Soil Stress Research Articles

A Method for Determining Yield Stress of Unsaturated Soils from Lateral Pressure

Abstract Predicting the stress–strain behavior of unsaturated soils is essential for determining yield stress. This paper explores a new method for determining the yield stress of unsaturated soils from the lateral pressure curve. A series of earth pressure at rest (K0) ondometer tests were conducted on unsaturated Yangqin silt clay. Lateral stress was obtained under different saturations and compactness. The relationship curves between lateral and vertical net stress were drawn for each condition. An obvious turning point was observed in the curve, which can be used to determine the yield stress. The oedometer tests were conducted, and the Casagrande and the bilogarithmic methods were used for comparison purposes. The difference between the proposed and traditional methods was less than 17 %. The initial saturation and compactness influence on the yield stress was discussed. The yield stress increased with the decrease in saturation and increases in compactness, which is consistent with that of the classic method. The test results and comparison prove the rationality of the proposed method. No coordinate transformation is required in the proposed method, which is more convenient for data processing. It can be used to determine the yield stress of unsaturated soils from another perspective.

A Hydraulic Gradient and Stress-Controlled Erosion Apparatus for Assessing Soil Internal Erosion

Abstract Among the four dominant mechanisms of internal erosion, suffusion appears as one of the most complex. It is indeed the result of the combination of three processes: dislodgement of fine particles, transport of them, and filtration of some fluidized fine particles. These processes depend on the soil’s stress state and on the hydraulic gradient path. Thus, to ensure the repeatability of the suffusion test and to study with accuracy the influence of the aforementioned parameters, a new apparatus was developed. This apparatus is designed to test specimens under a vertical downward flow in hydraulic gradient controlled condition while controlling the confining pressure and the stress deviator, which can be either positive or negative. Ten tests on one cohesionless soil were performed in triaxial conditions, with the same mean effective stress and four different values of stress deviator. To compare with conventional suffusion results, one test is also performed in rigid wall conditions. For all performed tests, the same hydraulic gradient path was applied and particular attention is paid to the repeatability, which implies control of each test step. At the end of each test, the specimen was divided into four layers to measure post-suffusion grain size distributions. The time evolutions of the hydraulic conductivity and the erosion rate permit to identify four different phases. Each phase is characterized by two methods: one based on the hydraulic gradient and the second based on the expended energy by the fluid. The results show the great influence on the suffusion kinetics of the preferential flow paths, which localize in the body of the specimen in triaxial conditions and on the circumference in rigid wall ones. Under a constant mean effective stress, the effect of the stress deviator on the suffusion kinetics appears limited, for the tested soil and shear stress ratios.

Seismic response of a mid-story isolated stilted structure in mountainous areas

Research on the SSI effect on flat sites has yielded many valuable conclusions. However, current research on the impacts of various special local terrains on structural dynamics remains limited. For mountainous areas, it is common to construct houses in a multi-step, climbing, and laterally staggered architectural form that follows the mountain terrain. Only through the analysis of the combined action of the upper and lower parts can the seismic performance of this type of structural form be better revealed; considering the influence of SSI effects will be closer to the actual seismic effects. Therefore, to identify the damage factors of the mid-story isolated stilted structures under earthquakes and provide optimized design plans for the structures, six models are established considering three slopes and two types of foundations based on the engineering case in Chongqing, China. Through the elastic-plastic time-history analysis under earthquakes in the down and transverse-slope directions, concludes, compared with not considering SSI, the seismic response of the mid-story isolated stilted structures considering SSI in mountainous areas is amplified. With the increase of the mountain slope, the seismic response of the structures considering SSI increases, and the amplification coefficients are between 1–1.8. The amplification coefficients of the structures without SSI are concentrated around 1, which is less influenced by the slope. The damage to the stilted isolated layer is mainly concentrated in the column and the beam end, and the maximum seismic response appears in the short columns. The foundation soil stress increases with the increase of the mountain slope.

Mesopredator release moderates trophic control of plant biomass in a Georgia salt marsh.

