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This document serves as a follow-up to a previous paper on the use of lime and rice husk ash (RHA) to stabilize clayey soil. The original paper found that the addition of lime and RHA increased the strength of the soil, with the highest strength observed in samples containing 7% lime and 12% RHA. The document also includes additional research studies that support the use of RHA to improve soil strength. These studies found that the inclusion of RHA increased the California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) values of the soil, with the maximum strength achieved at an optimal RHA content. The increase in strength was attributed to the formation of cementitious products and agglomeration of soil particles. The degree of strength development varied depending on the type of soil and RHA used. The article also suggests future research directions, such as considering the effect of dry density and evaluating the suction effect. [Extracted from the article]

This document is a discussion of a research paper titled "Probing the Stochastic Unconfined Compressive Strength of Lime–RHA Mix Treated Clayey Soil." The paper explores the use of lime and rice husk ash as binders to stabilize clayey soil. The authors conducted tests to measure the unconfined compressive strength of soil-binder specimens with varying amounts of rice husk ash and lime. They used artificial neural networks and Gaussian process regression to analyze and predict the data. The discussers raise questions about the influence of suction on the strength of the blends and the effect of dry density, suggesting further evaluation of these factors. [Extracted from the article]

Tacca chantrieri André (1901) is a valuable evergreen rhizomatous herbaceous species that plays a crucial ecological and economic role in Vietnam's evergreen broadleaf forests. However, the degradation of forest ecosystems poses a significant threat to its survival in the wild. This study aimed to develop a model for determining the potential land suitable for Tacca chantrieri in Ba-Vi Natural Park, utilizing SoilGrid data. The results revealed that the species primarily thrives in Ba Vi, Minh Quang, and Yen Bai communes, covering approximately 20.92% of the total area. Despite its adaptability, Tacca chantrieri is highly scarce in the wild, with only 30 identified population spots concentrated along streams and slopes. The Jackknife standard analysis identified five key variables influencing the potential distribution of Tacca chantrieri in Ba-Vi National Park: clay composition in soil (36.9% contribution), bulk (22.6%), organic carbon density (OCD) (16.4%), coarse fragments (CF) (13%), and silt (9.3%). These findings highlight the applicability of SoilGrid data in species distribution modeling for small areas, particularly in the absence of site-specific soil data. However, for precise and site-specific information, field data collection remains indispensable. The high AUC values (training data: 93.9%, test data: 94.9%) indicate the feasibility of developing an effective model for evergreen rhizomatous herbaceous species. [ABSTRACT FROM AUTHOR]

Background: Soil organic carbon stocks (SOCs) play a critical role in supporting soil quality and ecosystem functions. Information on SOCs content in coastal lands is scanty and the types of clay minerals and soil fraction size that affect SOCs are still debated. We evaluated the SOCs content and identified the mineral type and soil fraction affecting the SOCs on coastal land. Methods: Soil samples were collected from each layer of nine different soil profiles in three subdistricts: Seunuddon (SD), Lapang (LP) and Dewantara (DT) in Aceh Utara Regency of Indonesia. The soil profiles were taken from different distances (300, 900 and 1500 m from the shoreline-d.f.s). Result: The results revealed that SOCs possessed by each soil layer of coastal land in Aceh Utara varied between 0.64 to 43.45 MgC ha-1. The highest to lowest average total of SOCs content for the location is SD>DT>LP, while for the position, the distance to the shoreline is 900 m>1500 m>300 m. Clay minerals such as labradorite, smectite, vermiculite and chlorite positively increase the SOCs content. Very fine sand is a size of the soil fraction that affects the increase in the levels of SOCs in coastal land. [ABSTRACT FROM AUTHOR]

Tropical pasture legumes such as Desmanthus are expected to improve pasture productivity in the extensive grazing systems of Northern Australia. However, the soils in these areas are often hostile (e.g., hard-setting and nutrient-deficient), which reduces legume emergence and establishment. Furthermore, these soils are often not ameliorated with amendments such as gypsum or starter fertilisers before planting. A pot trial was conducted to investigate differences in the emergence and early growth of four Desmanthus species. The legumes were grown in three alkaline clay soils that were unamended or amended with either gypsum (1 t CaSO4.2H2O ha−1 equivalent), a starter MAP fertiliser (12 kg P ha−1 equivalent), or both gypsum and the starter fertiliser. Seedling emergence was recorded daily and shoot yield was determined after six weeks' growth. Final seedling emergence (as a percentage of viable seeds) varied among the Desmanthus species (c.f. D. leptophyllus = 63%, D. pernambucanus = 68%, D. bicornutus = 85%, and D. virgatus = 86%). On average, across the treatments, gypsum increased seedling emergence by 15%, whereas the starter fertiliser had no effect. The shoot yields and shoot phosphorus content of the Desmanthus species generally increased in response to the starter fertiliser. The collective results demonstrated that there were differences in emergence and early growth among the four Desmanthus species, which indicates that Desmanthus cultivar selection may be important in the relatively hostile soils of Northern Australia. Gypsum was an effective amendment for seedling emergence, whereas the starter fertiliser was an effective amendment to increase legume productivity. [ABSTRACT FROM AUTHOR]

Piles as onshore and offshore foundation structures are often horizontally loaded. The usual calculation method for the behaviour of piles under such loads is the p‐y method. For piles in cohesive soil, several p‐y methods are proposed in literature, leading in general to differing results. A finite element model dealing with the behaviour of horizontally loaded piles in clay soils was established and validated against field tests. Utilising the results of a vast number of numerical simulations, a new p‐y method was developed, which gives reasonable results over the entire range of possible loads for piles of almost arbitrary diameters and embedded lengths in clay soils of varying consistency. The method requires in total six soil parameters and accounts for the actual deflection of the pile and also the effect of pile tip shear resistance by iteratively adapted y‐multipliers which depend on the course of the deflection line and the distance of the considered point to the pile tip. The new method can be generally used for calculation of the bearing behaviour of piles in soft clay under monotonic loading and can serve as a reference for consideration of cyclic load effects or softening effects in stiff clays. [ABSTRACT FROM AUTHOR]

Current ware potato yields in the Netherlands are approximately 70% of their potential. It is hypothesised by several stakeholders within the potato value chain that part of the potato yield gap is caused by a lack of phosphorus (P) and potassium (K) application. In this study, we analysed for 46 farmers' fields if increasing P and K fertiliser application rates led to a higher yield and yield quality. We found that, on average, increased P and K fertiliser application did not result in a significantly higher yield for two currently cropped potato cultivars on two different soil types in the Netherlands (Innovator on clay soils and Fontane on sandy soils) and in two years (2019 and 2020). However, on sandy soils at relatively lower farmer K application rates, our K application led to a small positive yield response up to 5 t ha−1. On clay soils, there was an average positive yield response to our K application at lower yield levels of the control. For P, we did not find any correlation between yield response to P application and the amount of P applied by farmers or any of the measured soil parameters. In terms of yield quality, the K application led to a slight reduction in underwater weight on sandy soils in 2019 and a slight increase in the yield of large tubers in 2020. We conclude that, although in some fields there was a small positive yield effect of increased K application, increasing P and K application rates will not narrow the potato yield gap and improve potato yield quality in the Netherlands. Instead, increasing the P and K application will decrease P and K use efficiency and hence is not recommended from an environmental and economic perspective. [ABSTRACT FROM AUTHOR]

