Natural Water Content Research Articles

Study on the Effects of Different Fertilization Times on Crop Yield and Soil Fertility Changes

The level of soil fertility plays a decisive role in the growth and development of crops and agricultural production. Reasonable fertilization time is of great significance for maintaining and improving soil fertility, increasing crop yield, and economic benefits. Rice is one of the main grain crops in China, and its yield and quality are influenced by natural environment, variety, water content, and fertility. Among them, fertility has the greatest impact on the yield and quality of rice. Within the scope of Design of experiments, rice yield is directly related to fertilizer application time. With the increase of fertilizer application time, rice yield increases significantly, and fertilizers and nutrient promoters play a good ecological and economic benefit. Although Biopesticide do not have a large yield increase effect, they can play the same effect as chemical pesticides. The amount of fertilizer used is the main factor in increasing crop yield, and the longterm application of nutrient promoters can also become an important factor in increasing yield. Different fertilization treatments also have different effects on the soil nutrient content of vegetable fields, and fertilization can significantly increase the soil nutrient content. This article takes rice as an example to study the effects of different fertilization times on rice yield and soil fertility changes.

Geotechnical characterization of index and deformation properties of Stockholm clays

<abstract> <p>This paper describes the geotechnical characteristics of index and deformation properties of Stockholm clays. These clays exhibit large variations both geographically and with depth. The clays range from highly organic clays with high plasticity to silty clays with low plasticity. First, the geological conditions of the clays are outlined to qualitatively explain the typical soil stratigraphy encountered in the Stockholm area. Second, two large generic databases are presented, containing 3,500 and 1,600 data points, respectively. The data originates from routine testing and constant rate of strain oedometer tests conducted in commercial projects. The data is analyzed and compared with results from high quality block sampling. It is seen that a common feature of the clays are low undrained shear strengths, and consequently low yield stresses and oedometer moduli. Further, several deformation properties such as preconsolidation pressure and several oedometer moduli is shown to depend on the soils natural water content and its plasticity. Differences in sample quality is shown to highly affect some properties, highlighting the importance of quality sampling and handling of samples. Criteria for sample quality for this type of clay is proposed based on the oedometer moduli before and after the preconsolidation pressure. The paper can hopefully work as a useful reference to engineers working on similar soils worldwide.</p> </abstract>

Relationship between soil 15N natural abundance and soil water content at global scale: Patterns and implications

Investigating the relationship between the natural abundance of soil nitrogen stable isotope (δ15N) and soil water content (SWC) in the globe can help to explain the different controls of soil δ15N in different regions, yet this was few concerned on. Based on the Craine et al. (2015) summarized soil δ15N data (https://doi.org/10.1038/srep08280), and the satellite retrieved SWC in 910 grids (size of 0.1° × 0.1°) of the globe, an upward-concave relationship between soil δ15N and SWC was observed. Higher soil δ15N existed at both the dry and wet ends (i.e., respectively below and above the intermediate range of SWC, which was about 0.20–0.30 m3/m−3(-|-)). Inconsistent relationships in five Köppen-Geiger climate zones constituted this upward-concave relationship. Positive relationship between soil δ15N and SWC in the Tropical zone determined the increasing trend of soil δ15N at the wet end in the globe. This can be explained by the increased hydrologically regulated soil N losses with the increase of SWC under the warm and moist condition. Negative relationship in the Arid zone determined the decreasing trend at the dry end in the globe. Increased abiotic N losses like ammonia volatilization and proportion of N supplement through bedrock weathering (higher δ15N) with the decrease of SWC under the dry, hot and infertile soil condition may be the main reasons. In addition, poor relationships between soil δ15N and SWC in the Temperate, Cold and Polar zones constituted the transition range of the upward-concave relationship in the globe. This reflected that not hydrologically but climatically determined low soil N losses was responsible for the low soil δ15N in these zones. These findings can help to deepen our understandings on the spatial pattern of soil δ15N and the indicated N cycle at the global scale.

