Fluctuations In Moisture Content Research Articles

Non-invasive geophysical methods for monitoring the shallow aquifer based on time-lapse electrical resistivity tomography, magnetic resonance sounding, and spontaneous potential methods

The Ningdong coalfield has played a pivotal role in advancing local economic development and meeting national energy. Nevertheless, mining operations have engendered ecological challenges encompassing subterranean water depletion, land desertification, and ground subsidence, primarily stemming from the disruption of coal seam roof strata. Consequently, the local ecosystem has incurred substantial harm. Water-preserved coal mining presently constitutes the pivotal technology in mitigating this problem. The primary challenge of this technique lies in identifying critical aquifer layers and understanding the heights of water-conducting fracture zones. To obtain a precise comprehension of the seepage patterns within the upper coal seam aquifer during mining, delineate the extent of water-conducting fracture zones, non-invasive geophysical techniques such as time-lapse electrical resistivity tomography (TL-ERT), magnetic resonance sounding (MRS), and spontaneous potential (SP) have been employed to monitor alterations within the shallow coalfield’s aquifer throughout the mining process in the Ningdong coalfield. By conducting meticulous examinations of fluctuations in resistivity, moisture content, and self-potential within the superjacent strata during coal seam extraction, the predominant underground water infiltration strata were ascertained, concurrently enabling the estimation of the development elevation of water-conducting fracture zones. This outcome furnishes a geophysical underpinning for endeavors concerning local water-preserved coal mining and ecological rehabilitation.

Field experiment on a vegetation-wicking geotextile-reinforced base for a permeable sidewalk

Wicking geotextiles have proven effective in reducing water content in road bases under both saturated and unsaturated conditions, thereby increasing granular base strength and mitigating moisture-related damage to the pavement. Despite their effectiveness in paved roads, the use of wicking geotextiles in permeable road and sidewalk, particularly in areas requiring robust drainage such as sponge cities, is not well explored. In “sponge city” roads, moisture content fluctuations and subsequent damage to the structure often cause concern, and the wicking geotextile’s drainage could be a potential solution. Therefore, this study aims to investigate and quantify the effectiveness of wicking geotextiles in reducing the moisture content and improving the resilient modulus of permeable sidewalk base layers. The moisture contents of unstabilized and one-directional wicking geotextile- and two-directional wicking geotextile-stabilized bases under permeable paving bricks were monitored with an interval of 7–10 days for over a year. An analytical approach to reconstruct daily moisture content in the base layer was proposed based on the simulated rainfall saturation test. This approach further assesses the enhancements in resilient modulus due to the drainage capabilities of wicking geotextiles. The experimental results indicated that the two-directional wicking geotextile outperforms its one-directional counterpart and both wicking geotextiles outperformed the control condition in terms of drainage efficiency. By reconstructing the daily moisture content and utilizing the relative damage model, the two-directional wicking geotextile significantly improved the annual equivalent resilient modulus of the base layer under permeable paving bricks.

Assessment of Deterioration Risk of the Wooden Columns of Historical Buildings in Southern China Based on HAM Transfer Model

Chinese historical buildings are mainly made of wood structure system, however, as an organic material, wood is prone to decay under the fluctuation of hygrothermal environment. This study aims to assess the risk of decay of two types of wooden columns (exposed column under eaves and semi-exposed column embedded in walls) and further propose reasonable protection measures for Nanjing area where with a hot and humid summer and cold winter and with a high groundwater level. A two-dimensional heat and moisture (HAM) transfer model is established to simulate the fluctuations of temperature and moisture content at the bottom of columns in a historical Chinese building. Then, the risk of decay of columns was evaluated. The results show that because the stone column base isolates the groundwater and the amount of air condensation is limited, the risk of decay at the bottom of the exposed column under the eaves is lower than the semi-exposed column embedded in wall which is more prone to be affected by the high level of groundwater.

