Fine Soil Research Articles

Relationship Between Fine Root Biomass and Soil Physico-chemical Properties of Grassland Ecosystem in Bhadrapur Municipality of Jhapa district, Eastern Nepal

This study investigated the distribution of fine root biomass and various soil properties in a grassland ecosystem within Bhadrapur Municipality, Nepal. Soil samples were systematically collected from randomly selected blocks in undisturbed, disturbed, and roadside areas during the late rainy season. Analyses included soil texture, moisture content, temperature, pH, and quantification of fine root biomass (FRB; <5 mm diameter) within the top 15 cm soil depth. Results showed the mean FRB was significantly higher in undisturbed areas (7.77 t/ha) compared to disturbed (7.053 t/ha) and roadside (1.76 t/ha) areas. Across all sites, FRB exhibited a positive correlation with soil moisture content. Soil pH was slightly more acidic in undisturbed versus disturbed and roadside areas. Soil temperature demonstrated a positive correlation with FRB in undisturbed and roadside areas but a negative correlation in disturbed areas. Additionally, FRB negatively correlated with sand content in disturbed and roadside areas. The findings highlight how soil moisture is a key driver of fine root proliferation in this grassland ecosystem. Variations in soil texture, pH, and temperature between sites reveal their influence on root growth dynamics. Understanding these root-soil interactions has implications for sustainable grassland management, biodiversity conservation, and ecosystem resilience under changing environmental conditions.

Severity of topsoil compaction controls the impact of skid trails on soil ecological processes

Abstract Skid trails are a major management‐induced disturbance in temperate forest ecosystems with considerable impact on soil ecological processes that are so far poorly understood. In German forests, skid trails comprise 10%–20% of the forest area that is potentially affected by soil compaction through heavy machinery. We systematically investigated the influence of skid trails on physical, chemical and microbiological soil parameters at 84 paired plots across four Central European forest types. In low mountain forests with steeper topography, skid trails had more drastic effects than in lowland forests. Skid trails in low mountain areas showed a decrease in the C to N ratio of microbial biomass (MBC/MBN), as well as increased microbial (MBC/SOC) and enzyme activities leading to faster carbon turnover (lower C/N, EOC/EN) and increased CO2 losses (CO2/SOC) from the soil. The overall effects of the skid trails in lowland forests were small. On base‐poor soils, we found an increase in the MBC/MBN ratio, while skid trails in base‐rich lowland soils showed a reduction in CO2/SOC, suggesting a proportional increase in soil carbon storage. Regardless of region‐specific effects, the relative increase in the bulk density of the fine soil was identified as a ‘golden trait’ that determined the effects of skid trails on many soil parameters, as shown by negative correlations with SOC, N, MBC, MBN, MBP, MBC/SOC and CO2/SOC and positive ones with the activities of certain hydrolytic enzymes. Synthesis and applications: Our data clearly showed that carbon conversion processes and soil respiration leading to significant carbon and nutrient losses increased significantly on skid trails in low mountain regions with relatively steep slopes, which was in sharp contrast to lowland sites. The strong context dependence of our findings suggests that the mapping of soil conditions in terms of slope, substrate and moisture with high spatial resolution is mandatory to assess the vulnerability of sites to soil compaction by heavy machinery. Based on such vulnerability analysis, negative impacts can be minimised through the designation of permanently fixed skid trails, technical adaptation of vehicles (e.g. wide base tyres) as well as careful planning and timing of management operations that should be restricted to dry weather and soil moisture conditions or periods of frost.

