a relative stress ratio is based on a shift factor linking the effect of stress and density. Limit states were also defined for the possible ranges of behaviour with respect to the degree of compaction.

Stress-dependent water retention of granite residual soil and its implications for ground settlement

Granite residual soil is widely used as a subgrade material in pavement engineering. Previous studies have not investigated the influence of stress on the soil water retention curve for this type of unsaturated soil or its significance for predicting ground settlement. Thus, the aims of the present study were: (i) to experimentally investigate the water retention curves for granite residual soil at various stress levels and under different degrees of compaction; and (ii) to numerically explore the influence of stress-dependent water retention on the suction distribution and ground settlement during both rainfall and evaporation periods based on coupled seepage and deformation analyses. The experimental results showed that the applied vertical stress (from 0 to 90 kPa) decreased the retained water content by up to 13% when the suction was less than 200 kPa. The reduction in the retained water content was much more obvious when the degree of compaction decreased from 100% to 85%. The effects of stress on the water retention curves were almost negligible when the suction was higher than 200 kPa, regardless of the degree of compaction. The numerical results showed that the current analysis considering the influence of stress on water retention could predict a higher ground heave and a larger ground settlement, compared with the conventional method without stress effects. This was because the current analysis captured the larger suction reduction during rainfall and higher suction increase during evaporation. The ground deformation became larger when the rainfall intensity increased while the corresponding rainfall duration decreased under the same return period of rainfall. This study implied that the method employed in the present study was more scientific and conservative for assessing ground settlement in pavement engineering.

Effects of oleogels prepared with fish oil and beeswax on the gelation behaviors of protein recovered from Alaska Pollock

In this study, the effects of three groups of oleogels comprising 10 wt% beeswax as the gelator and different proportions of rapeseed and fish oils on the structures of surimi gels were investigated. X-ray diffraction revealed that the crystal structures of the oleogels were mainly dependent on the presence of the beeswax, where the oleogels formed via molecular association into crystalline structures. Texture profile analysis indicated that all studied oleogels comprehensively improved the textures of the surimi gels. The water holding capacities of the oleogel based surimi gels were significantly higher (p < 0.05) than those of the control samples obtained by the direct addition of liquid oil. However, the whiteness of the gels decreased significantly because of the yellow color of the beeswax. Rheological studies confirmed that the protein in the oleogel based surimi gel had a higher degree of cross linking than that of the control group, and its network structure was more stable. Finally, scanning electron microscopy observations indicated different degrees of compactness and uniformity among the surimi gel networks. Overall, the oleogels with added beeswax significantly improved the structures of the surimi gels. These findings could broaden the range of oils used in food products.

Effect of the application of two plant residues on the density and porosity of soils subjected to compaction

This study evaluates the effect on the density and porosity of three differently textured soils when they were subjected to different degrees of compaction, following the addition of two crushed vegetable residues, palm leaf and hay straw. Mixtures were prepared incorporating the plant residues to each soil following the proportions: 10%, 20%, 30% and 40% (&lt;em&gt;V&lt;/em&gt;/&lt;em&gt;V&lt;/em&gt;). To quantify the incidence of compaction on physical properties, cylindrical PVC containers were used. The soil-waste mixtures were subjected to pressures of 0 (kg/cm&lt;sup&gt;2&lt;/sup&gt;), 1.12 (kg/cm&lt;sup&gt;2&lt;/sup&gt;) and 2.24 (kg/cm&lt;sup&gt;2&lt;/sup&gt;). The results obtained showed that the addition of the residues reduces the apparent density in the three soils, with the use of hay straw having the greatest decrease. As an example, in soil 1, without applying compaction, the apparent density varies with the application of palm leaf from 1685 (kg/m&lt;sup&gt;3&lt;/sup&gt;) to 890 (kg/m&lt;sup&gt;3&lt;/sup&gt;) and with the straw reaches values of 781 (kg/m&lt;sup&gt;3&lt;/sup&gt;).