This study was necessary because in Peru the application of resources such as artificial intelligence in the optimization of treatment doses in soil stabilization is not promoted. The purpose of the study was to evaluate the influence of the application of an artificial intelligence model on the optimization of the dosage of natural hydraulic lime, plastic and metallic fibers on the geological characteristics of a gravelly clay soil. The dosages of stabilizers and laboratory tests were used as input variables (predictors) and the values of mechanical tests as output variable. As main conclusions, an interesting application in terms of additive optimization was demonstrated in comparison with experimental results in the field. The model suggests a reduction of predominant materials, such as lime, to obtain acceptable results based on actual test results. The implications of including artificial intelligence, achieves substantial strength maintenance superior to the natural sample of 6 times, respectively, with an optimization of 4% natural lime, 2.25% plastic fiber, 10% metallic fiber and 83.75% natural soil. It is concluded that the influence of applying the artificial K-OPLS model on the real experimental dosages, implies in the reduction of lime up to 50% less, and the increase of plastic fiber in 0.75% more, the metallic fiber maintains its real dosage and the natural soil varies slightly. [ABSTRACT FROM AUTHOR]

Expansive clay soils, characterized by their propensity to undergo significant volume changes in response to moisture variations, present considerable challenges in construction engineering. These challenges manifest as structural damage, including fractures, asymmetrical settlements, and erosion. This study investigates the application of sustainable waste materials, specifically a mixture of plastic and glass waste, as an innovative approach to soil stabilization. In the context of Anbar, Iraq, laboratory experiments were conducted to evaluate the efficacy of incorporating plastic and glass waste in various proportions (0%, 4%, 5%, 6%) into clayey soil. The primary focus was to assess changes in geotechnical properties, notably the reduction in swelling potential and alterations in the maximum dry unit weight of the soil. Results indicated that the inclusion of waste materials in the specified proportions significantly mitigated the soil's swelling behavior, with reductions of 2%, 3%, and 5% observed for the respective waste content. Concurrently, enhancements in soil density were recorded, with increases in the maximum dry unit weight by 4%, 5%, and 9% corresponding to the same proportions of waste additives. These findings underscore the potential of using recycled waste materials in soil stabilization, aligning with environmental sustainability goals through the repurposing of waste. Additionally, this approach offers an economically viable alternative to traditional stabilization methods. The utilization of waste materials not only addresses the environmental impact of construction activities but also contributes to the broader goal of waste management and resource conservation. [ABSTRACT FROM AUTHOR]

Evaluation of soil sustainability should take into account chemical and mineralogical changes due to cultivation. Potassium (K) application is a key farming practice that may potentially affect phyllosilicate composition and soil properties. Irrigation is another agent that affects soil composition. This study aims to evaluate the imprints of cultivation on the chemical and mineralogical compositions of lowland soils under semi-arid and Mediterranean climate regimes and to assess them with the natural pedogenesis. The sites examined include two permanent plot experiments with crop rotation, and three single-plant plots. Cultivated, control, and fallow soils were analyzed for their chemical and mineralogical composition. The X-ray diffraction patterns of the clay fraction were decomposed to achieve quantitative detection of changes among the illite–smectite (IS) phases and in kaolinite amounts. In loamy and clayey soils dominated by IS phases, cultivation caused minor changes and diverse behavior of the IS phases. Yet, the K balance was negative under high fertilization levels and higher plant mass production. Fertilization enhanced the natural process of transforming IS into kaolinite and illite in the sandy soil, leading to a positive K balance. This study emphasizes the importance of IS minerals as a dynamic K pool that responds to plant needs. [ABSTRACT FROM AUTHOR]

Trace elements (Co, Cr, Mn, Mo, Ni, Rb, Th, U, and V) in surface soil of AlAslah (NH1), Nasiriyah refinery (NH2), Gharraf (NH3), and Tall Al-Laham (NH4) at Thi-Qar governorate, southeast Iraq, were studied. The study aims to detect their distribution and pollution levels to reduce the subtracted from industrial sources and avoid using contaminated areas for agricultural purposes before the soil treatment process. Inductivity Coupled Plasma Mass Spectrometry (ICP-MS) technique was used to determine the concentrations of these elements, and the results showed that there is a high concentration of Cr, Ni, Mo, and Mn in the soil of the study area, which exceeded the international levels compared with other elements (Co, Th, U, and V). The Geo accumulation index (I geo) values showed that the soil area was classified as low contamination in all sites and for all trace elements except for Mo, which is polluted in Al-Gharraf and strongly polluted in Tall Al-Laham. The values of the enrichment factor (EF) were indicated to be minimal enrichment of (Mn and V) in all sites and moderate enrichment of (Co) in all sites except in the Gharraf soil sample, which is considered as minimal enrichment. At the same time, it suffers from significant enrichment of (Cr) in all sites. The values of contamination factor (CF) showed extreme contamination of Cr and Ni in all sites due to the oil industry (Nasiriyah refinery), except for Ni in the Gharraf soil sample, which is considered as high contamination and moderately contamination with Co in all sites, and low contamination with Mn and V. The main cause of the increasing trace element concentrations in the study area that the samples located in industrial sites where trace elements are one of the waste products from fuel combustion from the oil fields and the waste of the brick factories near the study area, also the nature of the study area soil which is clay soil that absorb the trace elements on its surfaces. [ABSTRACT FROM AUTHOR]

The capillary pressure curve is a crucial basis for studying the pore structure and multiphase flow characteristics in oil and gas reservoirs. Due to the loose and unconsolidated nature of the clayey-silt sediment of natural gas hydrate reservoirs in the South China Sea, conventional methods such as mercury intrusion and centrifugation struggle to obtain capillary pressure curves for these sediments. In this study, X-ray diffraction analysis, scanning electron microscopy, nitrogen adsorption, and water-gas contact angle measurements are utilized to characterize the mineral composition, pore structure, pore size distribution, and wettability of the clayey-silt sediment. Subsequently, the filter paper method from soil mechanics is employed to determine the capillary pressure curve for the clayey-silt samples. The results indicate that the capillary pressure curve obtained through the filter paper method exhibits a saturation range of 18.39%-80.31% and a capillary pressure range of 19.04 to 46,481.42 kPa. It exhibits a distinct two-stage characteristic, where capillary pressure changes rapidly with water saturation below 61.05% and slowly above 61.05%. The pore radius calculated from the capillary pressure curve ranges from 2.41 nm to 5.91 µm. This alignment with the pore ranges obtains from nitrogen adsorption and Scanning Electron Microscopy confirms the accuracy of the obtained capillary pressure curve. Furthermore, in comparison with a literature capillary pressure curve obtained through centrifugation, the paper filtration method covers a broader range, providing better representation of capillary pressure in the multiscale pores of clayey-silt samples. [ABSTRACT FROM AUTHOR]

