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1
Satyanaga, Alfrendo, Jong Kim, Sung-Woo Moon i Martin Wijaya. "Exponential Functions for Modelling Hysteresis of Soil-Water Characteristic Curves". E3S Web of Conferences 195 (2020): 02002. http://dx.doi.org/10.1051/e3sconf/202019502002.
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Soil – water characteristic curve (SWCC) is an important property of unsaturated soils that can be used to estimate various parameters to describe unsaturated soil behavior. SWCC is reported to be hysteretic because the water content at a given suction in the wetting process is less than that in the drying process. In order to simulate the hysteretic characteristics of SWCC, many models have been proposed by different researchers. However, majority of the existing models are complex and their parameters are not related to the physical significances of SWCC variables. In this study, the new equations are developed to model drying and wetting SWCC. In addition, some indexes are proposed to estimate the wetting SWCC from drying SWCC. The new equations for SWCCs were evaluated with the laboratory data from published literatures. The results showed that the proposed equations performed well in modelling drying and wetting SWCC. The new equation has less parameters than the existing published equation.
2
Yang, Hong, Harianto Rahardjo, Eng-Choon Leong i D. G. Fredlund. "Factors affecting drying and wetting soil-water characteristic curves of sandy soils". Canadian Geotechnical Journal 41, nr 5 (1.09.2004): 908–20. http://dx.doi.org/10.1139/t04-042.
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Drying and wetting soil-water characteristic curves (SWCCs) for five sandy soils are investigated using a Tempe pressure cell and capillary rise open tube. The test data are fitted to two SWCC equations using a least-squares algorithm. The obtained fitting parameters and some hysteretic behaviour are discussed and correlated with grain-size distribution parameters. A concept of total hysteresis is proposed to quantify the hysteresis of SWCC. The measured SWCC for one soil is also compared with the SWCC estimated from its grain-size distribution. The SWCC was also obtained at a high dry density for one of the soils. The results show that the shapes of the SWCCs are similar to the grain-size distributions of the soils and are affected by the dry density of the soil. A coarse-grained soil has a lower air-entry value, residual matric suction, and water-entry value and less total hysteresis than a fine-grained soil. The residual matric suction and water-entry value tend to approach the same value when the effective grain size D10 of the soil is small, in the range of 3-6 mm. SWCCs of uniform soils have steeper slopes and less total hysteresis than those of less uniform soils. Soils with a low dry density have a lower air-entry value and residual matric suction than soils with a high dry density. The SWCC predicted from grain-size distribution is found to be sufficiently accurate.Key words: soil-water characteristic curve, water content, suction, hysteresis, grain size.
3
Zeng, Ling, Fan Li, Jie Liu, Qianfeng Gao i Hanbing Bian. "Effect of initial gravimetric water content and cyclic wetting-drying on soil-water characteristic curves of disintegrated carbonaceous mudstone". Transportation Safety and Environment 1, nr 3 (12.12.2019): 230–40. http://dx.doi.org/10.1093/tse/tdz018.
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Abstract The soil-water characteristic curve (SWCC) is often used to estimate unsaturated soil properties (e.g. strength, permeability, volume change, solute and thermal diffusivity). The SWCC of soil samples is significantly affected by cyclic wetting-drying. To examine how water content and cyclic wetting-drying affect the SWCC of disintegrated carbonaceous mudstone (DCM), SWCC tests were implemented using a pressure-plate apparatus. In addition, SWCC models for DCM considering the initial gravimetric water content and cyclic wetting-drying were developed. The test results showed that the volumetric water content (θ) of the DCM first decreased rapidly and then became stable as matric suction (s) increased. The initial water content affected the SWCC by altering the pore structure of the DCM. For a given number of wetting-drying cycles, the higher the initial water content, the higher the stabilized θ. At a given s value, θ decreased as the number of wetting-drying cycles increased, which suggests that cyclic wetting-drying reduces the water-holding capacity of DCM. The Gardner model for DCM was constructed considering initial water content and cyclic wetting-drying, and was effective at describing and predicting the SWCC model for DCM.
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Zhang, Yuwei, Zhanping Song, Xiaolin Weng i Yongli Xie. "A New Soil-Water Characteristic Curve Model for Unsaturated Loess Based on Wetting-Induced Pore Deformation". Geofluids 2019 (15.04.2019): 1–14. http://dx.doi.org/10.1155/2019/1672418.
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The soil-water characteristic curve (SWCC) is the basis for describing seepage, strength, and constitutive model of unsaturated soil. The existing SWCC models do not work accurately for evaluating loess, because they do not consider the pore deformation that is induced by wetting. The present study develops a new SWCC model for unsaturated loess. The model considers the effect of wetting-induced pore deformation (WIPD) on the SWCC. The new model includes 6 parameters, which could be confirmed by laboratory tests. The pore volume function (PVF) was described by the WIPD. The shift factor ξ1i and the compression factor ξ2i were introduced into the model. The relationship between the void ratio e and ξ1i and ξ2i was established using the average pore radius. The new SWCC model for saturated loess was improved based on the classical van Genuchten (V-G) model. If the WIPD had not been considered, the new model would regress into the classical V-G model. SWCC tests of unsaturated loess with different void ratios were carried out to verify the new model. The model parameters were calibrated in the original state, and the SWCCs of different void ratios were predicted by the new model and found to be in good agreement with the test results.
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Li, Xuebo, Tianlun Shen, Ke Xiang, Qian Zhai, Harianto Rahardjo, Alfrendo Satyanaga i Shijun Wang. "Effect of the Wetting Hydraulic Property of Soil on 1-D Water Infiltration". Sustainability 15, nr 3 (18.01.2023): 1822. http://dx.doi.org/10.3390/su15031822.