Analysis of Capillary Water Migration Law of Compacted Loess in Ningxia

Capillary water is the main cause of freezing damage and collapsible damage of compacted loess. Therefore, researching capillary water migration law of compacted loess is the key to solve various damage in the infrastructure construction of loess. Different regions have different climatic conditions, which make the physical and mechanical properties of the loess is different. In order to reveal the capillary water migration law of compacted loess in Ningxia, the moisture migration law of compacted loess with different degrees of compaction was studied by using standpipe method. The results show that the migration rate of capillary water is rapid at the early stage and gradually became slower with the increase of time, which is negatively related to the degree of compaction and migration height. The maximum migration height of capillary water increases exponentially with the increase of compactness. Migration rate and migration height of capillary water are related to capillary water potential, gravitational potential, and pipe-resistance of capillary. In this study, the relational equation can predict capillary water distribution and the migration height of compacted loess was newly established. This equation can also provide a reference to reduce various damage and freeze-thaw effect in compacted loess.

Environmental impact assessment of introducing compact city models by downscaling simulations

In this study, first, three compact city models with different degrees of compactness for a prefecture in a large metropolitan area of Japan were designed. Based on the urban classifications “population-induced area,” “population-unchanged area,” and “withdrawal area,” we constructed the compact city models. Next, the impact of introducing the designed compact city models on the summer thermal environment in the 2050s was quantitatively assessed by downscaling simulations from a global scale to an urban scale. Moreover, we examined the effect of a land use change in the withdrawal area on the future thermal environment in the urban area (the population-induced and population-unchanged areas). As expected, a temperature increase in the urban area occurred due to urban densification in the compact city models. On the other hand, the temperature decrease in the urban area as a result of changing the land use of the withdrawal area, i.e., by replacing the withdrawal area with grassland, approximately offset the above-mentioned temperature increase. This implies that, in compact city planning, it is necessary to properly plan not only for the concentrated urban area but also for treatment of the withdrawal area from the viewpoint of environmental impact.

Soil compaction effect on black oat yield in Santa Catarina, Brazil

ABSTRACT Cultivated soils, when submitted to agricultural practices, tend to compact due to the pressure exerted by agricultural machines and implements, a process that compromises soil quality and system sustainability. Specific properties of each soil, such as particle size and organic matter content, interfere with the process and degree of compaction and, consequently, plant growth. This study aimed to analyze the effect of different degrees of compaction (DC) on soil physical properties and black oat (Avena strigosa Schreb) growth. For [...]

Effects of biochar content on gas diffusion coefficient of soil with different compactness and air contents.

Biochar has been found to be a potentially suitable amendment for landfill cover material and agricultural soil. The addition of biochar can improve the physical (e.g., adsorption capacity) and hydrological properties (e.g., water/gas permeability) of soil. However, no experimental study is available about the effect of biochar content (BC) on the gas diffusion coefficient (DP) of soil. The present study investigated the effect of BC on DP under different degree of compaction (DOC; 85%, 90%, and 95%) and soil air contents (SAC; 5%, 10%, and 15%). It was found that DOC and BC had negligible effects on DP when SAC was low (~ 5%). In contrast, when the SAC was relatively high (~ 15%), soil with DOC of 85% had the largest DP for BC ranging from 0 to 15% (w/w). Only when the SAC was large (~ 15%), the addition of biochar generally increased DP.

Transcription Factors and DNA Play Hide and Seek.

Transcription factors (TFs) bind to specific DNA motifs to regulate the expression of target genes. To reach their binding sites, TFs diffuse in 3D and perform local motions such as 1D sliding, hopping, or intersegmental transfer. TF-DNA interactions depend on multiple parameters, such as the chromatin environment, TF partitioning into distinct subcellular regions, and cooperativity with other DNA-binding proteins. In this review, how current understanding of the search process has initially been shaped by prokaryotic studies is discussed, as well as what is known about the parameters regulating TF search efficiency in the context of the complex eukaryotic chromatin landscape.

