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Measurements of slope displacements can be effective tools for the early warning of the collapse of slopes under excavation in construction projects in mountainous areas, while evaluating of instability based on measured displacement has not yet been accomplished for slopes under excavation. Measurements of displacements on sandy soil slopes under multistep excavation were made, and the measured data were analyzed to determine the characteristics of creep deformation of the slope during and after the excavation and to establish a procedure for evaluating instability of the slope under excavation in this paper. The following facts were derived from the examination of the measured data. Displacement was generated significantly in the latter stage of excavation, and it was generated not only during excavation but also after excavation. The ratio of the displacement after excavation to that from the start of the excavation to the start of the next excavation became larger as the displacement developed immediately before failure. It indicates that creep displacement after the excavation was more significant at latter excavation just prior to failure. The normal displacement converged to constant as the shear displacement increased under a steady state immediately before the failure in direct shear conditions, and the normal displacement can be an indicator of the instability of the slope. The normal displacement cannot remain constant when the inclination of the slope surface is different from that of the slip surface in the excavated slope in this paper. Different indicators are necessary in this case. The angle α between the slope surface and synthetic displacement (RD) on the slope derived from measured data was introduced instead of normal displacement. The synthetic displacement (RD) on the slope indicated the scalar of the synthesis of the displacements normal and downward to the surface of the slope and surface displacement. It converged to constant after excavation immediately before failure, and shear displacement showed an accelerative increase for constant α. This indicated that the angle α could be an indicator of the instability of the slope. This result showed that the angle α being constant indicated that the stress condition was almost in failure and the displacement increased acceleratively. Further examinations based on the measured data on other slope under excavation should be necessary for confirming the results in this paper based on only a case of experiment. [ABSTRACT FROM AUTHOR]

Sulfur (S) is an essential nutrient vital for ideal plant growth and optimal crop yield. Potatoes in sandy soils of northeast Florida often face challenges due to low organic matter content and a high water table. The S application guidelines must be developed to avoid the under and over-application of S and to optimize integrated nutrient management plans for potatoes in Florida's sandy soils. A comprehensive study evaluated the response of S application in potatoes with S uptake, tuber yield, and quality. For 2 years (2021 and 2022), separate field experiments were conducted at three different locations, while location 1 had a trial replicated (Trial 1 and 2). The study was established in a randomized complete block design with four replications, in which five different rates (0, 45, 90, 135, and 180 kg S ha−1, as gypsum [17% S]) were applied at pre-planting. The results of this study show variations in soil-available S concentrations in response to different application rates and sampling times. The dry above-ground biomass production, S uptake, and potato tuber yield remained largely unaffected by S application. However, specific gravity at location 1 reported the response of the S application in interaction with trials. Location-specific effects, compounded by yearly variations, played a significant role, particularly at location 1. External and internal tuber quality showed inconsistent responses to the S application and interactions with trials and year factor. This study reported the significant influence of irrigation water (containing high amounts of SO42−) on the overall experiment. So, these findings underscore the importance of water nutrient concentration in developing crop nutrient recommendations. In conclusion, this study provides valuable insights into the complex relationship between S application, S uptake, and yield in the unique agricultural context of the sandy soils of Florida. [ABSTRACT FROM AUTHOR]

The increase in pore water pressure, directly associated with the compressibility of loose sands under seismic loading, induces liquefaction, resulting in a decrease in effective stresses and, consequently, a loss of soil strength and stiffness in saturated sandy soils. For a long time, geotechnical engineers have found it difficult to understand the phenomenon of soil liquefaction. It is crucial to look into the factors influencing the liquefaction and/or softening of soil as well as the production and evolution of pore water pressure to have a deeper knowledge of the liquefaction phenomena. The size of the particles is one of the important factors. The purpose of this work is to examine how sand particle size, repetitive loading, and undrained circumstances affect the development of excessive pore water pressure. SEM and EDX imaging were conducted to determine the characteristics of three different sands. To ascertain the parameters of shear resistance, three sands with varying gradations were chosen and subjected to direct shear tests. For each of the three sands with varying particle sizes, cylindrical triaxial test specimens were made, and a set of dynamic triaxial tests under stress control were performed. The specimens were tested at various repeated stress ratios (CSR) using loading frequency of 0.1 Hz after being isotropically consolidated under an effective stress of 100 kPa. Experiments on three different sands with varying grain sizes and shapes revealed increased liquefaction potential with a reduction in grain diameter. It was observed that as the cyclic shear strain increased, the sand samples reached liquefaction at lower cycles. Additionally, it was noted that incorporating empirical coefficients that consider grain size and shape into the prediction of pore water pressure improved compatibility with models commonly used in the literature, leading to better results. [ABSTRACT FROM AUTHOR]

To date, the important problem of Terzaghi's ground arch model in 1946 has not been solved for loads on circular tunnels. This study comprehensively presented a general analytical solution of Terzaghi's ground arch model for loads on circular tunnels by the limit equilibrium method, considering the complete boundary conditions of the loosening zone, the effects of water pressure, and the stiffness of the lining and ground. The proposed solution indicates the relationship between the load on circular tunnels and that on trapdoors, and there is a negative correlation between the lateral and vertical earth pressures in the ultimate state. Model tests and field measurements were used to verify the proposed solution. The results indicated that the proposed solution agrees well with the experimental results of circular tunnels in dense sand, loose sand, saturated sand, and saturated clay; the solution is significantly less than the design load from Terzaghi's formula in good ground conditions. Moreover, the solution demonstrated an interesting rule: the distribution of total loads (including water pressure) on nonrigid circular tunnels is nearly uniform in saturated granular soil. A particular solution was obtained for circular tunnels in saturated granular soil. In addition, the vertical pressure on a circular tunnel in sand increases and the lateral pressure decreases as the groundwater table increases within the tunnel range; the case where the groundwater table is located at the crown is proved to be a critical condition for shield tunnels in sand. Practical Applications: Previous studies indicate that the load on shield tunnels in good ground conditions would be overestimated by Terzaghi's formula, which was proposed in 1943 and is widely adopted in tunnel design nowadays. In this study, a general analytical solution for loads on circular tunnels was established based on Terzaghi's ground arch model, which was improved by Terzaghi in 1946 for arched tunnels but has not been solved. For various overburden depths, the proposed solution agrees well with the experimental results of circular tunnels in dense sand, loose sand, saturated sand, and saturated clay, but Terzaghi's formula based on trapdoors fails to explain the test results of circular tunnels in sand. The proposed solution is significantly less than the design load from Terzaghi's formula in good ground conditions. The solution is applicable for both shallow and deep circular tunnels, and it will be very helpful for the economical and rational design of shield tunnels normally in good ground conditions, such as sandy soil, crushed rock, and stiff or hard clayed soil. [ABSTRACT FROM AUTHOR]

Several approaches have been proposed to improve oil-contaminated soil remediation. However, the role of zeolite, a safe, clean, economical, and environmentally friendly material, in removing crude oil (CO) from contaminated soils remains unclear. This paper addresses this gap with respect to CO-contaminated sands (COCS) and aims to assess zeolite's capability as a geo-environmentally adaptable material to mitigate the adverse impacts of oil pollution on sandy soils. The cyclic simple shear behavior and chemical analysis of coarse and fine-grain silicate sands are investigated and compared in response to CO contamination. Clean sand specimens were prepared with 60% relative density, whereas COCS specimens were prepared using a 6% crude oil contamination level. This study examines the impact of CO contamination and the use of an environmentally friendly stabilizer through simple shear tests (under static and cyclic conditions), consolidation experiments, and Fourier-transform infrared spectroscopy (FTIR). Optimal pollution adsorption was achieved by adding 6% zeolite to fine-grained sand, resulting in a 31.61% increase in the shear modulus index and an 18.70% increase in the friction angle index. Using 8% zeolite improved the shear modulus and friction angle indexes in coarse-grained sand by 21.69% and 11.83%, respectively. FTIR results showed a 45% and 59% enhancement in coarse and fine sands, respectively, indicating the positive role of zeolite in stabilizing COCS through pollutant adsorption. The superior performance of zeolite in fine-grained compared with coarse-grained sand is justified by its higher specific surface area and porous surface. [ABSTRACT FROM AUTHOR]