Probabilistic-forecasting method for determination of low flow discharge of Pivdennyi Buh, Black Sea area, and Lower Dnieper rivers

The aim of the study is to substantiate the probabilistic-forecasting method for forecasting the low flow discharge and its implementation for the Pivdennyi Buh, Black Sea area and Lower Dnieper rivers, taking into account climatic patterns of precipitation distribution and establishing probabilistic characteristics of low flow discharge in multi-year period. The study area is in a zone of significant risk due to the shortage of water resources, the formation of extremely low runoff in the dry flow period, which requires its definition and forecasting. The methodological basis of forecasts is to solve the equation in determining the components of the low flow of rivers by constructing regional dependences for forecasting the average decade summer-autumn low flow from previous water discharge (in runoff modules), establishing their probabilities water discharge for a number of intakes. Results. The paper substantiates the probabilistic-forecasting method for forecasting low flow discharge (in summer, autumn and winter periods) based on the construction of regional dependences of average decadal runoff modules on previous water discharge for groups of basins of studied rivers taking into account climatic dependences of precipitation distribution in the territory and the establishment of probabilistic characteristics of the low flow water discharge in a multi-year period. The methodology of territorial short-term forecasts of average decade water discharge of low flow of summer, autumn and winter river runoff is assessed as satisfactory with a margin of error of 70 % to 97 %, with a number of members of more than 500 points. To determine the cumulative probability of the forecast values of the average decade water discharge of the summer, autumn and winter dry weather flow, the empirical distribution of the average monthly water discharge in the limited seasons, which are generalized in the basins of the studied rivers of Ukraine, is established. Scientific novelty. For the first time for the zone of insufficient natural water content of rivers the method of territorial forecasts of low flow discharge, determination of their probability of occurrence in a multi-year period and cartographic representation of prognostic values have been developed and practically implemented. The practical importance is the use of forecast modules maps of low flow for spatial monitoring and assessment of low water levels on rivers in the whole region, including ungauged rivers, and their probabilistic characteristics – to assess the possible occurrence of low runoff, even when it reaches values close to the environmental runoff, which are critical for the functioning of the river ecosystem.

Macroscopic Heterostructure Membrane of Graphene Oxide/Porous Graphene/Graphene Oxide for Selective Separation of Deuterium Water from Natural Water.

Deuterium water (D2 O) is a strategic material that is widely used in and scientific research and has applications in fields such as nuclear energy generation. However, its content in natural water is extremely low. Therefore, the development of a room-temperature technology for achieving simple, efficient, and low-cost separation of D2 O from natural water is challenging. In this study, porous graphene (PG) nanosheets with "crater-like" pores are sandwiched between two layers of graphene oxide (GO) membranes to prepare a GO/PG/GO membrane with a macroscopic heterostructure, which can be used to separate D2 O and H2 O by pressure-driven filtration. At 25°C, the rejection rate of D2 O is ≈97%, the selectivity of H2 O/D2 O is ≈35.2, and the excellent performance can be attributed to the difference of transmembrane resistance and flow state of H2 O and D2 O in the confinement state. In addition, the D2 O concentration in natural water is successfully enriched from 0.013% to 0.059% using only one stage, and the membrane exhibits excellent structural and cycling stability. Therefore, this method does not require ultralow temperatures, high energy supplies, complex separation equipment, or the introduction of toxic chemicals. Thus, it can be directly applied to the large-scale industrial production and removal of D2 O.

Statistical analysis of Nkoulou soils properties and suitability for earthen constructions

The present work consists of sampling, characterizing, classifying, and studying the soils of the locality of Nkoulou for the manufacture of cement-stabilized compressed earth bricks (CEBs) and possible use in road building. 08 samples were taken on 02 sites. Chemical and mineralogical characterization identified these soils as ferric-dominated laterites consisting of quartz, illite, hematite, kaolinite, goethite, gibbsite, muscovite, and magnesite associated with trace minerals. The studied soils have an average natural water content of 11.73% and average values of specific gravity of 2.51 and 2.48 (respectively for site N°1 and site N°2). These soils are mainly composed of gravel followed by sand and are classified as Group B fine-grained soils according to the French Road Grading Manual (GTR). The natural water content (W) shows a good correlation with clay content (R = 0.75), and silt content (R = 0.73). The CBR Index (ICBR) meanwhile has a good correlation with the silt content (R = −0.69), similar between ICBR and maximum dry density (R = 0.73). According to CRATERRE Nkoulou soils can be used as well in the manufacture of CEBs as in the realization of road works in layers of fill. The cement stabilization of the compressed soil specimens allows the mechanical strength to increase with the stabilization rate, just as the water absorption of the specimens which also varies with the fines content, and the curing time according to the correlation study. These results allow us to establish the predictive model of compressive strength and flexural strength as a function of cement content and time with R2 = 0.75 and R2 = 0.93, respectively.