The northern coastal strip of Venezuela with a semiarid climate presents conditions for the development of extensive areas with the presence of expansive clays, and, this is the main pathology of its communication routes due to deformation in the surrounding civil works. This contribution characterizes the presence of expansive clays in northern Venezuela in 81 samples distributed in several states of the country. The study included the determination of geomechanical properties through field work and laboratory tests by Atterberg limits, consistency indices and expansion tests as well as the relationship between the indexes and information from edometer tests. The soil grain size is mainly fine (silts and clays), in the Anzoátegui state the average content of fine grains is 86%, while in Falcón and Miranda they are a little lower, 82% and 67%, respectively. In general, the plasticity index (PI) of these expansive clays is high, with an overall average of 23, although the region of Falcón state presented a moderate average (18). The correlations between the expansion pressure and the PI showed a high correlation. These results corroborate that the criterion used to evaluate the Expansion Potential of a clay soil based on the PI proposed by Chen (1988), is a fairly adequate criterion to be used in the study and identification of the expansive behavior of these types of soils. [ABSTRACT FROM AUTHOR]

Sang Yod Phatthalung rice is indica rice and grown as Geographical Indications (GI) in Patthalung province. Its dark red color seed contains high antioxidant activity that helps reduction in the risk of some chronic diseases such as diabetes, cancer, and cardiovascular diseases. So far, yield per planting area of this rice is still low. Thus, application of PGRs might play an alternative role in agronomical and physiological characteristics leading to improving yield of this rice. First, shoot tips of Sang Yod Phatthalung rice were cultured to induce multiple shoots and root on liquified PGR-free oil palm culture medium (OPCM) with different concentrations of 6-benzyladenine (BA) (0, 0.5, 1, 1.5 mg/L) alone or in combination with 1-naphthaleneacetic acid (NAA) (0 and 0.5 mg/L). Complete plants were acclimatized to field condition at Phatthalung Rice Research Station (PRRS). After acclimatization for 120 and 140 days, some agronomical and physiological characteristics of rice plant obtained from different PGR containing OPCM were statistically compared. A 2×4 factorial design in RCBD with 4 replication was performed. The results were clearly demonstrated that adding BA in the culture medium increase plant height, number of panicles, panicle length and leaf chlorophyll content. Plantlets obtained from in vitro culturing shoot tip on 0.5 mg/L BA containing medium gave the highest results in average plant height at 189.50 cm, number of panicles at 34.00 panicles, panicle length at 32.50 cm and leaf chlorophyll content at 39.65 SPAD unit. The results from this present study indicated the production of new plant types or characteristics for Sang Yod Phatthalung rice for high yield in future. [ABSTRACT FROM AUTHOR]

Acquiring comprehensive insights into soil properties at various spatial scales is paramount for effective land management, especially within small catchment areas that often serve as vital pastured landscapes. These regions, characterized by the intricate interplay of agroforestry systems and livestock grazing, face a pressing challenge: mitigating soil degradation while optimizing land productivity. This study aimed to analyze the spatial distribution of eight topsoil (0–5 cm) properties (clay, silt, sand, pH, cation exchange capacity, available potassium, total nitrogen, and soil organic matter) in a small grazed catchment. Four machine learning algorithms—Random Forest (RF), Support Vector Machines (SVM), Cubist, and K-Nearest Neighbors (kNN)—were used. The Boruta algorithm was employed to reduce the dimensionality of environmental covariates. The model's accuracy was assessed using the Concordance Correlation Coefficient (CCC) and Root Mean Square Error (RMSE). Additionally, uncertainty in predicted maps was quantified and assessed. The results revealed variations in predictive model performance for soil properties. Specifically, kNN excelled for clay, silt, and sand content, while RF performed well for soil pH, CEC, and TN. Cubist and SVM achieved accuracy in predicting AK and SOM, respectively. Clay, silt, CEC, and TN yielded favourable predictions, closely aligning with observations. Conversely, sand content, soil pH, AK, and SOM predictions were slightly less accurate, highlighting areas for improvement. Boruta algorithm streamlined covariate selection, reducing 23 covariates to 10 for clay and 4 for soil pH and AK prediction, enhancing model efficiency. Our study revealed spatial uncertainty patterns mirroring property distributions, with higher uncertainty in areas with elevated content. Model accuracy varied by confidence levels, performing best at intermediate levels and showing increased uncertainty at extremes. These findings offer insights into model capabilities and guide future research in soil property prediction. In conclusion, these results urge more research in small watersheds for soil and territorial management. [ABSTRACT FROM AUTHOR]

Termites contribute to the spatial heterogeneity of the ecological processes of the highly degraded lands called the bowé in West Africa, but the underlying determinants of the distribution of the mounds remain poorly understood. Thus, the study aims to determine the principal abiotic and biotic factors shaping mound densities on bowé in Benin, West Africa. A number of 64 plots were randomly sampled on sites with mounds and adjacent off‐mounds sites on bowé. Data were collected on abiotic (soil variables (pH, bulk density, particle sizes and soil organic carbon) and altitude) and biotic (the number of live termite mounds, plant richness and cover) factors. Correspondence analysis (CA) was applied to assess the pattern of vegetation and termite mounds on bowé; while principal component analysis (PCA) was used to assess the relationship between soil variables (pH, bulk density, particle size and soil organic carbon), altitude, number of mounds, plant richness and cover. Generalised mixed effects and linear mixed effects models with Poisson error distribution were used to analyse the variation in soil variables, number of mounds, species richness and cover between termite species. The findings revealed that the pattern of termite mounds on bowé was driven by altitude (topography) and soil clay content that contribute to termite activities as well as improving soil bulk density, plant species richness and cover. These factors were positively associated with all termite species considered, except for those belonging to the genus of Macrotermes. [ABSTRACT FROM AUTHOR]

Moisture migration in unsaturated soils is a result of the interaction between temperature and soil microstructure. In order to reveal the mechanism of moisture increase of subgrade soils under diurnal cycle conditions, a series of macro and microscopic tests were carried out on the unsaturated silty clay and sand soil, including liquid–vapor mixed migration tests simulating a one-dimensional subgrade, environmental scanning electron microscope (ESEM), and matrix suction test. Then, the soil microstructure in microscopic images was investigated using the particle (pores) and cracks analysis system (PACS). Next, the relationship between the thermal effects of the soil–water characteristic curve (SWCC) and changes in soil microstructure was analyzed. Finally, the change mechanism of liquid–vapor mixed migration based on the change in soil microstructural under thermal effects was analyzed. The results showed under the diurnal cycle, both the silty clay and sand soil columns appeared in the phenomenon of a "diurnal cycle of water vapor migration", which led to moisture accumulation at the top of the soil layer. In silty clay soil column, moisture was primarily driven by water vapor pressure and migrated upwards. Additionally, moisture redistribution led to changes in soil microstructure, which in turn influenced the process of moisture migration. The moisture content in the upper soil layer increased making both inter-aggregate and intra-aggregate pores decrease. The moisture content in the lower soil later decreased, leading to the water-holding capacity of the lower soil layer to increase. So, the moisture migration gradually decreased at night. In the sand soil column, moisture migration was mainly driven by gravity potential and migrated downwards. Moisture redistribution made inter-aggregate pore and matrix suction of the upper soil layer increase, leading to an increase in moisture migration at night. [ABSTRACT FROM AUTHOR]