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Rainwater infiltration is primarily governed by the soil-water characteristic curve (SWCC) and hydraulic conductivity function (HCF) of soil. Both the SWCC and the HCF are hysteretic during the drying and wetting processes. In a numerical simulation, different seepage results can be obtained by incorporating different hydraulic conductivity functions of soil. In practice, the wetting HCF is commonly estimated from the wetting SWCC using the statistical method, which is named HCFswcc,w in this note. However, there is no study that has verified the results from seepage analyses using HCFswcc,w. Therefore, the objective of this study is to investigate the influence of wetting SWCC and wetting HCF on 1-D water infiltration. The results from the numerical simulations were verified with the instrumentation reading from a soil column. It was observed that the results from the model using wetting HCFPSDF, which defines the wetting HCF estimated using the concept of pore-size distribution function, gave better agreement with the instrumented data. Therefore, both wetting SWCC and wetting HCFPSDF are advised to be used as input information for the numerical simulation of rainwater infiltration.
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Li, J. H., L. M. Zhang i X. Li. "Soil-water characteristic curve and permeability function for unsaturated cracked soil". Canadian Geotechnical Journal 48, nr 7 (lipiec 2011): 1010–31. http://dx.doi.org/10.1139/t11-027.
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Cracks are widely present in natural and engineered soils. As water infiltration into a cracked soil often starts from unsaturated conditions, the soil-water characteristic curve (SWCC) and permeability function for the cracked soil are required when conducting seepage analysis. This paper presents a method to predict the SWCC and permeability function for cracked soil considering crack volume changes during drying–wetting processes. The cracked soil is viewed as an overlapping continuum of a crack network system and a soil matrix system. The pore-size distributions for the two pore systems at a particular state can be determined and used to estimate the SWCCs and permeability functions. The estimated SWCCs and permeability functions for the two pore systems can be combined to give the SWCC and the permeability function for the cracked soil at that state. Then, the SWCC and permeability function for the cracked soil at different states along a crack development path can be obtained and combined to give the SWCC or permeability function for the cracked soil considering crack volume changes. Examples are presented to illustrate the prediction of the SWCCs and permeability functions for a cracked soil along five crack development paths.
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Fredlund, Delwyn G., Daichao Sheng i Jidong Zhao. "Estimation of soil suction from the soil-water characteristic curve". Canadian Geotechnical Journal 48, nr 2 (luty 2011): 186–98. http://dx.doi.org/10.1139/t10-060.
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Soil-water characteristic curves (SWCCs) are routinely used for the estimation of unsaturated soil property functions (e.g., permeability functions, water storage functions, shear strength functions, and thermal property functions). This paper examines the possibility of using the SWCC for the estimation of in situ soil suction. The paper focuses on the limitations of estimating soil suctions from the SWCC and also suggests a context under which soil suction estimations should be used. The potential range of estimated suction values is known to be large because of hysteresis between drying and wetting SWCCs. For this, and other reasons, the estimation of in situ suctions from the SWCC has been discouraged. However, a framework is suggested in this paper for estimating the median value for in situ soil suction along with a likely range of soil suction values (i.e., maximum and minimum values). The percentage error in the estimation of soil suction from the SWCC is shown to be lowest for sand soils and highest for clay soils.
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Al-Mahbashi, Ahmed M., Tamer Elkady i Mosleh Al-Shamrani. "The Role of Stress States on the Hysteric Behavior of Expansive Soil under Multiple Drying-Wetting Cycles". Buildings 13, nr 7 (26.06.2023): 1619. http://dx.doi.org/10.3390/buildings13071619.
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Expansive soils in the field are typically exposed to cyclic wetting and drying due to climatic fluctuations and subjected to a variety of stress conditions in nature or when used as compacted layers for the construction of hydraulic barriers or waste disposal facilities. The hysteric behavior of the soil-water characteristic curve (SWCC) is a key parameter for understanding, modeling, and interpreting the unsaturated behavior of these soils under such conditions. This study investigates the effect of stress states on the hysteresis behavior of soil-water characteristic curves (SWCCs) for compacted highly expansive clay over a range of matric suction between 0 and 1500 kPa. Two test series were performed, the first test series investigated the effect of stress states on the hysteresis of SWCCs during a single drying-wetting (DW) cycle. The second test series studied the combined effect of stress applied and multiple drying-wetting cycles on the SWCC hysteresis. For the sake of comparison, the overall SWCC hysteresis due to drying-wetting cycles was quantified using the average degree of hysteresis in terms of volumetric water content (ADHθ). Furthermore, contributors to the observed hysteresis were defined using two newly proposed measures; namely, average degree hysteresis in terms of gravimetric water content (ADHw) and in terms of volume change (ADHe*). The outcomes of this study indicate that consideration of stress states on the hysteresis of SWCC for expansive clay is of great importance. The results show a dual trend for the variation of ADHθ with applied vertical stress. Furthermore, multiple DW cycles induced a significant reduction in the hysteresis (ADHθ) under low- and high-stress states up to a certain level of DW cycles, then, no further changes in the hysteresis trend were detected. It was also found that hysteresis loops under a low-stress state were concentric in shape while hysteresis loops for specimens under a high-stress state were non-concentric, with a downward shift in hysteresis loops with the increase in DW cycles.
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Kong, Lingwei, Hossain Md Sayem i Huihui Tian. "Influence of drying–wetting cycles on soil-water characteristic curve of undisturbed granite residual soils and microstructure mechanism by nuclear magnetic resonance (NMR) spin-spin relaxation time (T2) relaxometry". Canadian Geotechnical Journal 55, nr 2 (luty 2018): 208–16. http://dx.doi.org/10.1139/cgj-2016-0614.
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Due to the formational environment and climatic variability, granite residual soils with grain-size distribution ranging from gravel to clay undergo multiple drying–wetting cycles. The influences of multiple drying–wetting cycles on the soil-water characteristic curve (SWCC) and pore-size distribution (POSD) of undisturbed granite residual soils are investigated using the pressure plate test and nuclear magnetic resonance (NMR) spin-spin relaxation time (T2) distribution measurement, respectively. Results show that the water-retention capacity and air-entry value decrease and pores become more uniform with increasing drying–wetting cycles. After four drying–wetting cycles, the soil reaches a nearly constant state. The POSD change of multiple drying–wetting cycle samples is consistent with the SWCC of the soils. Furthermore, a modified van Genuchten model in terms of cumulative pore volume is used to obtain the best-fit POSD of the drying–wetting cycle samples. The shape and changing tendency of both curves of SWCC and POSD are quite similar and achieved a better correlation. It can be concluded that the SWCC is strongly dependent on the POSD of the soil and NMR T2 relaxometry can be used as an alternative to the assessment of microstructural variation of residual soils subjected to the periodic drying and wetting process.
