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Three quarters of the world's significant urban centers are located in coastal regions where clay minerals are prevalent. The microstructures and physico-mechanical properties of clay sediments are highly susceptible to alterations in pore water chemistry. The pore water chemistry in soil changes easily due to groundwater pollution, seawater erosion, degradation, etc. However, there are several inconsistencies in the literature on the change of physical and mechanical properties of clay soils caused by the change of pore water chemical properties, i.e., disparate experimental results were reported for the same soil property, or varying explanations were proposed for the identical experimental results. Currently, the research in this field mainly focuses on the macroscopic behavioral modifications while lacking the explanations of microscopic mechanism. Therefore, this paper presents a comprehensive review of researches conducted over the past four decades on the impact of pore water chemistry (including salt type, salinity, ion valence, pH) on soil properties such as the microstructure, settlement, Atterberg limits, shear strength, conductivity, unsaturated soil mechanics properties and thermal properties. The fundamental mechanisms underlying the varied experimental observations on clay sediments affected by salt and pH are systematically explored, and deficiencies in this field are identified. The observed dispersion in the literatures is attributed to the spatial variation and heterogeneity of soil compositions, different test methods, and insufficiency of the fundamental microscopic mechanisms of the observed soil behaviors, etc. Therefore, it is necessary to further explore the essential mechanisms of the test results in the future to establish a unified conclusion. [ABSTRACT FROM AUTHOR]

Soil salinity is a major challenge in agriculture, particularly in calcareous soils with high calcium carbonate levels. Biochar, produced from biomass pyrolysis, is being considered as a potential solution for mitigating salinity effects. A greenhouse pot experiment was conducted using calcareous soil from a saline field to investigate the effects of sugarcane biochar applied at different rates (0.0%, 2.0%, and 5.0%) on soil properties and wheat (Triticum aestivum L.) growth. Results showed that both Low Rate (2.0% biochar) and High Rate (5.0% biochar) treatments significantly improved soil pH, reduced electrical conductivity (EC), and increased soil organic matter (SOM) content. Plant growth indicators such as plant height, stem diameter, and leaf chlorophyll content also showed significant improvement with biochar application. High Rate had more pronounced effects compared to Low Rate. The analysis confirmed the significant effects of biochar on soil properties and plant growth, indicating its potential as a beneficial soil amendment. Sugarcane biochar has the potential to mitigate salinity stress and enhance crop productivity in calcareous soils. Further research is needed to explore the long-term effects of sugarcane biochar application and its interactions with other soil management practices in different crop systems. These findings highlight the promising role of biochar as a sustainable approach for mitigating salinity stress in agriculture and improving soil quality for crop production. The study's findings highlight the potential industrial applications of sugarcane biochar in addressing soil salinity issues prevalent in calcareous soils, particularly in agriculture. The research underscores the positive impact of biochar on soil attributes, plant growth, and nutrient availability. With its ability to improve soil pH, reduce salinity, increase soil organic matter, and enhance plant growth, sugarcane biochar emerges as a promising soil amendment for agricultural use. This presents an opportunity for industries involved in sustainable agriculture, soil management, and crop enhancement to explore the integration of biochar into their practices. Additionally, the study emphasizes the need for further research and field trials to optimize biochar application rates, assess economic feasibility, and ensure environmental sustainability. The insights gained from this study offer a pathway for industrial stakeholders to explore biochar's role in enhancing soil quality, promoting plant growth, and ensuring sustainable agricultural practices. [ABSTRACT FROM AUTHOR]

The paper presents the results of systematic investigations on the gamma dose rates in air, natural radioactivity in soil and the dependence of radioactivity on the mineralogy of soils in the environs of the Belagavi, Karnataka, India. The gamma dose rates were measured using a portable survey metre and the activity in soils were measured using NaI(Tl) based gamma ray spectrometer and the mineral composition was studied using FTIR spectroscopy. The activity of 40K varies from 72.52 to 324.76 Bq kg−1 with an average of 153.17 Bq kg−1. The 226Ra activity varies from 16.53 to 70.53 Bq kg−1 with an average value of 23.88 Bq kg−1 and the activity of 232Th varies from 10.95 to 59.07 Bq kg−1 with an average value of 25.75 Bq kg−1. Elevated levels of 226Ra, 232Th and 40K in soils were observed in some part of Belagavi, which was traced to the mineralogy of the region. The higher activity of natural radionuclides poses radiological implications to the population of the region. The activity utilisation index was found to be is above the normal levels in some locations. The pattern of distribution of radionuclides in the region was studied using SPSS statistical software. The soil with clay minerals Haematite, Calcite, Kalonite, Albite and Feldspar showed higher radionuclide content. [ABSTRACT FROM AUTHOR]

The study investigated the adsorption of dissolved organic carbon (DOC) on Chinese soils from four long-term experiments involving five treatments: (1) no fertilization (control), (2–4) inorganic nitrogen (N), phosphorus (P), and potassium (K) fertilization (N, NP, and NPK), (5) NPK plus manure (NPKM). The results showed that DOC adsorption followed a modified Langmuir isotherm model effectively (R2 = 0.912 ~ 0.991). The maximum adsorption capacity (Qmax) (i.e. saturation deficits) generally increased with increasing soil organic carbon (SOC) due to fertilization in Luvic Phaeozem, Haplic Gypsisols, and Eutric Cambisols. However, it decreased significantly in acidic soils (Haplic Acrisols) from 15.59 g/kg for control, to 13.96, 13.03, 9.30 and 8.02 g/kg for N, NP, NPK and NPKM, respectively. Moreover, long-term fertilization, particularly with organic fertilization (e.g. NPKM), resulted in an increase of carbon (C) saturation by 1.42 g/kg (5.52%) in Luvic Phaeozem, 9.27 g/kg (44.29%) in Haplic Gypsisols, and 3.75 g/kg (27.66%) in Eutric Cambisols; however, there was a slight decrease by 1.70 g/kg (−7.49%) in Haplic Acrisols. Canonical correlation analysis (CCA) revealed that clay content and soil available iron (AFe) might be the crucial factors controlling C deficits, and subsequently, C saturation, along with current SOC. In conclusion, long-term fertilization contributed to C saturation in neutral-to-alkaline soils, but not in acidic soils. Thus, further attention should be paid to the long-term effects of fertilization on C saturation. [ABSTRACT FROM AUTHOR]

In recent times, large-scale infrastructural projects are being constructed on varieties of soil, especially in highly compressible marine clays and soft soil. The coefficient of consolidation (cv) is one of the most important technical parameters used to estimate the consolidation characteristics of the soil. The experimental laboratory techniques used to obtain cv are time-consuming and possess different practical limitations. In this study, a reliable method for predicting cv is presented based on machine learning (ML). The study considered 11 inherent soil variables, among which the least significant variables are discarded using univariate feature selection technique. Different ML models were developed like the random forest, artificial neural network, and support vector machine for nonlinear mapping of the cv using dimensionally reduced independent variables. Verification against experimental data demonstrates that the Random Forest model accurately predicts the cv (with MAE = 0.0231, MSE= 0.00148, and RMSE = 0.03854). Further, a comparative study of the proposed model is presented with available empirical equations and numerically simulated data. Moreover, the strengths and shortcomings of different ML algorithms are also discussed in detail. [ABSTRACT FROM AUTHOR]