Foundation plays a vital role in weight transfer from the superstructure to substructure. However, foundation characteristics such as pile group, piled raft, and footing remain unfolded due to their highly non-linear behaviour in different soil types. Bibliography analysis using VOSvierwer algorithm supported the significance of the research. Hence, this study investigates the load-bearing capacity of different types of foundations, including footings, pile groups, and piled rafts, by analyzing experimental data using finite element tools such as PLAXIS 2D and GEO5. The analysis involves examining the impact of various factors such as the influence of surcharge and the effect of different soil types on the load-bearing capabilities of the different types of foundation. For footing, parametric investigations using PLAXIS 2D are conducted to explore deformational changes. Pile groups are analyzed using GEO5 to assess their factor of safety (FOS.) and settling under various criteria, such as pile length and soil type. The study also provides insight into selecting the right type of foundation for civil engineering practice. Findings showed that different soil types have varying deformational behaviours under high loads with sandy soil having less horizontal deformation than clayey soil. Also, it was observed that increasing the pile thickness by 50% resulted in a reduction of 13.88% in settlement and an improvement of 16.66% in the FOS. In conclusion, this study highlights the importance of professionalism, exceptional talent, and outstanding decision-making when assessing the load-bearing capabilities of various foundation types for building structures. [ABSTRACT FROM AUTHOR]

The paper investigates the effect of hydrated lime on shear strength properties and behaviour of London clay, triaxial. Unconsolidated undrained tests were performed to identify the effect of lime dosage, compaction water content and curing time on the shear strength and stress–strain behaviour of the treated soil. The mineralogical and physicochemical transformations occurring during the curing of the soil were also monitored. The results showed that strength gain was strongly influenced by lime content and the curing period, whereas compaction water content was less influential. It was found that the strength evolution is likely to continue over long periods of time and result in very considerable strength gains on the hardening of pozzolanic reaction products. It was also shown that adequate early strength gains can be obtained with reduced material consumption, thus further increasing the sustainability of the treatment processes. The paper also highlighted the importance for engineering design of considering the brittle stress–strain response of the lime-treated soil, and the benefit of using lower amounts of lime to alleviate this undesirable effect. The implications of various aspects of soil brittleness in different situations merit further attention and should be explored by way of modelling in future work. [ABSTRACT FROM AUTHOR]

Clay minerals in soils and rocks exhibit large volume change upon interaction with water and this behavior becomes even more complex when the strata are being stressed by the engineering and environmental loads. Therefore, a realistic prediction of the hydro-mechanical behavior of the clay-bearing strata is always a challenge due to their coupled swelling-mechanical response in the cases of geotechnical and geoenvironmental engineering problems, nuclear waste storage in clay-bearing rock repositories, shale gas extraction, and other uses of clay in the manufacturing industry. All the existing behavior models have restricted applications in the engineering and other fields of practice mainly due to the partial consideration of the structure and fabric of clay-bearing strata in the model formulation. In this study, a hydro-mechanical behavior model has been formulated using the parameters acquired from the molecular-level simulations and modeling of the volume change and stress–strain behavior of the clay-bearing structure. The Molecular Mechanics and Molecular Dynamic simulations were performed on the natural structure of the clay-bearing strata formulated using Monte Carlo technique. The mathematical model, developed from the simulation results, can predict the overall hydro-mechanical behavior of clay-bearing strata for all possible combinations of clay minerals, non-clay minerals, salts causing cementation of the soil/rock structure, confining pressures, and the induced strain levels. The developed model has successfully been validated through laboratory and field testing on the clay-bearing strata in both the elastic and elasto-plastic regions of the stress–strain behavior and also from the data of two (02) swelling clays (MX-80 and FEBEX Bentonite) from the existing literature, supporting the universal nature of the developed behavior model. [ABSTRACT FROM AUTHOR]

In‐depth knowledge about the impact of organic matter (OM) on soil water vapor sorption (SWVS) and associated hysteresis related to various water activity (aw) levels is limited. The objective of this study was to elucidate the effect of OM on SWVS and sorption hysteresis for different aw levels. We measured water sorption isotherms and physicochemical properties of eight soils with varying clay (6%–47%) and OM (2.0%–7.8%) contents before and after OM removal. In general, OM increased SWVS, but the effect of OM on SWVS varied for different aw ranges. The presence of OM generally increased water vapor sorption during the adsorption process. For soils with OM content above 4.6%, the presence of OM decreased water vapor sorption during the condensation process. The local hysteresis (Hw) of soils with OM was higher than that of soils without OM for soils with OM contents above 3.4%. For aw < ∼0.75, the water vapor sorption hysteresis of soils with and without OM showed a significant correlation with cation exchange capacity (CEC), and the Hw values of soils with OM were lower than that of soils without OM for the same CEC. The OM can affect water vapor sorption and the associated hysteresis at low aw levels through adsorbed cations and organic functional groups, and at high aw levels through the structures of pores and OM. Core Ideas: An increase in water vapor sorption due to OM mainly occurred during adsorption.A decrease of water vapor condensation due to OM is caused by a reduced pore volume.The OM content affects water vapor sorption hysteresis.The CEC is a key factor affecting sorption and hysteresis in soils with and without OM. [ABSTRACT FROM AUTHOR]

Phytoremediation of arsenic (As) by Pteris vittata (P. vittata) is a cost-effective and environmentally friendly method for restoring As-contaminated sites. However, the phytoextraction efficiency is low in some cases, such as clay soil, thus biochar was applied to enhance the efficiency of As extraction. The paper investigated the effect of biochar on soil characteristic, As mobility, and As uptake in P. vittata with a 90-day greenhouse experiment. Biochar derived from rice straw was added at rates of 0.5, 1.5, and 4% (w/w). The results showed that, under biochar amendment, soil pH raised from 5.24 to 6.03 and 4.91 to 5.85, soil dissolved organic carbon (DOC) increased 11.1–46.1% and 2.8–11.2%, respectively, in rhizosphere and bulk soils. Biochar also increased soil catalase (CAT) activity significantly, especially for the rhizosphere soil. Besides, biochar increased the labile As in the soils and transfer coefficient from roots to aboveground, thereby enhancing As accumulation by P. vittata tissues. The accumulation of As in fronds of P. vittata was up to 350 mg kg−1 in 1.5% biochar, which was more than twice the control and far beyond other biochar treatments. The results indicate that biochar addition is favorable to improve phytoremediation of P. vittata in As-contaminated soil and 1.5% (w/w) biochar may be a reasonable application ratio, thus providing an effective solution to enhance the efficiency of As phytoextraction. Biochar increased soil catalase activity in the rhizosphere of P. vittata. Biochar increased the labile concentration of arsenic in soil and arsenic accumulation in P. vittata significantly. Combining biochar and P. vittata reduced arsenic in soil. Biochar amendment was favorable for phytoremediation of P. vittata in arsenic-contaminated soil. [ABSTRACT FROM AUTHOR]

