Soil Stress Research Articles

Simulation and Optimization of Profitability of Jofeyr (Isargaran) Irrigation and Drainage Network Products Using System Dynamics Approach

Responses of Some Soil Bioindicators to the Interaction Between Sugarcane Bagasse Biochar and Salinity Stress in a Cadmium-Polluted Soil

Responses of Some Soil Bioindicators to the Interaction Between Sugarcane Bagasse Biochar and Salinity Stress in a Cadmium-Polluted Soil

Responses of Some Soil Bioindicators to the Interaction Between Sugarcane Bagasse Biochar and Salinity Stress in a Cadmium-Polluted Soil

Combined Effects of Soil Stress History and Scour Hole Dimensions on Laterally and Axially Loaded Piles in Sand and Clay under Scour Conditions

Removal of soil around a bridge foundation due to scour results in a reduction of the lateral and vertical foundation capacity due to the loss of soil support. The common approach in modeling the scour phenomenon of removal of soil springs without modifying the parameters of the remaining soil fails to consider the change of stress state of the remaining soil and the formation of scour hole geometry around the pile foundation. In practice, both of these factors impact the mechanical properties of the remaining soil and the resulting expected structural response of the pile under loadings. This paper proposed a methodology to comprehensively evaluate the combined effects of stress history and scour hole dimensions on piles under scour conditions in uniform soil. It enabled the examination of the lateral and axial behaviors of a loaded pile subject to scour and is applicable for both cohesive and cohesionless soils. The methodology was validated with results from field tests for no-scour scenarios and verified with existing numerical models for scour scenarios. Quantification of the soil effects was investigated through lateral pile deflection and load-settlement curves for lateral and axial behaviors, respectively. Load-settlement curves demonstrated that including the effect of stress history results in increases of up to 34.1% and 61.1% in estimated pile settlement for sand and clay, respectively, leading to potential unconservative designs if soil effects are not properly included in the analysis.

Genome-Wide Association Studies of Salt-Alkali Tolerance at Seedling and Mature Stages in Brassica napus.

Most plants are sensitive to salt-alkali stress, and the degree of tolerance to salt-alkali stress varies from different species and varieties. In order to explore the salt-alkali stress adaptability of Brassica napus, we collected the phenotypic data of 505 B. napus accessions at seedling and mature stages under control, low and high salt-alkali soil stress conditions in Inner Mongolia of China. Six resistant and 5 sensitive materials, respectively, have been identified both in Inner Mongolia and Xinjiang Uygur Autonomous Region of China. Genome-wide association studies (GWAS) for 15 absolute values and 10 tolerance coefficients (TCs) of growth and agronomic traits were applied to investigate the genetic basis of salt-alkali tolerance of B. napus. We finally mapped 9 significant QTLs related to salt-alkali stress response and predicted 20 candidate genes related to salt-alkali stress tolerance. Some important candidate genes, including BnABA4, BnBBX14, BnVTI12, BnPYL8, and BnCRR1, were identified by combining sequence variation annotation and expression differences. The identified valuable loci and germplasms could be useful for breeding salt-alkali-tolerant B.napus varieties. This study laid a foundation for understanding molecular mechanism of salt-alkali stress adaptation and provides rich genetic resources for the large-scale production of B. napus on salt-alkali land in the future.

Numerical Implementation of Three-Dimensional Nonlinear Strength Model of Soil and Its Application in Slope Stability Analysis

Based on previous research results and the three-dimensional strength characteristics of different soil types, a three-dimensional nonlinear strength model of soil considering tenso-shear (T-S) coupling strength and compressive-shear (C-S) strength is established. The proposed model can better describe the influences of intermediate principal stress and T-S coupling stress in soil. The secondary development of user material subroutine (UMAT) is conducted in ABAQUS. The UMAT procedure is programmed using an implicit backward Euler integral algorithm, and numerical experiments verify its accuracy. This procedure is then applied to the analysis of slope stability. Using the strength reduction method, the stability of the saturated slope and unsaturated slope are analyzed. The numerical results show that when the slope approaches instability, the T-S coupling plastic zone and T-S coupling failure surface develop downward from the top surface of the slope. The critical slip surface is a composite slip surface composed of a C-S slip surface and a T-S coupling failure surface. Compared with the M-C strength model, the three-dimensional nonlinear strength model can describe the failure mechanism of the slope more clearly and reasonably and can provide an accurate stability evaluation.