Green roofs' (GR) positive impact on indoor thermal conditions in hot areas may have possible negative impacts during hot and cold weather. Most previous studies have focused on GR's positive effects as a standalone strategy without mitigating these side effects of GR application. This study contributes to a more comprehensive understanding of the impact of GR and how to mitigate the negative aspects by integrating it with other passive techniques (natural ventilation and thermal insulation). Therefore, this study experimentally compares the seasonal impact of various soil layer configurations, integrated with natural ventilation, on improving Indoor Thermal Comfort (ITC) throughout the day in summer and winter. Field experiments were conducted using two identical validated test boxes. The results revealed that clay soil reduced Indoor Air Temperature (IAT) during the daytime in summer by up to 4.7 and 4°C for low and high soil thickness, respectively. Increasing clay soil thickness improved average IAT during the daytime in summer and winter by up to 6.49% and 2.61%, respectively. Additionally, adding thermal insulation is preferred in winter, while uninsulated soil had a slight positive effect on IAT and Indoor Relative Humidity (IRH) in summer. The use of natural ventilation at night and closed-ventilated systems during the daytime in summer and winter is recommended. Clay soil could save cooling and heating energy by up to 34.8% and 12.18%, respectively. These findings might inform designers by adjusting different GR soil parameters and the importance of natural ventilation in improving multi-seasonal thermal and energy performance. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the straw to decrease the bulk density of sandy clay loam and clay soils and to determine the effect of this on the development of soybean and maize plants. The soils were compacted using Proctor test with different amounts of crushed straw on the soil surface corresponding to 0, 3, 6, 9 and 12 t ha−1. After this, the soils in pots were compacted with same levels of straw on its surface using the maximum bulk density each soil. Then, soybean and maize were sown and after 42 days, biometric characteristics and physiological parameters were evaluated. The results showed that the maximum bulk density and critical soil moisture for the sandy clay loam soil were 1.51 t m−3 and 0.15 kg kg−1, respectively, while those for the clay soil were 1.54 t m−3 and 0.19 kg kg−1. The straw reduced soil compaction for the two soils, resulting in lower soil bulk density with 9 and 8 t ha−1 of straw on the surface of sandy clay loam and clay soils, respectively. When evaluated the plant, the amounts 6 to 9 t ha−1 of straw promoted better initial development of soybean and maize plants. Thus, this study suggests that a minimum of 6 and 8 t ha−1 of straw be used on the surface of sandy clay loam and clay soils, respectively were efficient in promoting physical soil improvements and better plant development. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study that aims to enhance the cracking resistance of clay soil. Laboratory tests were performed in order to assess the effect of fiber content and length on the desiccation cracking of clay soil. During these tests, a digital image acquisition system was used to depict the development and spread of cracks. The results were analyzed using the DIC digital image correlation technique for the full-strain obtaining and image processing analysis for the crack feature measurements. The results show that date palm fibers have a considerable impact on the wide spread of cracks in clay soil during desiccation, in addition to their area and width. The DIC approach was useful for monitoring the displacement evolution and strain field detection on the surface of the specimen. The addition of fibers slows the water evaporation rate of the specimens. Optimum crack reduction ratio of about 47% was found in fiber-reinforced clay with 0.75% fiber content at 10 mm fiber length. [ABSTRACT FROM AUTHOR]

One of the potassium (K) sources for plant growth are the soil clay minerals (such as vermiculite) that have K element in their structure. The purpose of this research was the investigation of non-exchangeable K release from vermiculite clay soil to citric acid and calcium chloride extractants. Treatments included two vermiculite clay soil samples (with carbonatic (CV) and non-carbonatic (NCV)) and two extractants (0.01 M CaCl2 and citric acid). Thirteen successive extractions of K were done during 1, 2, 4, 6, 16, 24, 48, 72, 120, 168, 312, 384 and 552 h. Cumulative K release was determined and data was fitted to five kinetic equations. Results showed that there was a significant difference between treatments and extractants in K release. Cumulative K release to CaCl2 for CV and NCV was 3161 and 2935 mg kg−1, respectively while this was for citric acid 2172 and 1503 mgkg−1, respectively. The best kinetic models describing K release to CaCl2 and citric acid were Elovich (r = 0.98 and 0.80, p <.01) and power function equations (r = 0.96 and 0.76, p <.01). Maximum K release was observed in carbonatic vermiculite extracted with CaCl2 (1873 mgkg−1). Results of X-ray diffraction analysis showed that the peak intensity of vermiculite reduced with extraction time and no complete conversion were observed but its peaks showed the presence of mixed minerals such as mica-vermiculite and chlorite-vermiculite. Scanning electron microscopy analysis revealed that vermiculite clay soil structure was changed and more voids were observed in the mineral structure with extraction time. It's recommended that release experiment is done in longer time for better monitoring of vermiculite structural changes. The present study showed that vermiculite clay soil taken from Jiroft mine can be used as a natural source of potash fertilizer in sustainable agriculture. [ABSTRACT FROM AUTHOR]

Argentina stands as one of the leading consumers of herbicides. In a laboratory incubation experiment, the persistence and production of degradation metabolites of Atrazine, 2,4-D, and Glyphosate were investigated in a loamy clay soil under two contrasting agricultural practices: continuous soybean cultivation (T1) and intensified rotations with grasses and legumes (T2). The soils were collected from a long-term no-till trial replicating the influence of the meteorological conditions in the productive region. The soil was enriched with diluted concentrations of 6.71, 9.95, and 24 mg a.i./kg-1 of soil for the respective herbicides, equivalent to annual doses commonly used in the productive region. Samples were taken at intervals of 0, 0.5, 1, 2, 4, 6, 8, 16, 32, and 64 days, and analysis was conducted using high-resolution liquid chromatography UPLC MS/MS. An optimal fit to the first-order kinetic model was observed for each herbicide in both rotations, resulting in relatively short half-lives. Intensified crop sequences favored the production of biotic degradation metabolites. The impact of the high frequency of soybean cultivation revealed a trend of soil acidification and a reduced biological contribution to attenuation processes in soil contamination. [ABSTRACT FROM AUTHOR]

