Soil Layer Research Articles

Significant interaction between root system architecture and stratified phosphorus availability for the initial growth of rice in a flooded soil culture

Phosphorus (P) deficiency is a major limiting factor for rice production in the tropics. The root system architecture (RSA) may play a significant role to capture P efficiently in soils; however, its function is poorly understood in flooded and puddled soil cultures. Two near-isogenic lines (NILs) contrasting RSA—qsor1-NIL (nonfunctional allele of qSOR1; shallow RSA) and Dro1-NIL (functional allele of DRO1; deep RSA)—were repeatedly grown for approximately 6 weeks in pots with three stratified P treatments. The treatments simulated P deficient conditions in puddled and subsoil layers, P available in the puddled layer, and P available in puddled and subsoil layers, that is, −P−P: no P applied in either the top-half (0–14 cm) or bottom-half (14–28 cm) layers; +P−P: P applied only in the top-half layer; and +P+P: P applied in the top-half and bottom-half layers, respectively. A significant interaction was observed between genotype and P treatment. The Dro1-NIL had a greater root surface area in the bottom half layer, which was advantageous for capturing P in the subsoil layer and resulted in greater biomass and P uptake in the +P+P treatment. Contrarily, the qsor1-NIL had a greater root surface area and longer root hair, resulting in greater biomass and P uptake in the −P−P treatment. The mechanism is unclear; however, the pleiotropic effect of qsor1, namely enhancing root hair elongation, might be more advantageous to explore P with minimal carbon costs than elongating nodal and lateral roots when P is not available in deep soil layers. No genotype differences were observed in the +P−P treatment, implying no apparent topsoil P-foraging effect of the shallow RSA in the flooded soil culture. The roles of RSA and root hairs should attract further attention for the genotypic improvement of lowland rice under P deficiency conditions in the tropics.

Grass (Poa annua L.) cover for eight years as an effective strategy for recovering soil moisture

Deep soil desiccation has become a major obstacle to restoring vegetation in the Loess Plateau region of China. The restoration of deep soil water plays an important role in ecosystem health. In the present study, we compared the effects on moisture variations in deep dry soil of grass cover and clean tillage treatments based on in-situ soil column monitoring for eight years. The results showed that the dry soil layers could temporarily disappear and reappear again with rainfall under clean tillage. However, grass cover effectively increased the deep soil moisture. Grass primarily consumed soil moisture from the shallow layer (0–2 m), and the total amount of water consumed during the whole growth period was less than the annual rainfall in dry years. The average soil desiccation index decreased by 24.20 % and the deep soil water moisture (2–10 m) recovered from 7.5 % to 12.8 % after eight years, with an annual average recovery of 0.66 %. Thus, it would take half a year to recover to the stable field capacity and 14 years to reach the field capacity. Recovery of the soil moisture also depended on the rainfall supply. We found that precipitation had an obvious lagged effect of approximately two years on the supply of deep soil moisture. Our findings contribute to understanding how to alleviate dry soil layer, with potentially helpful implications for the ecological health in arid and semiarid regions.

Galerkin boundary element method for simulating lightning response of grounding grid in horizontal multilayered soil model considering soil ionization effect

AbstractThis work proposes a novel mathematical model based on the Galerkin time‐domain boundary element method for accurately calculating the lightning current distribution and lightning impulse response of the buried substation grounding grid, in a multi‐layer horizontal layered soil model, by taking into account the soil ionization effect. To improve computational efficiency, the quasi‐static complex image method and its closed form time‐domain Green's function have been introduced into the model that has the ability to analytically calculate the mutual inductance coefficient between the branch currents of any two conductor segments and the mutual resistance coefficient between the leakage currents. The Galerkin time‐domain boundary element method proposed in this work can simulate the transient lightning impulse response of a substation grounding grid buried in the multi‐layer horizontal layered soil.