Predators regulate communities through top-down control in many ecosystems. Because most studies of top-down control last less than a year and focus on only a subset of the community, they may miss predator effects that manifest at longer timescales or across whole food webs. In southeastern US salt marshes, short-term and small-scale experiments indicate that nektonic predators (e.g., blue crab, fish, terrapins) facilitate the foundational grass, Spartina alterniflora, by consuming herbivorous snails and crabs. To test both how nekton affect marsh processes when the entire animal community is present, and how prior results scale over time, we conducted a 3-year nekton exclusion experiment in a Georgia salt marsh using replicated 19.6 m2 plots. Our nekton exclusions increased densities of plant-grazing snails and juvenile deposit-feeding fiddler crab and, in Year 2, reduced predation on tethered juvenile snails, indicating that nektonic predators control these key macroinvertebrates. However, in Year 3, densities of mesopredatory benthic mud crabs increased threefold in nekton exclusions, erasing the tethered snails' predation refuge. Nekton exclusion had no effect on Spartina biomass, likely because the observed mesopredator release suppressed grazing snail densities and elevated densities of fiddler crabs, whose burrowing alleviates soil stresses. Structural equation modeling supported the hypotheses that nektonic predators and mesopredators control invertebrate communities, with nektonic predators having stronger total effects on Spartina than mud crabs by controlling densities of species that both suppress (grazers) and facilitate (fiddler crabs) plant growth. These findings highlight that salt marshes can be resilient to multiyear reductions in nektonic predators if mesopredators are present and that multiple pathways of trophic control manifest in different ways over time to mediate community dynamics. These results highlight that larger scale and longer-term experiments can illuminate community dynamics not previously understood, even in well-studied ecosystems such as salt marshes.

Prediction of Resilient Modulus Value of Cohesive and Non-Cohesive Soils Using Artificial Neural Network

This paper investigates the application of Artificial Neural Networks (ANNs) for predicting the resilient modulus (Mr) of subgrade and subbase soils, which is a critical parameter in pavement design. Utilizing a dataset of 1683 Mr observations, the ANN model incorporates eight input variables, including soil gradation, plasticity, and stress conditions. The model was optimized using a quasi-Newton method, achieving high predictive accuracy, with a coefficient of determination (R2) of 0.9613 and low error rates for both selection and testing datasets. To further enhance model interpretability, SHAP (SHapley Additive exPlanations) analysis was conducted, revealing the significant influence of specific input parameters, such as saturation ratio, plasticity index and soil gradation, on Mr predictions. This study underscores the potential of ANNs as a practical tool for estimating resilient modulus, offering a reliable alternative to conventional laboratory testing methods. The findings suggest that integrating ANNs into pavement design processes can lead to more accurate predictions of pavement performance, ultimately supporting the development of more efficient and durable road structures.

Effect of Water Content and Degree of Compaction of Clay Subgrade Soil on the Interface Shear Strength Using Geogrid

Pavement performance in clay soil roads can be enhanced with the help of the geogrid concept by increasing lateral confinement, bearing capacity, and overall rigidity of the pavement. Also, geogrid is useful in minimizing vertical and lateral pavement deformations. In this study, 65 tests are performed without and with two types of geogrid, and the aim behind it is to investigate the effect of the moisture content and degree of compaction of clay soil on the interface shear strength. The number of materials used to conduct this study, included subbase granular (type B), clay subgrade soil, the Biaxial and SS2 geogrid which is used as a reinforcing material. Testing the direct shear is conducted by a large-scale direct shear manufactured device contains an upper box with side lengths of (20×20×10) cm, and a lower box with side lengths of (20×25×10) cm. Results show that for all tests the normal applied stresses are 25, 50, 75 and 100 kPa, the shear stress displacement curves for all cases follow similar trends and they are affected by normal stress, density and water content of subgrade soil and type of geogrid. Also, it is obvious that the shear stress increases by increasing the normal applied stress and degree of compaction of clay subgrade soil reaching its maximum value at 95% degree of compaction while it decreases by increasing the water content of subgrade soil. The maximum value of shear strength is observed when water content is equal to 8% (dry side) and finally, the Biaxial geogrid BX1100 (G1) is more efficient in reinforcing clay-subbase interface as compared with SS2 geogrid (G2).