Evaluation of ANFIS and Regression Techniques in Estimating Soil Compression Index for Cohesive soils

Generally, direct measurement of soil compression index (Cc) is expensive and time-consuming. To save time and effort, indirect methods to obtain Cc may be an inexpensive option. Usually, the indirect methods are based on a correlation between some easier measuring descriptive variables such as liquid limit, soil density, and natural water content. This study used the ANFIS and regression methods to obtain Cc indirectly. To achieve the aim of this investigation, 177 undisturbed samples were collected from the cohesive soil in Sulaymaniyah Governorate in Iraq. Results of this study indicated that ANFIS models over-performed the Regression method in estimating Cc with R2 of 0.66 and 0.48 for both ANFIS and Regression models, respectively. This work is an effort to practice the advantages of machine learning techniques to build a robust and cost-effective model for Cc estimation by designers, decision makers, and stakeholders.

Comparison of Performance of Machine Learning Models for Predicting Compression Index Based on Clay Properties

As the construction of large structures increases primarily on the soft ground along coasts, prevention of damage to the structures due to subsidence should be prioritized. Ground subsidence has been investigated actively. Because the amount of settlement can be calculated based on the compression index of clay, the latter must be calculated accurately. In this study, data pertaining to the natural water content, liquid limit, plasticity index, initial void ratio, and compression index of clay are acquired from Busan, Gwangyang, and Mokpo to construct a dataset for predicting the compression index. Correlation analysis between factors is performed using the dataset, and compression index prediction models are developed using machine learning algorithms, random forest, multiple linear regression, ridge, Lasso, SVM, XGBoost, LightGBM, and DNN. Subsequently, the results of each model are compared in terms of the RMSE and R2. The results show that the natural water content, liquid limit, plasticity index, initial void ratio, and compression index are correlated significantly. Among the machine learning models, LightGBM demonstrates the best performance.

Failure process and characteristics of three-dimensional high-stress circular tunnel under saturated water content

True-triaxial compression tests were carried out on cubic granite samples with a circular through hole using a true-triaxial testing system to investigate the influence of saturated water content (SWC) on the failure process and characteristics of a circular tunnel of surrounding rocks. The spalling failure under SWC can be divided into four periods: calm period, buckling deformation period, period of rock fragment gradual buckling and exfoliation, and period of formation of symmetrical V-shaped notches. When the horizontal axial and vertical stresses were constant, the spalling failure severity was reduced with the increase in lateral stress. Under natural water content, a strong rockburst with dynamic failure characteristics occurred on the circular hole sidewall. Under SWC, the failure severity was reduced and the circular hole sidewall experienced spalling failure, exhibiting progressive static failure characteristics. Therefore, water can reduce the failure severity of surrounding rocks in deep underground engineering, which has a certain guiding significance for the prevention and control of rockbursts.

Novel Approach to Predicting Soil Permeability Coefficient Using Gaussian Process Regression

In the design stage of construction projects, determining the soil permeability coefficient is one of the most important steps in assessing groundwater, infiltration, runoff, and drainage. In this study, various kernel-function-based Gaussian process regression models were developed to estimate the soil permeability coefficient, based on six input parameters such as liquid limit, plastic limit, clay content, void ratio, natural water content, and specific density. In this study, a total of 84 soil samples data reported in the literature from the detailed design-stage investigations of the Da Nang–Quang Ngai national road project in Vietnam were used for developing and validating the models. The models’ performance was evaluated and compared using statistical error indicators such as root mean square error and mean absolute error, as well as the determination coefficient and correlation coefficient. The analysis of performance measures demonstrates that the Gaussian process regression model based on Pearson universal kernel achieved comparatively better and reliable results and, thus, should be encouraged in further research.