The Effect of Layered Soil with Two Textures on Wetting Pattern of Two Adjacent Trickle Sources

The Effect of Layered Soil with Two Textures on Wetting Pattern of Two Adjacent Trickle Sources

A coupled regional-scale numerical model for hydrological processes and interactions between groundwater and surface water in a controlled drainage district

Controlled drainage (CD) has emerged as an effective strategy to prevent filed waterlogging and mitigate drought during crop growth by altering the hydrological process, while few studies have quantified its effect on groundwater-surface water interactions and groundwater recharge at a regional scale. In this study, a new model is developed for the coupled numerical simulation of water flow in ditches, soil, and underground aquifers under CD conditions. The domain is partitioned into horizontal sub-areas and two vertical layers, with ditches discretized into segments based on groundwater flow grids. The Saint-Venant equations, Richards equation, and MODFLOW are applied to describe water movement processes in ditches, soil, and underground aquifers, respectively. The proposed model is calibrated and validated using five years of observations of ditch water levels (DWL) and groundwater levels, demonstrating excellent agreement with observed data. Subsequently, water balance components of the shallow aquifer below 1 m depth (GW), 1 m of root layer soil profile (SW), and ditch water (DW) under seven scenarios with different control schemes during flood and dry seasons are analyzed to quantify variations in hydrological processes caused by CD. The results show that CD significantly impacts water within SW, GW, and DW, soil evaporation, infiltration, and net recharge from GW to SW (GtoS) by altering regional groundwater table depth (GWT) through the exchange between DW and GW (DtoG and GtoD). GWT and DW show moderate correlation with GtoD, while their correlation with DtoG varies significantly under different rainfall conditions. Smaller precipitation results that precipitation and GWT have a higher linear correlation with water balance components during the dry season compared to the flood season. The correlation values (r) between transpiration (T) and GWT range from −0.99 to 0.96 and −1 to −0.85 during the flood and dry seasons, respectively, indicating a pronounced influence of CD on crop growth. On average, a 1 m increase in DWL control scheme leads to a 0.51 m increase in DWL, and regional GWT decreases by 0.35 m and 0.24 m during flood and dry seasons, respectively. Furthermore, for every 1 m decrease in GWT, net GtoS increases by 36.1 mm and 28.1 mm, respectively, resulting in an increase in SW by 13.9 mm and 11.8 mm, respectively. Considering the varying main crop water stress and the impact of CD under different rainfall conditions, an appropriate CD scheme needs to be adjusted accordingly. These findings provide a quantitative reference for the effect of CD on regional hydrological process and serve as a typical case for similar areas aiming to implement CD strategies for waterlogging and drought control.

MODELACION NUMERICA EN DOS DIMENSIONES PARA ANALISIS DE MUROS MECANICAMENTE ESTABILIZADOS UTILIZANDO MACSTARS

For the modeling of mechanically stabilized walls, it involves performing a two-dimensional analysis through numerical methods, given the complexity of variables for their evaluation. One methodology frequently used in the field of geotechnical engineering is that of limit equilibrium, describing in the article the Macstars computer code, this allows to introduce the geometry of the wall, the main reinforcements, the type of front facing, the geomechanical properties of the different soil layers that make up the area to be evaluated, the phreatic layer, the earthquake and the way in which the voussoirs are divided according to the geometry of the slope. It becomes a complementary computational tool, in the determination of stress-strain values, where the introduction of the collected data is focused on the sequence, selection and iteration, to obtain with it, the safety factor that satisfies the conditions for the evaluation of the critical failure surface.

DEVELOPMENT OF PEAK GROUND ACCELERATION USING A NON-LINEAR APPROACH TO EVALUATE LIQUEFACTION POTENTIAL IN SEI WAMPU BRIDGE, LANGKAT, NORTH SUMATRA, INDONESIA

The design of building structures requires compliance with seismic codes and all their consequences. Based on geotechnical investigation reports, the construction of Sei Wampu Bridge in Langkat, North Sumatra, Indonesia, is located in an area where the soil layers are predominantly sand with shallow water levels because of its proximity to a river and is a high earthquake zone due to the Semangko fault. That condition will affect the potential of liquefaction occurring. This study aims to identify the liquefaction potential in the Sei Wampu Bridge. Based on Indonesian National Standard (SNI) 1726-2019, sites prone to liquefaction are categorized as site class-specific soil (F) and requires site-specific response analysis (SSRA) methods. Non-linear analysis 1-D is chosen to propagate earthquake waves with the software DEEPSOIL V7. The input parameter for soil movement utilizes an average spectral matching method with a minimum of 7 pairs of soil movement selected from the earthquake recording website, PEER Ground Motion Database. The selection of earthquake considers a 1000-year earthquake load return period, or a 7% probability exceeded within 75 years. Site-specific response analysis (SSRA) resulted in a peak ground acceleration (PGA) value for each borehole depth used in liquefaction potential analysis. Using a historical earthquake scenario with a 6.3 Mw shows that the research location has liquefaction potential at 0 m-15 m deep with high vulnerability levels, where the LPI value reaches 36.21.