Optimizing wheat supplementary irrigation: Integrating soil stress and crop water stress index for smart scheduling

A two-year field experiment was conducted to integrate soil moisture stress with the Crop Water Stress Index (CWSI) for optimizing irrigation in winter wheat (Triticum aestivum L.) under varying irrigation regimes. The study took place at the Water Technology Centre (WTC-02) of ICAR-IARI, New Delhi, where the climate shows a blend of monsoon-influenced humid subtropical and semi-arid conditions. Using a randomized block design (RBD), five irrigation treatments were applied: full irrigation and deficit irrigation (DI) at 15 %, 30 %, 45 %, and 60 % levels. Canopy and ambient air temperature data, along with vapor pressure deficit (VPD), were recorded using a developed integrated sensing device to empirically determine the lower baseline equations and upper threshold for CWSI computation at pre-heading and post-heading stages. The slope (m), intercept (c) of the lower baseline equation, and upper threshold (UL) for pre-heading and post-heading were found: m: −1.94, c: −1.33, UL: 1.92°C and m: −1.30, c: −2.37, UL: 2.0°C, respectively. Results showed that increasing water deficit levels led to significant reductions in grain yield, biomass production, and harvest index. A strong negative correlation (R² = 0.95 and 0.93) between mean seasonal CWSI and yield attributes highlighted the utility of CWSI in yield prediction under varying irrigation regimes. It is recommended to schedule irrigation based on the CWSI approach when CWSI ≥0.35 for optimum wheat yields. Integrating CWSI with soil moisture stress provides valuable real-time insights into crop water status, enabling more precise and smart irrigation scheduling.

A new calculation method for the response of active-passive bridge piles considering pile-soil interface friction

The pile foundation of bridges under unregulated surcharge loads experiences a complex force pattern, which is subject to active loads and passive loads. In this paper, a more comprehensive calculation method for the response of active-passive piles was proposed, which considered the effect of pile-soil interface friction and soil stress states on the passive loads. First, the Ito theory was improved by adopting the adhesion c a and external friction angle φ a to characterize the pile-soil interface friction. Then, the soil around the pile in elastic, elastoplastic, and plastic flow states was considered to calculate the variation of the passive load. Finally, a nonlinear p-y curve was introduced to establish the calculation model of active-passive piles, and the finite difference program CPAPP was prepared for the solution. The results show that the pile response calculated by CPAPP is consistent with the field measurement, indicating that the proposed calculation method has high accuracy. When the soil is in an elastic state, the pile-soil interface friction does not affect the passive load. When the soil is in a plastic state, the passive load is closely related to soil strength parameters and pile-soil interface friction parameters.

Residual Effect of Microbial-Inoculated Biochar with Nitrogen on Rice Growth and Salinity Reduction in Paddy Soil.

Increasing soil and water salinity threatens global agriculture, particularly affecting rice. This study investigated the residual effects of microbial biochar and nitrogen fertilizer in mitigating salt stress in paddy soil and regulating the biochemical characteristics of rice plants. Two rice varieties, Shuang Liang You 138 (SLY138), a salt-tolerant, and Jing Liang You 534 (JLY534), a salt-sensitive, were grown under 0.4 ds/m EC (S0) and 6.84 ds/m EC (S1) in a glass house under controlled conditions. Three types of biochar-rice straw biochar (BC), fungal biochar (BF), and bacterial biochar (BB)-were applied alongside two nitrogen (N) fertilizer rates (60 kg ha-1 and 120 kg ha-1) in a previous study. The required salinity levels were maintained in respective pots through the application of saline irrigation water. Results showed that residual effects of microbial biochars (BF and BB) had higher salt mitigation efficiency than sole BC. The combination of BB and N fertilizer (BB + N120) significantly decreased soil pH by 23.45% and Na+ levels by 46.85%, creating a more conducive environment for rice growth by enhancing beneficial microbial abundance and decreasing pathogenic fungi in saline soil. Microbial biochars (BF and BB) positively improved soil properties (physicochemical) and biochemical and physiological properties of plants, ultimately rice growth. SLY138 significantly had a less severe response to salt stress compared to JLY534. The mitigation effects of BB + N120 kg ha-1 were particularly favorable for SLY138. In summary, the combined residual effect of BF and BB with N120 kg ha-1, especially bacterial biochar (BB), played a positive role in alleviating salt stress on rice growth, suggesting its potential utility for enhancing rice yield in paddy fields.