Effect of Different Abiotic Stresses on Allium Cepa Plants: Results from a Field Study of Two Different Seasons

Abiotic factors have the capacity to influence the nature and quantity of secondary metabolites. Alteration of environmental factors during plant growth can affect the production of bioactive phytoconstituents. A six-month field study was carried out in two different seasons to assess the effect of different abiotic stresses on bioactive compounds, i.e. flavonoids and phenols and plant yield of selected Allium species, i.e. Allium cepa L. (AC). (Family Amaryllidaceae). AC plants were grown for six months from November to April and for another six months from May to October on three different soil types (i.e. black, red, clay-loamy) and various stresses (salinity, water deprivation, flooding, fertilizer, metal, shade) were applied on the plants. At the end of the season, plants were collected, dried, and plant yield was determined. Hydroalcoholic extracts of all samples were prepared. Plant yield, TFC, TPC were determined in all the extracts. The results show varied response of AC plants to different soil types, stresses, and seasons. AC plants cultivated on red soil with fertilization give higher biomass yield in both seasons. AC plants grown in black soil under metal stress have highest TFC, TPC. Hence these conditions may be recommended for incorporation in cultivation practices of these valuable medicinal plants to ensure commercial supply of plants with higher phenol and flavonoid content and better plant yield.

Research on the analysis method of soil stress path during foundation pit excavation

Research on the analysis method of soil stress path during foundation pit excavation

Prediction of fluvial erosion rate in Jamuna River, Bangladesh

ABSTRACT River bank erosion of alluvial rivers is one of the major challenges for river management. This paper deals with the prediction of the fluvial erosion rate along the left bank of Jamuna River in Bangladesh using the excess shear stress method. Surface water modelling systems i.e. SMS and SRH-2D, were used to estimate the hydrodynamic effects on the riverbank along the 8.21 km reach of the river. Riverbank along the selected reach of Jamuna River consists of two layers of soil type. The upper layer soil is sandy silt with a median size of D 50 = 0.028 mm and the bottom layer is silty sand with D 50 = 0.167 mm. Results of the present analysis show that shear stress along the riverbank attains its maximum and initiates the bank erosion, when the flow rate is about 45,000 m3/s. Based on the results obtained from model run and empirical analysis, riverbank materials have been categorized as ‘erodible’ to ‘very erodible’, as far as erodibility parameters are concerned. Critical shear stress of bank soil is found to be varied between 0.15 and 0.22 Pa using erodibility co-efficient ranges between 5.05 and 6.03 cm3/N s. From this study, the maximum bank erosion rates have been estimated as 51.95 m/year to 69.82 m/year. However, average erosion rates have been estimated which range between 38.65 and 40.57 m/y. It is hoped that the results obtained from the study will be helpful in determining the riverbank stability for the implementation of appropriate river protective measures along the riverbank of Jamuna River.

Plant growth promoting rhizobacteria (PGPR) and their eco-friendly strategies for plant growth regulation: a review

As a natural engineer, Plant Growth Promoting Rhizobacteria (PGPR) play an important role in increasing plant growth, yield and enhancing plant tolerance to stressful conditions. These beneficial bacteria take up their position in the rhizosphere, around the plants’ root tissues. They may be in, or on their host tissues and help to provide nutrients to their host plants. For sustainable agriculture, PGPR transmit their extensive assistance in ecosystem management, soil structure maintenance, stress management and plant morphology and physiology modulation in an environmentally friendly manner. Plant- PGPR interactions also stimulate nutrient acquisition and accumulation, improve plant performance and enhance plants’ tolerance to abiotic and biotic stresses. Beside these, PGPR are good biofertilizers and safe for our environment. Nanotechnological advances with PGPR applications are important today to increase the impact of PGPR in agriculture. Undoubtedly, PGPR concept is intimately involved with agriculture, horticulture, forestry and they are too enough to establish a vibrant environment. In this review we have focused on the versatility of PGPR-their performance and aimed to address some future prospects of PGPR as an eco-friendly tool for plant growth regulation.

Computation of pull-out resistance of pressure-grouted soil nails in sand using cavity expansion and contraction solutions

ABSTRACT Pressure-grouted soil nailing has been extensively used as a soil stabilization technique in transportation infrastructure projects, wherein resistance against pull-out failure is offered by shear resistance mobilized along the nail–soil interface. However, the different stages of soil nail installation significantly alter the soil properties and residual normal stress at the grout-soil interface and thereby the maximum pull-out shear stress. This article presents a computational procedure to predict the maximum pull-out shear stress of pressure-grouted soil nails in sand, incorporating the variation in soil properties and stresses throughout the installation processes and loading. The procedure is formulated within the framework of cavity expansion-contraction solutions as the entire installation and testing phases resemble either expansion or contraction of a cylindrical cavity. The proposed approach was validated using grouting and pull-out test data of soil nails in sand. The influence of various parameters on pull-out shear stress has also been examined.