Surface Runoff Estimation in Kubaisa Watershed Using SWAT, Western Desert, Iraq

Surface runoff significantly impacts the region's ecosystem and is closely linked to sustainable development and human well-being. The mathematical model SWAT running in an ArcGIS environment was used to estimate surface runoff in the Kubaisa watershed. The period simulated in this model is 31 years, sufficient to give good results regarding surface runoff volume and water yield contribution from each sub-watershed. The Kubaisa watershed has an area of 2485.50 km2 and comprises six sub-watersheds. The watershed consists of 172 HRUs distributed among sub-watersheds depending on the variation in soil layers, land use, vegetation, and slope. The volume of water calculated from the annual surface runoff rate for the simulation period was about 2699 million cubic meters, and its value was higher than the volume of water calculated from surface runoff due to lateral flow, groundwater discharge, and the contribution of each sub-watershed to the water yield. The highest value in water yield was in 2012, and the largest contribution was made by the sixth sub-watershed; thus, the difference is temporal and spatial in terms of water yield. Finally, through the analysis of multiple scenarios, the difference in hydrological response units is controlled by the difference in surface runoff, discharge, and water yield to the watershed. For this purpose, the SWAT model divides the watershed into many different units and starts the simulation on their basis.

Geotechnical characterization of tropical soil via laboratory testing

This manuscript presents the evaluation of relevant geotechnical properties of the soil profile in the northern region of Campinas, which are important for geotechnical engineering practice and development in São Paulo State. Disturbed and undisturbed samples from the subsoil were collected through the excavation of inspection shafts at the experimental site for Soil Mechanics and Foundations research at the State University of Campinas, located at the Faculty of Civil Engineering, Architecture and Urbanism (FEC). Laboratory tests were conducted, including soil characterization, soil shear strength, soil compressibility, soil permeability, and soil suction tests. The characterization tests indicated that the upper soil layer is subject to surface effects and more direct weathering action, with noticeable variations in the liquid and plasticity limit values. The permeability test results showed no significant variation between the values obtained in the vertical and horizontal directions. The soil-water characteristic curves for the studied profile were bimodal, typical of tropical soils with macro and microaggregated structures.

Species Evenness and Diversity of Soil Invertebrates at Different Agricultural Lands and a Forest Reserve at Kota Belud, Sabah

Increasing agricultural activities can lead to changes in soil ecosystems, potentially impacting soil invertebrate communities as they are highly responsive to soil disturbances. The composition of soil invertebrates within each agricultural habitat provides insights into how these communities respond to their environmental conditions. This study aimed to investigate the evenness and diversity of soil invertebrates in agricultural areas of Kota Belud, Sabah. Soil samples were collected from three different agricultural sites, a rubber plantation, an oil palm plantation, and a paddy field, as well as a forest reserve as a control site. Pitfall traps and Berlese-Tullgren funnels were used to collect soil invertebrates. A total of 180 soil samples and 474 individuals of soil invertebrates were collected and analyzed. Physicochemical analyses, including moisture content, soil texture, pH, soil nutrient content, and organic matter, were conducted on all soil samples to assess their influence on the composition of soil invertebrates. Results indicated that Julida, Coleoptera, Gastropoda and Araneae were frequently associated with high organic matter, pH, moisture content and phosphorus. On the other hand, Haplotaxida appeared to be more sensitive to potassium levels. Notably, the Blattodea, Orthoptera, Hymenoptera, Isopoda, Polydesmida and Diptera, were found to be abundant in areas with lower organic matter and pH in the control site, i.e., forest reserve area. These findings underscore the significance of soil layer activities in influencing the presence and survival of soil invertebrates. Given their vital role in sustaining life, prioritizing the enhancement of soil invertebrate populations is crucial, particularly in Sabah, a prominent food crop-producing state in Malaysia.