Discrete measurement targets were frequently utilized in image-based methods on the specimen's surface to monitor the soil specimen during triaxial testing. However, the required density of measurement targets that should be used in triaxial testing to achieve highly accurate volume measurement has not been investigated. To overcome this limitation, this paper presents a parametric study to determine the optimum target/point densities to be utilized on the triaxial soil specimen surface to achieve the desired level of volume measurement accuracy in image-based methods. LiDAR scanning was applied to establish the "ground truth" volume of the specimen. The effects of deformation and failure modes were investigated by calculating the volume measurement accuracy at different strain levels and for different undisturbed soil specimens of clay and sand with silt. An interpolation method was proposed to increase the number of discrete targets representing the triaxial specimen's surface. The analysis results show that a higher target density is required at a larger strain. Also, adding the number of interpolation points can only increase the accuracy to a certain level. As the volume measurement accuracy was different for each of the clay and sand with silt specimens, the non-uniform deformation, and failure mode of the specimen can affect the required optimum density of discrete measurement targets. In conclusion, it is recommended to choose the optimum density of targets based on the accuracy requirement, the maximum soil deformation level, and the expected failure mode of the specimen. [ABSTRACT FROM AUTHOR]

Adhesion between track shoes and clay soil has a significant effect on vehicle track-terrain interaction. To correctly evaluate the adhesion between track shoes operating on clay soil, tri-axial shear test (TST), traction test (TT) and direct shear test (DST) were performed on clay loam (C), sandy loam (S) and loamy clay (L) under different moisture contents (w), shear rates (v) and normal loads (σ). In the TST, the effect of w on cohesive strength and internal friction angle was investigated. Cohesive strength initially increased rapidly with the increase of w then decreased slowly when w reached the plastic limit (PL). Internal friction angle decreased gradually as w increased and then decreased sharply when w ＞PL. In the TT, shear strength increased slowly with the increase of shear rate (v) and then stabilized. In the DST, shear strength increased linearly with the increase of normal load (σ). Thereafter, soil shear strength equation considering w , v and σ was modified based on the results of TST, DST and TT. On this basis, considering the structural parameters of track shoe, adhesion models were developed and verified. The predicted and measured values of normal adhesion and tangential adhesion on C, S and L had strong linear correlations with the coefficients of determination ranging from 0.9665 to 0.9932, and the relative errors were 2.56%, 3.16% and 2.67%, indicating that model derivation and correction were effective. The proposed adhesion models can therefore provide a theoretical basis for the desorption design of track shoes for operation on clay soils. • The novel adhesion models for track shoes operating on clay soils were proposed. • Soil shear strength model considering moisture content, shear rate and normal load. • The interaction mechanism between track shoes and clay soils was analyzed. • The laboratory tests verified the novel adhesion models. [ABSTRACT FROM AUTHOR]

The effects of soil texture on trace metal concentrations and geochemical fractions in an apple orchard soils were investigated. For this purpose, soil samples were taken from the apple orchards with two different soil textures located on the same geomorphological unit in Çanakkale, Turkey. A wet digestion was used to determine total trace metal concentrations, and a sequential extraction method was used to determine geochemical fractions of the metals. According to average total concentrations of all metals, except Pb, were found to be significantly higher (p < 0.05) in clay soils. Sequential extraction analysis showed that potential mobile fractions were ordered as Cd (68.8%) > Pb (52.4%) > Cu (42.0%) > Zn (34.8%) > Ni (32.3%) > Cr (22.9%) in clay soils and as Cd (61.6%) > Pb (51.6%) > Cu (40.2%) > Zn (30.7%) > Ni (30.8%) > Cr (24.9%) in loamy soils. The results revealed that all metals, except Pb, in exchangeable/acid soluble, oxidizable and, potential mobile fractions were found to be significantly higher in clay soils (p < 0.05). It was figured out that clay contents played an effective role in total concentrations of metals and their distribution in geochemical fractions. [ABSTRACT FROM AUTHOR]

Coastal clayey soil has a great potential for food production and safety while poor physico-mechanical properties have impeded its sustainable utilization. A field experiment was conducted to assess the influence of biochar on physicomechanical properties of coastal clayey soil. The biochars were applied to the coastal soil with the rate of 0, 1%, and 3% (w/w), respectively. Compared with control treatment, the application of three biochars (at the rate of 3%) had significantly improved soil fertility, i.e. organic carbon, total nitrogen, available nitrogen and available phosphate, respectively. Biochar treatments significantly increased soil porosity, and aggregates stability, while reduced the soil salinity compared to the control treatment. Meanwhile, biochar application significantly increased the plastic index of coastal clayey soil while decreased soil tensile strength and shrink swell properties compared to the control. Biochar clearly altered soil pore characteristics, consequently rebuilding the new ions leaching channels. Overall, the cow manure biochar (650 °C) at the rate of 3% treatment showed maximum efficiency on soil salinity, fertility, physicomechanical properties, and crop yield. The biochar amendment improved coastal soil by ameliorating soil pore space and structure, improving soil tillage operation and rice yield, decreasing salt stress, and reducing mechanical strength. [ABSTRACT FROM AUTHOR]

In addition to creating environmental threats, the leakage and entrance of chemical fertilizers into soil, which is possible in various ways, dramatically changes the physical and mechanical properties of soil. Furthermore, clay soils in the vicinity of monoammonium phosphate (MAP) contamination show substantially negative behavior, thus, improving the engineering geological factors of soil has become a huge challenge for engineers. Extensive programs such as triaxial compression test, consolidation test, compaction test, Atterberg limits, and collapse tests, in addition to X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) were performed on samples containing 10%–30% MAP over 7 days, 1, and 3 months. The mentioned trend was repeated when 0.5%–3% nano A (Al2O3 in alpha phase), nano F (Fe2O3 in alpha phase), and AF in form of a nanohybrid were added to soil which had been contaminated by MAP. Gained reports demonstrated significant declines in maximum dry density, plasticity index, and shear strength of contaminated soil when compared with natural soil. Conversely, increases in liquid limit, plastic limit, consolidation settlement, as well as soil collapse index were observed. Furthermore, a decrease in the amount of minerals in the XRD results and the formation of a flocculated structure in the SEM images in MAP-contaminated soil are evident. According to microstructural analysis, adding nano A, nano F, and AF nanohybrid as an improvement phase caused remediation of the soil structure and created cementation bonds between soil particles, thereby increasing the maximum dry density and soil shear strength, and decreasing the consolidation settlement and soil collapse index. Therefore, the use of AF as an efficient additive to remediate physical and mechanical properties of soils that have been contaminated with MAP, and to decrease the geological hazards of these kinds of contamination is recommended. [ABSTRACT FROM AUTHOR]