Impact of Date-Palm Fibers on Fine Soil’s Compaction and Strength Properties

This paper investigates the influence of date-palm fibers on the compaction and strength properties of fine soil. The laboratory tests, including specific gravity, compaction tests, and unconfined compression strength tests, were conducted, integrating different proportions (ranging from 0 to 2%) of date-palm fibers into the soil mixture. The palm fibers were divided into two distinct lengths (30 mm and 60 mm) to be mixed with the soil. Nine samples were prepared with varying proportions of date-palm fibers for the experimental investigation, aiming to specifically examine the influences exerted by both palm-fiber length and palm-fiber content on the soil's compaction and strength characteristics when mixed with date-palm fibers. The compaction test results demonstrate a decrease in the dry unit weight and an increase in the optimum moisture content by approximately 10%. Additionally, the length of the date-palm fibers impacts the optimum moisture content and the maximum dry unit weight of the soil mixture. In contrast, the unconfined compressive stress increased by about 30% with higher date-palm fiber contents. This increase in unconfined compressive stress due to increased date-palm fiber content is a significant finding, indicating improved soil strength. This finding holds the enhancing construction performance, sustainability, and cost-efficiency. In conclusion, this soil-fiber mixture shows suitable hydraulic applications. The utilization of natural materials in civil engineering demands the exploration of available natural fibers.

Clogging of toe drain drastically affects phreatic seepage in earth dams

In aged levees, toe (blanket) drains get clogged with time due to seepage-induced suffusion and translocation of fine soil fractions from the upstream to the downstream part of the embankment. These particles deposit on the top of the drain (usually, Terzhagi's graded gravel) as a cake. Also, high hydraulic gradients in the vicinity of the drain move the fine particles into the body of the coarse filter material such that “internal colmation” takes place. In this paper 2-D seepage to a clogged drain is studied experimentally, analytically and numerically. In a sandbox, we illustrate the difference in the position of a phreatic surface and the seepage flow rate between an equipotential toe drain and a clogged one. In the analytical solution, a potential flow model is used and the Neumann (Kirkham-Brock) boundary condition on the clogged drain surface (horizontal segment) is imposed. A circular triangle is mapped conformally onto a reference half-plane, where Hilbert's boundary value problem for a holomorphic function is solved. For a given size of the levee, clogging causes a significant rise of the phreatic surface, although the seepage flow rate drops. In HYDRUS2-D simulations, a FEM-meshed Richards’ equation for a saturated-unsaturated 2-D flow is used for solving in a composite polygon, which mimics a vertical cross-section of a rectangular levee and a clogged-colmated blanket drain. Numerical results are in rough agreement with the analytical model.

Geotechnical Properties of Fly Ash Blended Expansive Soil: A Review

Fly ash, an industrial byproduct, is used as both a building material and a soil stabilizer due to its pozzolanic properties. Moreover, it is challenging to extrapolate the results based on an inadequate amount of laboratory data because of the non-homogeneous character of the soil and the diversity in the chemical properties of fly ash. This review article fills in the gaps by providing an overview of the existing data related to the geotechnical characteristics of expansive soil stabilized with fly ash. The chemical composition of fly ash is provided in terms of oxides of various elements to help identify the kinds produced in different nations. Additionally, information about the physical and geotechnical characteristics of fly ash blended expansive soil is provided in order to comprehend the influence of the fly ash's chemical composition and the expansive soil's fines percentage. While the geotechnical property comprises Atterberg's limit, compaction, UCS, shear strength, free swelling index, CBR, and consolidation, the physical property includes specific gravity and durability. Shear modulus, damping ratio, and Poisson's ratio are used to describe the dynamic properties of the modified expansive soil. The published data in this field and the research gap will be identified by the researchers with the aid of this article. Doi: 10.28991/CEJ-SP2024-010-06 Full Text: PDF

Design of a washing ejector and column flotation based on the microbubble for heavy metal contaminants removal from contaminated soils: A pilot and laboratory-scale studies