Impacts of land use and management methods on soil quality dynamics in central highlands of Ethiopia.

Land degradation often results in poor soil quality in many parts of Ethiopia, including the study area. To address this issue and promote sustainable land management practices, various land use and management methods (LUMMs) have been implemented. However, little information is available regarding how these management practices influence overall soil quality dynamics of the study area. This study aimed at evaluating soil quality dynamics in the Urago micro-watershed, central highlands of Ethiopia, under major LUMMs: barren land (BL), grassland (GL), established farm boundary (EFB), restored degraded land (RDL), and stone-supported soil bund (SSB). Forty-five disturbed and fifteenundisturbed soil samples were collected from the ploughed soil layer (0-20cm) of each LUMM and analysed for selected physicochemical properties to be used as indicators of soil quality. Principal component analysis and multiple correlation were used to select the minimum data set (MDS) to evaluate the overall soil quality index (SQI). The MDS included SOC, clay content, exchangeable Mg2+, and available P, which could replace other indicators for assessing the overall soil quality dynamics of the study watershed. The result showed notable variations in particle-size fractions, soil organic carbon (SOC), total nitrogen (TN), available P (av. P), and exchangeable Na+, K+, and Mg2+ levels among the LUMMs. RDL had higher sand and silt contents than SSB, whereas SSB had higher clay content compared to RDL, GL, and BL. GL, RDL, and EFB showed significantly higher levels of SOC, TN, and av. P, respectively, compared to other LUMMs. The obtained SQI showed that GL had the highest score (0.847), followed by SSB (0.703), RDL (0.701), EFB (0.644), and BL (0.628). This underscores the significance of stone-supported soil bund and restored degraded land as an efficient management method to enhance soil quality and agro-ecosystem through conserving soil and encouraging sustainable farming practices.

Straw return under deep tillage increases grain yield in the rice-rotated wheat cropping system

ContextStraw return under rotary tillage has been used for two decades in the rice-rotated wheat cropping system in the lower Yangtze region of China, but it has become prone to reduce wheat emergence and yield in recent years, and alternative tillage methods are required to ensure the high wheat yields. AimsTo determine whether straw return under deep tillage can improve wheat yield and under what mechanisms. We hypothesize that straw return under deep tillage can increase wheat seedling number by reducing rice stubble and straw coverage, and expand the nutrient pool and root system of the plow soil profile to keep post-anthesis viability for increasing wheat yield. MethodsA field study was conducted during two consecutive years and included four treatments: rotary tillage after straw removal (RT); rotary tillage after straw return (RTS); shallow rotary tillage followed by straw mulch (STS) and deep tillage after straw return (DTS). Wheat seedling number, yield, aboveground nutrient uptake, growth period, root characteristics, and soil nutrients were measured. ResultsCompared to RT, seedling number under RTS and STS decreased by 8.3 % and 13.4 %, respectively, while DTS increased by 14.7 %. Wheat yield under RTS and STS decreased by 3.0 % and 7.3 %, respectively, while DTS increased by 8.2 %. The reduction in seedling number under RTS and STS would be partially offset in wheat yield by an increase in effective tiller number per plant and grain weight. Consequently, the variation in wheat yield among treatments was less than the variation in seedling number. Aboveground N and P accumulation in wheat under DTS were higher than the other treatments. Among four treatments, DTS had the highest root distribution and soil N and P contents in the middle and deep soil layers, thus prolonged grain filling duration. Wheat nutrient uptake at maturity and yield were significantly correlated with root weight density and root length density in both middle and deep soil layers. ConclusionsStraw return under deep tillage can increase nutrient supply capacity and root distribution in deep soil while ensuring wheat emergence, enabling better filling of post-anthesis wheat and yield. It is therefore an effective alternative tillage method suitable for the rice-rotated wheat cropping system.