Genome-Wide Identification of Cellular Pathways and Key Genes That Respond to Sodium Bicarbonate Stress in Saccharomyces cerevisiae.

Sodium bicarbonate (NaHCO3) is an important inorganic salt. It is not only widely used in industrial production and daily life, but is also the main stress in alkaline saline soil. NaHCO3 has a strong ability to inhibit the growth of fungi in both natural environment and daily application. However, the mechanism by which fungi respond to NaHCO3 stress is not fully understood. To further clarify the toxic mechanisms of NaHCO3 stress and identify the specific cellular genes and pathways involved in NaHCO3 resistance, we performed genome-wide screening with NaHCO3 using a Saccharomyces cerevisiae deletion mutant library. A total of 33 deletion mutants with NaHCO3 sensitivity were identified. Compared with wild-type strains, these mutants had significant growth defects in the medium containing NaHCO3. Bioinformatics analysis found that the corresponding genes of these mutants are mainly enriched in the cell cycle, mitophagy, cell wall integrity, and signaling pathways. Further study using transcriptomic analysis showed that 309 upregulated and 233 downregulated genes were only responded to NaHCO3 stress, when compared with yeast transcriptomic data under alkaline and saline stress. Upregulated genes were mainly concentrated in amino acid metabolism, steroid biosynthesis, and cell wall, while downregulated genes were enriched in various cellular metabolisms. In summary, we have identified the cellular pathways and key genes that respond to NaHCO3 stress in the whole genome, providing resource and direction for understanding NaHCO3 toxicity and cellular resistance mechanisms.

Simulating root length density dynamics of sunflower in saline soils based on machine learning

Root length density (RLD) is an indispensable input for driving almost all agro-hydrological models, but it is difficult to measure and has strong plasticity to soil environments, thus it is a challenge to characterize the dynamics of RLD if crops suffering adverse soil stress at field scale. Soil salinity is a major abiotic stress that restricts crop shoot growth and yield formation, but it may stimulate root growth of salt-tolerant crops. In this study, based on 256 datasets of actual root length density (ARLD) for sunflower grown under saline conditions and influencing factors as days after sowing (DAS), root depth (RD), soil salt content (SSC), soil water content (SWC), and leaf area index (LAI), we (1) clarified the limitations of cubic polynomial, exponential, and power elementary functions of root depth (RD) for ARLD prediction; and (2) established and compared three novel machine learning models (MLMs) including gaussian process regression (GPR), multivariate adaptive regression spline (MARS), and random forest (RF) with eight combinations of inputs (COIs). Results show the distribution of the sunflower’s ARLD was significantly different in fields with different salinity levels, the peak value of ARLD in the low-salt field was smaller than 1.2 cm·cm−3, but it could be over 3.0 cm·cm−3 in the high-salt field. Except at the early growth stage (DAS = 28–30), all the elementary functions failed to fit the ARLD accurately with the RMSE ranging from 0.39 to 0.97 cm·cm−3 and R2 lower than 0.38. The higher prediction accuracies for ARLD were obtained in MLMs, especially with the COI of DAS + RD + SSC + LAI. Moreover, the accuracies of RF and GPR models (RMSE ranging from 0.36 to 0.37 cm·cm−3 and R2 greater than 0.73 in the test) were higher than the MARS. The spatiotemporal distribution of simulated ARLD in the GPR model was relatively smooth, while it presented certain discontinuity in the RF model. In general, the RLD plasticity of sunflower in saline soil should not be ignored, the MLMs models, such as the GPR and RF models, are more applicable for RLD prediction than the elementary function models.