The efficiency of manure application is a function of quantity and time of application. Two field trials were conducted to determine the effects of time and quantity of manure application on soil nutrient dynamics and proximate contents in Abeokuta, Nigeria, by cultivating egusi melon with 0, 5, 10, and 15 t.ha−1 poultry manure (PM) applied at 2 and 4 weeks before planting (WBP). Melon was planted at 2 and 4 weeks after manure application (WAMA). The year of cultivation affected post cropping soil nutrient contents. Soil organic matter was not reduced with 10 t.ha−1 application. It also maintained soil nitrogen content and increased exchangeable potassium. Soil calcium and magnesium content increased with cropping. In 2017, planting with 5 t.ha−1 PM applied at 2 WBP gave the highest exchangeable acidity content, but from 10 t.ha−1 PM applied at 4 WBP, in 2018. Soil calcium and magnesium contents were higher with 2 years cropping. It was highest with either 10 t.ha−1 PM at 2 WBP or 5 t.ha−1 PM at 4 WBP. Soil magnesium content was highest with 10 t.ha−1 PM at 2 WBP. Cropping increased soil sand and clay particles but reduced silt particles. Seed crude protein was reduced with 2 years cropping. It was highest from 15 t.ha−1 PM applied at 2 WBP in 2017. Seed fat and carbohydrate contents were increased with 2 years cropping. For soil calcium and magnesium contents, 10 t.ha−1 PM applied at 2 WBP poultry manure is optimum. [ABSTRACT FROM AUTHOR]

The current techniques utilized for estimating seasonal fluctuations in earthing system resistance, including artificial neural networks (ANNs) and correlation/correction factors, rely on resistance records, soil resistivity measurements, and meteorological data collected across broad areas. However, they frequently fail to consider the impact of soil conditions and properties at the actual earthing location. As a solution, this research introduces a new method that models atmospheric conditions as soil suction and incorporates hydraulic soil properties (soil water retention characteristics and hydraulic conductivity) to estimate the seasonal changes in earthing resistance and performance. To illustrate this approach, this study constructs geometric models of vertical earthing rods for three homogeneous soil textures (clayey, silty, and sandy) utilizing COMSOL Multiphysics software. By coupling the differential equations governing electric current and water flow using Archie's formula and solving numerically with the finite element method (FEM) for various soil suctions, this research reveals that soil water retention and resistivity variations are notably influenced by soil texture. Sandy soil displays higher variability, silt soil demonstrates moderate changes, while clayey soil exhibits lower fluctuation. By linking soil resistivity changes to soil suction and hydraulic properties, this innovative method predicts seasonal trends in earthing resistance and performance. [ABSTRACT FROM AUTHOR]

The identification of clay soils is of great importance for the construction industry. Indeed, this type of soil presents an economic interest related to the exploitation of its clayey materials. Furthermore, the assessment of the potential for differential ground movement through the dryness of the soils and their rehydration is also an important issue to identify in order to reduce the swelling-shrinking hazard. The region of Mers El Kébir located in northwest Algeria, is at risk of this phenomenon because it is known for its marly clay compositions. Mapping this type of soil using satellite imagery offers an alternative to the engineering practice of establishing soil mineralogy, based on X-ray diffraction analysis, which is expensive and time-consuming. The objective of this research is to use ASTER satellite images to map different clay minerals. This analysis is based on remote sensing of spectral signatures corresponding to illite, kaolinite, and montmorillonite. The study of satellite images of the Mers El Kébir region validates the methodology developed, which could be used to help in the development and planning of new infrastructures adapted to the different types of soil. [ABSTRACT FROM AUTHOR]

The use of lime in sulfate-bearing clayey soils has historically caused structural damage to infrastructures due to the formation of an expansive ettringite mineral. In this paper, a research was conducted to study the effectiveness of natural pozzolana (NP) for providing better stabilization of sulfate-bearing soils. Compaction and free-swell potential tests were first performed on lime-stabilized grey and red clayey soils (GS and RS) containing different contents of added sodium and calcium sulfates (2, 4 and 6% Na2SO4 or CaSO4⋅2H2O). Then, the same tests were repeated by adding 20%NP. The test results indicated that the presence of 4% and 6% Na2SO4 in the soil resulted in an abnormal increase in the swell potential of both lime-stabilized GS and RS. The X-ray diffraction (XRD) results confirmed the growth of the ettringite mineral responsible for this higher swell potential. However, the use of 8% lime with 20%NP in stabilizing sulfate-bearing clayey soils produced significant improvements in the optimum moisture content (OMC) and maximum dry density (MDD), as well as in the swell potential. The addition of 20%NP into the lime-stabilized GS and RS eliminated the harmful effect of Na2SO4. In addition, for 120-day curing period, the use of 6% CaSO4⋅2H2O was found very effective by reducing the swell potential of NP-lime-stabilized GS and RS from 7.33% to 0.4% and from 2.79% to 0.2%, respectively trips. [ABSTRACT FROM AUTHOR]

The Qingliucun mountainous area is characterized by steep terrain, large topographic variation, a considerable free face, and massive highly fissured clayey soils. A high landslide started on June 29 2020, rapidly evolving and eventually causing, on December 4, 2020, a global sliding mass to move downward rapidly. This event seriously damaged houses and the main mountainous road to Qingliucun village on the mountainous platform, and temporarily blocked the Mengtun River, causing a 100-m long dammed lake. This work introduces the main features of this landslide and the earlier results of studies on this event. The main geological characteristics of the site and the morphological features of the landslide are presented. Moreover, the failure mechanism of the landslide is revealed according to the outcomes of site reconnaissance and monitoring as well as limit equilibrium stability analysis. Finally, this work focuses on the empirical estimation of landslide runout distance, which is instrumental in the prevention and mitigation of similar high landslide hazards. [ABSTRACT FROM AUTHOR]

The absence of calcium decreases the production of peanuts compared to any other element. To investigate the influence of calcium (Ca) applications on the production and seed quality of four diverse peanut cultivars from different regions—USA (NC-7), Egypt (Giza-6) and Nigeria (Samnut-23 and Samnut-24)—under clay soil conditions, two experiments were carried out at the Agricultural Experimental and Research Station, Cairo University, Egypt, during the two seasons of 2016 and 2017. The experimental design was a randomized complete block in a spilt-plot arrangement with three replications. The main plots were allocated to four peanut cultivars (Giza-6, Samnut-23, Samnut-24 and NC-7), and the sub-plots were devoted to calcium applications (soil application in the form of calcium sulfate dihydrate, foliar application in the form of calcium oxide and the control treatment of distilled water). Results indicated that all four peanut cultivars responded differently to the application of calcium fertilizers. The calcium application significantly enhanced peanut growth, yield components, biological, pod, seed, oil yields, seed oil, free fatty acids and seed calcium percentages in different cultivars. Soil calcium application significantly improved peanut production compared to foliar calcium application. NC-7 cultivar treated with the soil Ca application resulted in the maximum values of biological yield (92.9-ton ha−1), pod yield (6.8-ton ha−1), seed yield (4.4-ton ha−1), oil yield (2247.0 kg ha−1), pod index (203.2 g) and seed index (84.1 g). The interaction between the NC-7 cultivar and soil calcium applications is recommended to attain the best combination, leading to the highest yield and seed quality of peanuts. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) emissions affect the environment, the climate, and human health and originate mainly from agricultural sources like urea fertilizers. Such losses from urea fertilizer can be avoided by different application techniques like incorporation. However, the knowledge of the effect of these techniques on NH3 emissions is very limited and ambiguous since incorporation can also promote nitrous oxide (N2O) emissions. Three different principles of fertilizer incorporation methods were compared in three different soils (sandy, loamy, and clayey) at two moisture levels of 70% and 30% water-holding capacity (WHC), shallow mixing at 2 cm, injection with the slit technique at 5 cm, and deep complete incorporation at 5 cm simulating plow incorporation. The laboratory study was conducted with open dynamic incubation chambers where NH3 emissions were monitored with washing bottles while N2O emissions were studied with gas chromatographic (GC) measurements. The highest cumulative NH3 emissions occurred at low soil moisture levels in sandy soil (34% of the N applied). A maximum reduction in emissions by 87% was achieved with slit injection and 82% with deep injection compared to standard surface application. The reduction effect was positively related to increasing clay content. N2O emissions were delayed and highest from sandy soil. Overall, all urea incorporation techniques showed great potential for mitigating NH3 emissions on the clayey soil; for sandy and drier soils, only deeper or closed slot injection were consistently effective. However, connected to the surface incorporation at the higher moisture level, a relevant increase in N2O emissions compared to surface application was observed. Therefore, an increase in N2O emissions by urea incorporation may rule out specific incorporation techniques for NH3 emissions reduction from field-applied urea. In agricultural practice, a lower reduction in NH3 by fertilizer incorporation can be assumed in sandy soils or under dry soil conditions, as well as a more challenging technical implementation. [ABSTRACT FROM AUTHOR]