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Ahmed, Asif, Md Jobair Bin Alam, Pratibha Pandey i MD Sahadat Hossain. "Estimation of unsaturated flow parameters and hysteresis curve from field instrumentation". MATEC Web of Conferences 337 (2021): 01008. http://dx.doi.org/10.1051/matecconf/202133701008.
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Abstract: The negative pore water pressure or soil suction has significant effect on the performance of geotechnical infrastructures (e.g., slope, pavement, embankment etc.). The unsaturated behavior of soil is not static, rather offers variation in response to climatic loading. The objective of the study was to evaluate field-based techniques of SWCC construction in terms of capturing these variation as compared to laboratory methods and predictive models. The field assessment could allow the quantification of hysteresis effect on the SWCC. Instrumentation data from one Texas, USA highway was used in this study. Soil Water Characteristic Curves (SWCCs) were regenerated utilizing co-located moisture and suction data from the field. Laboratory and field measured SWCCs from the instrumented site were fitted by van Genuchten model. Previously developed predicted models were also utilized to evaluate the SWCC parameters. Based on the evapotranspiration and rainfall amounts, distinct drying and wetting cycles were recorded. Though hourly data was collected in this study, average daily values were used for the analysis. Unsaturated flow parameters (α, n, m) were determined from both laboratory testing and field moisture-suction data along with the predictive models. Clear differences were observed between the values obtained from predictive models and field generated SWCC. The outcome from this study revealed that field reconstructed SWCCs can be used to simulate higher precision in numerical modeling in numerous geotechnical applications.
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Syarifudin, Achmad, i Alfrendo Satyanaga. "Variability of Bimodal Soil-Water Characteristic Curves under Different Confining Pressures". Applied and Environmental Soil Science 2021 (5.06.2021): 1–10. http://dx.doi.org/10.1155/2021/5569491.
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Soils with two subcurves of Soil-Water Characteristic Curve (SWCC) (dual porosity soils) might be found within various residual soils. Soils located in different depths have different confining pressure. Residual soils are found in the unsaturated zones due to the deep groundwater table. There is a linear correlation between the hydraulic properties of the soil in the unsaturated area and that of its unsaturated properties. This study aims to examine the influence of the confining pressure towards the SWCC of dual porosity soil. The scope of this study involves measurements of the drying and wetting SWCC using Tempe cells, pressure plates, and an advanced triaxial apparatus. In this study, the mathematical equations were developed to explain the effect of confining pressure on SWCC. The experimental results indicated that the dual porosity soil exhibits bimodal characteristics for the drying curve of SWCC and it exhibits unimodal characteristics for the wetting curve of SWCC. As the confining pressure increases, the air entry values, the inflection points, and the standard deviation of drying SWCC increase. In addition, the hysteresis of SWCC is becoming smaller with the increasing confining pressure.
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Xu, Xu-tang, Dao-qi Liu, Zhen-xing Xian, Feng Yang, Wen-bin Jian, Xiang Xu i Jian-bin Huang. "Influence of Drying–Wetting Cycles on the Water Retention and Microstructure of Residual Soil". Geofluids 2022 (30.08.2022): 1–15. http://dx.doi.org/10.1155/2022/9948658.
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Due to frequent changes in the humid and hot environment, the residual soil with a particle-size distribution (PSD) from gravel to clay experiences multiple drying–wetting cycles. The pressure plate test and nuclear magnetic resonance (NMR) spectroscopy were used to investigate the influence of drying–wetting cycles on the soil–water characteristic curve (SWCC) and pore-size distribution (POSD) of undisturbed residual soil. The results showed that the water-holding capacity of the residual soil decreased as the number of drying–wetting cycles increased and gradually stablilized, and then the van Genuchten (VG) model was found to perform well on the SWCC during the drying–wetting processes. The NMR results indicated a double-pore structure, and the porosity of the residual soil as well as the internal water content increased smoothly with more drying–wetting cycles. The obtained POSD curve of soil implied that drying–wetting cycles had a more obvious effect on small pores and macro-pores than on micro-pores and meso-pores. Theoretical calculations evinced that the product of the matric suction and relaxation time should be constant at a constant temperature. However, the experimental results did not effectively reflect such a relation between the matric suction and relaxation time. A modified VG model based on the cumulative pore volume was utilized to describe the POSD under drying–wetting cycles. Subsequently, the proposed Rational2D surface equation was used to accurately reflect the internal relationship between the SWCC and POSD curve under different numbers of drying–wetting cycles. Moreover, the fractal model for the SWCC derived from the capillary theory confirmed that the matric suction had a strong linear relationship with the relative volumetric water content in the log-log scale. Also, the fractal dimension can be approximated as a constant, because its attenuation is small with more drying–wetting cycles.
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Peranić, Josip, Željko Arbanas, Sabatino Cuomo i Matej Maček. "Soil-Water Characteristic Curve of Residual Soil from a Flysch Rock Mass". Geofluids 2018 (29.07.2018): 1–15. http://dx.doi.org/10.1155/2018/6297819.