In recent years, magnesium oxide (MgO) has been considered by researchers as a new agent for the remediation of contaminated soils. In this paper, the effect of MgO and hydrated lime on the remediation of a clay soil contaminated with MTBE (Methyl Butyl Ether) was studied. The contaminated soil was made artificially by adding 2.25 g MTBE per kg of soil. MgO with different percentages (0.125, 0.25, 0.5, 5, 10, and 20%) and lime with 2.5, 5, and 10% percentages were added to the natural and contaminated soil. The results showed that by increasing the percentage of MgO or lime and curing time, the strength of natural and contaminated soil was improved. The results of the leaching tests showed that by adding 5, 10, or 20% MgO, all the existing MTBE in the soil samples were removed while for the smaller percentages of MgO (0.125, 0.25, and 0.5%) there was a decrease in the concentration of MTBE with time. The results of the leaching tests also revealed that the hydrated lime was effective in reducing the concentration of MTBE. The amount of reduction in the concentration of MTBE was dependent on the percentage of MgO or hydrated lime. The comparison of the results of the two binders showed that MgO was more effective than the hydrated lime in removing the MTBE from the soil. [ABSTRACT FROM AUTHOR]

Eucalyptus (Eucalyptus spp.) leads to depletion of nutrients from the soil due to its fast growing nature. Therefore, a pot experiment was conducted to study the effect of zinc (Zn) application on clonal eucalyptus growth, biomass output and its uptake, as well as response of eucalyptus to Zn in soils of three textures. The treatments consisted of eight levels of Zn (0, 5, 10, 15, 20, 25, 30, and 35 mg kg−1 applied through ZnSO4.H2O) in a completely randomized design triplicated in soils of three distinct textures (loamy sand, sandy loam and sandy clay). The plant height, collar diameter, dry weight of shoot and roots, soil plant analysis development (SPAD) readings, Zn concentration and uptake by leaves, stem+branches and roots increased significantly with Zn application. Average dry weight of shoot and roots (31.93 and 15.12 g plant−1, respectively) was significantly highest at 15 mg Zn kg−1 whereas Zn concentration and uptake (18.35 mg kg−1 and 286.2 µg plant−1, respectively) by roots were highest at 20 mg Zn kg−1. The above parameters differed significantly among soils as sandy clay>sandy loam>loamy sand except Zn content and uptake by roots and SPAD values which were highest in sandy loam soil. Loamy sand and sandy loam soil exhibited higher Zn use efficiency, shoot biomass response and uptake response to applied Zn than sandy clay soil. It is concluded to apply 20 mg Zn kg−1 in light soil and 15 mg Zn kg−1 in heavy textured soil for better growth and productivity of eucalyptus. [ABSTRACT FROM AUTHOR]

The agricultural frontier in Brazil advances mainly in areas of sandy soils, where the management of soil fertility is still a challenge, including the practice of liming. Limestone dissolution was investigated under varying doses (0–40 t ha−1) in soil samples with a wide range of textural gradients (5%–74% clay). In view of textural variations and limestone rates, the objective was to generate information regarding pH, the residual liming effect, and exchangeable calcium (Ca) and magnesium (Mg) levels, including under overliming conditions. Throughout the textural gradient, the pH was between 4.2 and 8.5. On more sandy soils (5%–18% clay), overheating (pH > 7) was obtained with ~ 2 t ha−1 of limestone. On clayey soils (37%–74% clay), a similar effect was obtained with ~ 10 t ha−1 of limestone, indicating the marked difference in the acid buffering capacity of these soils. In addition, the equilibrium pH in the context of overliming in sandy soil was higher (8.2) compared with clayey soils (7.8). The residual liming effect was greater in sandy soils due to the lower potential acidity. Regardless of the soil texture, the Ca/Mg ratio increased in the context of overliming. Liming must be carefully applied and requires proper recommendations, especially on sandy soils, avoiding pH ≥ 6.5, a condition that is not suitable for most crops. [ABSTRACT FROM AUTHOR]

The management of plant wastes and the development of soil quality characteristics have a key role in ensuring the harmony of the agriculture cycle with the environment. By adding the straw of plants directly to the soil as a source of organic matter, time poor soil quality characteristics can be improved. In the study, which was planned as a pot experiment, the effects of increasing the addition of sunflowers straw and maize straw by the increased proportions to clay soil. For this purpose, sunflower and maize harvest residue was added to the soil in 0% control (C), 0.5% (SS0.5 and MS0.5), 1% (SS1 and MS1), 2% (SS2 and MS2), and 4% (SS4 and MS4). Compared to the C, the water stable aggregate value increased by approximately 2.2 and 2.5 times in SS4 and MS4 implementations, mean weight diameter values increased approximately 2.7 and 3.3 times, respectively. In SS4 and MS4 implementations, the available water capacity increased by 80% and 102% compared to the control, respectively, and the modulus of rupture values were decreased by approximately 4.1–4.7 times. The 0.5% and 1% doses of straw implementations did not have great effects on the mechanical properties of the soils. According to the results of this study, 4% straw implementations it has been proven that the addition of SS and MS to the soil that by breaking them into small particles have great importance in rapidly increasing the physical quality of the soils and it can be used as an effective agricultural method. [ABSTRACT FROM AUTHOR]

Suction bucket installation in pure clay or pure sand is well established. However, in layered soils, particularly in sand over clay soils, the soil plug uplift is considered a major installation risk and feasibility of installation is often questioned. In this paper, the experience from installation of two suction bucket jackets at two offshore wind farms in layered soils is reported. The installation at both sites was successful and no excess plug uplift was observed. The transfer of suction to the clay-sand interface is believed to have contributed to the success of the installations. The two cases presented in this paper provides confidence in suction bucket foundation installation in similar soil conditions. [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]

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]

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]

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]

Desiccation cracking in clayey soils is a complex phenomenon investigated by researchers over many decades. Understanding and mitigating this issue will have a significant influence on the performance of raw earth construction materials and geotechnical engineering. In the current study, the digital image correlation technique was used to provide a thorough insight about the shrinkage anisotropy and the cracking mechanisms during drying. A series of free shrinkage tests were performed on an initially saturated slurries in order to assess the effects of the intrinsic characteristics of the material, the surface tension, the sample thickness and the geometric boundary conditions on the crack initiation and propagation in clays. The results show that increasing sample thickness prevents cracks formation in a non-swelling clay and delays it in a swelling clay. A vertical uplift was observed in the swelling clay due to a concave bending of the material during the desiccation shrinkage. An important anisotropy in the vertical shrinkage was observed compared to the horizontal shrinkage. The geometric boundary conditions indirectly influence the internal drying stress that becomes anisotropic. The intrinsic characteristics have a greater effect on the shrinkage behavior of the material than the hygrothermal and geometric boundary conditions. [ABSTRACT FROM AUTHOR]