Soil moisture dynamics regulates the release rates and lability of copper in contaminated paddy soils

The climate changes have caused more extreme precipitation and drought events in the field and have exacerbated the severity of wet-dry events in soils, which will inevitably lead to severe fluctuations in soil moisture content. Soil moisture content has been recognized to influence the distribution of heavy metals, but how temporal changes of soil moisture dynamics affect the release rates and lability of heavy metals is still poorly understood, which precludes accurate prediction of environmental behavior and environmental risk of heavy metals in the field. In this study, we combined experimental and modeling approaches to quantify copper release rates and labile copper fractions in two paddy soils from southern China under different moisture conditions. Our kinetic data and models showed that the release rates and lability of copper were highly associated with the soil moisture contents, in which, surprisingly, high soil moisture contents effectively reduced the release rates of copper even with little changes in the reactive portions of copper in soils. A suite of comprehensive characterization on soil solid and solution components along the incubation suggested that soil microbes may regulate soil copper lability through forming microbially derived organic matter that sequestered copper and by increasing soil particle aggregation for protecting copper from release. This study highlights the importance of incorporating soil moisture dynamics into future environmental models. The experimental and modeling approaches in this study have provided basis for further developing predictive models applicable to paddy soils with varying soil moisture under the impact of climate change.

An experiment to measure changes in violin frequency response due to playing-in

There is a widespread (but not universal) conviction among luthiers and performers of stringed instruments that a new instrument will sound “better” after it has been played for a certain amount of time. It is not uncommon for instruments to be mechanically stimulated to accelerate the process. The goal of the present experiment is to determine whether sustained mechanical stimulation of previously unplayed violins produces measurable changes in bridge admittance or radiativity. Our test instruments comprised three sibling violins (Andre Tellis, model 200), two of which were excited continuously for 12 weeks using different methods, while the third served as a control. Once per week during the excitation period, we measured bridge admittance with a laser vibrometer and radiativity in an anechoic chamber for each violin using the hammer tap method. The mass of each violin was also recorded prior to each measurement to account for fluctuations in moisture content. The resulting frequency response functions were analyzed within specific bands for changes that followed a trend over time or exceeded the standard deviation derived from a set of baseline measurements. Preliminary results do not show any significant changes in either the bridge admittance or radiativity for any of the violins.

A study of geotechnical properties on high and intermediate - compressible clay stabilized with eco-sand

The most of the clayey soils are problematic for various construction tasks because their susceptibility to fluctuations in moisture content which can drive up construction expenses. Such soils can make it challenging to work for the construction projects. To solve this problem, we should change the clay's characteristics by blending the suitable admixture for producing the stabilized material. Eco-sand is one of such stabilizing admixture which is generated from a cement Industry as a by-product, produced an amount of 1100 tonnes per 20 hrs. In this study, the two different types of clayey soils are used such as high compressible clay (CH) and Intermediate compressible clay (CI). They were blended with varying amounts of eco-sand, such as 10%, 20%, 30%, 40%, and 50%, respectively. The optimum percentage of eco-sand is derived from conducting the various tests on engineering properties on clay mixes namely unconfined compression tests with different curing intervals, dispersion studies, durability studies and hydraulic properties. Based on the results of the aforementioned experimental tests, the optimal percentage of eco-sand is determined to be 40% for clay with a high compressibility and 20% for clay with an intermediate compressibility.

Research and Application of Key Technologies for the Construction of Cemented Material Dam with Soft Rock

In order to safely and efficiently use soft rock aggregate cemented dams in red bed regions and promote the development of widely sourced cemented sand and gravel dam materials, the Jinjigou project in China applied soft rock for the first time in the construction of cemented material dams. This article further explores the concept of cemented material dams from conducting on-site direct shear tests and research on soft rock material ratios and explores and invents a new structure and construction method by combining soft rock cemented sand and gravel with cemented rockfill. This article also proposes a digital mixing and intelligent dynamic control method for cemented material dams with soft rock. The research results show that soft rock aggregate content not exceeding 60% can produce soft rock cemented gravel with a compressive strength of no less than 6 MPa. The stress on the dam body is small and does not produce tensile stress. The dam body with added soft rock has certain shear-bearing capacity, with a shear friction coefficient of 0.99~1.10 MPa, cohesion of 0.26~0.53 MPa, and high residual strength, accounting for 60~80% of the peak strength. At the same time, the problems of large fluctuations in moisture content and the uneven grading of the soft rock and riverbed gravel mix during the mixing and production process, and the significant influence on safety caused by the large strength dispersion of the cemented sand and gravel, are resolved, ensuring the quality of soft rock cemented sand and gravel preparation. The successful application of soft rock cemented material dams in Jinjigou has achieved a breakthrough in key technologies for soft rock cemented dam construction in red bed regions, proving the feasibility of soft rock cemented material dam construction and having broad prospects for application and promotion.