Effect of Wheat-Derived Biochar on Soil Nutrients Availability and Nutrients Uptake by Two Safflower (Carthamus tinctorius L.) Cultivars under Water Stress

ABSTRACT Biochar may improve the negative effects of water stress on plant dry weight and nutrients uptake of Safflower (Carthamus tinctorius L.). The effects of 1.5 and 3% biochar application to a calcareous soil cultivated with two cultivars of safflower under normal and 50% of normal irrigation on soil nutrients availability, plant dry weight, and nutrients concentration were studied. Results indicated that the biochar application increased soil electrical conductivity (from 0.52 to 1.46 dS m−1) and the availability of the soil phosphorus (from 8.0 to 13.2 mg kg−1), potassium (from 185 to 1107 mg kg−1), iron (from 0.76 to 1.40 mg kg−1) and manganese (from 1.10 to 4.57 mg kg−1). Water stress and plant cultivar treatments had no effect on the soil nutrients availability. The dry weight of Goldasht and Esfahan cultivars was 1.89 and 1.73 g pot−1, respectively, and decreased 12 and 26% with 1.5 and 3% biochar application, respectively. The decreases in the plant dry weight with water stress in soils treated with 0, 1.5, and 3% biochar were 34, 27, and 18%, respectively. The plant concentration of phosphorus, potassium, iron, and manganese was increased with biochar application and was associated with soil nutrients availability.

Computational intelligence models for predicting the effective stress of unsaturated soil

In the design of underground spaces, the value of the effective stress (χ) parameter is important while dealing with unsaturated soils. The estimating procedure might be complex due to the non-linearity of the connection between χ parameter and dependant parameters. As a result, two novel hybrid optimization models are proposed in this paper: relevance vector regression (RVR) optimized using artificial bee colony (ABC) and harmony search (HS) algorithms (RVR-ABC and RVR-HS models). The RVR-HS and RVR-ABC models' prediction abilities were demonstrated using 120 datasets from open-source literatures. In this dataset, characteristics of unsaturated soils such as bubbling pressure, soil–water characteristic curve fitting parameter, saturated volumetric water content, net conning pressure, residual water content, and suction were used as the inputs, while χ parameter was used as the output. The proposed models performances were assessed by comparing them regarding some statistical metrics, e.g., correlation coefficient (R2). For the RVR-ABC and RVR-HS models, the R2 of 0.86 and 0.89 were attained, respectively. The findings showed that the RVR-ABC and RVR-HS models were effective in predicting the χ parameter. However, the RVR-HS model, outperformed the RVR-ABC model as this issue shows, the HS algorithm contributed significantly to the optimization of the suggested model.

Field monitoring of vertical stress distribution in GRS-IBS with full-height rigid facings

This paper presents a case study of the first geosynthetic reinforced soil-integrated bridge system (GRS-IBS) with full-height rigid facings in China. Open graded gravel and biaxial geogrid were used for the GRS-IBS. Steel frames and three-dimensional (3D) vegetation nets were used as temporary facing support during construction of the GRS abutments. Full-height rigid facings were cast in place on strip foundations. Field monitoring results of vertical stress distribution for different construction stages and loading conditions are presented and discussed. For both bridge dead load and truck loads, measured incremental vertical stresses under the beam seat increase significantly with increasing elevation, especially for higher applied vertical stress. The calculated incremental vertical soil stresses using the Boussinesq solution are in reasonable agreement with the measured values, while the 2 : 1 stress distribution method overestimates the incremental stresses in the lower section of the abutment. The transferred vertical stresses from bridge load application for the GRS abutment with full-height rigid facing are larger than those for the GRS abutment with modular block facing near the top of the abutment, but are smaller near the bottom.

Breakage effect of calcareous sand on pile tip resistance and the surrounding soil stress

Due to the irregular shape, high porosity and fragility of calcareous sand particles, the construction of reef engineering is seriously affected, and the application of pile foundation engineering technology in calcareous sand stratum is also faced with great challenges. Based on the discrete element method (DEM), the pile installation process in the fractured calcareous sand stratum and non-fractured silica sand stratum are simulated, respectively, and the influence of particle breakage of calcareous sand on soil stress around the pile and pile tip resistance are discussed. The results show that the particle contact has no obvious dominant direction, and the particle breakage has little contribution on the variation of the particle contact normal directions while has great influence on the number of contact normals and the magnitude of contact normal force which is more uniform after particle breakage. The vertical and horizontal stresses in calcareous sand stratum are obviously lower than that in siliceous sand stratum. With the increase of the pile penetration depth, the number of crushing particles increases gradually. The particle breakage only can be found within the range of 3 times of pile diameter at the bottom of the pile and also within the range of 1 time of pile diameter around the pile. The effect of particle breakage on pile tip resistance is mainly reflected in the later stage of pile sinking. In calcareous sand, when the pile tip resistance increases to a certain extent, particle breakage occurs and the stresses in the soil cannot continually increase. Therefore, the pile tip resistance fluctuates around a stable value (∼0.3MPa). This is the reason that the pile tip resistance in calcareous sand is far less than that in siliceous sand, which is prone to pile foundation failure.