The mineralization processes of plant residues in the soil vary depending not only on many factors such as climate and soil properties but also significantly on the C/N ratios. Increasing the surface area of these materials can also affect the mineralization process. This study increased the surface area of sunflower and maize harvest residues by fine grinding and applied 0.5%, 1%, 2%, and 4% doses by weight to soil with high clay content. After the application, the ammonium and nitrate nitrogen contents of the soils brought to the field capacity water content were measured on the 30th, 60th, 90th, and 180th days during the 180-day incubation period. The NH4 and NO3 nitrogen amounts of the starting soil were 12.76 and 13.99 mg kg−1, respectively. The highest NH4 and NO3 nitrogen were observed as 28.29 mg kg−1 and 96.53 mg kg−1 in the M4 application on days 90, respectively. The lowest nitrogen contents were determined as 3.74 mg kg−1 in the M2 application on the 180th day and 8.65 mg kg−1 in the control application on the 90th day. Applications have remarkably increased the mineral nitrogen content of the soil and hence soil MNSR. As a result, it has been determined that establishing more controlled processes in stubble management, converting the nitrogen from stubble materials into a useful form for the plant, and reducing chemical fertilizer costs can contribute to the improvement of agricultural sustainability. [ABSTRACT FROM AUTHOR]

The effect of amending "barren" sandy and clay soils with different organic origins on soil organic carbon (SOC) accumulation and permeability is not well known. Therefore, proposing desirable practices to improve their qualities and fertility is a major challenge. To improve soil organic carbon, permeability (PR) and productivity, the two barren soil textures were amended with 0.39 and 0.78 tha−1 (ton per hectare) of manure and lignite, respectively, and irrigated with treated wastewater. During the four years of experimentation, the ranges of increase in SOC of sandy and clay soils were 1.9–3.87 kgm−2, and 0.29–1.40 kgm−2, respectively, and in PR of 35.2–69.3% in sandy soils and 39.3–74.8% in clay soils. These improvements have a major effect on nutrient cycling, significantly improving water and nutrient availability to roots and plants. The levels of improvement increase with the amounts of organic compounds introduced, especially in the clay soil amended with 0.78 tha−1. The proportions of mineralized (lost) SOC were 35.3–62.3% in the sandy soils and 1.0–3.1% in the clay soils. The maximum crop weights produced were approximately 41.2 gm−2 in sandy soils and 1152 gm−2 in clay soils. Thus, amendment of barren sandy and clay soils by all three sources of organic carbon was beneficial, especially for the clay soil. achieved the desired objectives. The gain in clay soils is significantly greater than in sandy soils, which require further study. The type of practice desired by farmers will depend on cost and crop yield. Laboratoire Géoressources. Univerversité de Carthage-Centre des Recherches et Technologies des Eaux, B.P. 273, Soliman 8020 (Tunisia). [ABSTRACT FROM AUTHOR]

The spectral behavior of soil will change through degradation, which makes it difficult to retrieve soil properties using previously developed models. This study aims to use linear [including partial least squares regression (PLSR) and ratio soil index (RSI)] and nonlinear [including partial least squares-backpropagation neural network (PLS-BPNN) and partial least squares-random forest (PLS-RF)] models to estimate soil electrical conductivity (EC) and clay content in dust sources. For this purpose, 142 soil samples were collected in Khuzestan province. After laboratory spectroscopic analysis, the area and depth of diagnostic absorption features (AFs) of continuum removed (CR) spectra were calculated. The results revealed that with increasing clay content, the depth of AFs at 1400, 1900, and 2200 nm will increase. Meanwhile, an increase in the soil salinity will increase the depth and area of AFs in 1450 and 1915 nm and decrease the depth and area of AF in 2200 nm. Spectral ranges of 2100–2300 and 1400–1600 nm were identified as the most important portions of the visible and near-infrared spectrum for analyzing clay content and EC, respectively. The RSI method performed poorly in soil salinity and clay content estimation. PLSR and PLS-RF methods overestimated clay content and salinity in low values. The PLS-BPNN model had the best performance for estimating clay content (RPIQ = 4.51) and EC (RPIQ = 4.76). Considering the expected non-linear relationship between soil properties and corresponding spectral reflectance, the results of this study were acceptable. [ABSTRACT FROM AUTHOR]

In this study, the effects of polypropylene fibre content and length on the mechanical properties of municipal solid waste incineration (MSWI) bottom-ash-mixed (BA-mixed) clay soil were investigated through triaxial tests. By varying the fibre length and content, the stress-strain relationship and strength characteristics of polypropylene fibre-reinforced soil were analysed under different confining pressures. The main stress difference and shear resistance of polypropylene fibre-reinforced BA-mixed soil were discussed. The law of strength variation was used to analyse the reinforcing mechanism of fibres during the process of soil shearing. The results demonstrate that the strength and deformation resistance of polypropylene fibre-reinforced soil are significantly enhanced when compared with the original soil and pure BA-mixed soil. With the fibre content increases, the internal friction angle of the reinforced soil increases slightly, whereas the cohesion of the reinforced soil increases significantly. The sample can reach the maximum strength and have the best reinforcement effect when the control polypropylene fibre length is 2.5 cm, and fibre content is 0.3%. [ABSTRACT FROM AUTHOR]

The geotechnical properties, chemical reaction mechanisms, and microstructure evolution of alkali-activated fly-ash-stabilised construction and demolition waste (C&D) and the main components recycled concrete aggregate (RCA) and clay brick (CB) were investigated in this study. The alkali activator was a composite solution of sodium hydroxide and water glass. XRD, FTIR, SEM, and UCS testing methods were used to analyse the properties and mechanisms of the alkali-activated fly-ash-stabilised C&D and main single-component RCA and CB. The test results demonstrate that using alkali-activated fly ash in stabilising C&D improves the UCS of the material significantly. When C&D is mixed with fly ash at a mass ratio of 60/40, its UCS reaches 37 MPa at 28 days, which is much higher than the strength requirement of cement-stabilised soil mixture and meets the strength requirements of inorganic binder stable materials for road base and sub-base layers. C-A-S-H and N-A-S-H (where N = Na2O, A = Al2O3, C = CaO, S = SiO2, and H = H2O) generated by the alkaline activation have several similarities with cement hydration products and also show high cementing ability. Alkali-activated fly ash improves the strength and stability of C&D as a roadbed filler and has prospective applications in road engineering. [ABSTRACT FROM AUTHOR]

A new species, Cathissa villasina, endemic to the Sierra de Las Villas (Jaén province, Eastern Andalusia, Spain), is described, illustrated and compared to its closest relative (C. reverchonii), with which it was initially confused in this area. A comparative morphometric study (quantitative and qualitative) of both species including a statistical analysis of 39 macroscopic characters and the detailed microscopic observation of stigma, seminal testa and pollen was performed. In terms of its ecology and phytogeography, C. villasina grows in pockets of clayey soils on limestone pavements on terrain with little or no incline. Humidity levels in these soils are high and they can become temporarily waterlogged. This species is a narrow endemic to the Cazorlense biogeographical district. By comparison, C. reverchonii is clearly a rupicolous species that grows in the shade of vertical or steeply sloping limestone rocks, and is found in numerous scattered localities in the biogeographical Rondense district. [ABSTRACT FROM AUTHOR]