This study presents novel mathematical formulations of the Soil Conservation Service curve number (SCS-CN) method that incorporate both temporally decaying retention parameters and storm intensity/duration. To evaluate its performance, we compared it with the existing versions of the SCS-CN model using a large data set of 35,546 storm events of 113 different US watersheds. Obtained results indicate that the proposed model outperforms other models in almost all 113 US watersheds with the highest Nash-Sutcliffe efficiency (NSE). Furthermore, the results are supported by the percent bias (PBIAS) being close to 0 and the lowest root mean square error (RMSE), RMSE-observations standard deviation ratio (RSR), normalized root mean square error (NRMSE), and mean absolute error (MAE) statistics. The general form of the proposed model performed particularly well in clayey and sandy soils with different land uses and catchment areas larger than 1 ha. Rainfall (P) and the coefficient (β) parameters are identified as the most and least sensitive parameters of the proposed model, respectively. [ABSTRACT FROM AUTHOR]

This study evaluates the efficacy of discrete bacterial consortia in bioremediating sandy loamy soil deliberately contaminated with 20 mg/kg of chlorantraniliprole (CAP). It monitors alterations in total bacterial populations and CO2 emissions, tracking residual CAP levels through UV scanning and HPLC analysis. Six active bacterial degraders (four Bacillus strains (B. subtilis subsp. subtilis AZFS3, B. pumilus AZFS5, B. mojavensis AZFS15, and B. paramycoides AZFS18), one Alcaligenes strain (A. aquatilis KZFS11), and one Pseudomonas strain (P. aeruginosa KZFS4)) were used in single or combined preparations and grown on trypticase soy broth for 24 h at 30 °C before preparing the inoculants and adjusting the bacterial cell count to 107 CFU/dwt g soil. The bacterial consortia were added to the CAP-contaminated soil and incubated for 20 days at 30 °C. The di-, tetra-, and hexa-bacterial consortia recorded the highest levels of viable bacteria, reaching their peak after 3 to 11 days of incubation. Then, they declined to the minimum levels at the end of the 20 days, which coincided with their complete removal of CAP from the soil. At the end of the incubation period (20 days), the CAP was mainly biodegraded, scoring biodegradation rates of 90.05%, 93.65%, and 98.65% for T3, T4, and T5, respectively. This concurred with the highest average CO2 production. Based on the results of the HPLC analysis, the hexa-bacterial consortium T5 demonstrated the highest rate of CAP biodegradation (99.33%) after a 20-day incubation period, resulting in the lowest residual level of CAP in the soil (0.67%). Bioinformatic analysis predicted that the CAP biodegradation pathway reached CO2 and H2O. Under optimized conditions, the hexa-bacteria consortium is the most effective CAP biodegraded and is recommended as an eco-friendly treatment for eliminating CAP pollution in the field. [ABSTRACT FROM AUTHOR]

Planting forests is an effective way to improve desertification. In order to elucidate the impacts of different vegetation types on soil development and restoration of degraded lands, we compared the properties of soils at different depths in three plantation forests in the Hunsandak Sandy Land in the Chinese agro-pastoral ecotone (Ulmus pumila, Pinus sylvestris var. mongolica, and Populus simonii). The results show that all three plantation forests were able to significantly improve the soil properties, and they resulted in soil nutrient enrichment in the surface layer. As the soil depth increased, the soil became progressively poorer in nutrients, the fine particle content decreased, and the bulk density and water content increased. The orders of the fractal dimension characterization and soil improvement effects of the different tree species were as follows: U. pumila > P. sylvestris var. mongolica > P. simonii. Compared with the bare sand, the soil bulk density under the U. pumila plantation was 19% lower; the soil water content was 74% higher; the soil organic matter, total N, P, and K were 336%, 207%, 106%, and 31% higher; the available N, P, and K were 41%, 125%, and 21% higher; and the clay and silt contents were 498% and 387% higher, respectively. The ranges of the soil fractal dimension were 1.67–2.08 for the bare sandy land and 2.14–2.32 for the planted forests. The soil fractal dimension was strongly correlated with the soil physicochemical properties, especially with the soil nutrients and fine particle content, which exhibited highly significant correlations (p < 0.01), and the correlation coefficients were all greater than 0.8. Therefore, we believe that U. pumila is a suitable sand-fixing plant species in this area. In addition, the soil fractal dimension can be used as an important reference index for characterizing soil properties in sandy areas. [ABSTRACT FROM AUTHOR]

This paper uses Fluent software to create a 3D leakage model for hydrogen-blended natural gas pipelines and analyzes how hydrogen blending ratio (HBR), soil type, and leakage hole shape affect gas dispersion. Results show that hydrogen and methane have different concentration distributions in soil: hydrogen forms an 'n' shaped distribution while methane forms an 'M' shaped distribution, with higher hydrogen concentrations observed further from leakage holes. HBR has a minimal effect on diffusion; higher HBR leads to lower concentrations at saturation. Soil type significantly impacts diffusion, with sandy soils showing higher gas concentrations than clay. Slit-type holes result in faster concentration saturation compared to square-type holes. Increasing the number of leakage holes from two to four enhances concentration differences and accelerates diffusion. The optimal axial spacing for fast diffusion is 200 mm. These findings support monitoring and risk assessment for hydrogen-blended natural gas pipelines. [Display omitted] • The effect of hydrogen ratio and leakage hole shape on gas dispersion with a three-dimensional model. • The diffusion behaviors of hydrogen and methane were analyzed with a multi-component diffusion approach. • The influence of the number of leakage holes and their spacing on the diffusion of mixed gases were analyzed. [ABSTRACT FROM AUTHOR]

IntroductionMethodsKey results and conclusionsLocated on the extreme edge of its range, Didymodon cordatus is exceptionally rare in Britain and is considered a priority for conservation. In the present study, its current population status and ecology were investigated.All previously known locations for the species were surveyed, plus other potential locations nearby. Abundance was measured in terms of ‘individual-equivalents’, defined as an occupied 1  m grid cell. Geographical coordinates of each individual-equivalent were recorded with a GPS unit. Habitat and community composition were recorded by relevés.Didymodon cordatus continues to survive at its only location in Britain, at Saunton Down, North Devon, including a length of nearby coastal cliff from where it has been known since 1916 and an adjacent roadside bank from where it has been known since 1962. No other locations were found. It occupies open, dry, calcareous and thermophilous habitat, together with a diverse assemblage of other acrocarpous mosses. While the species is particularly associated with loess soils in continental Europe, at Saunton Down it is closely associated with soft, calcareous sandstone and thin, overlying sandy soil. Natural erosion is an important part of the occupied habitat, maintaining early successional habitat patches suitable for colonisation. A total of 102 individual-equivalents were found, and it is estimated that the entire population at Saunton Down comprises 250–1000 individual-equivalents. The habitat is generally in favourable condition and the population appears to be secure, although the species will remain vulnerable to extinction in Britain because of its extreme rarity. [ABSTRACT FROM AUTHOR]

The cohesive properties of lunar regolith, combined with a low-gravity environment, result in it having a distinct mechanical behavior from sandy soil on Earth. Consequently, empirical formulas derived from cone penetration tests (CPTs) for calculating the shear strength parameters of Earth's sand cannot be directly applied to lunar regolith. This study utilized the three-dimensional discrete element method (DEM) to numerically simulate triaxial shear tests and cone penetration tests in a lunar environment. The particle contact model for lunar regolith in the discrete element method (DEM) simulation incorporated the hysteresis effect of van der Waals forces, thereby simulating the cohesive properties of lunar regolith in a lunar environment. We proposed a relationship for calculating the shear strength index of lunar regolith based on normalized cone tip resistance using the results from triaxial and CPT simulations and referencing empirical formulas derived from ground-based CPT data. The results of this study provide a valuable reference for future lunar CPTs. [ABSTRACT FROM AUTHOR]

Sandy soils are widespread globally and are increasingly utilized to meet the demands of a growing population and urbanization for food, fiber, energy, and other essential services. However, their poor water and nutrient retention makes crop cultivation challenging. This study evaluated the effects of integrating compost and plant growth-promoting rhizobacteria (PGPR; Azospirillum brasilense SWERI 111 and Azotobacter chroococcum OR512393) on wheat (Triticum aestivum L. var. Misr 1) grown in sandy soil under varying levels of recommended NPK (50%, 75%, and 100%) fertilization. Conducted over two growing seasons, the experiment aimed to assess soil health, nutrient uptake, microbial activity, and plant productivity in response to compost and PGPR treatments. The results demonstrated that combining compost and PGPR significantly improved soil chemical properties, such as reducing soil pH, electrical conductivity (ECe), and sodium adsorption ratio (SAR), while enhancing soil organic matter (SOM). Additionally, compost and PGPR improved soil nutrient content (N, P, K) and boosted the total bacterial and fungal counts. The combined treatment also increased urease and phosphatase enzyme activities, contributing to enhanced nutrient availability. Notably, plant productivity was enhanced with compost and PGPR, reflected by increased chlorophyll and reduced proline content, along with improved grain and straw yields. Overall, the results underscore the potential of compost and PGPR as effective, sustainable soil amendments to support wheat growth under varying NPK levels. [ABSTRACT FROM AUTHOR]