A comprehensive assessment of heavy metals, VOCs and petroleum hydrocarbon in different soil layers and groundwater at an abandoned Al/Cu industrial site

Compound pollution at industrial sites impedes urban development, especially when there is a lack of understanding about the spatial variations of internal pollution in industrial areas producing light-weight materials. In this study, spatial distribution and ecological risks of potentially toxic elements (PTEs), volatile organic compounds (VOCs), and petroleum hydrocarbons (C10–40) in the soil and groundwater of an Al/Cu (aluminum/copper) industrial site have been analyzed comprehensively. Results revealed the progressive clustering of pollutants in different soil layers, which indicated varying levels of penetration and migration of pollutants from the surface downward. Furthermore, severity of pollution varied according to pollutant type, with Cu (5–10,228 mg kg−1) often exceeding the background levels significantly (>40). Cd (0.03–2.60 mg kg−1) and Hg (0.01–3.73 mg kg−1) were found at elevated concentrations in deeper soil layers, suggesting distinct variations of PTEs across different soil depths. Among the more hazardous VOCS, polychlorinated biphenyls (1.80–234 μg kg−1) were particularly prevalent in the deeper layers of soil. Petroleum hydrocarbons (C10–40) were widely detected (6–582 mg kg−1), showing significant migration potential from surface to deep soil. These findings suggest that prolonged industrial activities lead to deep-seated accumulation of pollutants, which also impacts the groundwater, contributing to long-term dispersion of contaminants. Furthermore, multivariate statistical analysis indicated certain positive correlations among the distribution of Cu, Pb and petroleum hydrocarbons, indicating possible coupling of these pollutants. Severe Cu pollution caused an ecological risk in the surface soil layer (covering >20 % area of high pollution site, contributing >40 % ecological risk). While the Hg and Cd posed significant risks in the deeper soil layers, showing higher risk coefficients and mobility. The study provides crucial insights into the transformation of urban areas with a history of industrial uses into community spaces and highlights the risks posed by the remaining pollutants.

Exploring soil nitrogen and sulfur dynamics: implications for greenhouse gas emissions on the Qinghai-Tibet Plateau.

The Qinghai-Tibet Plateau is particularly vulnerable to the effects of climate change and disturbances caused by human activity. To better understand the interactions between soil nitrogen and sulfur cycles and human activities on the plateau, the distribution characteristics of soil nitrogen and sulfur density and their influencing factors for three soil layers in Machin County at depths of 0-20cm, 0-100cm, and 0-180cm are discussed in this paper. The results indicated that at depths of 0-180cm, soil nitrogen density in Machin County varied between 1.36 and 16.85kg/m2, while sulfur density ranged from 0.37 to 4.61kg/m2. The effects of three factors-geological background, land use status, and soil type-on soil nitrogen and sulfur density were all highly significant (p < 0.01). Specifically, natural factors such as soil type and geological background, along with anthropogenic factors including land use practices and grazing intensity, were identified as decisive in causing spatial variations in soil nitrogen and sulfur density. Machin County on the Tibetan Plateau exhibits natural nitrogen and sulfur sinks; However, it is crucial to monitor the emissions of N2O and SO2 into the atmosphere from areas with high external nitrogen and sulfur inputs and low fertility retention capacities, such as bare land. On this basis, changes in the spatial and temporal scales of the nitrogen and sulfur cycles in soils and their source-sink relationships remain the focus of future research.

Monitoring Soybean Soil Moisture Content Based on UAV Multispectral and Thermal-Infrared Remote-Sensing Information Fusion.