The scarcity of water is a major problem in Tunisia. Thus, 50% of water resources are with salinity higher than 1.5 g L−1 and 16% with salinity exceeding 3 g L−1. To use this saline water in crop irrigation, new technologies for water treatment can be applied such us electromagnetic irrigation water device. In this context, a field experiment was carried out at Zitouna Agricultural Development Company in Zaghouan governorate to study the impact of magnetized irrigation water on clay soil and on leaf mineral content of Arbequina olive tree growing under drip irrigation with saline water. Bimonthly soil samples were taken with an auger every 20 cm over 1 m depth. Olive leaf samples were taken from the trees located above the soil sampling points. The results showed that soil parameters variations are the same throughout the depths 0–20, 20–40, 40–60, 60–80, and 80–100 cm. As a consequence, the interpretation of the effect of magnetized irrigation water was restricted to 0–100 cm soil depth. However, a slight decrease of the pH was observed with the use of magnetized water. On other side, we reported that the electromagnetic treatment of irrigation water increases the soil moisture (Hs) and favors the absorption of N, P, K+, and Na+ by olive tree leaf tissues. Also, water use efficiency (WUE) in the plot irrigated with treated water is equal to 1.3 compared to that irrigated with untreated water. Thus, 30% improvement in yield using treated water. [ABSTRACT FROM AUTHOR]

Chemical treatment with cementitious materials is a common and economic solution to improving the mechanical behavior of contaminated clay soil. In this research, Portland cement and lime were used to treat kaolinite contaminated with anthracene and glycerol. The samples were cured for 7 days and their unconfined compressive strength (UCS) was determined. The results showed that the UCS of kaolinite contaminated with anthracene and glycerol was less than that of clean clay. In samples contaminated with anthracene, treatment with 3% Portland cement was roughly equivalent to that of 10% lime. In samples contaminated with glycerol, treatment with 9% Portland cement was equivalent to that of 10% lime. The results were verified by scanning electron microscopy. Triaxial unconsolidated undrained testing was carried out at different confining pressures on samples having similar UCS values. The results revealed that anthracene and glycerol contamination reduced the ultimate deviatoric stress and that the maximum deviatoric stress decreased as the amount of contamination increased. Also, the cohesion and internal friction angle decreased as the amounts of anthracene and glycerol increased. This could be attributed to the polarity, dielectric constant and viscosity of the organic material. All Portland cement–treated and lime–treated samples at the different confining pressures had higher peak shear strength values than the untreated ones. The maximum triaxial compression strength of specimens with equivalent UCS values was similar at low confining pressures, but an increase in confinement caused the Portland cement to perform better. [ABSTRACT FROM AUTHOR]

Bioremediation has been proven to be efficient method of cleaning up oil contaminated soils through the application of proper microorganism to contaminated soils. Hence, this research involves the bioremediation of four different types of contaminated soil. The soils were categorized as laterite, sandy soil, clay soil, and loamy soil which are classified technically using American Society for Testing and Materials (ASTM) method as clayey sand, silty sand, clayey sand and poorly graded sand respectively. These soils were contaminated with Bonny light crude oil to the concentration of 33.3 g/l. The soils were inoculated with petroleum remediation microorganisms. Soil samples were taken after 14 and 25 days, and the residual total petroleum hydrocarbon (TPH) was checked using Environmental Protection Agency (EPA) Method 8015. The condition of the soils was kept almost constant during the process by preserving it in an insulated vessel to avoid evaporation of moist or organic gases. The results obtained showed percentage reduction 70%, 69%, 49%, and 26% in hydrocarbon after the period of 25 days in Sand, Laterite, Topsoil and Clay soil respectively. The removal percentage was the highest (70%) for the sandy soil, and the lowest for the clay soil (26%). The result indicate that the particle size distribution of soil affects bioremediation to an extent, since clay with lowest particle size proved more difficult to bio-remediate. [ABSTRACT FROM AUTHOR]

In geotechnical projects involving soft soils, cement-mixed soils are an excellent way to improve the mechanical behaviour and engineering performance of soils. The water-to-cement ratio, cement content, and porosity are the most critical parameters impacting the strength of cement-mixed soils, but their effects are less well understood. The proportional influence of cement amount, porosity, and moisture content on cement-mixed soil strength is investigated in this research. The results showed that as the water-to-cement ratio increases, the influence of cementation and porosity on unconfined compressive strength decreases. The blended volume ratio is proposed as a new and adequate index for evaluating cement-mixed soil strength based on the experimental results. The blended volume ratio is the product of the void/cement volume ratio and the water/cement volume ratio. While the current index has not fully addressed the important effects of the water-to-cement ratio and porosity, the blended volume ratio allows describing the concurrent influences of porosity, cement amount, and water amount on the strength development. The experimental results showed that the cement-mixed soil strength is a function of the blended volume ratio. An empirical equation based on the blended volume ratio was then proposed for predicting the strength of cement-mixed soils. The validation of the proposed equation is verified by strength analysis for several different test data sets. A good agreement between measured and predicted results indicated that the proposed model is applicable to predict well the strength of cement-mixed soils. [ABSTRACT FROM AUTHOR]

In other words, although soil mineralogy may well play a key role in the varying strength of clays with the water content, I c i SB u(FC) sb mobilised at the FC liquid-limit water content does not respond in any significant way to soil mineralogy; the same conclusion has been previously reported by O'Kelly I et al i . ([16]) employed a Geonor G-200 model 60°-60 g FC device to determine the apparent variations of I c i SB u(FC) sb with the water content about the I w i SB L-FC(BSI) sb (established using the 30°-80 g FC device) for the various fine-grained soils investigated. Keywords: Liquid limit; fall-cone; cone factor; undrained strength; fine-grained soil EN Liquid limit fall-cone cone factor undrained strength fine-grained soil 170 174 5 04/04/23 20230301 NES 230301 It is the authors' opinion that confusion could arise from the analyses and explanations of the experimental fall-cone (FC) results presented in the paper by Nagaraj I et al i . Figure 1(a): An x:y scatter plot showing the changes in undrained shear strength at the British Standard fall-cone liquid-limit water content against the British Standard fall-cone liquid-limit water content for six different fine-grained soils investigated by Nagaraj et al. (2018). [Extracted from the article]