As one of the world's most fragile and sensitive ecological regions, Xizang risks significant environmental damage from using traditional materials, including cement and lime, to improve and reinforce loose accumulated sandy soil slopes. To address this issue, this study utilized a low-concentration biodegradable polyvinyl alcohol (PVA) solution combined with sisal fibers (SFs) to stabilize loose accumulated sand in southeastern Xizang. A series of physical, mechanical, and microscopic analyses was conducted to evaluate the properties of the treated sand. The results indicated the following. 1) The stress-strain curves of the improved samples exhibited an elastic-plastic relationship. Failure was observed in two stages. At a strain of 3% or less, the samples demonstrated elastic deformation with a linear increase in stress, whereas the deviator stress increased rapidly and linearly with an increase in axial strain. Once the strain exceeded 3%, the deformation became plastic with a nonlinear increase in the stress-strain relationship, and the growth rate of the deviator stress gradually decreased and leveled off. 2) Under varying confining pressure conditions, the relationship curve between the maximum (σ1-σ3)max∼σ3 for both untreated loose accumulated sandy soil and soil improved with the PVA solution, and the sisal fiber was approximately linear. 3) The SFs created a skeletal-like network that encased the soil particles, and the hydroxyl functional groups in the PVA molecules bonded with both the soil particles and the fiber surface, thereby enhancing the interfacial properties. This interaction resulted in a tighter connection between the soil particles and SFs, which improved the stability of the structure. 4) The incorporation of a PVA solution and SFs significantly enhanced the mechanical strength and deformation resistance of the loose accumulated sandy soil. The optimal ratio for the improved soil was SP = 3% and SL = 15 mm, which increased the cohesion from 24.54 kPa in untreated loose accumulated sandy soil to 196.03 kPa. These findings could be applied in engineering practices to improve and reinforce loose accumulated sandy soil slopes in southeastern Xizang and provide a theoretical basis for such applications. [ABSTRACT FROM AUTHOR]

Understanding the role of open vegetation, particularly in white-sand ecosystems (WSE) and savannas, is crucial for elucidating their role in Amazonian biotic diversification. These ecosystems predominantly develop on sandy terrains, suggesting that the geological substrate significantly influences the vegetation upon it. Therefore, the interaction between landscape changes and biotic diversification is closely tied to the dynamics and resilience of these sandy substrates. Current WSE and savannas in lowland Amazonia colonized fluvial sediments deposited during the past 120 ka, with marked synchronicity over the last 23 ka, as shown by optically stimulated luminescence (OSL) and radiocarbon ages of such sandy substrates. In contrast, sandy substrates supporting open vegetation in highland areas, unsuitable for Quaternary sand accumulation, would have persisted beyond the Quaternary, as ancient sedimentary rocks in these areas are prone to developing sandy soils. The current distribution of open vegetation ecosystems in lowland Amazonia is coupled with the deposition and erosion of sandy sediments by Quaternary fluvial systems, while weathering sandy substrates in highland areas serve as long-term and resilient refugia beyond the Quaternary. The contrasting spatiotemporal dynamics of landscape changes in lowland and highland areas has implications for biodiversification or extinction events leading to current biogeography patterns in Amazonia. [ABSTRACT FROM AUTHOR]

Humic acid (HA) is considered a promising soil amendment for improving soil fertility. However, the effects of HA application on the microbial community, especially in aeolian sandy soils of semi-arid regions, remain insufficiently elucidated. To address this gap, a field experiment was conducted to investigate the changes in soil properties, bacterial and fungal diversity, and community structure in a buckwheat field in the fourth year after a single application of lignite humic acid (L-HA) at 0 (L-HA0), 2 (L-HA1), 4 (L-HA2), and 6 (L-HA3) ton·ha−1 in an aeolian sandy soil in Inner Mongolia, China. The results demonstrated that four years after L-HA application, there was a significant (p < 0.05) decrease in soil pH, accompanied by an increase in soil water content and nutrient levels, including organic matter and total N, available P, and K. Additionally, the application of L-HA enhanced microbial biomass C and N and stimulated enzyme activities, such as urease and invertase, with these effects being more pronounced at higher application rates (L-HA2 and L-HA3). However, HA addition did not significantly (p < 0.05) affect soil microbial biomass P or alkaline phosphatase activity. The L-HA amendment enhanced the α-diversity indices of soil bacteria but did not significantly (p < 0.05) affect soil fungal diversity. The addition of L-HA induced significant changes in the composition of the soil microbial community at both the phylum and genus levels, with significant variability in microbial responses observed across the different L-HA application rates. The incorporation of L-HA notably enriched the composition of bacterial and fungal communities at the phylum level, particularly those involved in carbon cycling, including the bacterial phyla Proteobacteria and Actinobacteriota and the fungal phyla Ascomycota and Rozellomycota. At the genus level, higher L-HA application rates, specifically L-HA2 and L-HA3, exerted statistically significant (p < 0.05) effects on most bacterial and fungal genera. Specifically, these treatments increased the abundance of bacterial genera, such as Rokubacterium and fungal genera, including Plectosphaerella, Tausonia, Talaromyces, and Clonostachys. Conversely, the relative abundance of the bacterial genera Vicinamibacter and Subgroup_7, as well as the fungal genus Niesslia, was significantly reduced. Redundancy analysis (RDA) indicated that bacterial community compositions were closely associated with soil parameters, such as available P (AP), microbial biomass carbon (SMC), microbial biomass nitrogen (SMN), microbial biomass phosphorus (SMP), and invertase, while all tested soil parameters, except for alkaline phosphatase, significantly influenced the fungal community structure. Given that the changes in these soil parameters were highly correlated with the amounts of L-HA addition, this suggests that the impacts of long-term L-HA amendment on the soil bacterial and fungal communities were linked to alterations in soil physicochemical and biological properties. [ABSTRACT FROM AUTHOR]

An experiment was conducted to analyse the potential for obtaining biomass for energy purposes and tall wheatgrass (TWG) seeds grown under conditions of varying pre-sowing fertilisation with compost and mineral fertilisation with nitrogen on sandy soils. Field trials were conducted between 2012 and 2015. The study factors were compost from municipal green areas with I-doses of 0, 10 and 20 Mg∙ha−1 added before sowing and nitrogen II-doses of 0, 40, 80 and 120 kg∙ha−1 added each year in the form of ammonium nitrate. During the experiment conducted on sandy soils, a favourable effect of fertilisation on the morphological parameters of above-ground vegetative and generative parts was found. The experiment resulted in high dry matter yields (DMYs) in the range of 9.08–31.38 Mg∙ha−1 and high seed yields (SYs) (635 kg∙ha−1 to as much as 2397 kg∙ha−1), which depended on the applied fertilisation variant. The applied levels of compost fertilisation had a positive effect on the obtained dry matter yields (DMYs) and SY. Analysing the effect of the applied doses of mineral nitrogen fertilisation (40, 80 and 120 kg∙ha−1) on the dry matter yield of TWG under sandy soil conditions, it should be noted that this factor significantly increased the DMY and SY in all years of the study. At the same time, the response of plants to this factor of the study over the years varied and depended on weather conditions. The high energy yield (192.50 GJ∙ha−1–408.93 GJ∙ha−1) closely related to the high DMY indicates the high suitability of TWG as a new grass species under temperate climate conditions grown for biomass energy production and the possibility to harvest seeds when adequately cultivated. [ABSTRACT FROM AUTHOR]

This study was carried out on the rotation of cowpea-rye + cowpea in successive crops for green manure-sorghum grains, with the objective of increasing the fertility of sandy soils by incorporating green cowpea manure into the soil in combination with chemical fertilization with NPK. In this sense, after harvesting the rye plant, the cowpea was sown, which was then incorporated into the soil during the formation of the beans in the pod. Before incorporating the cowpea biomass into the soil, the initial fertility status of the soil was assessed, and in the spring, the soil was sown with sorghum grain in two fertilization variants (N80P80K80 and N150P80K80). The soil chemical analyses carried out at the end of the vegetation cycle of the sorghum plant showed that by incorporating 52.4 t/ha green cowpea biomass (9.24 t/ha dry biomass), the quality properties of the soil were significantly improved, with annual increases of 0.17–0.29 g/kg in total nitrogen, 9.5–13.33 mg/kg in extractable phosphorus, 11.33–24 mg/kg in exchangeable potassium, and 0.08–0.12 g/kg in organic carbon, also depending on the sorghum fertilization system. It has also been shown to reduce the acidity of the soil pH and improve the water holding capacity of the soil. [ABSTRACT FROM AUTHOR]