Characterizing incipient motion of low fines content soils with varying compositions, water contents, and relative densities

Laboratory flume experiments were conducted to quantify the effects of the soil characteristics on the critical shear stress of low fines content soil samples collected from the Montauk shores in New York. The collected soils were reconstituted at five different fines contents, ranging between 0 and 20%. These soil mixtures were composed of two initial water contents, dry of optimum and optimum moistures, and two relative densities, one moderate dense and the other dense. The strength indices of the soils, including the effective cohesion and effective angle of internal friction, were measured using the consolidated undrained (CU) triaxial test. The initiation of erosion tests was conducted on the soil mixtures under a unidirectional steady current condition. The near-bed flow velocity, at the onset of erosion, was used to determine the critical velocity and shear stress for each soil sample. The results indicate that the critical shear stress increases with the fines content and effective cohesion. The soils with the optimum initial water contents demonstrate a higher erosion resistance than those with the initial water contents dry of optimum. The higher relative density appears to overshadow the effects of the fines content such that the critical shear stress of the denser soils remains relatively insensitive to the soil composition. The denser soils compacted at the optimum initial water content show the highest resistance against erosion. The critical Shields parameter is modified to include the fines content, relative density, and initial water content.

Active failure characteristics and earth pressure distribution around deep buried shield tunnel in dry sand stratum

The stability of the tunnel face is a key issue in shield tunnel engineering. In this paper, a series of 1 g model tests were conducted in dry sand for various buried depth ratios H/D = 2, 3, 4, 5, and 6 to study the failure characteristics, earth pressure distribution and the soil arching effect. Each test provided a measurement of the earth pressure with the face withdrawal displacement. And the soil deformation and the failure characteristics were investigated by Particle Image Velocimetry (PIV) system. The development of the failure characteristics was discussed for the buried depth ratios H/D = 3. The relationships between the failure characteristic and buried depth ratios were investigated. The variation of limit support pressure, soil stress distribution at different depths and earth pressure around the tunnel are analyzed. The soil arching effect around the tunnel at deep burial conditions is revealed. With the withdrawal displacement increasing, the tunnel face is in close contact with the support panel at first, and then gradually separated from the support panel. The larger the H/D is, the smaller the increment of horizontal soil stress is. It could be concluded that the increase of tunnel depth directly leads to the soil arching effect.

Experimental study on the load bearing behavior of geosynthetic reinforced soil bridge abutments with different facing conditions

This paper presents an experimental study on reduced-scale model tests of geosynthetic reinforced soil (GRS) bridge abutments with modular block facing, full-height panel facing, and geosynthetic wrapped facing to investigate the influence of facing conditions on the load bearing behavior. The GRS abutment models were constructed using sand backfill and geogrid reinforcement. Test results indicate that footing settlements and facing displacements under the same applied vertical stress generally increase from full-height panel facing abutment, to modular block facing abutment, to geosynthetic wrapped facing abutment. Measured incremental vertical and lateral soil stresses for the two GRS abutments with flexible facing are generally similar, while the GRS abutment with rigid facing has larger stresses. For the GRS abutments with flexible facing, maximum reinforcement tensile strain in each layer typically occurs under the footing for the upper reinforcement layers and near the facing connections for the lower layers. For the full-height panel facing abutment, maximum reinforcement tensile strains generally occur near the facing connections.

Effective stress in unsaturated soils: Lessons from capillarity in regular sphere arrangements

In this paper, capillary stresses and water retention of regular arrangements of rough spherical particles are analysed to shed light on the effective stress in unsaturated soils. These arrangements can be used to model soils with uniformly graded round particles such as sand as they are simpler to analyse due to their symmetries. Capillary stress determines the effective stress in unsaturated sphere arrangements and is highly dependent on the morphology of the soil voids.In general, it is shown that capillary stress and water retention dependence on suction and degree of saturation in regular arrangements of spheres is more complex than usually assumed with relevant implications for unsaturated soil mechanics and its effective stress. It is also shown that: (i) sphere roughness explains the observed disappearance of capillary stresses in sand with drying; (ii) the capillary stress evolution with suction (or RH) is non monotonic; (iii) it is possible to have significant capillary stresses at zero suction in regular and irregular sphere arrangements, and the Bishop’s effective stress cannot represent this or even the capillary stresses in regular arrangements; (iv) the water in the pores can assume diverse and complex configurations besides the simpler isolated menisci that prevail at larger suctions, and the alternative configurations for the same suction or degree of saturation support hysteretic response.