Artificial macropores improve maize performance at the seedling stage under poor aeration.

Maize is susceptible to hypoxia stress in soils with poor aeration, but the macropores have the potential to improve soil aeration. We studied the impact of artificial macropores on maize performance under poor aeration. Three levels of air-filled porosity (5%, 10% and 15%) were established, and soil columns with (28 vertical artificial macropores with 0.5 mm diameter) or without macropores were created for each level of air-filled porosity with a bulk density of 1.3 g cm-3. Root-macropore interactions were visualized using CT scanning (41 μm in resolution). Our results showed that root length density significantly increased by 114%, as air-filled porosity increased from 5% to 15%. However, when artificial macropores were present, an increase in air-filled porosity had no significant effect on root length density. The treatment of 5% air-filled porosity with macropores significantly increased root length density and root biomass by 108% and 65%, respectively, relative to the treatment of 5% air-filled porosity without macropores, whereas there was no significant difference in root growth between the treatments of 15% air-filled porosity with and without macropores. Compared to the treatment of 5% air-filled porosity with macropores, there was a significant reduction of 49% in the number of macropores colonized by roots under the treatment of 15% air-filled porosity with macropores. Our results demonstrate that macropores provide preferential paths for the colonization of maize roots, thereby promoting root growth under poor aeration. Creating macropores with bio-tillage can serve as a crucial strategy for enhancing crop performance in poorly aerated soils.

Fulvic and Salicylic Acids Improve Morpho-Physio-Biochemical Attributes, Yield and Fruit Quality of Two Mango Cultivars Exposed to Dual Salinity and Heat Stress Conditions

Abstract Purpose The present research’s main objective was to explore the potential stimulative effect of fulvic acid (FA) as a soil conditioner and salicylic acid (SA) as foliar spraying on morpho-physio-biochemical attributes, fruit yield, and quality of ‘Sediek’ and ‘Ewais’ mango cultivars (cvs.) grown under saline calcareous soil and heat stress conditions Methods Eight treatments, namely, 200 (FA200) and 400 (FA400) g FA tree−1 as a soil addition, 200 (SA200) or 400 (SA400) mg SA L−1 as foliar spraying, and their bilateral combinations (e.g., FA200 + SA200, FA200 + SA400, FA400 + SA200, and FA400 + SA400) compared to untreated control on morpho-physio-biochemical attributes, yield, and fruit quality of ‘Sediek’ and ‘Ewais’ mango cvs. grown under saline calcareous soil and heat stress conditions were assessed. These treatments were carried out using a split-plot arrangement in a randomized complete block design replicated three times during the 2022 and 2023 seasons. Results Cultivar Sediek had higher SPAD value, leaf proline and phenolic content, leaf area, fruit weight, yield and vitamin C than Ewais which had higher tree water status and shoot length. Saline calcareous and heat-stressed mango trees without FA or/and SA treatment had a significant decline in their water status, photosynthetic traits, biochemical responses that adversely affected growth and yield and fruit quality. However, soil FA addition and foliar SA spraying alone or in combination at any application level attenuated the negative effects of saline calcareous and heat-stress conditions via enhancing the morpho-physio-biochemical attributes, positively reflecting in tree growth, yield, and fruit quality. FA treatment alone improved tree water status (membrane stability index; MSI and relative water content; RWC), photosynthetic traits (SPAD value and maximum photochemical efficiency; Fv/Fm), leaf area, fruit weight, fruit yield, and fruit vitamin C (fruit vit.C), while SA treatment alone enhanced leaf proline and phenolic content, shoot length, and fruit total soluble solids (fruit TSS) compared to the non-FA or SA-treated control. Moreover, co-application of FA400 and SA400 effectively alleviated the harmful impacts of dual stress of heat and salinity on mango trees by improving MSI, RWC, SPAD value, Fv/Fm, proline and phenolic content, fruit weight, fruit yield, fruit TSS, fruit vit.C by 19.7, 26.1, 46.7, 18.7, 101.7, 390.7, 42.7, 6.8, 22.6, 69.6% (averages of the two seasons), respectively, compared to the non-FA or SA-treated trees. Conclusion It is recommended to add 400 g FA tree−1 to soil integrated with 400 mg SA L−1 foliar spraying four times at 30-day intervals for improving water status and photosynthetic traits, proline and phenolic accumulation, thereby growth, yield, and fruit quality of mango trees exposed to dual stress of heat and salinity under arid conditions.