Improving and preserving soil quality in areas managed under no-tillage, especially in clayey soils, is extremely important for achieving high productivity along with environmental preservation. In this study, we evaluated the effect of three states of soil compaction and initial water saturation on pre-consolidation pressure (σp) and compaction index (CI) of two Oxisols, in order to estimate maximum loads to be applied by pneumatic machinery and agricultural implements without causing irreversible damage to soil structure. Oxisol-LVd (0.55 kg kg−1 clay) and Oxisol-LVdf (0.62 kg kg−1 clay) soils from the plateau region of Rio Grande do Sul were studied. An isoline map was generated for soil penetration resistance in the 0.07–0.12 m soil layer, with the highest state of compaction. Soil bulk density was used to characterize three state of compaction, used as treatments. Statistical analysis consisted of comparing soil σp and CI means for state of compaction, initial water saturation, and soil layers. Increase in clay content and bulk density and reduction in soil moisture is associated with increase in soil σp and decrease in CI. Average values of critical σp of the three states of compaction at field capacity are 245 kPa for Lvd, and 347 kPa for LVdf. In an annual timeframe for already consolidated no-tillage Oxisols, further soil wheeling and natural reconsolidation does not affect soil pre-consolidation and compaction susceptibility. [ABSTRACT FROM AUTHOR]

Co-application of fertilisers and biofertilisers increases solubility and concentration of nutrient elements in the soil. However, information on the effect of P fertiliser and rhizobium inoculation on the concentration of mineral elements in the rhizosphere of field-grown chickpea in contrasting soil types is lacking. We assessed the effect of phosphorus fertiliser, rhizobium inoculation, and rhizobium inoculation plus P fertilizer on the concentration of nutrients in the rhizosphere of 2 chickpea genotypes (ACC#1 & ACC#5) at clay and sandy soil sites in two consecutive years. ACC#5 accumulated higher amounts of rhizospheric nutrients than ACC#1 in both soil types despite the variable response to fertiliser treatment. Rhizobium inoculation plus P fertiliser resulted in higher accumulations of rhizosphere N (7-219%), P (20-348%), K (9-365%), Ca (2-155%) and Zn (15-259%) compared to the other fertiliser treatments suggesting an additive effect of P fertiliser and rhizobium inoculation. Moreover, the effect of fertiliser treatments was more pronounced in the clay than the sandy soil. Our investigation is the first to document the effects of fertiliser treatment, genotype, and soil type on the accumulation of rhizosphere nutrients in field-grown chickpea. However, we propose further studies, incorporating more cultivars and environments, before making practical recommendations. [ABSTRACT FROM AUTHOR]

Building with raw earth is a responsibility that translates into safe, lowimpact and small carbon footprint constructions. However, beyond its current use, it is imperative to validate the different earth construction systems, starting with their components, under standards that ensure the safety of this type of constructions. In countries where construction with earth is allowed, it is verified by Standards and Technical Documents or Construction Regulations. Therefore, the objective of the research is to contrast a series of compressed earth blocks (CEB) subjected to compression tests with the Brazilian and Colombian standards, and the Mexican standards with clay soils in the region, identifying the deviations between the results and their possible causes. In the results, it was observed that the compression test procedure varies for each Standard, the Brazilian and Colombian Standards being similar, and these in turn adhere more to the construction system, while with the Mexican Standard the results are higher than the previous one since the norm requires to test the complete block. [ABSTRACT FROM AUTHOR]

The specimens of contaminated clay improved with Portland cement and lime were cured for seven days and were subjected to uniaxial compressive strength (UCS) testing. The results for anthracene-contaminated specimens improved with three percent Portland cement (by weight of clay) were approximately equivalent to those improved with 10% lime. The results for glycerol-contaminated specimens improved with nine percent Portland cement was approximately equivalent to that improved with 10% lime. According to the results, both Portland cement and lime were able to improve the clay soil contaminated with anthracene and glycerol, but Portland cement had a greater effect than lime on the anthracene-contaminated specimens because of the non-polar behaviour of anthracene and the grain-like (flocculated) behaviour of the contaminated soil. These factors were the result of a decrease in the diffuse double layer thickness by anthracene, which has a lower dielectric constant relative to water. The lime had a greater effect than cement on the specimens contaminated with glycerol because of the polar behaviour of glycerol, the increase in the required moisture content for hydration, and because the dielectric constant of glycerol is close to that of water. These results were evaluated and confirmed by scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Spatial information on land and soil resources are critical towards addressing land degradation for ensuring sustainable soil and crop management. To address these needs, digital soil mapping techniques have emerged as an efficient and low-cost solution. Although digital soil mapping has typically leveraged geospatial environmental variables (e.g. remote sensing), the application and integration of spectroscopic data with those environmental variables remain limited. Hence, this study combines visible and nearinfrared (Vis-NIR) spectroscopy, remote sensing, and topographic data and applies random forests, hybridized with particle swarm optimization algorithm (RF + PSO), to predict the spatial variability of soil clay content, electrical conductivity (EC), and calcium carbonate equivalent (CCE) for 370km² of agricultural land in western Iran. Using a conditioned Latin hypercube approach, 220 soil samples at the 0–20 cm depth increment were acquired throughout the study area. Three sets of environmental covariates were tested: Scenario A (Vis-NIR spectroscopy data), Scenario B (environmental data), and Scenario C (Vis-NIR spectroscopy þ environmental data). According to the 10-fold crossvalidation procedure with 100 replications, the RF + PSO model showed an acceptable level accuracy for all scenarios, although the accuracy of the RF + PSO model using the Scenario C data was higher than all other scenarios: the Lin’s Concordance Correlation Coefficient values were 0.77, 0.83, and 0.74 for the clay contents, EC, and CCE, respectively. The results demonstrated that the combination of Vis-NIR spectroscopic data and commonly available environmental covariates provided the best input data for the hybridized model and enhanced its performance. [ABSTRACT FROM AUTHOR]

Clayey soils have fine particles and contain clay minerals. Therefore, they are sensitive to water and cause stability problems. Nowadays, soil stabilization is an accepted method to resolve the problem of stability. In this study, hemp fiber was used as an additive material for stabilization of clayey soil. The use of fibers in the stabilization of clayey soils is becoming widespread, particularly with regard to applications involving the stabilization or reinforcement of shallow steep earth slopes and steep cover systems for landfills. In these applications, the use of natural fibers use is very important due to their environmentally friendly properties. Hemp legally planted in different countries is used in several industries, such as paper, textiles, clothing, biodegradable plastics, construction, body products, health food, and biofuel. In this study, hemp fiber was preferred because of its natural and environmentally friendly properties. To observe the effect of hemp fiber on the compressive strength of clayey soil material, the unconfined compression tests and shear box tests were carried out under laboratory conditions. The experimental results showed that hemp fiber is effective on the compressive strength of clayey soils. As a result, hemp fiber can be used successfully in clayey soil stabilization as an environmentally friendly material. [ABSTRACT FROM AUTHOR]