Discussion of “Physio-Chemical Properties, Consolidation, and Stabilization of Tropical Peat Soil Using Traditional Soil Additives — A State of the Art Literature Review” by Afnan Ahmada, Muslich Hartadi Sutantoa, Mohammed Ali Mohammed Al-Bareda, Indra Sati Hamonangan Harahapa, Seyed Vahid Alavi Nezhad Khalil Abada, Mudassir Ali Khana

This discussion article provides commenting on the sections of the review paper by Ahmad et al. (the authors) concerning consistency limits determinations for peats and peaty soils, drawing on the writer's experiences regarding the usefulness of liquid limit (LL) and plastic limit (PL) testing/results for these soils in explaining their geotechnical behaviors/properties. From the writer's experience, despite being regularly specified in geotechnical engineering practice and used in research work, the conventional consistency limits tests generally do not produce physically meaningful results when testing peat soils, especially for more fibrous peats. Hence, the writer does not agree with the authors' recommendations on consistency limits testing of peats; namely, they recommended that an utmost effort is needed to improve the quality and standard of the thread rolling test and the fall-cone test for consistency limits determinations of highly organic soils such as peat. Rather than grappling with various known inherent shortcomings of consistency limits testing for peats and other highly organic soils, a suggested way forward for assessing the likely geoengineering behavior/properties of these materials points to the routine measurement of a more useful suite of index tests; namely, their natural water content, organic content, fiber content, and humification (decomposition) level. In this discussion, the above aspects are explored in detail, including greater elaboration of the writer's earlier research work in this area, which was touched on in the authors' paper.

Effect of KOH Treated Coir Pith on Compressive Strength of Clayey Silt

Kuttanad soils are low strength soft clay or silt deposits found in the Kuttanad areas of the Alappuzha district, Kerala. Due to its low load-bearing and high shrinkage characteristics, the structures and pavements constructed over were unstable. Treatment with appropriate chemical additives is one of the accustomed and economic techniques in soil stabilization practice for improving the characteristics of weak soil. Traditional stabilizing agents like cement, lime, etc. are becoming less environmentally friendly and costly. Coir pith (treated and untreated) is proposed in this study. Coir pith was treated using potassium hydroxide. Initial tests like natural water content, specific gravity, Atterberg’s limit test, hydrometer analysis, compaction test, unconfined compressive strength tests were conducted to find the properties of natural soil. Proctor compaction tests, unconfined compression tests are to be performed to investigate the effectiveness of the coir pith to control the volume change and increase the soil strength. Maximum dry density increases with treated coir pith whereas OMC decreases. UCS test results shows an increase in strength which confirm that treated and untreated coir pith are able to effectively stabilize the natural expansive soil.

Experiment study on normalized compression behaviour of marine diatomaceous soil considering microstructure of biogenic silica

There are many sites in the world where diatom microfossils have been detected, but very little is known about their effect on sediment geotechnical properties. Diatomaceous soils (herein called “biogenic silica soils”) are usually composed by a mix of sand, fine-grained clay and diatom (and, or radiolarian). This paper presents an experimental investigation on the compression behaviour of biogenic silica-kaolin (BSi-K) clay mixtures and natural marine diatomaceous soils. The results show that the BSi composition dominates the compression when the BSi content is higher than 50%. The microstructure of biogenic silica frustules is first characterized and a skeletal void volume model (BSi-SVV model) is proposed. By using this model, the addition water in biogenic silica frustules can be quantitatively evaluated, which is up to 92.6% as the BSi content is 78%. It can be explained as the cause of high natural water content and low plasticity of diatomaceous soils. By introducing the effective void ratio, the compression curves can be normalized; furthermore, a new intrinsic compression line (BSi-ICL) suitable for BSi-K clay mixtures is developed based on the intrinsic compressibility concept of Burland (1990). It is considered as an extension of Burland's ICL. Finally, the effect of initial water content on the normalized compression behaviour is investigated. The findings in this study can provide a deeper insight into the geotechnical properties of marine diatomaceous soils.