The low productivity of shallot 'Bima Brebes' during the rainy season contributed to increasing Indonesia's economic inflation. This study aimed to assess the sustainability of shallot cultivation in low-organic sandy clay soil during the rainy season in South Sumatera, Indonesia. The study observed the farmer group's actual shallot cultivation method. The research findings were expected to explain the phenomenon of shallot production (Cohen f2) at least 0.50 with a maximum error rate (α) of 0.05 and a probability of making the right decisions (1-β) at least 80%. The variables included climate, soil characteristics, cultivation methods carried out by farmers, plant growth, and shallot production. The cultivated field has sufficient porosity to drain water quickly. Still, it tends to make compaction easier. The diameter of the shallot bulb produced fell into category 1 (size over 2.5 cm) by as much as 31.0%, category 2 (between 2.0-2.5 cm) by 38.0%, and category 3 (between 1.5-2.0 cm) by 17.8%. The loss caused by Fusarium disease was 20.29%. Sustainability of low disease-resistance shallot variety cultivation in low-carbon sandy clay soil during rainy seasons was possible by regulating soil humidity rather than fungicide application. [ABSTRACT FROM AUTHOR]

Phyllite soil and red clay belong to the soils that negatively impact the engineering performance of railway subgrade and may cause subgrade bulges, uneven subgrade settlement, and other subgrade distresses. In order to make full use of these two soils, a collaborative improvement plan was proposed. A series of tests were conducted to analyze the synergistic effects of lime and red clay on the improvement of phyllite soil. The tests included the no loading swelling ratio, swelling pressure, consolidation, and direct shear tests. Additionally, scanning electron microscopy was used to investigate the role of lime and red clay in soil improvement. The test results show that a red clay ratio of 60% + lime content of 3% is the optimal composite improvement scheme. The scheme led to a 93% reduction in the no loading swelling ratio and an 88% reduction in swelling pressure. Additionally, cohesion, the internal friction angle, and the compression modulus increased by 345%, 73%, and 373%. Red clay and lime had weak synergistic improvement effects on the no loading swelling ratio, the swelling pressure, and the internal friction angle of phyllite soil, that is, the synergistic improvement effect of red clay and lime was less than the sum of the single improvement effect but greater than the single improvement effect. Red clay and lime had a strong synergistic improvement effect on the cohesion and the compression modulus of phyllite, that is, the synergistic improvement effect of red clay and lime was greater than the sum of the single improvement effect. The microstructure analysis test results show that red clay can fill the pores of phyllite soil and improve its immediate strength. Through hardening and cementation, lime can enhance the strength of phyllite soil as well as address the issue of the reduced engineering properties of phyllite soil and red clay when exposed to water. Red clay and lime promote each other's reactions and have a synergistic improvement effect on phyllite soil. [ABSTRACT FROM AUTHOR]

Featured Application: We found that in the areas with high seasonal rainfall, to stabilize clay soils, if the amount of Montmorillonite mineral is greater than a certain amount (for example, in this study, 45%), with any amount of chemical additives, they do not maintain their stability and collapse. Conversely, soils containing certain amounts of Illite and Kaolinite minerals with the smallest amount of chemical additives have the best performance. Although the interaction between clay minerals and lime is the most effective factor in lime stabilization techniques, it has not been deeply evaluated. This research study investigated the microstructural characteristics of lime-stabilized Bentonite and Kaolin soils using X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray (EDX) analyses. To consider the variation in clay mineralogy, these soils were mixed at varied ratios, stabilized, and then subjected to a durability process. The microstructural findings showed that the pozzolanic reactions with lime did not occur or occurred at a low level for Bentonite soil. However, they occurred at a very high level for Kaolin soil. The durability test confirmed the microstructural results and showed that the samples in which Bentonite soil had a share of 40 to 100% by dry weight of the soil did not last with any percent of lime. When the Kaolin soil content reached 100% by dry weight of the soil, the specimens lasted in the best possible way, even with 4% of the lime. This study concluded that the determination of optimum lime content based on the amounts and types of soil clay minerals is an important innovation for geotechnical projects and may be very cost-effective. [ABSTRACT FROM AUTHOR]

Soil properties have an important role in the movement of minerals in the environment. Therefore, the study of mineral adsorption and soil properties can help solve environmental pollution problems. In the present work, batch adsorption of zinc and lead was studied on some Algerian soils (clay soil, sandy loam soil, and sandy soil), as a function of contact time, pH, metal concentration and physicochemical properties. The results showed the metal adsorption amount depends on soil pH and initial ion concentration, soil type, temperature, exchange capacity, and metal hydrolysis. Ionic strength and organic matter content investigation indicate that, clay soil presents greater adsorption of both metals than the two other soils. The metal ions' adsorption decreases with decreasing pH and increasing ionic strength. The results showed that the adsorption amount of lead is better than that of zinc in all studied samples. The equilibrium data good fit well with Langmuir and Freundlich's models. The tested kinetic models showed that soil adsorption of these metals are biphasic and diffusioncontrolled process. For all pH values, the adsorption was relatively fast at the beginning followed by a slower phase at reaching the equilibrium time. [ABSTRACT FROM AUTHOR]

Engineering project assessment at Al-Muthana Airport in Baghdad, Iraq, has been studied using a 3D electrical resistivity imaging survey. The site investigation is crucial for assessing the future of the region's infrastructures since it reveals the location of buried facilities or weak zones below the surface and measures localized groundwater levels. Wenner-Schlumberger array was used to conduct four parallel 2D electrical resistivity spreads (MU1 to MU4). Each spread line was 100 m in length with 1 m electrode spacing and an average spacing of 9 meters between any two adjacent lines. The depth of the investigation was around 23.8 m. Survey lines were drawn going from northwest to southeast. These spreads were combined to provide a 3D image of a 2700 m2 space.The robust inversion method and the inverse model generated using the standard least-squares method showed horizontal slices identified three zones with resistivity distribution ranging from 2 to 45.5 ohm.m. The first zone, from surface to 3.37 m, had relatively high resistivity of sandy silty clay soil with relatively low moisture content; the second zone, approximately from 3.37 to 12.2 m, had very low resistivity representing groundwater table; and the third zone, from 12.2 to 23.8 m representing high stiffness and density and relatively high resistivity due to gravel presence in the deposits. The second zone highlights potential risk zones for construction projects; as a result, it is advised that the zone surrounding the foundation be filled with a low permeability layer and that the towers be built on deep foundations. [ABSTRACT FROM AUTHOR]