It can be seen that the soil with straw fibers has the largest moisture content as opposed to the soil with polypropylene fibers which, however, has a higher moisture content than the soil without fibers. Before the soil sample cracking, the fibers in the soil are surrounded by the soil particles assuming that the soil particles, pore water, and air void are regularly arranged around the fibers. Keywords: Soil cracks; natural fibers; polypropylene fibers; fractal dimension of cracks; soil reinforcements; evaporation; ; ; ; ; ; EN Soil cracks natural fibers polypropylene fibers fractal dimension of cracks soil reinforcements evaporation ZH 9547 9561 15 11/21/22 20221220 NES 221220 Introduction The mechanical properties of soil are sensitive to changes in moisture content. [Extracted from the article]

Stone columns are used as an efficient ground improvement technique, which could increase the bearing capacity of native soft soil, reduce settlement, increase rate of consolidation and mitigate liquefaction potential. In this study, the finite element limit analysis (FELA) with the adaptive mesh, including both upper bound and lower bound approaches, was applied for prediction of ultimate bearing capacity of single stone column. It was observed that a critical slenderness ratio exists in which the failure mechanism changes from punching to bulging. An equation was derived for prediction of the critical slenderness ratio as a function of cohesion of the native clayey soil and friction angle of the stone column. A two-criteria equation is also presented to predict the ultimate bearing capacity of single stone column under both punching and bulging mechanisms. Moreover, the effect of footing roughness on the ultimate bearing capacity of the stone column was investigated. It was observed that the influence of footing roughness is more significant for bulging-type failure. The results of this study are also compared with some of the previously published analyses in the literature. [ABSTRACT FROM AUTHOR]

Lime treatment of soil is a widely adopted technique to improve its properties. However, the durability of lime-treated soil under varying environmental conditions such as contamination with chemical agents is still a matter of concern. An attempt has been made to examine the swelling behaviour of untreated and lime-treated expansive soil subjected to sulphate contamination (i.e. soluble gypsum). Series of the free swell index and one-dimensional oedometer swell tests have been performed in untreated and lime-treated soil inundating with soluble gypsum of varying sulphate concentration (i.e. low to high; 0 to 30000 ppm). The results of one-dimensional oedometer swell tests revealed that the sulphate contamination leads to the reduction in the maximum swelling percentage of untreated soil. On contrary, a drastic increase in the swelling percentage has been observed in the lime-treated soil subjected to contamination up to 16000 ppm, which diminishes thereafter with an increase in sulphate concentration. It is revealed that the sulphate contamination has observed promising effect on untreated soil; whereas a susceptible behaviour is pronounced in the lime-treated soil up to 16000 ppm sulphate concentration. Further, experimental outcomes are elucidated based on the detailed microanalyses (XRD, SEM, EDAX and FTIR) of samples. [ABSTRACT FROM AUTHOR]

During the drying process, an initially saturated clay deforms mainly due to the loss of water. It causes clay shrinkage that represents one of the fundamental reasons of cracking by desiccation. It is of great interest to understand the desiccation process in such complex soils. However, the main point is that many properties of the material, such as water content distribution, displacement, strain and stress fields, remain difficult to reach by experimental approach only. Numerical simulations may help estimate these variables, and reinforce in a significant way the experimental measurements. The proposed method of analysis allows to understand more deeply the process of drying in clays including shrinkage, crack initiation and finally, crack network development. This research, combining numerical simulations and laboratory tests allows to go further in investigating the drying phenomenon in remolded and initially saturated kaolinitic clay. [ABSTRACT FROM AUTHOR]

Selenium is important to human health and must be consumed in adequate amounts through a variety of food sources, particularly vegetables. In order to identify availability of soil Se to crops, Se adsorption-desorption process in soil must be understood. In this study, an adsorption-desorption study of inorganic Se in soils of various textural classes was performed with the following concentration of Se (0–2 mg L−1) applied as Se(VI) and Se(IV). A glasshouse experiment was then conducted in a factorial (2 × 5) completely randomized design, with two Se form—Se(IV) and Se(VI)—and Se at five rates (0–60 g ha−1 Se in solution form) to green spinach. First, soil texture appeared to be the main factor controlling Se adsorption in soils. Selenite was adsorbed more, however, Se(VI) was desorbed at higher rate compared to Se(IV). Contrary to other soil types, in peat, Se(IV) was desorbed at higher level compared to Se(VI), where more than 70% was retained. Higher retention of Se(IV) was found in clayey soil. Meanwhile, from glasshouse experiment, Se uptake was higher in plants when treated with Se(VI) than with Se(IV). However, higher dry matter and antioxidant activity of green spinach was observed when Se(IV) was applied. Selenium applied as Se(IV) had greater benefits to spinach yield and antioxidant activity than Se(VI) or conventionally grown spinach (0 g ha−1), even though plants treated with Se(VI) had greater Se uptake. [ABSTRACT FROM AUTHOR]

Lime-cement stabilisation of clayey soils has been successfully used for many years. However, limited published studies have investigated the influence of varying mellowing period for two-stage lime-cement stabilisation on the secant elastic and resilient moduli of subgrade soils. The two-stage stabilisation starts with mixing the soil with lime, allow it to mellow for a specific period to improve soil's workability and reduce plasticity. Cement is mixed with the treated soil and compacted to ensure strength development. The effects of lime-cement stabilisation on compaction, bearing capacity, compressive strength, elastic modulus, and resilient modulus of a medium plasticity clayey soil were investigated. A continuous reduction in the E50 of soaked lime-cement stabilised specimens was observed with longer mellowing periods specimens with 24 h mellowing showed the highest ability to absorb energy under the applied load. Repeated load triaxial test showed that the resilient moduli were significantly improved after the two stages stabilisation, and mellowing the lime treated soil will considerably enhance the soil stiffness. The three-parameter regression model showed that the two-stages stabilised materials have a strain hardening property. Increasing the mellowing period beyond 48 h, before adding cement and compaction will reduce in compressive strength, elastic modulus, and resilient modulus. [ABSTRACT FROM AUTHOR]

Consolidation and creep are two types of time-dependent deformation of clay soil. However, the soil deformation presents probabilistic behaviours when the spatial variability is considered. The Monte–Carlo method is used to sample anisotropic random fields that are mapped into two-dimensional random finite element models (RFEM) to analyse the influences of spatial variability on the time-dependent deformation of clay soil. The anisotropic random fields of soil parameters are generated by a spectral representation method (SRM) to describe the spatial variability of clay soil. The consolidation and the creep problems are modelled by Biot's consolidation theory and the creep model proposed by Yin et al. (2010) respectively. The spatial variability of Young modulus and permeability coefficient in probabilistic consolidation analysis and the secondary consolidation coefficient in probabilistic creep analysis are emphasized by the RFEM simulation. The results show that the scale of fluctuation (SOF) in vertical direction and the coefficient of variation (COV) of Young modulus and permeability have significant influences on the probabilistic characteristics of consolidation behaviour. Besides, the bunched region of low permeability soil produces a blockage effect, which seriously affects the consolidation characteristics. It is found that the uncertainty of creep deformation will accumulate over time until it remains constant. The variability of creep deformation increases with the increase in the vertical SOF and COV of the secondary consolidation coefficient. The research also provides insightful clues for the time-varying reliability design related to the time-dependent deformation of clay soil. [ABSTRACT FROM AUTHOR]