3D response surface modeling based in-situ assessment of physico-mechanical characteristics of alluvial soils using dynamic cone penetrometer

Dynamic cone penetrometer (DCP) is the quickest and cheapest in-situ probing apparatus to estimate the soil stiffness; however, insufficient correlations are available to directly assess various physico-mechanical characteristics of natural alluvial soils using DCP. The key purpose of this study is to statistically equate the in-situ DCP test outcomes to different physico-mechanical characteristics of alluvial soils. For this purpose, in-situ DCP tests were performed at 26 different locations in the Indus plane, and corresponding undisturbed specimens were collected for laboratory testing. Various physico-mechanical characteristics of soil i.e., natural water content (wn), natural dry unit weight (γd), unconfined compressive strength (qu), deformation modulus (E50), strain at failure (εf), natural void ratio (en) and California bearing ratio (CBR) were determined in the laboratory. Initially, the regression-based models were established for γd, qu, E50, εf, en, and CBR using dynamic cone penetrometer index (DCPI) as a solitary predictor. Afterward, predictive models of the aforementioned parameters were developed based on wn integrated DCPI by quantifying the best-fit trend line and three-dimensional (3D) response surface among pertinent dependent and independent variables. In addition, it is found that the models developed using 3D response surface modeling hold 8.2–42.4% lesser error than the regression-based models developed in the current study. Moreover, results show that the DCP based assessment of soil is influenced by wn and independent of consistency limits and soil type of the alluvial soils.

Hybrid Model: Teaching Learning-Based Optimization of Artificial Neural Network (TLBO-ANN) for the Prediction of Soil Permeability Coefficient

The permeability coefficient (k-value) of the soil is an important parameter used in the civil engineering design of roads, tunnels, dams, and other structures. However, the determination of k-value by experimental methods in the laboratory or the field is still costly and time-consuming. Moreover, it requires special equipment and special care in the collection of soil samples for laboratory study. Therefore, in this study, we have proposed machine learning (ML) hybrid model: teaching learning-based optimization of artificial neural network (TLBO-ANN) to predict the k-value of soil based on limited parameters (natural water content, void ratio, specific gravity, liquid limit, plastic limit, and clay content) which can be determined easily in the laboratory. Test results of 84 soil samples obtained from the Da Nang-Quang Ngai expressway project in Vietnam are used in the model development. Statistical indicators such as correlation coefficient (R), root mean square error (RMSE), and mean absolute error (MAE) are used to validate and evaluate the accuracy of the model. The results show that the TLBO-ANN model is an effective tool in predicting correctly the k-value (R = 0.905) of soil for the consideration in the design of structures founded on the soil.

Fuzzy Random Prediction Model of Frost Heave Characteristics of Horizontal Frozen Metro Contact Channel in Coastal Area

The frost heave characteristics of artificial frozen soil are very important information for underground freezing engineering. It is found that both the frost heaving force and rate of the same soil layer increase with the decrease of freezing temperature. In addition, due to the comprehensive influence of freezing temperature, natural water content, dry density, and tidal flow peak value, the frost heave characteristics of different soil samples are evidently uncertain. With the aim of improving the deficiency of traditional BP neural network algorithms in solving fuzzy random engineering problems, random factor and mean square error between layers are used to modify the evaluation function of the network model. On this basis, taking tidal flow peak value, freezing temperature, natural water content, and dry density as inputs, the frost heaving force and rate of frozen soil as output values, and setting the number of hidden layer elements as 4, an improved fuzzy random BP network prediction model for frost heave characteristics was established. The new network prediction model has a smaller weight and bias, and the response tends to be smoother than the traditional one, which greatly reduces the overfitting phenomenon. The engineering example shows that the improved BP neural network prediction model can make the predicted value of frost heaving force and rate basically coincide with the measured value after effective training, and the error is controlled within 8%. Therefore, the prediction model can be used as an effective tool to predict frost heaving characteristics in Nantong metro freezing construction, and the corresponding model and method can also be extended to similar engineering cases.

Influence of Super Absorbent Polymer on Root Characteristics and Anchorage of Amorpha fruticosa on Rocky Slope

Super absorbent polymer (SAP), known as a water retention agent, has a high capacity for water absorption, which can help enhance the soil structure. This paper studied the effects of SAP dosages on the root characteristics and anchorage of Amorpha fruticosa on rock slopes. The internal relationship between root growth effect and soil was discussed, and a specific reference was provided for the rational application of SAP on slopes. Using the pull-out and tensile resistance tests, we systematically studied the changes of soil properties, root distribution, root tensile strength, and root anchorage under six different SAP dosages. The results indicated that: (1) With the increase in SAP dosage, the natural soil water content and water content after 24 h of watering increased significantly, whereas the contents of TN, TP, and TK decreased dramatically. (2) With the increase in SAP dosage, the amount and length of first-order and secondary lateral roots decreased significantly, and there was no significant difference in diameter. The amount of downslope first-order and unembedded secondary lateral roots is greater than upslope. The amount of upslope embedded secondary lateral roots is greater than in downslope. (3) Tensile strength: embedded secondary root > non-embedded secondary root > first-order lateral root; upslope root > downslope root. (4) With the increase in SAP dosage, the plant anchorage drops noticeably. This study concluded that the significant addition of SAP could enhance the tensile strength of upslope embedded secondary lateral roots but would adversely affect soil nutrients, root distribution, and root anchorage. The addition of SAP in this test had no significant effect on improving slope stability. From the perspective of reinforcement capacity, we cannot blindly pursue the survival rate and other high dosage use of water retention agents to increase the risk of slope destabilization.