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Depending on the nature of the material and suction range, laboratory measurements of the soil-water characteristic curve (SWCC) can be time-consuming and expensive, especially for residual soils, in which a wide range of particle sizes and soil structures typically results in SWCCs that cover a wide range of suction. Investigations of the SWCCs of residual soil from flysch rock masses are rare, and so far, no results were presented in the literature which were obtained by performing measurements on undisturbed specimens. In this paper, a detailed examination of water retention characteristics is performed for a specific type of residual soil (CL) formed by the weathering of a flysch rock mass. Measurements performed by using different techniques and devices on intact specimens were successfully combined to obtain the SWCC during both drying and wetting processes, under different stress conditions, and from saturated to air-dried conditions. Used procedures are suitable for the determination of SWCCs of soils that undergo volume changes during the drying or the wetting process, since instantaneous volumetric water content can be determined. Results presented in this paper can be used to assess the influence of desaturation of the residual soil covering flysch slopes during dry summer periods by providing key-in material properties required to analyze the transient rainfall infiltration process.
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Abbaszadeh, Mohammad M., i Sandra L. Houston. "Influence of Soil Cracking on the Soil-Water Characteristic Curve of Clay Soil". Soils and Rocks 38, nr 1 (1.01.2015): 49–58. http://dx.doi.org/10.28927/sr.381049.
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The hydraulic conductivity for unsaturated soil conditions is more difficult to estimate than for the saturated condition. In addition, as the soil transitions from intact to cracked, the difficulty in estimating the unsaturated hydraulic conductivity increases. One critical step in the determination of unsaturated flow hydraulic conductivity is the evaluation of the Soil-Water Characteristic Curve (SWCC). In this paper, a series of laboratory studies of direct measurements of cracked soil SWCCs is presented, including challenges associated with the control of very low suction levels associated with crack dewatering. An oedometer-type SWCC apparatus, capable of suction and net normal stress control, and volume change measurement, was used in these experimental studies. It is common that SWCCs are comprised of matric suction values below about 1500 kPa, and total suction values for suctions higher than about 1500 kPa (Fredlund et al., 2012). In this study, all measured or controlled suction values were less than 1500 kPa and obtained using the axis translation method, and the curve in the higher suction range was projected by forcing the SWCC through 106 kPa for completely dried conditions (Fredlund et al., 2012). Volume change corrections were made to the reported volumetric water contents, which is of particular importance when the soil under consideration undergoes volume change in response to wetting or drying. A technique for the determination of the SWCC for cracked clay soils is presented. Test results validated the fact that the SWCC of a cracked soil can be represented by a bimodal function due to the Air Entry Value (AEV) of the cracks being much lower than the AEV of the soil matrix. It was also found that differences between the SWCC for cracked and intact soil appears only in the very low suction range.
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Xie, Xiao, Ping Li, Xiaokun Hou, Tonglu Li i Guowei Zhang. "Microstructure of Compacted Loess and Its Influence on the Soil-Water Characteristic Curve". Advances in Materials Science and Engineering 2020 (8.01.2020): 1–12. http://dx.doi.org/10.1155/2020/3402607.
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Soil-water characteristic curve (SWCC) is a key constitutive relationship for studying unsaturated soil, and as is known, microstructure of the soil has great influence on the mechanical behaviour of the soil. In this study, the wetting and drying soil-water characteristic curves (SWCCs) of loess compacted at three different water contents were measured using the filter paper method. And microproperties of compacted loess were obtained by the mercury intrusion method (MIP) and scanning electron microscope (SEM). Results show that the compaction water contents have significant influence on the SWCC and microstructure. The pore size distribution (PSD) curves have great differences in macropore range and are similar in micropore range. Loess compacted at optimum and dry of optimum are generally connected, while there are certain number of nonintruded pores in loess compacted at wet of optimum. The SWCC curves vary significantly in low suction (ua − uw < 1000 kPa) and tend to converge together in high suction (ua − uw ≥ 1000 kPa). Hysteresis in the SWCCs is more obvious for loess compacted at optimum and dry of optimum in the matric suction of 0∼100 kPa; however, there is a pronounced hysteresis for loess compacted at wet of optimum in full matric suction range. The characteristic of the SWCCs including their hysteresis can be well interpreted from the loess microstructure.
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Ng, Charles WW, i Y. W. Pang. "Experimental investigations of the soil-water characteristics of a volcanic soil". Canadian Geotechnical Journal 37, nr 6 (1.12.2000): 1252–64. http://dx.doi.org/10.1139/t00-056.
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Rain-induced landslides are common around the world. To analyse transient seepage and to predict pore-water pressure distribution in unsaturated slopes subjected to rainfall infiltration, it is essential to study soil-water characteristics and water permeability functions. The soil-water characteristic curve (SWCC) is a relationship between suction and water content or degree of saturation. Conventionally, only the drying soil-water characteristic curve of soil specimens is determined in a pressure-plate extractor without the application of any external stress. In this paper, the influences of initial dry density and initial water content, history of drying and wetting, soil structure, and the stress state upon the desorption and adsorption soil-water characteristics of a completely decomposed volcanic soil in Hong Kong are examined and discussed. The experimental results presented are obtained by using a conventional volumetric pressure-plate extractor and a newly modified one-dimensional stress-controllable pressure-plate extractor with deformation measurements. The SWCC of a recompacted specimen is very different from that of a natural specimen with the same initial soil density and initial water content. The SWCC of the recompacted specimen is highly dependent on the history of drying and wetting. The rates of desorption and adsorption are substantially higher at the first drying and wetting cycle than at the second drying and wetting cycle. The size of the hysteresis loop of the recompacted specimen is considerably larger than that of the natural specimens. The SWCC of soil is stress-state dependent. For recompacted specimens subjected to different stress states, the higher the applied stresses, the lower the rate of desorption and the smaller the size of the hysteresis loops. However, for natural specimens, the size of the hysteresis loops seems to be independent of the stress state. Under a higher applied stress, natural specimens exhibit lower rates of desorption and adsorption.Key words: volcanic soil, SWCC, drying and wetting, stress-state dependent.
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Veena, V., Sobha Cyrus, Benny Mathews Abraham i Babu T. Jose. "Soil Water Characteristic Curves of Compacted Marine Clay". Journal of Solid Waste Technology and Management 47, nr 4 (1.11.2021): 717–25. http://dx.doi.org/10.5276/jswtm/2021.717.