Optimizing nitrogen (N) fertilizer combination is a crucial measure to maximize yield and production efficiency in a maize-soybean strip intercropping system (MSSI). In this field experiment, six maize/soybean N input combinations (0 kg ha−1, F0; 255/30 kg ha−1, F1; 255/45 kg ha−1, F2; 255/60 kg ha−1, F3; 210/45 kg ha−1, F4; 300/45 kg ha−1, F5) were set in 2022 and 2023. The results indicated that optimizing N combination (maize/soybean, 255/45 kg ha−1) could synergistically increase yield and economic benefits. Path analysis results showed that the grain numbers in maize and soybean emerged as the most critical yield-affecting factors. Compared with F0, F5 showed the highest grain yield during the 2-year experiment, and the net return increased by 86.1% (F1), 133.3% (F2), 87.4% (F3), 104.7% (F4), and 128.3% (F5), respectively. Optimizing N input under F2 and F5 notably enhanced the leaf area index (LAI) of maize at the milk stage (R3) and soybean at the full pod stage (R4). Additionally, optimization of N distribution in maize stems at the tassel stage (VT) and soybean leaves at the initial flowering stage (R1) facilitated increased dry matter and N accumulation at the maturity stage, resulting in final land equivalent ratios (LER) of 1.44 and 1.55, respectively. Our results provide a more valuable field N combination for summer maize planting areas (sandy soil areas) in Huang-Huai-Hai and southern China, thus promoting the wider application of MSSI. [ABSTRACT FROM AUTHOR]

The soil temperature in the eastern foothills of the Helan mountain, where wine grapes are buried in layers of soil during winter and spring, is important for grape growth and annual yields. Therefore, the variation law of soil temperature in buried soil layers for different soil types has been analyzed to provide a reference for scientific management of planting sites. In the winter to spring of 2021/2022 and 2022/2023, four buried soil layers with different soil types were selected at the eastern foot of Helan mountain, site 1(F1): heavy stone and sandy soil; Site 2(F2): 40% stony soil and 60% sandy soil; Site 3(F3): light lime soil; Site 4(F4): fine sandy soil, and the soil temperature at 10cm (T1), 20cm (T2), 30cm (T3) and 40cm (T4) from the surface soil was monitored in real time, to analyze the characteristics of soil temperature changes of buried soil layer in winter (December to February of the next year) and spring (March to the excavation). The results showed that: (1) in winter, the daily mean soil temperature and the daily minimum soil temperature fluctuated in line with the trend of the air temperature, and the fluctuations decreased as the soil depth increases. The maximum difference in average temperature and average minimum temperature of buried soil layers at the same depth at test site 1 to 3 were 1.2℃ and 2.2℃, respectively. The temperature of the buried soil layer in F4 was lower than that at the other test sites. With the increase of buried soil depth, the average soil temperature and the minimum soil temperature increased by 0.2−1.3℃ and 0.9−2.2℃ per 10cm. (2) The starting date of the lowest 5 days of buried soil temperature for each test appeared within 1d after the cooling process. The occurrence time of the daily minimum soil temperature in the buried soil layer was gradually delayed as the depth of buried layer increased, and the duration of the low temperature was extended. (3) In spring, the average daily soil temperature decreased gradually with increasing depth, and decreased by 0.1−1.2℃ every 10cm. The accumulated temperature of ≥10℃ increased with time in a single linear relationship, the accumulated temperature of T1 and T2, T3 and T4 had little difference, with a daily growth rate of 13.1−14.4℃ and 12.2−13.7℃, the average accumulated temperature difference of T1/T2 and T3/T4 was 25.4−33.8℃·d. Based on the soil temperature index of Cabernet Sauvignon germination, the ≥10℃ accumulated temperature of germination start date from T2 to T4 was 277.9−307.6℃·d. (4) The relationship equation between ≥10℃ active accumulated soil temperature and ≥10℃ air accumulated temperature was established for buried soil T1/T2 and T3/T4 in test site F1−F3. It can be seen that the equations show the change trend of one variable equation, and the fitting effect was good, the efficiency coefficients of models were above 0.95, and the average absolute error was below 22.4℃·d. In conclusion, the risk of overwintering freeze damage to grape branches is small in different types of soil layers buried during winter, and the temperature of the buried layer increases with depth, with a gradual decrease in fluctuation. The temperature of fine sandy soil is slightly lower than that of other soil types. The ≥10℃ active accumulated temperature index of grape soil germination starting date and the linear relationship model between air accumulated temperature and buried soil accumulated temperature in spring can provide reference for spring excavation [ABSTRACT FROM AUTHOR]

Sandy soils contain around 70% sand in their composition, making them highly fragile and susceptible to land degradation. Practices such as no-tillage cultivation, the use of bioinoculants, and the application of organic amendments can restore the organic matter in these soils, ensuring sustainable production. In this context, this work aimed to study the microbiological aspects of two sandy soil areas (Brazilian Northeast and South) under contrasting climatic conditions (tropical and temperate). With this purpose, prokaryotic communities were evaluated, and the plant growth-promoting potential of isolated bacteria was assessed by rice inoculation in sandy soil. Despite the high sand content in both soils, soil from the NE was related to the highest phosphorous, calcium, potassium, copper, sodium, zinc, magnesium, and manganese contents, organic matter percentage, and pH. The Shannon diversity index indicated that prokaryotic communities in NE were more diverse than in SU, and PCA revealed that microbial composition exhibited distinct patterns. The rice inoculation experiments were executed to verify if the bacterial isolates displayed a similar growth promotion potential when inoculated in sandy soil areas subjected to different climatic conditions. When all PGP characteristics evaluated were pooled in a PCA, a similar pattern was observed for SU and NE. Burkholderia sp. SU94 was related to highest PGP characteristics evaluated. Paraburkholderia sp. NE32 showed similar results to those of the non-inoculated control. This similar effect of rice growth in the Northeast and South of Brazil suggests that isolate SU94 adapts to different environmental conditions. [ABSTRACT FROM AUTHOR]

Artificial cementation of granular soils results in improved stabilization, increased stiffness, and greater mechanical strength. The porosity index and volumetric cement content η / C i v a is presented as a key measure to study the evolution of different soil stabilization types. However, this index had not been previously studied or adjusted for sands in Colombia. Therefore, this study evaluates the applicability of the η / C i v a index on unconfined compressive strength (q u ) and stiffness ( G o ), complemented by microstructural analysis, in four sandy soils from Luruaco (Atlántico), Lorica (Córdoba), Medellín (Antioquia), and Bogotá D.C. The soils were stabilized with Type III Portland cement in dosages of 3%, 5%, 7%, and 9%, and subjected to UCS, ultrasound, and SEM-EDS tests after a curing period of 7 days. It was found that increasing cement content results in higher q u values for the samples, and higher molding density also leads to higher q u values. Additionally, the grain size distribution influenced the adjustment of parameter "a". In the sands from Bogotá and Lorica, with high uniformity, the value of "a" was 1.00. In contrast, mineralogy and particle shape played a predominant role in the sands from Medellín and Luruaco, where the coefficient of uniformity is higher, suggesting a possible inverse relationship between particle angularity and the value of "a". [ABSTRACT FROM AUTHOR]

Synthetic fertilizers are the main nitrogen (N) input used in specialty crop systems established on sandy soils of Florida, although organic amendments and fertilizers can be used as a substitute. Organic N contained in these products must be mineralized before crop uptake, which is affected by amendment properties, soil properties, and temperature. A better method for predicting N release can help maximize the nutrient cycling benefits of organic amendments and fertilizers while avoiding negative environmental impacts. The main objective of this study was to measure N release and CO2 emissions from two poultry manure-based amendments (PMA) and two processed organic fertilizers (OF) made from livestock byproducts (e.g., feather meal). We conducted an 8-week incubation using two sandy Florida soils belonging to two soil orders (Entisol and Spodosol) and with a greater than two-fold difference in soil organic C. We incubated these soils at 10 °C, 17 °C, 24 °C, and 30 °C, measured plant-available N at 0, 1, 4, and 8 weeks, and measured CO2 emissions weekly. In both soils, OF released more inorganic N and at a faster rate compared with PMA, but CO2 emissions were greater from PMA than OF. Nitrogen mineralization and CO2 emissions increased with temperature, but temperature effects were less important than expected. These results on the mineralization of PMA and OF in sandy soils are key to optimize their use and management in Florida and other areas dominated by sandy soils. [ABSTRACT FROM AUTHOR]