WITHDRAWN: Enhancing Maize Growth Under Drought and Lead Stress with Deashed Biochar and Growth-Promoting Rhizobacteria

The agricultural sector faces significant challenges due to water scarcity and increasing lead (Pb) contamination, adversely affecting crop productivity by generating reactive oxygen species (ROS) during Pb stress and drought. Biochar and plant growth-promoting rhizobacteria (PGPR) are emerging as effective tools to manage oxidative stress, yet the combined use of deashed biochar (BC) and PGPR remains underexplored. This study aimed to investigate the synergistic effects of BC and Agrobacterium fabrum on maize growth and biochemical attributes. Two levels of BC (control and 0.5%) were applied with and without A. fabrum under no Pb stress (0 mg Pb/kg soil) and 400 mg Pb/kg soil stress conditions. Additionally, seeds inoculated with A. fabrum were subjected to no drought stress (65% field capacity w/v) and drought stress (40% field capacity w/v). Conducted with three replicates in a randomized design within controlled greenhouse conditions, the study demonstrated that BC+A. fabrum treatment significantly improved maize germination (53.33%), shoot length (69.32%), root length (11.76%), and total soluble protein content (32.36%) under 400 mg Pb/kg soil stress compared to controls. Furthermore, BC+A. fabrum effectively mitigated drought stress, enhancing chlorophyll a (55.02%), chlorophyll b (50.61%), and total chlorophyll (53.37%) levels compared to controls. Analysis of key antioxidants (peroxidase, superoxide dismutase, catalase, and ascorbate peroxidase) revealed BC+A. fabrum ability to modulate antioxidant defenses in maize, underscoring its potential as a sustainable strategy to enhance maize growth resilience under combined Pb and drought stress conditions. Future studies should explore the long-term effects and field applicability of BC+A. fabrum treatments to optimize agricultural sustainability and productivity in Pb-contaminated and drought-prone environments.

Can exogenous application of putrescine and priming modulate salinity stress in Camelina sativa L?

High salinity in soil significantly reduces growth and productivity; however, employing priming techniques and foliar spraying of putrescine can serve as an impressive method to reduce the impact of salt stress in saline soil. The current investigation intends to explore the effected of foliar spraying and priming methods on the growth, physiological, biochemical characteristics, and seed chemical compositions of salt-stressed Camelina sativa L. crop. A pot test was set up in a randomized complete block design by a factorial scheme with four replications. The experiment involved three factors: 1) salinity stress (0, 60, and 90 mM(, 2) priming techniques (no priming, hydro-priming, putrescine-priming (50 μmol L − 1), and 3) foliar application of putrescine at concentrations of 0, 100, and 200 μmol L−1. Camelina plants subjected to salinity stress showed decreased growth and performance, which correlated with lower chlorophyll levels, reduced photosynthesis maximum quantum efficiency, potassium concentration, and total soluble sugars and proline content. This decline was associated with increased lipid peroxidation (malondialdehyde content), sodium concentration, and electrical leakage, leading to diminished antioxidant enzyme activities. In contrast, under salt stress (60 mM), priming with putrescine led to an increase in grain yield (45 %), chlorophyll content (43 %), shoot length (54 %), maximum quantum efficiency (16 %), Superoxide dismutase (49 %), Catalase (58 %), Ascorbate peroxidase (47 %), linoleic acid (20 %), linolenic acid (38 %), oleic acid (27 %), eicosanoic acid (13 %) and shoot K+ ion (50 %) compared with non-treated plants. The application of 100 μmol L−1 putrescine through foliar application elicited the efficiency of camelina plants with increasing proline content, total soluble sugars, and antioxidant enzyme activities against salinity stress. In addition, the putrescine-priming method could improve photosynthetic efficiency and antioxidant enzyme activity under salt stress levels. Overall, our results supply an important outlook for the use of foliar putrescine spraying and putrescine-priming in modulating salinity tolerance in camelina crops.