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The soil water characteristics play an important role in predicting the engineering behaviour of unsaturated soils. An experimental programme was performed using pressure plate apparatus to investigate the effect of moulding water content, compactive effort and cycles of wetting and drying on Soil Water Characteristic Curves (SWCC) of compacted marine clay. The specimens were prepared with moulding water contents (optimum, dry of optimum and wet of optimum) for both Standard Proctor and Modified Proctor compactive efforts. The results obtained were fitted to Brooks and Corey (BC) and Van Genuchten (VG) models. The study indicated that SWCC for specimens with higher compactive efforts plotted above those with lower compactive efforts. It was observed that the variation in moulding water content had no significant effect in the resulting SWCC. With the increase in the number of cycles of wetting and drying, a decrease in the water retention capacity was observed.
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Bashir, Rashid, Jitendra Sharma i Halina Stefaniak. "Effect of hysteresis of soil-water characteristic curves on infiltration under different climatic conditions". Canadian Geotechnical Journal 53, nr 2 (luty 2016): 273–84. http://dx.doi.org/10.1139/cgj-2015-0004.
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This paper presents results of a numerical modelling exercise that investigates the effects of hysteresis of the soil-water characteristic curve (SWCC) on the infiltration characteristics of soils subjected to four different climatic conditions — from very dry to wet — within the Canadian province of Alberta. Multi-year climate datasets from four different natural regions and subregions of Alberta are compiled, classified, and applied as the soil–atmosphere boundary condition in one-dimensional finite element unsaturated flow models using Hydrus-1D software. Multi-year simulations are carried out with and without consideration of the SWCC hysteresis. Simulation results are analyzed in terms of water balance at the ground surface and temporal distribution and storage of water within the soil domain. It is demonstrated that hysteresis of the SWCC can significantly affect the prediction of flow, redistribution, and storage of water in the unsaturated zone. It is found that for soils that exhibit hysteretic SWCC, consideration of hysteresis in unsaturated flow modelling results in the prediction of lower infiltration and less movement of water through the soil. It is also found that the use of wetting parameters results in the prediction of increased infiltration and movement of water compared with the predictions using drying or hysteretic parameters. It is concluded that, for soils that exhibit a greater degree of SWCC hysteresis, it is important to measure both the drying and wetting branches of the SWCC accurately and that accurate simulation of hysteretic behaviour requires climate datasets at appropriate resolution. The results presented in this paper highlight the importance of considering SWCC hysteresis for a wide range of geotechnical problems, such as soil cover design, prediction of groundwater recharge, contaminant transport through unsaturated soils, soil erosion, slope stability, and swelling–shrinkage of expansive soils.
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NASCIMENTO, ÍCARO VASCONCELOS DO, THIAGO LEITE DE ALENCAR, CARLOS LEVI ANASTÁCIO DOS SANTOS, RAIMUNDO NONATO DE ASSIS JÚNIOR i JAEDSON CLÁUDIO ANUNCIATO MOTA. "EFFECT OF SAMPLE RE-SATURATION ON SOIL-WATER CHARACTERISTIC CURVE". Revista Caatinga 31, nr 2 (czerwiec 2018): 446–54. http://dx.doi.org/10.1590/1983-21252018v31n221rc.
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ABSTRACT Soil-water characteristic curve (SWCC) is an important tool for water management in irrigated agriculture. However, factors such as texture and structure of soils influence SWCC behavior. According to the literature, wetting and drying cycles alter SWCC. A similar process of re-saturation and drying occurs during SWCC obtainment under laboratory conditions. Based on the hypothesis that re-saturation process alters SWCC due to clay loss in the sample, this study aimed to obtain the SWCC, S index, and pore size distribution from samples submitted to re-saturation cycles, as well as from not re-saturated samples but under higher matric potentials (-2, -4, -6, -8, and -10 kPa). For this, disturbed and undisturbed soil samples, collected from the A (sandy texture) and Btg (sandy clay loam texture) horizons of a Argissolo Acizentado, were used. After obtaining SWCC, each air-dried soil sample was submitted to particle size and clay dispersed in water analyses to verify whether the soil lost clay. The experimental design was a completely randomized design with two methods of SWCC constructing (with and without re-saturation) and eight replications. The re-saturation process generates a loss of clay in the sample, not causing significant changes in SWCC considering the assessed textural soil classes. In addition, sandy soil samples are more sensitive to changes in pore size distribution when submitted to re-saturation.
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Witteman, M. L., i P. H. Simms. "Unsaturated flow in hydrating porous media with application to cemented mine backfill". Canadian Geotechnical Journal 54, nr 6 (czerwiec 2017): 835–45. http://dx.doi.org/10.1139/cgj-2015-0314.
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Unsaturated flow in hydrating porous media is pertinent to several engineering applications, including underground and surface use of cemented tailings. Proper description and modelling of flow is complicated by changes in material properties due to hydration as well as by the generation of suction by the net consumption of water volume by hydration, variously termed chemical shrinkage or self-desiccation. It is necessary to define changes in hydraulic properties with time; for instance, the soil-water characteristic curve (SWCC) is not unique in time in addition to being path (drying versus wetting) dependent. To address this problem, a theory for modelling unsaturated flow in hydrating materials is introduced. The theory deconstructs the SWCC into a pore-size distribution, which changes with time as hydration occurs, and the water content, which is a variable that must be tracked with space and time. Matric suction depends on the time-dependent SWCC and the water content variable. The theory is applied to a multi-layer deposition experiment performed in a column, and shows reasonable results.
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Carnavale, Thiago de Souza, Ana Carolina de Campos Viana, Paula Morais Canedo de Magalhães i Tácio Mauro Pereira de Campos. "Soil-water resistivity curve of a tropical soil". MATEC Web of Conferences 337 (2021): 01011. http://dx.doi.org/10.1051/matecconf/202133701011.