Research on the improvement of rainfall infiltration behavior of expansive soil slope by the protection of polymer waterproof coating

The repetitive expansion and contraction cracks, as well as the strength attenuation induced by the precipitation-evaporation cycles, are important factors influencing the instability of expansive soil slopes. In this study, a polymer waterproof coating was proposed to protect the expansive soil slope against slope instability caused by precipitation penetration. The bonding performance of expansive soil blocks (with different soil densities) and polymer waterproof coatings (with different coating thicknesses) were analyzed by performing a laboratory pull-out test. The impacts of different protection methods and protection layer coverage on rainwater infiltration behavior were studied using three groups of slope model tests and numerical simulation approaches. The results showed that the bond strength between the expansive soil test block and the coating increased with the increase in soil compaction density, and the test block strength was an important factor affecting the bond performance. The influence of density of test block on bond strength was greater than that of coating thickness. The calculation formula of bond strength was obtained by fitting the test results. Compared to the unprotected slope, the fluctuation of soil moisture content and rainwater infiltration rate in the slope protected by polymer coating was found to be the least. Protective layer of polymer coating proved to have the most significant role in blocking rainwater infiltration, followed by polymer coating + three-dimensional vegetation net protective layer. When the coverage rate of the protective layer exceeds more than 90%, the effect of blocking rainwater infiltration was remarkable. Simultaneously, the variation range of slope water content, rainwater infiltration depth, and infiltration rate decreased significantly. This research result provides a new solution for expansive soil slope protection and rainwater infiltration control.

Numerical investigation of the effect of water content variations in expansive clay subgrades

ABSTRACT The research presented in this paper was focused on a numerical model predicting moisture content fluctuation in expansive subgrades. The model leads to a mechanism-based calculation of the vertical movement of a pavement sitting on expansive soils due to climate changes. The model was created using VADOSE/W in analysing changes in moisture content over a certain period of time, with climate and environmental effects take as imposed boundary and initial conditions. Moisture content fluctuations from the numerical analyses were validated by the long-term moisture content measurements below the pavement of country road FM-2 on the expansive Frelsburg clay near the city of College Station in Texas, U.S.A. VADSOSE/W was then applied to analyse the pavement of I-220 at Bossier Parish, Louisiana, U.S.A., which sits on subgrades of highly expansive Moreland clay in northern Louisiana. The numerical modelling was completed for a one-year period with input climatic and environmental data.

Effect of frost heave deformation of bridge foundation on operation safety of high-speed railway

The frost heave deformation of the bridge foundation in seasonal frozen soil regions threatens the safe operation of high-speed trains. The first high-speed railway in extremely cold zones, the Harbin-Dalian Line, is used as the background in this study, and finite element analysis (FEA) is used to investigate the impact of freezing temperature and moisture content on the frost heave force and deformation of the bridge foundation. Furthermore, the dynamic response of the train crossing the frost heave deformation region of the bridge foundation is analyzed based on finite element (FE) and multi-body dynamics co-simulation. Conclusively, the frost heave threshold of the bridge foundation is proposed in accordance with the limit of the train’s dynamic response indicators. The results indicate that the normal frost heave stress at the bottom section of the cap is distributed in a “W” shape along the lateral direction of the cap. The magnitude of the stress at the edges of the cap and the inner hole of the pile foundation is relatively large. the frost heave deformation is negatively and positively linked with the fluctuations of temperature and moisture content, respectively. The train's vertical acceleration grows gradually as the pier's upward deformation increases, while there is no discernible relationship between the train’s lateral acceleration and the pier’s upward deformation. Additionally, variations in the train speed and the pier’s upward deformation are positively correlated with the derailment coefficient and wheel load reduction rate. To enable the high-speed railway’s operation safety, it is proposed that the deformation threshold of frost heave be 14.4 mm.