This study mainly examines the effects of combined washing ejector and column flotation process by remediation equipment for heavy metal remediation at a contaminated site. A washing ejector system is a sustainable technology that considers the concept of hydrodynamic cavitation. Soil aggregates strongly binding to poorly crystalline minerals and Fe oxide bonding with the soil create challenges for their elimination from soils contaminated with complex contaminants. The effects of the operating conditions of the cavitation flow on increasing the separation of fine particles were evaluated by determining the mass balance during the washing system process on a pilot scale. Cavitation flow in the washing ejector system can increase the dispersion of soil aggregates owing to the generation of hydroxyl radicals (•OH) and the increase in mixing intensity. Cavitation flow during the process can increased the dispersion of soil aggregates owing to the release of Fe oxides into the soil. The coarse and fine particles were readily separated from the bulk soil, and the fine particle distribution per mass increased after washing. The levels of Fe in the coarse fraction soil met the KS requirements after separation, whereas the Fe levels in the fine fraction soil were above than the KS limits. To reduce waste volume, column flotation was used to selectively separate Fe oxides from contaminated soil. Microbubbles in column flotation have the important function of facilitating the collision and attachment between air bubbles and Fe oxides and subsequently recovering the Fe oxides. When AF65 as a frother and oleic acid as an anionic collector were used in the column flotation, the concentration of Fe oxides increased from 9.67 % to 13.76 %, a recovery of approximately 10 % from the fine soil. According to the mass balance of the study area, after treatment using the washing ejector system, coarse (60 %) and fine (40 %) soils in the total soil were separated. Column flotation can be applied to fine soil to achieve a volume reduction of approximately 30 % of the total soil volume. The results of this study illustrate the feasibility of the proposed remediation process to reduce waste volume and improve sustainability while meeting Korean standards for heavy metal pollution in soil, thereby minimizing environmental risk.

Fine root biomass and soil properties in burnt and unburnt community grasslands of Cachar district, Assam, Northeast India

Fine root biomass and soil properties in burnt and unburnt community grasslands of Cachar district, Assam, Northeast India

Failure evolution and mechanism of ground collapse due to exfiltration of shallowly buried water pipeline

Exfiltration of defective water pipelines is one of the leading causes contributing to the frequent ground collapses in congested urban areas; hence, revealing the failure evolution and mechanism of this hazard is essential to its prevention and mitigation. In this study, comprehensive experimental model tests were conducted first to characterize the evolution of soil erosion and ground collapse due to exfiltration of shallowly buried defective water pipes and examine the effects of six critical parameters, i.e., opening size and location, pipe pressure and buried depth, groundwater level, and exfiltration condition. Three failure behaviors of strata around leaking waterpipe were identified, i.e., minor disturbance (slight), formation and collapse of an erosion cavity (moderate), and soil fluidization (severe). Moreover, the ground loosening zone induced by cavity collapse could be roughly estimated using the modified flow ellipsoid theory; soil fluidization would occur once the ratio of water pressure head inside the pipe to its buried depth was greater than 2. Subsequently, a validated computational-fluid-dynamics and discrete-element-method (CFD–DEM) coupling method was employed to explore the microscopic mechanism of cavity erosion under the exfiltration flow. It was disclosed that the formation and expansion of a temporary cavity resulted from internal soil erosion, including the emigration of massive fine particles and aggregation of coarse particles around the defective pipe. Finally, the numerical simulation results indicated that cavity erosion would be exacerbated by increasing flow velocity and particle size-ratio, reducing soil fines content, and changing the opening from the pipe crown to its invert.

Stress stress-strain behavior of hydraulic filled coral sand subjected to internal erosion

Coral sand foundations lose fine particles under the action of groundwater infiltration. As the soil skeleton structure deteriorates, the foundation becomes uneven and may even collapse. In this study, a triaxial drainage shear test of coral sand is used as a quantitative control method for the loss of fine particulate soil, and the effect of internal erosion on the mechanical behavior of coral sand is evaluated. An experiment is used to demonstrate that erosion leads to a decrease in the peak shear strength and residual strength of coral sand. Erosion has different effects on coral sand with different fine particle contents, and the effects on the friction angles of coral and terrestrial sand are also different. The secant modulus E50 and peak secant modulus Ep gradually decrease as the loss of fine particles increases. The effect of fine particle loss on the peak secant modulus Ep is significant at fine-particle losses exceeding 10% for a fine-particle content of 20%. The loss of fine particles creates new pore spaces in the coral sand, which, in turn, affects the stability of the original soil skeleton. Erosion has been shown to have an effect on the gradational features of coral sand, leading to the phenomenon that the dilatancy effect increases as a function of the amount of erosion that takes place. To prevent uneven foundation settlement caused by subsurface erosion in engineering designs, it is important to consider the gradation characteristics and fine particulate content of coral sand, which affect the stability of coral reef foundations.