By integrating the thermal characteristics from thermal-infrared remote sensing with the physiological and structural information of vegetation revealed by multispectral remote sensing, a more comprehensive assessment of the crop soil-moisture-status response can be achieved. In this study, multispectral and thermal-infrared remote-sensing data, along with soil-moisture-content (SMC) samples (0~20 cm, 20~40 cm, and 40~60 cm soil layers), were collected during the flowering stage of soybean. Data sources included vegetation indices, texture features, texture indices, and thermal-infrared vegetation indices. Spectral parameters with a significant correlation level (p < 0.01) were selected and input into the model as single- and fuse-input variables. Three machine learning methods, eXtreme Gradient Boosting (XGBoost), Random Forest (RF), and Genetic Algorithm-optimized Backpropagation Neural Network (GA-BP), were utilized to construct prediction models for soybean SMC based on the fusion of UAV multispectral and thermal-infrared remote-sensing information. The results indicated that among the single-input variables, the vegetation indices (VIs) derived from multispectral sensors had the optimal accuracy for monitoring SMC in different soil layers under soybean cultivation. The prediction accuracy was the lowest when using single-texture information, while the combination of texture feature values into new texture indices significantly improved the performance of estimating SMC. The fusion of vegetation indices (VIs), texture indices (TIs), and thermal-infrared vegetation indices (TVIs) provided a better prediction of soybean SMC. The optimal prediction model for SMC in different soil layers under soybean cultivation was constructed based on the input combination of VIs + TIs + TVIs, and XGBoost was identified as the preferred method for soybean SMC monitoring and modeling, with its R2 = 0.780, RMSE = 0.437%, and MRE = 1.667% in predicting 0~20 cm SMC. In summary, the fusion of UAV multispectral and thermal-infrared remote-sensing information has good application value in predicting SMC in different soil layers under soybean cultivation. This study can provide technical support for precise management of soybean soil moisture status using the UAV platform.

Montane evergreen forest deforestation for banana plantations decreased soil organic carbon and total nitrogen stores to alarming levels

Forest conversion to agricultural land has been shown to deplete soil organic carbon (SOC) and soil total nitrogen (STN) stocks. However, research on how soil properties respond to forest conversion to shifting cultivation has produced conflicting results. The conflicting findings suggest that the agricultural system may influence the response of SOC and STN to forest conversion to agriculture, depending on the presence of vegetative cover throughout the year. Due to the unique characteristics of montane evergreen forests (MEF) and banana plantations (BP), SOC and STN response to MEF conversion to BP may differ from existing models. Nevertheless, research on how soil properties are affected by MEF conversion to BP is scarce globally. In order to fill this research gap, the goal of this study was to evaluate how much deforestation for BP affects SOC, STN, and soil quality by analysing these soil parameters in MEF and BP fields down to 1-m depth, using standard profile-based procedures. Contrary to the specified hypothesis that SOC and STN losses would be restricted to the upper 20-cm soil layer, SOC losses were extended to the 40-cm depth layer and STN losses to the 60-cm depth layer. The soils lost 18.56 Mg ha – 1 (37%) of SOC from the upper 20 cm and 33.15 Mg ha – 1 (37%) from the upper 40 cm, following MEF conversion to BP. In terms of STN, the upper 20, 40, and 60 cm lost 2.98 (43%), 6.62 (47%), and 8.30 Mg ha – 1 (44%), respectively. Following MEF conversion to BP, the SOC stratification ratio decreased by 49%, implying a decline in soil quality. Massive exportation of nutrients, reduced C inputs due to complete removal of the arboreal component and crop residues, the erodibility of the soils on the study area’s steep hillslopes, and the potential for banana plantations to increase throughfall kinetic energy, and splash erosion through canopy dripping are thought to be the leading causes of SOC and STN losses. More research is needed to identify the extent to which each cause influences SOC and STN losses.

Geotechnical and Geophysical Assessment of the Soil Layers of the Missan Combined-Cycle Power Plant Project

Geotechnical and Geophysical Assessment of the Soil Layers of the Missan Combined-Cycle Power Plant Project

Effects of freeze-thaw leaching on physicochemical properties and cadmium transformation in cadmium contaminated soil