Experimental Study of the Pore Structure and Gas Desorption Characteristics of a Low-Rank Coal: Impact of Moisture.

Coal–water interactions have a prominent impact on the prediction of coal mine gas disasters and coalbed methane extraction. The change of characteristics in the microscopic pores of coal caused by the existence of water is an important factor affecting the diffusion and migration of gas in coal. The low-pressure nitrogen adsorption experiments and gas desorption experiments of a low-rank coal with different equilibrium moisture contents were conducted. The results show that both the specific surface area and pore volume decrease significantly as the moisture content increases, and the micropores (pore diameter <10 nm) are most affected by the water adsorbed by coal. In particular, for a water-equilibrated coal sample at 98% relative humidity, micropores with pore sizes smaller than 4 nm as determined by the density functional theory model almost disappear, probably due to the blocking effects of water clusters and capillary water. In this case, micropores with a diameter less than 10 nm still contribute most of the specific surface area for gas adsorption in coal. Furthermore, the fractal dimensions at relative pressures of 0–0.5 (D1) and 0.5–1 (D2) calculated by the Frenkel–Halsey–Hill model indicate that when the moisture content is less than 4.74%, D1 decreases rapidly, whereas D2 shows a slight reduction as the moisture content increased. In contrast, when the moisture content exceeds 4.74%, further increases in the moisture content cause D2 to decrease significantly, while there is nearly no change for D1. The correlation analyses show that the ultimate desorption volume and initial desorption rate are closely related to the fractal dimension D1, while the desorption constant (Kt) mainly depends on the fractal dimension D2. Therefore, the gas desorption performances of coal have a close association with the pore properties of coal under water-containing conditions, which indicate that the fluctuation in moisture content should be carefully considered in the evaluation of gas diffusion and migration performances of in situ coal seams.

Decoupling between soil moisture and biomass drives seasonal variations in live fuel moisture across co-occurring plant functional types

BackgroundWildfires are important global disturbances influencing ecosystem structure and composition. The moisture content of living and senescent plant components are key determinants of wildfire activity, yet our understanding of how seasonal fluctuations in water availability and biomass control live foliar moisture content (LFMC) across co-occurring plant functional types is limited in diverse forested landscapes.ResultsWe recorded root-zone volumetric water content (VWC) and sampled leaf mass area (LMA) and LFMC of three co-occurring plant functional types across six field sites. We used a linear mixed effects model to quantify the drivers of LFMC and understand whether LFMC dynamics were coupled or decoupled from site conditions. Both LMA and VWC were significant predictors of LFMC variability (p < 0.001), although the strength and direction of these relationships varied across functional types. LFMC dynamics of understorey plant functional types were strongly coupled to site conditions, where the site random effect explained 44.2% (shrub) and 74.8% (herb) of the variability in LFMC across the season respectively. In contrast, overstorey plants were decoupled from site conditions, which explained only 8.1% of the variability in LFMC.ConclusionsLFMC of understorey plants responded to changes in soil water availability (VWC), while overstorey trees responded to biomass fluctuations (LMA). We present a conceptual model describing the influence of these factors on LFMC, which aligns with our findings and draws on the broader literature. This knowledge and conceptual approach can be used to improve our ability to characterize seasonal LFMC variation across different plant functional types, in turn improving our capacity to predict wildfire risk.

Generalization of the Fourier Problem on Fluctuations in the Temperature of the Earth’s Crust

The problem of asymptotic fluctuations of temperature and moisture content in a half-space is solved by the method of complex amplitudes. The material filling the half-space consists of a solid base (capillary-porous body) and water. The well-known Fourier solution for temperature fluctuations in half-space in the absence of moisture and under the boundary conditions of heat exchange of the first kind is generalized to the case of a wet material under the boundary conditions of Newton for temperature and Dalton for moisture content. The results of the work can be used in geocryology to model seasonal fluctuations in the thermophysical characteristics of frozen rocks and soils.