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The evaluation of soil-water characteristic curve is one of the most important procedures in the matter of understanding the soil behaviour during wetting and drying processes. Even though it might be carried out by established methods, this practice is considered a time-consuming technique, and because of this it is still under-used in comparison with its potential applications. In this way, this paper aims to analyse the correlation of soil suction and soil resistivity to produce a time-reduced soil-water characteristic curve (SWCC), based on resistivity measured values. To perform this research, it was used a set of soil samples collected from Nova Friburgo, Rio de Janeiro – Brazil. The material was geotechnically characterized by standard methods. To determine the (SWCC), it was used the filter paper method and the volumetric water content/suctions were obtained by wetting and drying stages for two paths that emerged from the field moisture content. The results revealed a remarkable relationship between suction and the resistivity measured data, emphasizing the feasibility of determining the Soil-Water Characteristic Curve by resistivity measurements, here named Soil-Water Resistivity Curve (SWResC).
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Chowdepalli, Bhargavi, i Kenji Watanabe. "Empirical Equations Expressing the Effects of Measured Suction on the Compaction Curve for Sandy Soils Varying Fines Content". Geotechnics 3, nr 3 (8.08.2023): 760–80. http://dx.doi.org/10.3390/geotechnics3030042.
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To effectively apply various soil types for embankments, understanding their compaction characteristics is crucial. One crucial factor affecting compaction is suction, which plays a significant role as it is typically performed under unsaturated conditions. Suction varies with soil density, water content, and fines content. This study directly measures suction after soil compaction using the triaxial apparatus, unlike the Soil water characteristic curve (SWCC), assessing its impact on compaction characteristics. Immediate suction measurement after compaction provides apparent suction, resembling on-site conditions with open pore air pressure. Comparing SWCC with apparent suction at each compacted state reveals that suction and air entry value increase with initial density, positively impacting compaction. Notably, apparent suction aligns better with wetting process suction from the SWCC due to added water during specimen preparation. Empirical equations are derived to obtain suction contours across various density and saturation ranges, aiding in understanding suction variations on the compaction curve. Even slight variations in saturation causes noticeable changes in apparent suction during higher compaction efforts, affecting soil compaction characteristics. Therefore, the precise control of saturation control is needed to achieve desired properties of compacted soil, especially at higher compaction efforts and with various soil types. This understanding significantly impacts the mechanical behavior of unsaturated soils.
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Ma, Shaokun, Xiao Huang, Zhibo Duan, Min Ma i Yu Shao. "New Prediction Model for SWCC of Expansive Soil Considering Drying and Wetting Cycles". Journal of Mining Science 57, nr 3 (maj 2021): 393–404. http://dx.doi.org/10.1134/s1062739121030054.
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Shaokun, Ma, Huang Xiao, Duan Zhibo, Ma Min i Shao Yu. "New Prediction Model for SWCC of Expansive Soil Considering Drying and Wetting Cycles". Физико-технические проблемы разработки полезных ископаемых, nr 3 (2021): 38–50. http://dx.doi.org/10.15372/ftprpi20210305.
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Chen, Dong Xia, Ma Xiu Zhang, You Qiang Lin i Jian Ni. "Measurement of SWCC of Xiamen Residual Soil by Filter Paper". Applied Mechanics and Materials 256-259 (grudzień 2012): 1046–51. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.1046.
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Soil suction is one of the most important parameters for unsaturated soils. An experimental program was carried out to measure the maric suction of soil specimens of a residual soil in Xiamen by filter paper method. Initial water content, soil structure, and stress state were taken into account to investigate the hysteresis loop of SWCC. The air-entry value of test soil is about 140kPa and residual saturation is about 18%. The soil specimen at wet of optimum has the largest hysteresis loop for a relatively uniform pore-size distribution. However, the soil specimen at dry of optimum has the smallest hysteresis loop. The soil specimen at optimum lies between them. For specimens subjected to different stress states under various applied loads, the higher the applied load on the specimen, the smaller the size of hysteresis loop. In drying or wetting process, there is a significant difference in matric suction though soil specimens are at same water content. Therefore, for this kind of soil, it should be attention that the shear strength may be greatly reduced during rainstorms.
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Nie, Yongpeng, Wankui Ni, Xiangning Li, Haiman Wang, Kangze Yuan, Yexia Guo i Wenxin Tuo. "The Influence of Drying-Wetting Cycles on the Suction Stress of Compacted Loess and the Associated Microscopic Mechanism". Water 13, nr 13 (29.06.2021): 1809. http://dx.doi.org/10.3390/w13131809.
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To better understand and analyze the unsaturated stability of loess filling body, it is necessary to study the changes in suction stress before and after the drying-wetting cycles. In this study, the SWCC of compacted loess before and after drying-wetting cycles was tested using the filter paper method. Then, the suction stress was calculated and the microstructure of the loess sample was determined by the SEM and NMR. The results showed that the drying-wetting cycles had an important influence on the SSCC and microstructure of compacted loess. The change in suction stress before and after the drying-wetting cycles can be well explained by the loess microstructure. The drying-wetting cycles did not significantly change the basic trend of the compacted loess's SSCC, but it increased the porosity and the dominant pore diameter of loess, and reduced the suction stress under the same matric suction. The main significant change in suction stress with matric suction occurred within the range of the dominant soil pores. The larger the dominant pore diameter, the smaller the suction stress under the same matric suction. In addition, this study proposes a new method for calculating suction stress based on the PSD parameters.
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Meilani, Inge, Harianto Rahardjo i Eng-Choon Leong. "Pore-water pressure and water volume change of an unsaturated soil under infiltration conditions". Canadian Geotechnical Journal 42, nr 6 (1.12.2005): 1509–31. http://dx.doi.org/10.1139/t05-066.