Shifts in belowground processes along a temperate forest edge

ContextForests are increasingly fragmented, and as a result most forests in the United States are within one km of an edge. Edges change environmental conditions of the forest—especially radiation, roughness, temperature, and moisture—that can have consequences for plant productivity and ecosystem functions. However, edge effects on aboveground characteristics of plants and the environment are better understood relative to plant roots and soil in the belowground environment.ObjectivesOur main objectives were to determine if soil C pools and fluxes are higher at the edge relative to other landscape positions, and to understand how specific belowground processes contribute to bulk differences in pools and fluxes.MethodsWe measured environmental conditions, live and dead fine root traits, soil chemistry, and soil respiration along a 75 m transect from interior forest to meadow in Gaithersburg, MD.ResultsWe observed differences in the soil chemical, biological and hydrological environment between the forest interior, edge and adjacent meadow. In some cases, the forest edge represented a mid-point in environmental or belowground characteristics between the forest interior and meadow (e.g., pH, C-to-N ratio [C:N], live fine root biomass, heterotrophic respiration), likely reflecting the change in litter type and quality associated with the transition from grass to woody species. In other cases, neighboring landscape positions were different from the forest edge, which was drier and had higher dead fine root biomass. Although soil C contents were not significantly different across landscape positions, there was a tendency towards higher average soil C content at the edge relative to other landscape positions, suggesting that increased C loss related to root decay and greater soil respiration at the edge relative to the forest interior may have been offset by increased C gain from high plant productivity and subsequent inputs to soil.ConclusionsThis research provides insight into how forest edge environments may differ from the interior and how concurrent processes above- and belowground may contribute to those differences.

Multi-year analysis of physical interactions between solar PV arrays and underlying soil-plant complex in vegetated utility-scale systems

Concerns over the land use changes impacts of solar photovoltaic (PV) development are increasing as PV energy development expands. Co-locating utility-scale solar energy with vegetation may maintain or rehabilitate the land's ability to provide ecosystem services. Previous studies have shown that vegetation under and around the panels may improve the performance of the co-located PV and that PV may create a favorable environment for the growth of vegetation. While there have been some pilot-scale experiments, the existence and magnitude of these benefits of vegetation has not been confirmed in a utility-scale PV facility over multiple years. In this study we use power output data coupled with microclimatic measurements in temperate climates to assess these potential benefits. This study combines multi-year microclimatic measurements to analyze the physical interactions between PV arrays and the underlying soil-vegetation system in three utility-scale PV facilities in Minnesota, USA. No significant cooling of PV panels or increased power production was observed in PV arrays with underlying vegetation. Fine soil particle fraction was the highest in soils within PV arrays with the vegetation which was attributable to the lowest wind speeds from the compounding suppression of wind by vegetation and PV arrays. Soil moisture and soil nutrient response to re-vegetation varied between PV facilities, which could be attributed to differing soil texture. No statistically significant vegetation-driven panel cooling was observed in this climate. This finding prompts a need for site-specific studies to identify contributing factors for environmental co-benefits in co-located systems.

Adaptive multi-paddock grazing increases mineral associated soil carbon in Northern grasslands

Grassland soils play an important role in sequestering carbon (C) and are primarily used for livestock grazing. Grazing management can increase the amount of C stored in soils and the distribution of C in different soil fractions by altering soil microbial community structure, thereby influencing the persistence of soil C over time. Adaptive multi-paddock grazing (AMP), grazing cattle at high stock densities with long periods between grazing events, is considered to enhance grassland sustainability, productivity, and soil C compared to more conventional grazing practices (continuous to slow rotational). However, whether and how AMP grazing might affect the amount of C stored in different soil fractions has received little attention. Soil samples (0–15 cm depth) were collected from 24 ranches in a paired design, where 12 ranches practiced AMP grazing and 12 neighboring ranches practiced conventional grazing. Soil organic C (SOC) and total nitrogen were measured in different soil particle size [fine (<53 µm), medium (53–250 µm) and coarse (>250 µm)], and density [light (>1.6 g cm−3), and heavy (<1.6 g cm−3)] fractions. Soil bacterial and fungal biomass and abundances were obtained from phospholipid fatty acid analysis. Mean weights of soil microaggregates and heavy fractions were higher in soil exposed to AMP grazing, whereas mean weights of macroaggregates and light fractions were higher in conventionally grazed soils. In warmer and drier climatic conditions, SOC in both bulk soils and within various size and density fractions tended to decrease. Soil organic C (both concentration and stock) were significantly higher in the fine soil fractions under AMP management than conventionally grazed grasslands. Given that SOC in fine fractions, is more mineral associated and recalcitrant, our results indicate that AMP grazing increased the size of the stable SOC pool. The increased carbon pool in the fine fraction was associated with greater fungal to bacterial ratios, suggesting a possible biological mechanism for the increase. Overall, the results indicate that AMP grazing may be beneficial for sequestering more stable carbon that helps mitigate the effects of climate change.