This study aims to investigate the effect of the combined method of freeze–thaw and leaching on the removal of cadmium (Cd) in soil and to provide a theoretical basis for the remediation of farmland soil polluted by heavy metals. The removal process and mechanism of Cd were deduced through oscillatory leaching experiments and freeze–thaw leaching simulation experiments, and the influence of the freeze–thaw leaching technology on the soil environment was evaluated. The results of oscillatory leaching showed that a mixture consisting of 0.80 mol/L citric acid and 0.80 mol/L ferric chloride in a 1:19 vol ratio effectively remove 47.75 % of Cd, indicating that the composite leaching agent could effectively remove Cd from the soil. The results of the freeze–thaw leaching simulation experiment showed that although the freeze–thaw leaching treatment increased the total Cd content in the 0–5 cm soil layer, the total Cd content in the 5–10 cm, 10–15 cm, and 15–20 cm soil layers decreased by 5.08 %, 2.39 %, and 5.68 %, respectively. The freeze–thaw leaching increased the content of exchangeable Cd (p<0.05), carbonate bound Cd, but decreased organic bound Cd and residual Cd (p<0.05), thereby increasing the bioavailability of Cd. Freeze–thaw leaching not only increased the competitive adsorption of Cd2+ by decreasing soil pH, cation exchange capacity, and increasing the content of exchangeable calcium and exchangeable magnesium, thus reducing the adsorption of Cd in soil. And the results of XPS and FTIR similarly showed that the freeze–thaw leaching could promote the chelation between Cd2+ and hydroxyl, carboxyl and carbonyl functional groups. Although the freeze–thaw leaching destroyed the large particle structure (0.05–2 mm) and large pores in the soil, and increased the clay content (<0.002 mm) and the proportion of small pores in the soil, the XRD results showed that freeze–thaw leaching had no significant effect on the minerals in the soil. In summary, this study shows that freeze–thaw leaching has a significant effect on the removal of soil heavy metals, suggesting that the synergistic effect of freeze-thaw and leaching should be considered in the process of removing soil pollutants in seasonal freeze–thaw zones, and that this method provides a new insight into the remediation of contaminated soils.

Inverse analysis of soil hydraulic parameters of layered soil profiles using physics‐informed neural networks with unsaturated water flow models

AbstractInformation about the spatial distribution of soil hydraulic parameters is necessary for the accurate prediction of soil water flow and the coupled movement of chemicals and heat at the field scale using a process‐based model. Physics‐informed neural networks (PINNs), which can provide physical constraints in deep learning to obtain a mesh‐free solution, can be used to inversely estimate soil hydraulic parameters from less and noisy training data. Previous studies using PINNs have successfully estimated soil hydraulic parameters for homogeneous soil but estimating such parameters of layered soil profiles where the interface depth and the parameters are unknown still has some difficulties. The objective of this study was to develop PINNs to inversely estimate the distribution of soil hydraulic parameters, such as saturated hydraulic conductivity and α and n of the Mualem–van Genuchten model directly within layered soil profiles by predicting changes in the pressure head from training data based on simulation results at given depths during infiltration. The impact of factors affecting PINNs performance, such as the weights assigned to each component of the loss function, time range used in error computations, and number of samples used to assess the physical constraint, was investigated. By assigning a larger weight to the physical constraint and excluding the earlier stage of infiltration in the loss function, the changes in the pressure head and the three soil hydraulic parameter distributions within the layered soil were successfully estimated. The developed PINNs can be further applied to more complex soils and can be improved.

Centrifugal Model Test of Multi-Level Slope under Combined Support of Pile-Anchor and Frame-Anchor

The combination support structure of pile-anchor and frame-anchor is widely used in multi-level slope engineering, but the relevant theoretical research lags behind engineering practice. To make up for this deficiency, this paper takes the multi-level slope under combined support of pile-anchor and frame-anchor as the research object, conducts a model test using the geotechnical centrifuge, analyzes the most relevant structural force and slope deformation in engineering, and provides some reinforcement suggestions. The test results show that the combination support structure of pile-anchor and frame-anchor has a good reinforcement effect on multi-level soil slopes, but the deformation range of the slope is greatly affected by the anchoring structure and the anchor rods located within the deformation zone. The structural force condition is significantly different from traditional structures that place the anchor rod anchoring section in a stable soil layer. According to the structural force characteristics, it is recommended that the support design fully consider the positional relationship between the anchor rods and the sliding surface. The design of the frame-anchor support section should strictly control the anchoring depth, so that the potential sliding surface of the slope can be moved backward, thereby increasing the difficulty of sliding. The design of pile-anchor support should ensure that the anchor rods have sufficient length to provide greater anchoring force, thereby improving the bearing capacity of the pile. These research results can enrich and improve the support design theory of multi-level soil slopes, providing guidance for engineering practice.