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Triaxial shearinginfiltration tests were conducted to study the pore-water pressure and volume change of unsaturated soils subjected to infiltration conditions. A modified triaxial apparatus with three Nanyang Technological University (NTU) mini suction probes along the specimen height was used for the experimental program. Elastic moduli were obtained for the soil structure with respect to changes in net confining pressure (E) and matric suction (H). Water volumetric moduli associated with changes in net confining pressure (Ew) and matric suction (Hw) were also obtained from the shearinginfiltration tests. Water volumetric strain and pore-water pressure during the shearinginfiltration tests were computed based on volume change theory. This paper presents the significance of obtaining the parameter Hw from an appropriate scanning curve of a soil-water characteristic curve (SWCC) for the computation of water volumetric strain and pore-water pressure changes during a shearinginfiltration test. The appropriate scanning curve should be obtained from the wetting curve of the SWCC at the matric suction where the infiltration test commences.Key words: infiltration, matric suction, triaxial, unsaturated soils, pore-water pressure, water volume change.
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Zamin, Bakht, Hassan Nasir, Muhammad Ali Sikandar, Waqas Ahmad, Beenish Jehan Khan, Mahmood Ahmad i Muhammad Tariq Bashir. "Comparative Study on the Field- and Lab-Based Soil-Water Characteristic Curves for Expansive Soils". Advances in Civil Engineering 2022 (2.05.2022): 1–9. http://dx.doi.org/10.1155/2022/6390442.
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Expansive soils are problematic and viewed as a potential hazard for buildings and structures due to swell and shrink phenomena. The damaging effect of these soils is strongly correlated with the soil-water characteristics of expansive soils present in the shallow depth. The seasonal wetting-drying cycle is vital in fluctuating moisture content in the surficial soils. As such, soils remain unsaturated most of the time due to high absorption capacity. Therefore, it is crucial to assess them as unsaturated soil, and the soil-water characteristic curve (SWCC) is an essential tool for measuring unsaturated soils’ mechanical and hydraulic properties. The main objective of this study was to establish both field- and lab-based SWCCs for the expansive soils and compare them for determining the possible difference between them. For this purpose, eight sites of expansive soils were selected for sampling and in situ testing. These sites include three locations of Karak, three locations of Kohat, and two locations of D.I areas. Based on the experimental results, Karak’s expansive soil indicated a high suction value of 705 kPa, while D. I Khan’s soil showed the least suction equal to 595 kPa. The comparison of field and lab SWCCs for the potential sites presented a close agreement in the matric suction values beyond the air entry values (AEVs), particularly in the residual suction zones. It was also concluded that for expansive soils, the field- and lab-based SWCCs are comparable beyond the AEVs. The established curves can be successfully utilized to assess local expansive soils in the framework of unsaturated soils.
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Isidro, Miguel, Pablo Trejo i Marko López. "Soil water characteristic curve parameters of collapsible sand in Lambayeque, Peru". MATEC Web of Conferences 337 (2021): 01005. http://dx.doi.org/10.1051/matecconf/202133701005.
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Several structures are built on collapsible soils in the mining and petroleum industries and on civil sites. In order to analyze the stability of such structures, one must properly study the unsaturated soil behavior. Collapsible soils are frequent sand soil that are susceptible to a significant and sudden reduction in volume upon wetting. An important factor is matric suction, which es related to moisture content through the soil water Characteristic Curve (SWCC), the SWCC is obtained through a filter paper technique and provides a valuable relationship between suction and water content unique to soils. This measures the influence of parameters on the behavior of the structure of collapsible soil. Interactions between structure and soil must be properly evaluated as the bearing capacities of shallow and deep foundations are linked to properties of soil suction, moisture, and grade saturation. This work has experimentally measured the parameters of suction and moisture on the behavior of collapsible sands, where an oil storage tank will be built in the city of Lambayeque in Peru. Undisturbed soil specimens obtained from geotechnical exploration campaigns were used. The filter paper method used in this study was that proposed by models of Brooks-Corey and Van Genuchten. Results show consistent values near reported values from literature.
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Shi, Zhen Hua, i Zhao Wan Gao. "A Model for the Soil-Water Characteristic Curve and its Application in Dam Engineering". Applied Mechanics and Materials 94-96 (wrzesień 2011): 1930–35. http://dx.doi.org/10.4028/www.scientific.net/amm.94-96.1930.
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A mathematical model for the soil-water characteristic curve is proposed in the light of bounding surface plasticity. The main drying and wetting curves are taken as the asymptotes of the scanning curves, and only one additional parameter is introduced to simulate such scanning curves. To pave to the way for the application of the proposed model, the governing equation of unsaturated seepage problems and the finite element formulations are derived. A FEM program incorporating the SWCC model is then developed and used to study the hydraulic behaviour of an earth dam undergoes a repeated change of reservoir level. Numerical results confirm the possibility and necessity of using such a hysteresis model in unsaturated seepage problems.
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Cao, Ling, Zhijian Wang i Yong Chen. "Unsaturated Seepage Analysis of Cracked Soil including Development Process of Cracks". Advances in Materials Science and Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/2684297.
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Cracks in soil provide preferential pathways for water flow and their morphological parameters significantly affect the hydraulic conductivity of the soil. To study the hydraulic properties of cracks, the dynamic development of cracks in the expansive soil during drying and wetting has been measured in the laboratory. The test results enable the development of the relationships between the cracks morphological parameters and the water content. In this study, the fractal model has been used to predict the soil-water characteristic curve (SWCC) of the cracked soil, including the developmental process of the cracks. The cracked expansive soil has been considered as a crack-pore medium. A dual media flow model has been developed to simulate the seepage characteristics of the cracked expansive soil. The variations in pore water pressure at different part of the model are quite different due to the impact of the cracks. This study proves that seepage characteristics can be better predicted if the impact of cracks is taken into account.
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Zamin, Bakht, Hassan Nasir, Khalid Mehmood i Qaiser Iqbal. "Field-Obtained Soil-Water Characteristic Curves of KPK Expansive Soil and Their Prediction Correlations". Advances in Civil Engineering 2020 (20.11.2020): 1–13. http://dx.doi.org/10.1155/2020/4039134.