Background: Particle size distribution (PSD) is a fundamental soil measurement that is crucial for agriculture, engineering, hydrological, and environmental applications as well as in basic research such as in developing water release curves in flow and transport modeling. The accurate determination of PSD, particularly clay content, is especially critical in ascertaining the magnitude and rates of many physical, chemical, and hydrological processes in soils. The accuracy of the hydrometer method for PSD, which relies on the settling velocity of soil particles in a soil suspension, could be affected by the density of the suspension, which in turn, depends on the initial sample mass, texture, and mineralogy of the soil. Aims: We hypothesized that (1) initial mass determines the concentration and the physical interaction of particles in a soil suspension and affects particle settlement, recovery, and the accuracy of the hydrometer method, and (2) the widely used initial air‐dry mass of 50 g underestimates the clay percentage of medium to heavy textured tropical soils. The objective of this study was to investigate the effect of mass and KCl on clay recovery in tropical soils with varying texture and mineralogy using the hydrometer method. Methods: The experiment comprised seven soils, four soil masses (10, 20, 30, 50 g), and two KCl treatments in a 7 × 4 × 2 factorial design replicated three times. Results: Results showed a general trend of increasing estimates of clay % as the soil mass decreased from 50 to 10 g and the KCl concentration increased from 0 to 0.0025 M. This implies that using an initial sample mass of 50 g in sedimentation methods, underestimates, and 10 g overestimates the clay % in predominantly medium to heavy textured tropical soils. Interestingly, there was a drastic change in texture for most of the soils as the sample mass decreased to 10 g. Conclusions: We conclude that the initial air‐dry mass affects the clay recovery of medium to heavy textured humid tropical soils. Results suggest that the ideal initial mass for these soils lies between 20 and 30 g. Furthermore, the mechanistic pathway that drives the observed decrease in clay recovery as soil sample mass increase could be due to the flocculating tendency of KCl. [ABSTRACT FROM AUTHOR]

A method for the estimation of the non-linear, time-dependent settlement of piled raft foundations (PRFs) embedded in saturated clayey soils subjected to uniformly distributed load under the single-drainage condition was developed. A total of 20 different rectangular PRFs resting on four different types of normally consolidated to moderately overconsolidated clays (overconsolidation ratios of 1, 2 and 5) were analysed to quantify their short- and long-term settlements. Rigorous three-dimensional, elasto-plastic finite-element (FE) analyses were performed with the critical-state-based modified Cam Clay soil constitutive model. Biot's coupled consolidation theory was used to model the time-dependent dissipation of excess pore pressure under the single-drainage condition. The FE analysis results were used to investigate systematically the influence of time and various soil and PRF parameters on the settlement responses of piled rafts. Fitted equations correlating PRF settlements and the degree of consolidation with various influencing parameters were developed. The proposed equations predicted the immediate and primary consolidation settlements and the degree of consolidation with reasonable accuracy and can be used in initial design stages. [ABSTRACT FROM AUTHOR]

The present study aimed to assess the efficiency of monoammonium phosphate (MAP), with controlled-release technology, on cowpea, soybean, and corn in the Brazilian Eastern Amazon edaphoclimatic conditions. It were evaluated MAP conventional, FH Humics MAP that incorporates humic acid, and Potenza MAP that incorporates polymer, and two soils with different clay contents (23.1 and 37.6%), on the growth of cowpea, soybean, and corn, in a greenhouse. Simultaneously, it were evaluated four levels of P (0, 40, 80, and 120 kg ha-1 of P2O5), for the mentioned formulations on cowpea grain yield, in cerrado, and upland forest environments. Fertilization with MAP Humics and MAP Potenza promotes similar soybean, cowpea, and corn growth, and cowpea grain yield compared to conventional MAP, under greenhouse and field conditions, respectively. MAP formulations promote greater soybean, cowpea, and corn growth, and cowpea grain yield in the sandy loam and cerrado than in sandy clay soil and upland forest environment, respectively. Increasing levels of MAP formulations have no effect on cowpea grain yield in the cerrado but promote linear cowpea grain yield increase in the upland forest environment. [ABSTRACT FROM AUTHOR]

Compacted specimens prepared from four clayey soils were subjected to drying in order to monitor the volumetric shrinkage period. Specimen volumes were recorded with manual caliper readings and the proposed image-based method as the shrinkage continues. For the image-based method, a photogrammetry technique known as Structure from Motion was applied. This technique offers a complete three-dimensional solid model of objects from two dimensional images. In this technique, the object is photographed from different perspectives to construct a digital point cloud. Once a proper calibration is made, these points represent the real-world coordinates and comprehensive analyses can be made using surface data. To that end, an imaging setup was established and a parametric study was conducted on a solid calibration object for the accuracy assessment of the method. The volumes of the compacted specimens obtained with the image-based technique and conventional Vernier caliper readings were compared to each other and evaluations were made by means of volumetric strain graphs and soil shrinkage curves. The proposed shrinkage monitoring technique offered accurate, nondestructive and operator independent results. [ABSTRACT FROM AUTHOR]

This paper aims to assess the behavior of the unconfined compressive strength (UCS) of polypropylene fiber (PF) reinforced natural pozzolana-lime-stabilized expansive grey clayey soil (GS) contaminated by sulfates. Lime (0--8%), natural pozzolana (NP) (0--20%), and PF (0--3%) by dry weight of soil were used. GS was contaminated by different sulfate contents (0-6%) and UCS was assessed at various curing periods (7--120 days). Results showed that adding 8% lime alone or with 20% NP considerably improved UCS. Including 1% or 2% PF as reinforcement without sulfates in lime-stabilized GS transferred stress from GS to PF due to bonding. However, increasing PF beyond 2% formed lumps, reducing contact and friction coefficient, thus decreasing UCS. This means that the optimum PF dosage was found to be 2%. The UCS of GS increased with PF content up to 2% and then decreased. The UCS significantly increased with higher calcium sulfate content and curing period due to observed cementing agents in X-ray diffraction (XRD) and scanning electron microscopy (SEM). Adverse effect of ettringite mineral on UCS caused by sodium sulfate addition was suppressed with the combination of 20% NP and 2% PF in lime-stabilized GS. Binding forces from lime and NP resisted to ettringite expansion. Sensitivity of UCS to sulfate effect was more pronounced with sodium sulfate than calcium sulfate. In addition, NP--PF mixture in lime-stabilized GS was more effective, improving the strength of expansive soil, especially with sodium sulfate. In conclusion, reinforcement of NP-limestabilized expansive soils with PF is an effective method. [ABSTRACT FROM AUTHOR]