Use of plastic geocellular modules as a replacement gravel layer for natural turf rootzones

AbstractA trial was conducted to assess the suitability of a novel plastic geocellular drainage layer (Permavoid) as a replacement for a conventional gravel layer in a high‐quality sports pitch. The trial was conducted during the 2014–2015 and 2015–2016 United Kingdom football (soccer) seasons. Perennial ryegrass (Lolium perenne L.) was grown under five different rootzone depth treatments (50, 100, 200, and 300 mm over Permavoid and 300 mm over gravel as a control representing current practices). These were repeated for two contrasting rootzone types. The trial area was subjected to artificial football‐style wear throughout each playing season, with irrigation and nutritional inputs as would be normal for a high‐quality football pitch. Infiltration rates, rootzone moisture content, turf cover and tractional strength for the 200‐ to 300‐mm rootzone over Permavoid and 300 mm over gravel were the same throughout the trial. The replacement of the gravel drainage layer with Permavoid had no negative effect on the rootzone's hydraulic characteristics or turfgrass growth over the 2‐yr study period. In addition, it may be possible to use shallower rootzone depths in some circumstances, reducing the volume of material needed for construction. Shallower rootzones (50–100 mm) experienced greater fluctuations in rootzone moisture content, which was likely to be directly related to rootzone depth. Rootzone type had a minor effect, with finer rootzones holding onto more moisture and allowing slightly stronger turf. Therefore, when managing shallower and/or coarser rootzones, maintenance programs need to reflect the moisture and nutrient retention characteristics of these growing media.

Detection of historical landscape changes in Lake Victoria Basin, Kenya, using remote sensing multi-spectral indices

The Kenyan Lake Victoria basin has been experiencing land degradation and overexploitation as seen in various landscape changes. Quantifying and understanding the nature of these changes is essential for management decision-making. This study sought to apply the Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and Normalized Difference Built-up Index (NDBI) - Enhanced Normalized Difference Built-up Index (NDBI-ENDBI) indices to assess the changes in vegetation, water bodies, and build-up area, respectively, in the basin between 1978 and 2018. Landsat imageries for 1978, 1988, 1998, 2008, and 2018 with thematic-oriented bands were acquired, pre-processed, and subjected to spectral-based classification techniques in ArcGIS software to compute and generate NDVI, NDWI, and NDBI-ENDBI maps. According to the results, NDVI indicated an intense decreasing trend in the density of vegetated landscapes while NDVI, NDWI, and NDBI all depicted fluctuations in moisture content (in Lake Victoria and its wetlands). The NDBI-ENDBI showed an intense increasing trend in the built-up area expansion. Based on these changes, the study concluded that urban development has been rapidly progressing within the Lake Victoria basin over the years. Intensive and strategic planning that strikes a balance between economic development and environmental conservation is recommended to realize the sustainability of this important watershed.

Effect of Dynamic Bridging on Homogeneous Grain Movement in a Microwave Processing Zone

This article describes the influence of dynamic bridging in the unloading of a hopper at a processing plant on the grain flow homogeneity in a convective-microwave zone. In accordance with calculation methods for unloading hoppers, the parameters of the hopper unit and those of the outlet hole insuring that grain flows without static bridging formation is defined. It was found that moisture content fluctuations do not affect the process of grain transport. The equation for dynamic bridging rise depending on its position on the vertical axis of the unloading hopper has been deduced that enables the definition of the inhomogeneity of grain flow from its outlet hole. Calculations show that a certain inhomogeneity occurred between the right and the left parts of the unloading hopper in relation to its vertical axis in the course of grain discharging. This effect underlies the inhomogeneity of grain processing and reduction of its effectiveness in convective-microwave zones. An experimental model of unloading the hopper has been manufactured in order to perform investigational studies. The results of studies have completely confirmed the hypotheses. It has been found that dynamic bridge formation in unloading of the hopper results in the inhomogeneity of grain flow in convective-microwave zone.