Under long-term horizontal cyclic loading, the evolution characteristics of the loading and unloading stiffness of piles are an important representation of pile–soil interaction. However, research in this area is limited, particularly regarding the impact of factors like pile–soil relative stiffness. In this study, laboratory tests with a long-term horizontal cyclic loading strategy were conducted to study various factors, including different cyclic amplitude ratios (ζb), cyclic load ratios (ζc), and pile–soil relative stiffness (T/L) in sandy soil, on dynamic pile head stiffness. The results show that the normalized cumulative displacement increases with the number of cycles and the ratio of T/L but tends to decrease as ζc increases. As ζb increases, the normalized cyclic loading stiffness also rises, while it has little effect on the normalized cyclic unloading stiffness. On the other hand, as ζc or T/L increases, the cyclic loading stiffness increases while the unloading stiffness decreases. Based on these observations, prediction formulas for normalized cumulative displacement and cyclic loading and unloading stiffness were established and confirmed with test results. The findings of this study provide methodological references for establishing models of pile–soil interaction under cyclic loading and for predicting loading and unloading stiffness under different influencing factors. [ABSTRACT FROM AUTHOR]

Contamination from light nonaqueous phase fluids (LNAPLs) and their derivatives during mining, production, and transportation has become a concern. Scholars have extensively studied LNAPL contamination, but the role of water content variation on its migration process in the unsaturated zone has not been sufficiently researched. The specific issue addressed in this study is the impact of water content on the migration of light nonaqueous phase liquids (LNAPLs) in sandy soils, a critical yet under-researched aspect of subsurface contamination. To tackle this, we employed indoor simulated vertical, one-dimensional, multiphase flow soil column experiments, utilizing the orthogonal experimental method to systematically evaluate the effects of varying water contents on the occurrence state and migration rate of LNAPLs. The experimental results indicate the following: (1) The migration rate of LNAPL exhibits an L-shaped trend during subsurface imbibition and a nonlinear relationship with migration time. The migration rate and migration time of surface infiltration have a linear growth relationship. (2) The residual rate of LNAPL is negatively correlated with water content and positively correlated with oil content in the homogeneous non-saturated state. With the increase in the amount of leaked oil, 40% of the leaked LNAPL is sorbed within the soil. (3) When the water content of the test medium is below 14%, and the oil content is below 11%, LNAPL appears in the unsaturated zone in a solid phase. As the water content increases, the adsorption rate of the oil phase gradually decreases and eventually reaches the oil saturation point. (4) When the water content of the medium exceeds 8%, over time, LNAPL will be subject to oil–water interfacial tension, and the rate of LNAPL movement first decreases and then increases, displaying nonlinear growth. The innovation of this work lies in the comprehensive analysis of LNAPL migration under controlled laboratory conditions, providing results that enhance the understanding of LNAPL behavior in sandy soils. These quantitative insights are crucial for developing targeted remediation strategies for LNAPL-induced pollution in the unsaturated zone. [ABSTRACT FROM AUTHOR]

The semi-desert rangeland of Uzbekistan, characterized by gypseous and sandy soils, undergo significant changes due to grazing of different intensities. This study examines the water deficit characteristics of key plant species in these rangelands and focuses on how different grazing pressures affect plant water stress and overall ecosystem health. Field experiments were conducted to evaluate plant water potential parameters in fields with initial, low, medium and high grazing intensity. Our findings suggest that increased grazing intensity exacerbates plant water deficits, particularly in areas with sandy soils where water retention is inherently low. In contrast, gypseous soils showed higher resistance to grazing-induced water stress, but significant degradation was still observed under high grazing. These results highlight the critical need for sustainable grazing practices to mitigate adverse effects on plant water dynamics and ensure the long-term viability of these semi-desert ecosystems. [ABSTRACT FROM AUTHOR]

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The high-speed plough tip is the core soil-touching component in southern Xinjiang field cultivation, but the interaction of the plough tip with the soil results in severe wear of the tip. The friction behaviour of sand and soil on plough tips was investigated with a homemade rotary abrasive wear tester in a one-factor multilevel test with three parameters: moisture content, velocity/rotational speed and friction distance. The objective was to study the friction behaviour of the sand soil and plough tip and analyse and characterise the wear amount, wear thickness and compressive stress distribution, three-dimensional wear morphology and microscopic wear morphology of the plough tips. The results show that with increasing speed, the wear amount changes more gently; with increasing soil water content, the soil adhesion force and lubricating water film increase so that the wear amount follows a second-order parabolic law; and with increasing friction distance, the wear amount gradually increases, and the wear rate also shows an upward trend when the plough tip is in the abrasive wear stage. The tip makes contact with the firmer soil with higher surface compressive stresses, causing the most wear. As the friction distance increases, sand particles become embedded in the contact surfaces, creating a groove effect along with spalling pits caused by fatigue wear. During the whole wear period, the groove effect is always accompanied by spalling pits appearing repeatedly. The analysis of the wear micromorphology of the plough tip shows that the number of flaking pits gradually decreases in the direction of soil movement, and the form of damage changes from impact wear to plough groove scratches. Abrasive wear interacts with corrosive wear to exacerbate plough tip wear. [ABSTRACT FROM AUTHOR]

Charcoal, a byproduct resulting from incomplete combustion of biomass in fire events, can modify the physical properties of soil due to its high porosity and large surface area. To evaluate the impact of fire-deposited charcoal on soil hydraulic characteristics, soil–charcoal mixtures were analyzed to investigate the effects of different application doses (wt%: 0, 1%, 3%, 5%, 10% and 20%) of charcoal on soil bulk density (BD), porosity (total, capillary, and non-capillary), residual moisture after free drainage (RM), saturated water content (SC), and saturated hydraulic conductivity (Ks) of loamy and sandy soils collected from subtropical forests in south China. The results showed that the impact of charcoal on soil's physical and hydraulic properties depends on the soil type and the application dose. The incorporation of charcoal significantly decreased the BD of sandy soil (p < 0.001), while a significant decrease in BD in loamy soil was only observed as a result of the higher application doses (10% and 20%) (p < 0.001). Charcoal application doses of 5% or higher led to a significant increase in the total porosity (TP) of sandy soil (p < 0.001) and doses of 3% and 20% resulted in a significant increase in the TP of loamy soil (p < 0.001). The capillary porosity (CP) of both sand and loamy soils significantly increased when charcoal was applied at doses of 3% or higher (p < 0.001). The minimum charcoal application dose that significantly increased the RM in sandy soil was 5%, while for loamy soil, the minimum effective dose was 10%. Charcoal applied at a dose of 3% significantly increased the Ks of sandy soil (p < 0.001), while no significant effect on Ks was observed for loamy soil (p > 0.05). Collectively, our findings suggest that fire-derived charcoal enhances the soil water-retention capacity in subtropical forests, with the effects becoming more pronounced at higher application doses and being particularly notable in sandy soil compared to loamy soil. [ABSTRACT FROM AUTHOR]

Enhancing soil shear strength is of great importance in preventing soil collapse and erosion in the hilly granitic region of southern China. However, limited studies have been conducted on improving soil shear strength in collapsing gullies. Electrokinetic stabilization (EKS) involves applying an electrical current through a soil mass to promote the migration of chemicals from injection points, thereby altering the chemical composition of the treated soil to improve its physical properties. In this study, we investigated the effects of adding calcium chloride (CaCl2) and using EKS techniques on the soil shear characteristics (shear strength and its two components: cohesion and internal friction angle) of three different soil layers in collapsing gullies. The results showed that the EKS techniques significantly increased the migration of calcium ions from the anode to the cathode region of the power supply device used in the soils. Using the EKS process alone did not increase or even decrease the soil shear strength, but combining EKS with CaCl2 injection (Ca-EKS) increased the soil shear strength, and this increase was mainly due to the increase in soil cohesion. The soil cohesion after Ca-EKS treatment increased on average by 49.84%, 83.11% and 100.36% compared with the soil without treatments (CK) for the red soil, sandy soil and detritus, respectively. However, soil amended only by CaCl2 addition, Water-EKS or Ca-EKS does not show an increase in soil internal friction angles compared with the CK. These results demonstrate that Ca-EKS can be applied to improve the soil shear strength and stability of gully walls in hilly granitic regions. [ABSTRACT FROM AUTHOR]