Effects of binder types and other significant variables on the unconfined compressive strength of chemical-stabilized clayey soil using gene-expression programming

Soil stabilization is an in situ soil treatment in which soils are mixed with cementitious or other chemical stabilizing agents. Determining the unconfined compressive strength (UCS) of stabilized soil is a principal task in the design and construction of the ground improvement. Hence, this study aims to develop a reliable predictive model for the UCS of clay stabilization with common cementitious binders using the gene-expression programming (GEP) technique. Eleven parameters, including the soil characteristics, the binder types, the binder contents, the mixing method, and the curing period, were considered as the independent variables in the model. The research results show that the selected optimal GEP-based model performs well with an acceptable correlation coefficient (R = 0.951) and low errors (e.g., RMSE and MAE). Besides, parametric analyses indicate that the plastic index, the percentage of clay, and the total water content have a negative effect on the UCS of stabilized soil. In contrast, the percentage of silt and sand, the binder types, the binder contents, and the curing time show a positive effect on the strength of stabilized soil. In addition, the strength of stabilized clay could be significantly enhanced by combining cement with slag, lime, or fly ash with a reasonable ratio, or by reducing the natural water content in the soil. The research findings could help engineers choose suitable binder types and cost-effective methods to optimize the UCS of stabilized clay.

Investigating the effects of specimen diameter on the relationships between mechanical and physical properties of limestone

Engineering applications, either on or within rock bodies, typically require detailed characterizations of rock physical and mechanical properties, as both properties affect the design process and construction phase and are also related to safety and sustainability of structures. Various in-situ and laboratory tests have been used to quantify rock properties. However, the tests are expensive, time consuming and require high quality test samples, especially for laboratory tests. Additionally, available core samples may not meet test standards, which require about 54 mm (NX size) core, as suggested by the American Society for Testing and Materials (ASTM) and the International Society of Rock Mechanics (ISRM). This study aims to investigate the effects of core sample diameter on the relationships between mechanical and physical properties of rock, using the example of limestone as a test material. 190 limestone core samples were prepared in five different diameters: 24.94, 38.07, 47.7, 53.99 (NX) and 63.16 mm. Uniaxial compressive strength (UCS), diametrical and axial point load index (PLID-A), indirect tensile strength (ITS), Schmidt hammer (SHV), natural unit weight (γn), specific gravity (Gs), water content (wc) and porosity (n) tests were performed on these core samples. The results indicate that sample diameter clearly affects the relationships between mechanical and physical properties of limestone rock, leading to broad measurement variations for most tests. Substantial agreement was found between this study and previous studies of NX size samples of limestone.

Physico-Mechanical Properties of Bio-Based Bricks

The aim of this work is to improve the high performance of mud bricks. The latter was reinforced with rice straws as stabiliser leading to an improvement of the physico-mechanical properties. Thus, the physical characteristics of the clay such as natural water content, density, atterberg limit, plasticity limit (Wp) and plasticity index (Ip) were determined. Their values are respectively 8.39%, 2025.73 Kg/m3, 47.66%, 29.75% and 17.91%. The clay used is a low plastic organic silt. The normal proctocol provided an optimum dry density (&#611OP) of 1.28 Kg/m3 at an optimum moisture content of 12.42%. The actual density of the straw is 464 Kg/m3, its absorption rate reached 206% in 5 mins and stabilised at 385% at 480 mins of immersion. The maximum bending and compression strengths are respectively 1.52 and 0.164 MPa. The mud brick absorption coefficients obtained are between 4.875 at 0% straw and 20.573% at 3% straw.