Microstructural analysis of the effects of compaction on fatigue properties of asphalt mixtures

ABSTRACT In the current approaches to structural analysis for asphalt pavements, the entire pavement material is usually treated to identical material, which disregards the distinct heterogeneity of asphalt mixture. Asphalt mixture is actually a multi-phase heterogeneous material that is composed of air voids, aggregate and asphalt binder. In this study, asphalt specimens were drilled from a test track and the indirect tensile fatigue test was conducted to study the fatigue properties. Digital Image Processing (DIP) was used to investigate the microstructural changes of the asphalt specimens based on X-ray Computed Tomography (X-ray CT) images. The aggregate orientation and number of aggregate contact points were determined. The distribution of the air-voids content and shape index of air voids before and after the fatigue tests were comprehensively discussed. According to the results, the microscopic analysis can effectively predict the evolutions of the internal structures of asphalt mixtures during fatigue damage. The heterogeneity due to different degrees of compaction significantly affects the fatigue properties of the asphalt mixtures. This study not only provides support for the further research on the relationship between the microstructural characteristics and mechanical damages of asphalt mixture but also provides implications for conducting the structural mechanical analysis of asphalt pavement.

Strength and deformation characteristics of silty clay under frozen and unfrozen states

Frost damage of soil foundations of engineering structures is controlled by mechanical properties of soil under frozen and unfrozen states, existing widely in cold regions such as Genhe area that is termed as the “pole of cold” in China. For investigating engineering properties of soil in cold regions, a series of triaxial compressive tests were carried out on both frozen and unfrozen Genhe silty clay with different degrees of compaction under different confining pressures. The test results show that the stress-strain curves gradually change from softening to hardening with increasing confining pressure, temperature and decreasing compaction degree. Additionally, both axial and radial deformation is more sensitive to lower confining pressures. An accurate method was proposed for determining the elastic modulus. The elastic modulus and strength decrease significantly as the state of soil changes from frozen to unfrozen. The effect of compaction degree on radial deformation, strength and failure strain is gradually eliminated with the increase of confining pressure, which can be observed in both frozen and unfrozen soil. The isotropic tensile strength and the cohesion were obtained in the stress spaces of p-q and σ-τ respectively, and the ice cementing force was identified by adopting the difference of the two strength parameters between frozen state and unfrozen state. The results indicate that the ice cementing force calculated by two strength parameters is consistent, which increases with increasing compaction degree.

Soil‐Water Characteristics of the Low Liquid Limit Silt considering Compaction and Freeze‐Thaw Action

The soil‐water characteristic curve of silty soil in seasonal frozen area during freezing‐thawing process was studied in this study. By means of a laboratory test, specimens with different compaction degrees and different initial moisture content were prepared and put into the temperature change testing machine for freeze‐thaw action. The influence of different degrees of compaction and different times of freeze‐thaw action on SWCC of low liquid limit silt was analyzed, a V‐G model was used to fit the test data, and a set of fitting parameters with a reference value was obtained. At the same time, the change of microstructure between soil particles during the freezing‐thawing cycle is illustrated. The results showed that with the same water content and the same compactness, the matric suction of the test soil decreased with the increase of freeze‐thaw cycles. For the same number of freeze‐thaw cycles, the greater the compactness, the greater the matric suction of the soil. The V‐G model can well represent the SWCC of low liquid limit silt during the freeze‐thaw cycle.

СТЕПЕНЬ ПОДКИСЛЕНИЯ СЫРОГО ФУРАЖНОГО ЗЕРНА ЯЧМЕНЯ В ЗАВИСИМОСТИ ОТ УСЛОВИЙ КОНСЕРВИРОВАНИЯ

Fodder grain plays a priority role in ensuring high productivity of farm animals and poultry, revealing their genetic potential. Therefore, it is necessary to use the most advanced methods of grain preservation for the most complete preservation of the original feeding power. Such methods in recent years include the technology of sealed storage of raw fodder grain harvested before the complete maturation phase. Various biological and chemical additives are used to improve the preservation results. The use of such additives (due to the specific features of preserved raw materials) is obligatory. The authors conducted comparative tests of certain types of additives for processing raw fodder grains in the whole and flattened forms to determine the effect of different degree of compaction on the effectiveness of their preserving action. They made an experiment,and the quality of fermentation was determined using generally accepted methods. The raw grain isolated from air access is protected from spoilage due to acidification, so the effectiveness of using preservative additives was primarily determined by the effect on this indicator. The whole grain was put into storage with a higher moisture content (35%) than the flattened one (about 25%),which ensured its significantly better acidification regardless of the degree of compaction. A denser grain storage pattern provided better grain acidification regardless of grain moisture. From tested preparations, the flattened grain was better acidified by powdered sulphur at the medium degree of compaction for storage; the whole grain was better acidified by Biosil NN at the maximum degree of compaction. On average the preparations used in the experiment were arranged in the following sequence (as their influence on the degree of grain acidification weakened): powdered sulphur → biopreparations Biosil NN → chemical preservative Promir.