Seed Health of Chickpea as Influenced by Different Packaging during Storage

A storage experiment was conducted to know the influence of cloth, gunny, high density polythene (HDPE), and vacuum packed bags on the seed health of chickpea for 18 months. To investigate, chickpea seeds were packed in all the bags and were kept in ambient conditions. During the storage period, there was a lot of fluctuation in moisture content of the seeds based on the relative humidity in cloth, gunny, and HDPE bags due to the pervious nature of packaging materials whereas, there was no moisture fluctuation in vacuum packed bags due to lower water vapor and oxygen transmission rate and higher thickness of polythene bag used for vacuum package. After 8 months of storage period, there was bruchids infestation to the seeds stored in cloth, gunny, and HDPE bags whereas, no bruchids infestation were seen to vacuum packed bag even after 18 months of storage but germination, root length, shoot length, seedling vigour index, seedling dry weight has reduced and mean germination time, electrical conductivity of seed leachates has increased due to seed aging. Hence, vacuum packaging technology can be effectively used for storage of chickpea seeds for longer period without any aid of chemicals.

Generalization of the Fourier problem of temperature waves in half-space

The problem of asymptotic fluctuations of temperature and moisture content in a half-space whose boundary is blown by an air flow with a temperature varying according to the harmonic law is solved by the method of complex amplitudes. The material filling the half-space consists of a solid base (capillary-porous body) and water. The well-known Fourier solution for temperature fluctuations in half-space in the absence of moisture and under the boundary conditions of heat exchange ofthefirst kind is generalized to the case of a wet material under the boundary conditions of Newton for temperature and Dalton for moisture content. The results of the work can be used in geocryology to model seasonal changes in the thermophysical state offrozen rocks and soils, in the theory of building structures to study the thermal regime of indoor premises with fluctuations in ambient temperature, in the theory of drying by electromagnetic radiation to study the processes of heat and mass transfer inoscillating modes.

AN EXPERIMENTAL STUDY ON STABILIZATION OF BLACK COTTON SOIL USING FLY ASH

Black cotton soils are extensively distributed worldwide and covered about 20% of the land area, the foundation designing is a difficult task because they are source of great damage to infrastructure and buildings. In monsoon they swell and in summer they shrink on evaporation of water from there. Because of these fluctuations in moisture content there will be changes in volume, and due to this the civil engineering structures like buildings, pavements, canal linings etc. are severely damaged. It is, therefore, necessary to mitigate the problems posed by black cotton soils and prevent cracking of structures. Stabilization is the process of improving the properties of soils, stabilization methods are of mechanical and chemical. Chemical method is obtained by using stabilizers such as cement, sand, silt, lime, fly ash etc. As fly ash is freely available, for projects in the vicinity of the Thermal Power Plants, it can be used for stabilization of black cotton soils for various uses. The project describes a study carried out to check the improvements in the properties of black cotton soil with fly ash in varying percentages (10%, 20% and 30%).

Data driven sintering moisture control model based on neural network

Sintering production is an important part of ironmaking industry. The moisture content of sinter material will affect the output and quality of sinter. But at present, most sintering plants still use manual water to control the moisture content of sintering material, which leads to a great fluctuation of moisture content, and it is difficult to improve the sintering efficiency. Only stable control in the best range can stabilize the working condition of sintering machine. Therefore, this paper studies the water control scheme and designs the control system based on the existing data, and uses the established data driven moisture control model to control the appropriate amount of water, and compares and analyzes the advantages of the control ability of different models compared with manual water. Firstly, we eliminated the invalid data, found that five materials were significantly correlated with water content, and then established a multiple linear regression model to further study the influence of the proportion of different materials on water content. Secondly, we established a data-driven sintering moisture automatic control model. The neural network model is used, the input variable is the material usage, water addition and moisture measurement data, and the output variable is water addition. The prediction results obtained by simple BP neural network and NARX neural network with feedback are compared and analyzed. It is found that NARX neural network has smaller prediction mean square error, more stable prediction results. Thirdly, we compared the data-driven NARX model prediction results with the results of manually adding water to control the moisture content of sintering, and made quantitative analysis with standard deviation and coefficient of variation. It was found that the standard deviation and coefficient of variation of NARX model prediction results were smaller, so NARX neural network model was more stable and excellent. If this model can be popularized in industrial production, the output and quality of steel will be improved, the production cost will be reduced, the labor resources will be saved, and the enterprise will get more benefits.