Investigation of Cement and Fly Ash on the Improvement of Fine Sand Soil

Soil stabilization problems like liquefaction, bearing capacity, permeability, excessive settlement and swelling can be solved by improving soil’s engineering properties by using various methods. The use of fly ash as a stabilizer has become popular in recent years since it is eco-friendly and effective on soil stabilization, especially for fine-grained soils. This study investigated the reuse of fly ash as a stabilizer (5–25% by weight) and cement (constant 3% by weight) as an activator to enhance the geotechnical properties of poorly graded sand (SP). Standard proctor tests were conducted to determine optimum water content and maximum dry unit weight, followed by direct shear box, falling head permeability and CBR tests at the determined optimum water content. Direct shear box experiments were carried out at two relative densities (30% and 80%) and CBR experiments were performed after 7 and 28 days of curing time. The results demonstrated that the addition of fly ash and cement improved the geotechnical properties, including shear strength, permeability and bearing capacity of the fine sand soil.

Large Animal Carcass Mortality Composting: Impact on Soil Nutrients

Livestock producers and environmental agencies have expressed concern about nutrient loss to the soil from routine mortality composting on soil with no cover or site improvement. In 2011, a replicated study of carcasses composted on soil was conducted at the University of Maine’s Compost Research and Education Center. The purpose was to evaluate the potential loss and movement of nutrients to soil from carcass compost piles when constructed on an unimproved site. As carcasses decompose, many nutrients become soluble and are available for leachate losses to ground and surface waters. Most notable among those nutrients are phosphorus and the nitrogen species: ammonia, ammonium, nitrite and nitrate. Six compost piles, approximately 12 cubic yards, were constructed on a fine sandy loam soil (Paxton-Charlton very stony fine sandy loam) on sod similar to a farm field. Three piles had cow carcasses while the other three did not. Feedstock material consisted of a blend of three parts horsebedding and one part waste feed. To determine nutrient movement in the soil profile, soil samples were collected, pre and post pile construction, at 13 cm (6 inches) and 26 cm (12 inches) across a transient of each pile. All samples were analyzed at the Maine Soil and Analytical Lab for nitrogen species and 12 other elements. Composting carcasses on an unimproved site does not appear to contribute significant amounts of nutrients to the soil, providing a cost-effective and environmentally sound method for carcass management.

Slope Stability Analysis of East Ring Road Construction at Sadawarna Dam With Shear Strength Reduction Method

Slope stability has been a problem that studied on geotechnical works for the uncertainties such as varieties of soil behaviours to unpredicted failure of measurements and samplings. The Limit Equilibrium Method (LEM) has been popular for decades for its convenience but cannot determine displacement thus the result could be uncertain. As computational calculations have been developed, the Finite Element Method (FEM) began to use as a tool to not only determine factor of safety, but also determine displacement and forces that affect slope’s stability. This research was done to analysed slope stability using Shear Strength Reduction (SSR) and compared it to general method such as Limit Equilibrium Method (LEM). The research was conducted on a section in Sadawarna DAM ring road area, Subang, West Java. Slope on research area was divided into two layers with the bottom layer relatively non-cohesive compared to the top of layer. Both soil however dominantly consist with fine grain soil such as silt and clay. The upper layer of slope can contain more water with liquid limit of 73,46% compared to the lower layer with 68,27% liquid limit. Simulation result showed slope that analysed using SSR method has Factor of Safety (FoS) 0,12 lower than LEM method. SSR method could be used to analysed pessimistic value at worst scenario and could predicted deformation of slope.