This study employs variance-based and parametric analyses to quantify the impact of geometric and mechanical properties on the performance of pile foundations under axial tensile (Pa) and lateral (PL) loading. Utilizing 3D finite element analysis with the Drucker-Prager model, the research investigates pile-pile cap interaction across varying soil moduli (Es = 5, 20, & 50 MPa) and length-to-diameter (L/D) ratios (10, 20, & 33). The sensitivity analysis identifies the friction coefficient between sand and pile, as well as pile diameter, as the most influential factors, followed by pile length and the Young's modulus of both the pile and the sand. Parametric analysis reveals that pile deformation, contact pressure (Pc), and shear stresses (fs) are strongly affected by Es and the L/D ratio. Under Pa loading, as Es and L/D decrease, fs increases up to a certain depth before decreasing. Additionally, the normalized Pa to axial deformation ratio (Pa/δa) decreases with increasing relative stiffness of the pile to soil (Ep/Es), with L/D becoming increasingly influential as Ep/Es decreases. Under PL loading, increased L/D and Es result in greater pile flexibility and a concentration of Pc at the top. The pile's lateral deformation behavior with depth mirrors the Pc distribution. [ABSTRACT FROM AUTHOR]

There are different methods to assess the liquefaction potential of sandy soil sites. Meanwhile, the comparison of these methods in terms of the effect of soil heterogeneity and based on the system reliability index has received less attention. This study of sandy soil liquefaction potential using two different approaches, which are the standard penetration test (SPT) and shear wave velocity (Vs) have been analyzed stochastically. For this purpose, a real saturated site with ten heterogeneous soil layers and three boreholes was considered. The site was networking and SPT and Vs data in areas other than borehole's locations were predicted using the kriging method via a codded computer program in MATLAB. In the next step, each column of the assumed network is considered to be a borehole and using the predicted SPT-N and Vs data, and Monte Carlo Simulation (MCS) the reliability index of the system of the site by Sequential Compounding Method (SCM) were determined. The results show that for the assigned site the determined system reliability index using SPT-N data was larger than the Vs data which confirms that the SPT approach is more conservative. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) ranks as the third most significant greenhouse gas, capable of depleting the ozone layer and posing threats to terrestrial ecosystems. Climate change alters precipitation variability, notably in terms of frequency and magnitude. However, the implications of precipitation variability on N2O emissions and the underlying mechanisms remain inadequately understood. In this study, employing laboratory incubation methods on three representative sandy soil types (sandy soil, shrub soil, and crust soil), we examined the impacts of diverse precipitation levels (5 mm and 10 mm) and frequencies (7 days and 14 days) on N2O emissions from these soil types. This study aims to clarify the complex connections between soil N2O emission fluxes and soil physicochemical properties in the soil environment. Our findings reveal that the N2O emission flux exhibits heightened responsiveness to 5 mm precipitation events and a 14-day precipitation frequency, and compared to other treatments, the 5 mm precipitation and 14-day precipitation frequency treatment resulted in a 20% increase in cumulative nitrous oxide emissions. Consequently, cumulative N2O emissions were notably elevated under the 5 mm precipitation and 14-day precipitation frequency treatments compared to the other experimental conditions. The N2O emission flux in sandy soil displayed a positive correlation with available phosphorus (AP) and a negative correlation with pH, primarily attributed to the exceedingly low AP content in sandy soil. In shrub soil, the soil N2O emission flux exhibited a significant positive correlation with NH4+-N and a negative correlation with NO3−-N. Conversely, no significant correlations were observed between soil N2O emission flux and soil physicochemical properties in crust soil, underscoring the importance of considering plant–soil microbial interactions. Our findings suggest that soil nitrous oxide emissions in arid and semi-arid regions will be particularly responsive to small and frequent rainfall events as precipitation patterns change in the future, primarily due to their soil physicochemical characteristics. [ABSTRACT FROM AUTHOR]

Potassium (K) is the primary limiting nutrient for cassava, being essential to achieve sustainably satisfactory cassava yields in low K reserve sandy soils that require proper K fertilization to avoid depleting the soil K reserve. Soil K dynamics, the growth, and yield responses of cassava were investigated using varying K fertilizer rates (0, 25, 50, 75, 100, and 125 kg K2O/ha). Four on-farm experiments were conducted in major cassava-producing areas, Northeast Thailand during 2019–2021 year. Cassava responded positively to K, producing yield increases up to 132%, with the highest tuber yield obtained being in the range 100–125 kg K2O/ha. Mineral K was the main K source for cassava grown without K fertilization, which resulted in the poorest growth and yield quantities. Potassium fertilization significantly promoted the uptake of K by cassava, especially in the tuber, causing a negative K balance due to the large removal from the soil, even when the K fertilizer compensated to some degree. Potassium use efficiency of cassava was low, particularly with K fertilization at the highest rate, which reflected intense leaching of the soil. The critical level of soil-available K, identified using a linear-plateau model, was 40.55 mg/kg for 90% relative yield, suggesting the potential to increase K use efficiency through better fertilization guidelines. Our findings suggested that K fertilization of cassava annually is advisable for better yields and to avoid progressive depletion of the soil K capital, even though the residual K from K fertilizer contributed to available K in soils. [ABSTRACT FROM AUTHOR]

Mass transport in frozen ground is typically regarded slow. However, a highly permeable path can exist in frozen saline sand if the unfrozen water is interconnected at the pore scale. We therefore should consider when the unfrozen water is connected and how permeable can frozen saline sand be, yet there are few studies. This research utilizes in‐situ X‐ray CT to evaluate unfrozen water connectivity and permeability in frozen saline sand considering effects of initial salt content, temperature, freezing rate, and temperature gradient. Results show that higher initial salt content and/or temperature, both of which results in a higher unfrozen water content, easily maintains unfrozen water connectivity. Rapid freezing minimizes the brine expulsion and permits a higher unfrozen water content hence better connectivity. Permeability in frozen saline sand can be several orders higher than the typically reported value, highlighting the potential presence of rapid mass transport through the connected unfrozen water. Plain Language Summary: Frozen aqueous sandy soils in nature often contain a lot of substances such as dissolved salts, gases, contaminants. Mass migration via unfrozen water is of vital importance to groundwater flow, greenhouse gas emission, even contaminated soil remediation. Permeability determination of unfrozen water is well‐studied in salt‐free soils. Our study shows there can be a highly conductive path in frozen saline sand when the unfrozen water is interconnected, even at a low unfrozen water saturation of 14%. The connectivity of unfrozen water remains at −20°C with an initial salt concentration similar to seawater. Rapid freezing causes better connectivity because less unfrozen water is squeezed out of the frozen sand during ice growth. Permeability in frozen saline sand can be several orders of magnitude higher than the typically reported value. These findings indicate that mass transport in frozen ground, via the connected unfrozen water, can be much more active than previously thought. Key Points: Pore‐scale unfrozen water can be interconnected, enabling fast mass transport below 0°C when soil contains saltRapid freezing enhances unfrozen water connectivity and permeability due to less and slower salt migration during freezingPermeability of frozen saline sand can be several orders of magnitude higher than that of salt‐free soil [ABSTRACT FROM AUTHOR]

Microbially induced carbonate precipitation (MICP) technology is employed to reinforce the surface soil of a dam, aiming to prevent erosion caused by water flow and damage to the dam slope. The relationship between penetration depth, calcium carbonate content, and bonding depth was investigated at eight measuring points on the sand slope surface of a mold under different reinforcement durations. It was observed that as grouting reinforcement times increased, there was a gradual increase in calcium carbonate content but a rapid rise in penetration resistance. Moreover, the bonding depth of sand on the bio-reinforced sand slope increased with higher levels of calcium carbonate content. Microbial grouting reinforcement enhanced soil particle bonding force, requiring water flow to overcome this force for activation of sand particles. Consequently, microbial grouting reinforcement significantly improved shear strength and critical starting flow velocity on sand slope surfaces. The experimental results demonstrated that after MICP surface treatment through spraying, a dense and water-stable hard shell layer composed of bonded calcium carbonate and soil particles formed continuously on sample surfaces, effectively enhancing the strength and erosion resistance of sandy soils. These findings provide reliable evidence for silt slope reinforcement and dam erosion prevention. [ABSTRACT FROM AUTHOR]