Feasibility Study on Grouting Compactness Detection in Sleeves Using Piezoelectric Transducers

Steel sleeve grouting connections are widely used in prefabricated concrete structures. It is well known that insufficient grouting increases the chance of structural failure. As such, it is critical to monitor the density and compactness of grouting sleeve during the construction process, which however remains significant challenges as it is deeply buried in the beam and column. In this study, a lead zirconate titanate (PZT)-based sleeve grouting compactness detection method was systematically investigated. Five grouting sleeves samples with different degrees of compactness were prepared and four PZT transducers were surface-bonded on opposite sides of the outer wall of each sleeve. Two acts as actuators to generate stress wave signals, and the other two operate as sensors to receive the signals. The wavelet packet energy and Hilbert–Huang transform methods were applied to process the stress wave signals, and with the chosen characteristic parameters, the correction model of the grouting compactness was established. Experimental results show that the wavelet packet total energy values and the Hilbert energy peak values are related to the grouting compactness, indicating the feasibility of using PZT sensors to detect the compactness of grouting sleeves.

Mechanism of biochar soil pore–gas–water interaction: gas properties of biochar-amended sandy soil at different degrees of compaction using KNN modeling

Soil compaction has contrasting effect on soil strength (i.e., positive) and vegetation growth (i.e., negative), respectively. Biochar has been utilized mostly in combination with soils in both agricultural fields (i.e., loose soils) and geo-structures (i.e., dense soil slopes, landfill cover) for improving water retention due to its microporous structure. Biochar is also found to be useful to reduce gas permeability in compacted soil recently. However, the efficiency of biochar in reducing gas permeability in loose and dense soils is rarely understood. The objective of this study is to analyze effects of compaction on gas permeability in soil at different degrees of compaction (i.e., 65%, 80% and 95%) and also different biochar amendment contents (0%, 5% and 10%). Another aim is to identify relative significance of parameters (soil suction, water content, biochar content and compaction) in affecting gas permeability. Experiments were conducted before applying k-nearest neighbor (KNN) modeling technique for identifying relative significance of parameters. Biochar was synthesized from a coastal invasive species (water hyacinth), which has relatively no influence on food chain (as unlike in biochar produced from biomass such as rice husk, straw, peanut shell). Based on measurements and KNN modeling, it was found that gas permeability of biochar-amended soil is relatively lower than that of soil without amendment. It was found from KNN model that for denser soils, higher amount of soil suction is mobilized for a significant increase in gas permeability as compared to loose soils. Among all parameters, soil suction is found to be most influential in affecting gas permeability followed by water content and compaction.

Analytical modeling of the stick-slip motion of an oscillation drum

In this paper, a lumped parameter model of the interacting oscillation roller-subsurface system is proposed. The main aim of the model is to predict the response acceleration of the roller drum during near-surface compaction of non-cohesive soils. The compaction process of the soil itself is not captured, but different degrees of compaction are considered by varying the soil stiffness. The roller is represented by the oscillation drum and its viscoelastic connection to the roller frame. In the chosen modeling strategy, the curvature of the soil surface below the drum is prescribed. In this way, also the vertical drum acceleration can be computed. The discrete subsoil model consists of a vertical and a horizontal Kelvin–Voigt element. Contact between drum and soil surface is described by means of dry friction according to Coulomb’s law. As such, the stick-slip motion of the drum can be simulated. In the stick phase, pure rolling between drum and soil surface is assumed. The highly nonlinear equations of motion of this three degrees-of-freedom model are derived separately for the stick and the slip phase of the motion. Selective numerical studies show that this model captures the fundamental response characteristics of the dynamic drum–subsoil interacting system observed in the field.