Influence of Freezing Tunnel Excavation on Foundation Settlement of Buildings

In this paper, the effects of the cement content and excavation speed parameters on the improvement effect of the artificial freezing method and the characteristics of frozen walls are studied by means of a field test, numerical simulation and theoretical model. The optimization effect of the cement content in the artificial freezing method is studied. It is found that 10% is the best content, which can maximize the freezing wall thickness and grouting effect, and promote uniform distribution of the temperature field. At the same time, the influence of the excavation speed on the stress and settlement of the foundation soil is analyzed. It is pointed out that the increase of the excavation speed will aggravate the settlement and stress redistribution, which may threaten the building structure. The evaluation method proposed in this paper verifies that the construction deformation and settlement control are within the safety standards and provides theoretical support and construction guidance for tunnel engineering.

Numerical tests on dynamic response of pile-supported reclaimed embankment for high-speed railway in saturated soft ground using soil–water coupling elastoplastic FEM

High-speed train (HST) running in the saturated soft ground induces significant vibration that may threaten the running safety and serviceability of high-speed railway (HSR). Extensive studies have been conducted on the dynamic responses of HSR, yet, the soil–water coupling and plastic behavior in the saturated soft ground are rarely considered, and thus the build-up of excess pore water pressure (EPWP) and displacement cannot be accurately calculated. In this study, 2D soil–water coupling elastoplastic FEM was employed to investigate HST induced vibration in the pile-supported embankment using FE code called DBLEAVES. Dynamic soil stress, EPWP, acceleration and displacement under different cases were numerically analyzed in detail. Numerical tests confirm that liquid phase in soft ground plays important influence on the dynamic responses that vertical acceleration and displacement will be overestimated while the horizontal acceleration and displacement as well as EPWP will be underestimated if soil–water coupling is not considered. Single-phase analysis also exaggerates the acceleration attenuation and underestimate the vibration amplification in soft ground. The existence of piles can induce significant soil arching effect in the embankment, the distributions of vertical acceleration and EPWP are partitioned sharply by the piles while vertical displacement in soft ground becomes more uniform along the depth direction within the pile reinforced area. The existence of piles also induces stronger vibration beneath the pile end so that larger EPWP is generated below the pile end than around the pile body. The main influence area due to HST vibration for pile-supported embankment is overall 20 m away from the centerline of HSR track, therefore, it is reasonable to improve the ground by properly increasing the number of pile within this area. When the number of pile is determined, increasing the length of pile or reducing the pile spacing are two effective ways to mitigate the dynamic response.

Semi‐Analytical Solution for One‐Dimensional Nonlinear Consolidation of Multilayered Soil Considering Self‐Weight and Boundary Time Effect

ABSTRACTThe self‐weight stress in multilayered soil varies with depth, and traditional consolidation research seldom takes into account the actual distribution of self‐weight stress, resulting in inaccurate calculations of soil consolidation and settlement. This paper presents a semi‐analytical solution for the one‐dimensional nonlinear consolidation of multilayered soil, considering self‐weight, time‐dependent loading, and boundary time effect. The validity of the proposed solution is confirmed through comparison with existing analytical solutions and finite difference solution. Based on the proposed semi‐analytical solution, this study investigates the influence of self‐weight, interface parameter, soil properties, and nonlinear parameters on the consolidation characteristics of multilayered soil. The results indicate that factoring in the true distribution of self‐weight leads to a faster dissipation rate of excess pore water pressure and larger settlement and settlement rate, compared to not considering self‐weight. Both boundary drainage performance and soil nonlinearity have an impact on consolidation. If the boundary drainage capacity is inadequate, the influence of soil nonlinearity on consolidation diminishes.