Does no-till crop management mitigate gaseous emissions and reduce yield disparities: An empirical US-China evaluation

Global agricultural systems face one of the greatest sustainability challenges: meeting the growing demand for food without leaving a negative environmental footprint. United States (US) and China are the two largest economies and account for 39 % of total global greenhouse gases (GHG) emissions into the atmosphere. No-till is a promising land management option that allows agriculture to better adapt and mitigate climate change effects compared to traditional tillage. However, the efficacy of no-till for mitigating GHG is still debatable. In this meta-analysis, we comprehensively assess the impact of no-till (relative to traditional tillage) on GHG mitigation potential and crop productivity in different agroecological systems and management regimes in the US and China. Overall, no-till in China did not change crop yields, although soil CO2 (8 %) and N2O (12 %) emissions decreased significantly, while soil CH4 emissions increased by 12 %. In contrast to Chinese no-till, a significant improvement in crop yields (up to 12 %) was recorded on US cropland under no-till. Moreover, significant decreases in soil N2O (21 %) and CH4 (12 %) emissions were observed. Of the three cropping systems, only wheat showed significant reduction in CO2, N2O and CH4 emissions in the Chinese no-till system. In the case of US, no-till soybean-rice and maize cropping systems demonstrated significant emission reductions for N2O and CO2, respectively. Interestingly, yields of no-till maize in China and rice in US exceeded those of other no-till cereals. In China, no-till on medium-texture soils resulted in significant reductions in GHG emissions and higher crop yields compared to other soil types. In both countries, the relatively higher crop yields under irrigated versus non-irrigated no-till and the significant yield differences on fine textured soils under US no-till are likely due to the substantial N2O reductions. In summary, crop yield disparities from no-till between China and the US were related to the insignificant effects on controlling CH4 emissions and successfully mitigating N2O, respectively. This study comprehensively demonstrates how cropping system and pedoclimatic conditions influence the relative effectiveness of no-till in both countries.

Potential Application of Natural Fibres for the Reinforcement of Unpaved Forest Roads—Response after RL-CBR Tests

Unpaved roads are essential as transportation infrastructure. These roads are traditionally built utilizing local soils and aggregates. The application of different materials to improve the strength and the overall performance of these road solutions has been investigated. This study focuses on the assessment of the suitability of reinforcing a fine soil using natural fibres from the forest value chain—specifically, pine needles—for unpaved forest roads. The resilient response of both unreinforced and reinforced soils was assessed with RL-CBR tests (California Bearing tests with repeated load) for different percentages of natural fibres incorporated into the soil. The force–penetration response, CBR value, recoverable and permanent displacements, and equivalent modulus were estimated. The effect of different load stages on the elastic response of both unreinforced and reinforced soils was also evaluated. The CBR values improved with the addition of pine needles; the best response was observed for specimens reinforced with 1% (mass) of these natural fibres (the CBR value increased by 45%). The equivalent modulus also was improved, showing that the stiffness of the soil increased with the inclusion of reinforcement. The findings imply that RL-CBR studies offer a promising method for obtaining important design parameters, especially for unpaved forest roads where investments in soil characterization are frequently limited.

A fine digital soil mapping by integrating remote sensing-based process model and deep learning method in Northeast China