In situ soils of deep overburden layer of dam foundation are widely distributed in Southwest China, which are mixtures of gravel and silty clay in varying proportions and have cementation feature between soil particles. Based on a series of triaxial compression tests carried out on artificially cemented mixed soils (CMS) and remolded mixed soils (RMS) at confining pressures of 50, 100, 200 and 400 kPa with fine contents (silty clay) of 13%-70% in mass, a binary-medium constitutive model for artificially cemented mixed soils is proposed within framework of breakage mechanics theory for geological materials and homogenization theory. This model was formulated by regarding the soils as a binary medium consisting of bonded blocks (idealized as bonded elements) and weakened bands (idealized as frictional elements), whose deformation properties are described by the modified Duncan-Chang model and the Lade-Duncan elastoplastic model, respectively. The non-uniform distribution of stress and strain within a representative volume element can be given by introducing the structural parameters of breakage ratio and local stress coefficient. Comparisons of computed results with test results demonstrate that the binary-medium constitutive model can reflect mechanical properties of artificially cemented mixed soils well. [ABSTRACT FROM AUTHOR]

The moisture migration and high-volume changes due to swelling and shrinkage in the expansive soils have posed severe challenges at many project sites. Additionally, rapid industrialisation in last few decades has posed problems of huge amount of undisposed industrial wastes, which not only cause environment degradation but also occupy huge tracts of valuable land. The paper presents the results of an experimental investigation carried out to assess the effect of waste recycled product (WRP), an industrial waste from steel industries; on the engineering properties of expansive soil and to achieve dual objectives of improving the engineering performance of such soils combined with its gainful utilisation. Test results revealed that addition of WRP to expansive soil in appropriate proportion not only reduces its swelling and shrinkage behaviour but also there is a significant improvement in its strength and deformation characteristics. After adding 30% WRP (by dry weight of soil) in expansive soil, the percentage increase in subgrade modulus and unconfined compressive strength was 89.18% and 68.78%, respectively, and it is concluded that there is significant potential for its use in flexible pavement construction on expansive soil subgrade which in turn provides its safe and economical disposal. [ABSTRACT FROM AUTHOR]

The adoption of mechanistic-empirical approach to pavement design requires the use of resilient modulus of subgrade soils as a crucial input. The determination of in the laboratory is inexpedient due to the nature of the existing test protocols. This prompted the use of estimated values, which inadvertently has gained popularity lately. However, the accuracy of estimated values is questionable due to spatial variability of soil properties. This necessitated the aggressive search for robust and thorough approaches for predictive modelling of the . In the present study, a systematic approach was adopted for the descriptive analysis and estimation of . from routine soil properties using data from Long-Term Pavement Performance (LTPP) and considering the spatial variability of the soil properties. Descriptive analysis was executed using non-parametric correlation and principal component analysis (PCA), while the estimation was done using three machine learning methods which include gradient boosting regression (GBR), adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN). Based on the PCA, four factors which explained a total of 77.5% variance in the data had significant influence on the . These include the effect of moisture-induced changes on the soil consistency limits and physical condition, effect of the soil clay content, effect of the soil gradation and effect of the soil stress state. Various factors of the machine learning methods such as the learning rate, number of clusters and number of hidden layers had a significant effect on the prediction accuracy. The three machine learning methods were satisfactory for the prediction based on R2 values which were generally above 0.9. Also, when considering spatial variability of routine soil properties, the GBR and ANFIS have a comparative advantage over the ANN, since they exhibited a high stability in the prediction for both the training and testing dataset. [ABSTRACT FROM AUTHOR]

Civil engineers face significant challenges in the safe design and construction of durable road infrastructure in the presence of expansive soils. These problematic soils exacerbate undesirable serviceability concerns induced by pavement distress. Soil stabilisation has been recognised as a sustainable approach to alleviate the problematic nature of expansive subgrades. Road pavements constructed on top of expansive subgrade soils are generally under unsaturated conditions, where the moisture variations can significantly impact the pavement response. However, current pavement design and modelling frameworks overlook unsaturated soil behaviour by adopting simplified approaches. This study examines the hydraulic behaviour of expansive clayey soils stabilised with non-traditional and traditional chemical based additive. Tests were conducted to determine the state variation and stabilisation influence on the soil water characteristic curve using the dewpoint potentiometer for an expansive subgrade commonly found in Melbourne geology. Results show that the stabilisation has strong influence on soil hydraulic characteristics at various initial state conditions tested. Experimental data have been applied to illustrate the significance of incorporating realistic hydraulic response using a simulated practical application in road pavements. The research highlights the significance of incorporating accurate hydraulic characteristics for simulating and assessing the response of pavement constructed with stabilised unsaturated subgrade soils. [ABSTRACT FROM AUTHOR]

The conventional crumb test (CCT) is a simple and rapid test, originally used for assessing the dispersive tendency of clayey soils through visual observation of a small-scale soil specimen placed in a large volume of water. In this study, the disaggregation process occurring in soil in contact with water was followed in place of the soil dispersion in CCT. In order to describe quantitatively the process, an automated crumb test (ACT) was developed. The test method is based on temporal evolution of the soil specimen geometry during its disaggregation due to water infiltration. A series of tests were conducted on clay–sand mixtures with different initial water and clay contents, in order to show the potential of ACT. Image analysis applied on collected data with two digital cameras, revealed a general behaviour divided into a swelling step followed by a slump step starting as soon as the particles detach. By using temporal and geometric parameters, ACT revealed the ability of soils to absorb more or less water during the swelling step and then to disaggregate/crumble more or less rapidly. Finally, a correlation between the quantitative parameters from ACT and erosion characteristics from hole erosion test (HET) was attempted and discussed. [ABSTRACT FROM AUTHOR]

This research investigates the shrinkage behaviour of clay specimens subjected to different hydraulic paths. The volume change and microstructure of desiccated clay specimen directly dried from reconstituted slurry and compacted states, and the desiccated clay specimens obtained by subjecting the as-compacted clay specimen to cyclic wetting and drying process were compared. The experimental results showed that the initial microstructural difference between reconstituted slurries and compacted specimens influences their shrinkage behaviour. The compacted clay specimens retained the bimodal structure even after subjecting to cyclic wetting and drying, unlike the reconstituted slurry, which showed a predominant unimodal structure at the end of drying process. This is due to the absence of large macropores in the desiccated clay specimen dried from reconstituted slurry state, which is evidenced from the mercury intrusion porosimetry studies, scanning electron microscopy and nano-focus X-ray-computed tomography imaging experiments. [ABSTRACT FROM AUTHOR]