Enhanced understanding on permanent deformation behaviour of subgrade compacted clay under long-term cyclic loading

The long-term performance of pavement structures is heavily reliant on the sustained load-carrying capacity of the subgrade soil. Under repetitive traffic loads, permanent deformation (PD) gradually accumulates in the subgrade due to plastic yielding and soil particle rearrangement, which can compromise the serviceability and durability of overlying pavement layers. This study aimed to enhance the understanding of compacted clay response under long-term cyclic loads through a systematic repeated load triaxial (RLT) testing approach. The proposed approach considered depth-dependent static and dynamic stresses exerted on compacted clay beneath pavement structures and traffic loads. A series of RLT tests were conducted to investigate the impact of key factors, including soil properties (moisture content and compaction degree), stress conditions (confining pressure and deviator stress), and load characteristics (load duration and rest period), on the PD behaviour of compacted clay subgrade. Stress-strain hysteresis loops and damping ratios were analyzed to enhance the fundamental understanding of subgrade PD evolution. The results showed that higher moisture content and lower compaction degree significantly increased PD, with the PD response transitioning from plastic shakedown to plastic creep. Greater deviator stress also exacerbated PD accumulation. Variations in loading duration and rest period influenced the PD behaviour, demonstrating the importance of accurately simulating the stress history experienced by subgrade soil elements under traffic loading. The findings provide valuable insights to optimize subgrade design and implement performance-based management of pavements.

Laccase surface-display for environmental tetracycline removal: From structure to function

Facing the increasingly prominent tetracycline pollution and the resulting environmental problems, how to find environmental and efficient treatment means is one of the current research hotspots. In this study, the laccase surface-display technology for tetracycline treatment was investigated. Via study, the type of anchoring protein had a minor influence on the laccase ability, while the type of laccase showed a major impact. Bacillus subtilis spore coat protein (CotA) exhibited higher laccase activity, stability, and efficiency in degrading tetracycline than Pleurotus ostreatus laccase 6 (Lacc6). The superiority of bacterial laccase over fungal laccase was elucidated from the perspective of crystal structure. Besides, a variety of technical means were used to verify the success of surface-display. pGSA-CotA surface-displayed bacteria exhibited good tolerance to high temperature, pH, and various heavy metals. Importantly, surface-displayed bacteria showed faster degradation efficiency and better treatment effects than the intracellular expression bacteria in tetracycline degradation. This implies that surface display technology has greater potential for laccase-mediated environmental remediation. Due to the adverse impacts of tetracycline on soil enzyme activity and microorganisms, our study found that pGSA-CotA surface-displayed bacteria can alleviate tetracycline stress in soil and partially activate the soil, thereby increasing soil enzyme activity and certain nitrogen cycling genes.

Research on mechanical properties of weak expansive soil under conditions of different confining pressures and moisture contents based on triaxial test.

To explore the mechanical properties of weak expansive soil under different moisture contents and confining pressures. The triaxial remolded soil samples with different moisture contents (14%, 16%, 18%, and 20%) were prepared for the obtained Nanyang weak expansive soil. Four groups of 16 consolidated drained triaxial shear tests with a confining pressure of 50, 100, 200, and 300 kPa were carried out to study the effects of confining pressure and water content on the deviatoric stress and pore pressure of weak expansive soil with strain. The study showed that the shear strength of weak expansive soil samples gradually increased with the increase of the water content, but its increase nonlinearly decreased as the confining pressure increased. When the axial strain was small, the pore pressure significantly increased, and the pore pressure increased tended to be stable slowly and gradually as the axial strain gradually increased. Therefore, the research results could be used to avoid the diseases caused by the characteristics of weak expansive soil in engineering construction and provide theoretical references for improving engineering foundations in weak expansive soil areas.

基于 EDEM 离散元方法的盐碱土壤参数标定与测试

In this study, saline soil parameters were calibrated based on EDEM discrete element method, soil density, soil elastic modulus, soil shear modulus, soil particle size distribution and Poisson's ratio were determined. The Hertz-Mindlin with Johnson-Kendall-Roberts (JKR) model was used to simulate the characteristics of soil stress and strain of particles under external forces. The JKR contact parameter between saline soil particles was used as a test factor, and the soil accumulation angle was used as a test index to carry out the saline soil contact parameter calibration test. It was finally determined that an elastic recovery coefficient of 0.262, a static friction coefficient of 0.263, a dynamic friction coefficient of 0.234, and a JRK surface energy of 10.084 were the optimal combinations of contact parameters for saline soils.