Accurate soil type maps provide an important basis for agricultural decision-making and land degradation control. In soil classification studies, the various environmental covariates are often selected based on the soil-forming framework. Since the mapping area and available observation data are limited, meteorological and vegetation cover factors have not been fully developed, and their role in soil classification needs to be evaluated. In addition, whether deep learning has out-performance in soil classification remains to be tested. The aim of this paper is to evaluate the accuracy of deep learning modelling techniques in classifying soil type using different combinations of input variables, and evaluate the importance of soil-forming variables in soil type classification. Therefore, we collected commonly used environmental covariates in Northeast China (NEC), including multiple meteorological factors and adopted a satellite-based biophysical model (Boreal Ecosystem Productivity Simulator, BEPS) to enrich vegetation cover factors. Next, four modeling strategies were developed: the soil-forming factors of soil and relief were considered as traditional environmental covariates (T), as well as combined with meteorologic variables (T + C), vegetation cover variables (T + V) and all available environmental covariates (T + C + V). Then, the effectiveness of different modeling strategies for soil classification was explored with convolutional neural network (CNN) model and multi-layer random forest (MRF) model based on soil separability. Finally, a 30 m resolution soil type map was established. The results demonstrated that both MRF and CNN can achieve high accuracy soil classification, while the CNN model performs better. The descending order of classification accuracy based on different modeling strategies of the CNN model is shown as T + C + V: 91.08%, T + V: 88.84%, T + C: 86.82%, and T: 83.96%. Meanwhile, the separability of different soil-forming factors for soil classification is soil properties, vegetation cover, temporal variation, meteorologic and relief in descending order. For Castanozems and Brown soils, MRF has higher classification accuracy, while CNN has better performance in Meadow soils and Fluvo-aquic soils. The methodology proposed in this paper aims to achieve high accuracy soil classification, provide an approach to understand the importance of soil-forming factors for the region, as well as for different soil types, and provide references for facilitating the interpretation of misclassified areas. Our results are accurate in the core areas, and therefore, this work facilitates researchers to be able to focus more on areas where different soil types intersect, thus significantly improves efficiency and saves resources, and promises to be a useful tool for future soil surveys.

Research on the formation of weathering substances as reserve materials for collapse and climatic conditions

Heavy rainfall or natural disasters such as earthquakes can lead to slope failure, which is when a slope weakens and rapidly collapses without warning. The speed of slope failure means there is little chance for people to escape and so there can be significant numbers of injuries and deaths. Warnings of slope failures from authorities tend to be inaccurate due to myriad factors, including the different properties of soils, as well as factors such as temperature and annual rainfall. Researchers at Saitama University and the National Research Institute for Earth Science and Disaster Resilience in Japan, including Associate Professor Chiaki Oguchi and Principal Researcher of the project, Tsuyoshi Wakatsuki, are working to address knowledge gaps about sediment-related disasters, particularly slope failure. A key focus for the researchers is on estimating formation rates of slope materials that are waiting to collapse. The team is working to reduce unpredictability and improve the accuracy of disaster prevention measures. Currently, the researchers are investigating the formation of weathering substances as reserve materials for collapse and climatic conditions and, so far, they have ascertained that in areas with annual high temperatures, the slow failure materials tend to be those that are composed of a thick slope which contains a greater amount of fine soil particles. They have also confirmed that these materials show a higher potential for greater weathering, thereby exacerbating the issue and exponentially increasing the possibility of slope failure.

A Numerical Simulation of Moisture Reduction in Fine Soil Subgrade with Wicking Geotextiles.

A new wicking geotextile is proposed to control the water content of fine-grained soil subgrade. By comparing the spatial distribution of volumetric water content and matric suction before and after the installation of the wicking geotextile, the effectiveness of the geotextile in controlling the subgrade humidity is evaluated. Firstly, the hydraulic parameters of the wicking geotextile are obtained through laboratory tests using a pressure plate apparatus. Then, a numerical model for water flow in the subgrade is established using COMSOL to obtain the spatial distribution characteristics of humidity in the subgrade under different groundwater levels (2~8 m). The results show the wicking geotextile exhibits strong hydrophilicity, low water retention, and high horizontal permeability. Compared to the subgrade without geotextile, the water content of the soil above the geotextile decreases significantly by 7.6~9.6% at groundwater levels of 4~8m, while the saturation decreases by 18.3~23.0%, and the matric suction increases by 2~2.3 times. The wicking fabric functions as an effective drainage material to serve as a capillary barrier in the cross-plane direction and an effective drainage tunnel to transport water in the in-plane direction. The dynamic resilient modulus of the subgrade increases by 23.2~43.6%. The wicking geotextile effectively absorbs and drains weakly bound water in unsaturated soil due to the matric suction difference and its horizontal drainage capacity to improve the bearing capacity of the subgrade. It suggests that using wicking geotextile for drainage and reinforcement in fine-grained soil subgrades with groundwater levels ranging from 4 to 8 m is beneficial.