Soil thermal conductivity in the near-phase-transition zone is a key parameter affecting the thermal stability of permafrost engineering and its catastrophic thermal processes. Therefore, accurately determining the soil thermal conductivity in this specific temperature zone has important theoretical and engineering significance. In the present work, a method for testing the thermal conductivity of fine sandy soil in the near-phase-transition zone was proposed by measuring thermal conductivity with the transient plane heat source method and determining the volumetric specific heat capacity by weighing unfrozen water contents. The unfrozen water content of sand specimens in the near-phase-transition zone was tested, and a corresponding empirical fitting formula was established. Finally, based on the testing results, temperature variation trends and parameter influence laws of thermal conductivity in the near-phase-transition zone were analyzed, and thermal conductivity prediction models based on multiple regression (MR) and a radial basis function neural network (RBFNN) were also established. The results show the following: (1) The average error of the proposed test method in this work and the reference steady-state heat flow method is only 7.25%, which validates the reliability of the proposed test method. (2) The variation in unfrozen water contents in fine sandy soil in the range of 0~−3 °C accounts for over 80% of the variation in the entire negative temperature range. The unfrozen water content and thermal conductivity curves exhibit a similar trend, and the near-phase-transition zone can be divided into a drastic phase transition zone and a stable phase transition zone. (3) Increases in the thermal conductivity of fine sandy soil mainly occur the drastic phase transition zone, where these increases account for about 60% of the total increase in thermal conductivity in the entire negative temperature region. With the increase in density and total water content, the rate of increase in thermal conductivity in the drastic phase transition zone gradually decreases. (4) The R2, MAE, and RSME of the RBFNN model in the drastic phase transition zone are 0.991, 0.011, and 0.021, respectively, which are better than those of the MR prediction model. [ABSTRACT FROM AUTHOR]

This paper presents the findings regarding the displacement-load behavior of both plane strain model experiments' ultimate load and numerical analyses conducted on unreinforced and reinforced sand slopes loaded with strip footing. The investigated parameters include the impact of the reinforcement and varying eccentricity on the ultimate load and displacement of the strip footing. A group of finite element analyses was performed with the 3D plane strain model and the computer code ANSYS software to validate the results of the model experiments on a slope. The results from both the numerical analyses and model experiments suggested that the use of reinforcement could enhance the load–displacement behavior of the central and eccentrically loaded footings. The load–displacement curves demonstrated that a higher load eccentricity leads to a reduction in the ultimate load of the strip footing. The concordance between the computed and observed results was reasonably satisfactory for the load displacement and the overall behavioral trend. [ABSTRACT FROM AUTHOR]

Considerable amounts of irrigation water of vegetable crops grown in homogenous sandy soil profiles could be subjected to deep percolation water losses due to inappropriately designed surface or subsurface drip irrigation methods. This study aimed to investigate the combined influence of implementing clay soil layer in homogenous sandy soil profile of low-tech greenhouse ridges and using modified surface drip irrigation (M-DI) on soil moisture distribution and water productivity of tomatoes. In the greenhouse, a 7.5 cm thick clay soil layer was implemented 15 cm from the soil surface of each ridge as a hydraulic barrier. Three irrigation regimes (100%, 70% and 50% of ETo) were imposed with the M-DI on tomato plants and 100%ETo with surface drip irrigation (DI) as control. Regarding economic valuation, viability was preserved for the M-DI and DI methods. The outcome indicated that soil moisture spreads more horizontally than vertically on the sandy soil above the clay soil layer. The combined effect of the homogenous sandy soil profile amendment and full irrigation (100%ETo) with the M-DI irrigation method increased the tomato fruit yield by 64.5%. Furthermore, the combined influence enhanced water productivity by the M-DI to 54.7 kg/m3 compared to 32 kg/m3 by the DI. However, M-DI demonstrated dominance over DI regarding returns, yield, and profit. Economic-wise, the M-DI requires 50% less of the lateral pipelines needed by the DI in low-tech greenhouses. Adopting the M-DI with a hydraulic barrier can improve soil moisture, water productivity, yield, and returns for tomato crops in low-tech greenhouses under sandy soil conditions. Also, the M-DI with the hydraulic clay barriers was an economically viable investment compared to the DI without clay barriers for growing tomatoes in low-tech greenhouses. [ABSTRACT FROM AUTHOR]

Ongoing investments in irrigation technologies highlight the need to accurately estimate the longevity and magnitude of water savings at the watershed level to avoid the paradox of irrigation efficiency. This paradox arises when irrigation pumping exceeds crop water demand, leading to excess water that is not recovered by the watershed. Comprehensive water accounting from farm to watershed scales is challenging due to spatial variability and inadequate socio-hydrological data. We hypothesize that water savings are short term, as prior studies show rapid recharge responses to surface changes. Precise estimation of these time scales and water savings can aid water managers making decisions. In this study, we examined water savings at three 65-hectare sites in Nebraska with diverse soil textures, management practices, and groundwater depths. Surface geophysics effectively identified in-field variability in soil water content and water flux. A one-dimensional model showed an average 80% agreement with chloride mass balance estimates of deep drainage. Our findings indicate that groundwater response times are short and water savings are modest (1–3 years; 50–900 mm over 10 years) following a 120 mm/year reduction in pumping. However, sandy soils with shallow groundwater show minimal potential for water savings, suggesting limited effectiveness of irrigation efficiency programs in such regions. [ABSTRACT FROM AUTHOR]

To address the prominent problem of collapse instability in shallow buried soft ground tunnels, a non-invasive stochastic finite element method was introduced. Taking Fujian Puyan Wenbishan tunnel as the background project, ABAQUS finite element software was used to analyze the tunnel excavation mechanics and parameter sensitivity. And developed the software interface program based on Python to output explicit limit state equation for the key mechanical indexes of the tunnel, so as to evaluate the tunnel reliability under different excavation methods, quantitatively. Study results show a significant improvement in efficiency and accuracy when calculating the probability of failure in tunnel excavation by the non-invasive stochastic finite element method. The maximum displacement monitoring points for the Wenbishan tunnel portal section were all vault settlement, with displacements of 33.6 mm, 30.2 mm, and 25.3 mm, respectively, using the annular retained core soil method, single sidewall guide pit and double sidewall guide pit method, with probabilities of failure of 36.11%, 28.03%, and 20.02%. It is found that the reliability of the tunnel is mainly determined by the geotechnical weight, elastic modulus and cohesion of the weak sandy soil layer, which can provide ideas for this type of engineering researches. [ABSTRACT FROM AUTHOR]

Mopane worms (Gonimbrasia belina) are important sources of nutrition among many people in southern Africa. Threats of climate change and over-harvesting have provided compelling evidence to conserve and domesticate these edible insects through a better understanding of their natural habitat. A study was conducted in Zimbabwe, with the objectives of determining the influence of soil properties on mopane larvae habitation and its nutritional content. Field sampling was conducted in treatment (with known mopane worm occurrence) and control (without mopane worm) sites. Soil and leaf samples were taken from each site and analysed for selected physical and chemical properties. Data were analysed using detrended correspondence analysis and Student t-test. Results show that G. belina larval abundance was highest on trees rooted in soils with 80–97% sand. Pupae population was positively linked to soil organic matter content, litter content, and exchangeable Ca, Mg and K concentrations but negatively linked to soil bulk density. The concentrations of Mg and K in the mopane tree leaves and mopane worm were at least seven times that of soil. Protein (55.6% DM) and fat (18.5% DM) were relatively higher in mopane worm than foliar samples. From these results, it can be hypothesised that the nutritional composition of the leaves had no link in habituating mopane worms. We conclude that mopane worms are more likely to burrow and metamorphosise to pupae into less compacted sandy soils with relatively high content of organic matter and litter content. [ABSTRACT FROM AUTHOR]

In this article, a numerical calibration procedure for undrained cyclic triaxial tests is presented to evaluate the liquefaction potential in sand and silt samples from mining tailings in northern Chile. The numerical modeling of an axisymmetric specimen involved two stages: isotropic consolidation using the Hardening Soil Small (HSS) model and a cycling phase employing the UBC3D-PLM model to simulate the onset of liquefaction using the criterion that the excess pore pressure ratio R u should exceed 0.8. The results demonstrate that the UBC3D-PLM modeling calibrated with experimental data from cyclic triaxial tests effectively represents the excess pore pressure in both sandy and silty soils from mining tailings. The accuracy of the modeling decreases when a single set of parameters is applied to the same soil at different cyclic stress ratios (CSR), highlighting the need for specific calibrations for each loading. [ABSTRACT FROM AUTHOR]

Nitrogenous fertilizer drift from farmlands accelerates nitrogen loads in groundwaters. Biochar potential to mitigate nitrogen leaching in urea treated sandy soil was monitored in a four weeks screenhouse leaching column experiment. The trial was a factorial combination of two biochar types (B1 and B2 applied at 5 t/ha) and two urea treatments (with urea at 120 kg/ha and without urea) laid in completely randomized design with three replications. Control that received neither urea nor biochar was compared. Four weekly leaching events were conducted in each leaching column containing 300 g soil amended with appropriate treatments. Amaranthus hybridus was the test crop. The NH4-N and NO3-N leached were generally highest during the week 2 leaching event such that total NO3-N leached was 427.3 % higher than total NH4-N leached with highest contributions from sole urea treatment. Biochar pretreatment reduced total N leached by 9.5 (B1) and 26.8 % (B2) relative to sole urea. Percentage of N added lost to leaching was highest (34.1 %) in sole urea treatment with B1 and B2 pretreatment reducing the value by 54.5 and 46.9 % respectively. Correlation analysis revealed electrical conductivity of the leachate and soil as dominant indicators for N leached in the soil studied. [ABSTRACT FROM AUTHOR]

Highlights: Time dependent deposition of two Azospirillum brasilense strains in sand quantified. Three inclusions regimes examined: surface, subsurface and premixed. For surface and subsurface the bacteria accumulated near the point source and remained stagnant in the premixed. The attachment/detachment numerical model found adequate to describe the time dependent deposition profiles of the bacteria. Azospirillum brasilense strains Sp7 and Cd are commonly employed plant growth-promoting bacteria (PGPB) that produce phytohormones and fix nitrogen. The two basic methods of PGPB soil inoculation are direct mixing with the soil and irrigation with liquid inoculants. The integration of drip irrigation with delivering plant growth-promoting bacteria in desert areas with sandy soil is becoming more common. With the drip irrigation system, the mobility of PGPB in the sandy soil determines the range of root zone inoculation. Therefore, we examined the transport and fate of PGPB under transient water flow conditions in a 30-cm high segmented sand column with three sand-inoculation regimes: (1) surface irrigation, (2) subsurface irrigation, and (3) sand premixing. The water, bromide, and bacterial distribution in the sand profile was measured at 2 and 48 h after irrigation. The measured data were described using the attachment/detachment numerical model using the HYDRUS 2/3D code. Results showed that even though A. brasilense Sp7 and Cd exhibit similar hydrophilicities and zeta potentials, their deposition in the sand profile differs. Strain Cd consists of smaller cells that undergo less adsorption and less straining than strain Sp7, and the former's vertical movement therefore reaches greater depths under surface- and subsurface-inoculation regimes. Nevertheless, most of the PGPB accumulated near the water source. In the sand-premixing inoculation regime, the bacteria barely moved at all. Overall, when the target root zone was deep, subsurface-irrigation inoculation worked better than the other two inoculation regimes, because it was more likely to deliver large amounts of PGPB to the root zone. Furthermore, the first-order attachment model optimized two parameters (first-order attachment coefficient and die-off rate) and well simulated the bacterial vertical movement in the surface- and subsurface-inoculation regimes (R2 > 0.91). [ABSTRACT FROM AUTHOR]

Soil liquefaction response is significantly affected by soil gradation (particle size, angularity, coefficient of uniformity) and density. However, the literature on the factors affecting liquefaction resistance with initial static shear stress (e.g., sloping ground) is more limited and primarily based on clean, poorly graded sands. As a result, the influence of particle size and gradation on the liquefaction potential of soils with initial shear stress is overlooked. In this study, 223 large-size cyclic simple shear tests were conducted on poorly and well-graded sands and gravels to evaluate the effects of soil gradation on the liquefaction resistance with the presence of initial static shear stress. Sandy and gravelly soils with coefficients of uniformity ranging from 1.6 to 42 were tested in a large-scale cyclic simple shear device under constant volume conditions, and the initial static shear stress correction factor Kα values were obtained. The results show that poorly graded sand specimens exhibit flow liquefaction, have a more significant vertical effective stress reduction as the initial static shear stress increased, but also exhibit beneficial effects of initial static shear stress even if loosely packed, mainly due to their more dilative nature. Well-graded sandy soils, on the other hand, did not have as an abrupt loss of stiffness compared to poorly graded sand specimens, but due to their higher coefficient of uniformity may be more contractive, causing more pronounced shear strain development at the last few cycles. Gravel content also affected the void ratio of sand, which influenced the onset of strain softening or hardening during cyclic loading. Dense specimens with initial static shear stress exhibit cyclic mobility, but this may not necessarily provide beneficial effects of the Kα correction factor, especially for higher coefficients of uniformity. The experimental results suggest that the widely used Kα correction factor approaches that were originally suggested based on poorly graded sand may be overoptimistic for both loose and dense soils when considering a broader spectrum of soils such as those encountered in engineering practice. It is proposed that the Kα correction factor should consider not only relative density and initial static shear stress but also particle size and gradation (i.e., determining the gravel content and the coefficient of uniformity), as well as angularity. [ABSTRACT FROM AUTHOR]

This study focuses on how soil's inherent variability, driven by environmental changes, introduces substantial uncertainty into geotechnical considerations. Voids forming underground are a key source of this uncertainty, affecting subsoil structures like piles. Using a two-dimensional discrete-element method and considering both fundamental (micro) and engineering (macro) approaches, this study investigates the influence of voids in sandy soil on a pile's behavior, especially on the pile's bearing capacity and lateral pressure coefficient acting upon its shaft. The results reveal a critical zone around the pile where voids can dramatically reduce the pile's bearing capacity, with load reductions of up to 63% in the most extreme cases. Surprisingly, voids have a minimal impact on the lateral pressure coefficient along the pile wall. Thus, it is deduced that the primary cause of the pile's load reduction in the presence of the void is the decreased resistance at the pile's tip. In summary, this research underscores how voids in sandy soil significantly affect the bearing capacity of piles, emphasizing the importance of understanding these effects for safe and efficient subsoil structure design in geotechnical engineering. [ABSTRACT FROM AUTHOR]

The limit support pressure significantly influences the stability of the shield tunnel face and deformation control during tunneling. Current research predominantly focuses on soils under dried or saturated conditions. However, unsaturated soils, which are more commonly encountered in engineering practice and widely distributed, have not been as extensively studied. Based on limit equilibrium theory, a modified analytical wedge-prism model is proposed in this paper to predict the limit support pressure acting on the shallow shield tunnel face in unsaturated sandy soil where the soil arching effect is considered. Taking advantage of finite-element software ABAQUS (version 2021), a series of numerical trapdoor tests are conducted first to study the failure behavior of unsaturated sandy soil. Then, by combining the rotation trajectory of major principal stress with the shear strength theory of unsaturated soil, the loosening earth pressure solution above the shallow trapdoor can be derived analytically. The limit support pressure can be finally obtained through a force equilibrium analysis of the wedge body. The accuracy of the proposed model is validated by comparing the calculated results with current model tests and numerical simulations. Parameter analysis results reveal that both the loosening earth pressure and limit support pressure initially decrease and then increase with the rising degree of soil saturation. A critical saturation point is identified where the loosening earth pressure and the limit support pressure reach their minimum values, attributed to the full development of the soil arching effect. [ABSTRACT FROM AUTHOR]

As a new type of pile, the bearing characteristics of stepped variable-section DX piles (multi-joint extruded and expanded piles) are quite complicated; thus, their design concepts and pile-forming processes are still in the exploration stage, and their application in actual engineering is not particularly mature. The settlement law and load transfer law of the variable section DX pile have not been studied deeply, and the values of the parameters of engineering design are not clear, which are the problems to be solved for the variable section DX pile. To solve the above problems, the present study on the bearing characteristics of stepped variable-section DX piles under vertical loading is of great scientific significance and engineering practical value. In this study, the bearing capacity of a DX pile with two variable steps was first analyzed experimentally. Then, the bearing capacity of variable cross-section DX piles and equal cross-section piles were simulated under the same soil conditions. Later, the numerical simulation results were compared with the experimental results to verify the validity and accuracy of the numerical models established in ABAQUS software. Finally, the bearing capacity of stepped variable-section DX piles in different soil layers was analyzed numerically to compare the effect of different soils on the compressive bearing capacity of piles. The results indicated that the load-bearing plates had a greater influence on the bearing capacity of the stepped variable-section DX piles. At the optimum variable section ratio, which was close to 0.9, DX piles had a good bearing capacity. The relative errors of the numerical simulation ultimate loads were below 10%, which verified the accuracy of the developed numerical model. The simulated ultimate load of the equal-section pile was the smallest. The vertical compressive bearing capacity and the effect of controlling settlement under the same level of load of the variable section DX pile in sandy soil were both better than those in silt soil. There was little difference between the bearing capacities of the piles with a load-bearing plate. The bearing capacity of the pile with two load-bearing plates was the best, which can be used in practical engineering. [ABSTRACT FROM AUTHOR]