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Expansive clays are found worldwide in arid and semiarid regions. Such soils are considered a natural hazard for civil engineering infrastructures especially when they are lightly loaded. Expansive soils are often unsaturated due to the high absorption capacity of moisture. The damaging effect of expansive soils is intimately related to the distinctive soil-water characteristic in the surficial soil layers subjected to wetting-drying cycles. The soil-water characteristic curve (SWCC) also known as the water-retention curve shows the fluctuation of suction with the moisture content. It is one of the key parameters that have been developed and used by soil engineers for studying the properties of partially saturated soils. Currently, the SWCCs produced by most of the researchers are grounded on lab testing which is quite different from the field-obtained curves. In the current study, the SWCCs for Karak expansive soil have been obtained from in situ testing (field). For this purpose, three sites were selected at Amberi Village (Karak) for instrumentation. An open trench of six-foot depth was excavated in each site and instrumented. Electrical resistivity sensors (G-blocks) and tensiometers were used for matric suction measurements. The gravimetric moisture content was measured with the help of moisture sensors calibrated with a speedy moisture meter. To check the fluctuation of moisture and suction, these instruments were installed at three different depths, that is, 0–2, 2–4, and 4–6 feet. Based on results, the maximum suction of 705.79 kPa was observed in the site “A” in 0–2-foot depth (near the ground surface) with a moisture content of 15 percent. The variations in suction and moisture content follow the almost same trend at low suction; however, the trend was slightly different at the moderate suction range. The measured suction showed a strong correlation with the free swell index (FSI) and moisture content. It was found that the upper layers of expansive soil have high suction than lower layers due to more exposure to the environmental agencies and low density.
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Yoka Khail, Bilal, Mathilde Morvan i Pierre Breul. "Behavior of unsaturated pelitic soil in a railway context". E3S Web of Conferences 195 (2020): 01010. http://dx.doi.org/10.1051/e3sconf/202019501010.
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As part of the rehabilitation work on the Gabonese railway line, the Trans-Gabon Railway, it was necessary to analyse the behaviour of the materials constituting the subgrade soil. These soils are pelitic soils whose behaviour under unsaturated conditions and cyclic loading has not been studied before and which present differential settlements and lack of bearing capacity. In this article, we focus on the characterization of the subgrade soil. The objective of this work is first to determine the in-situ characteristics of the pelitic soil and be able to link these characteristics with the behaviour studied in laboratory. For that purpose, we propose an in-situ investigation based on the use of light dynamic penetrometric tests in order to assess the variability of the subgrade layer and a drying-wetting test to assess the influence of hydric stress on the drainage path of the studied soil. We present the results of in-situ tests performed on a study area. We also present the results of the tests to determine the soil water characteristic curves (SWCC) and the curves describing the volumetric behaviour of this soil when exposed to drying.
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Qian, Jing Song, i Hang Lu. "Effect of Compaction Degree on Soil-Water Characteristic Curve of Chongming Clay". Applied Mechanics and Materials 90-93 (wrzesień 2011): 701–6. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.701.
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The soil-water characteristic defines the relationship between the soil suction and gravimetric water content, w, or the volumetric water content, θ, or the degree of saturation, S. It is a convenient method to predict water content in the subgrade using the curve. But in the field tests of subgrades, the compaction degree of soil became lower with time than initially designed. With the purpose of finding out effect of compaction degree on soil-water characteristic curve, a study to the SWCC (soil-water characteristic curve) of Chongming low liquid limit clay using filter paper method was carried out and is presented in this paper. Specimens of different water contents were prepared by absorbing different amount of water, in order to better simulate the process of wetting of subgrade soil. After the filter paper test, the soil-water characteristic curve was fitted with two models, and then the effect of compaction degree on the curve was analyzed. The figures show that the compaction degree of the specimen will decrease with higher water content, and from the gravimetric water content-matric suction curve, it is found that compaction degree has an effect on air-entry value and water storage capacity.
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Liu, Ching-Yi, Yun-Da Hsieh i Yung-Chia Chiu. "Simplified power law relationship in the estimation of hydraulic conductivity of unsaturated sands using electrical conductivity". Soil Research 59, nr 4 (2021): 406. http://dx.doi.org/10.1071/sr20190.
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The unsaturated zone is a complex multiphase system, and modelling and prediction of flow and contaminant transport in this zone remain a challenge. In order to understand the mechanisms of fluid flow in unsaturated sands, an accurate and efficient approach to estimate unsaturated hydraulic conductivity (K) is essential. In this study, a power law relationship was derived from a combination of Archie’s law and van Genuchten’s model to relate bulk (apparent) electrical conductivity (ECa) with unsaturated K. The laboratory sandbox experiments were conducted first to delineate the soil water characteristic curves (SWCCs). Time domain reflectometry was used to simultaneously measure volumetric water content (θ) and ECa. Then, the experimental relationships of the effective saturation (S) and ECa and simulated S–K were combined to establish the relationship between ECa and unsaturated K. The developed power law relationships described the relative EC (ECr) and relative K (Kr) very well by just using one parameter, exponent β. When fluid EC was low, the β values for the drainage and wetting processes ranged within 2.09–2.74 and 2.50–3.79 respectively. The variations of β values of homogeneous material were smaller that of heterogeneous material and the effect of hysteresis on the ECr–Kr relationship was observed. When pore space was filled with the high-EC solution, it easily mimicked the S–Kr relationship and resulted in a smaller β value. The β value acted as a lumped factor accounting for pore tortuosity, pore connectivity, shape of pore space, and fluid EC. The power law relationship of ECr–Kr developed in this study could lead to a direct estimation of the spatial and temporal variations of unsaturated K, once the measurements of SWCC are available from estimation of saturated K and combination of time-lapse ECa measurements. Accurate and efficient estimation of unsaturated K could improve the prediction of flow in the unsaturated zone and allow a comprehensive understanding of unsaturated zone processes.
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Tao, Gaoliang, Ziyue Li, Lisheng Liu, Yangyang Chen i Kai Gu. "Effects of Contact Angle on the Hysteresis Effect of Soil-Water Characteristic Curves during Dry-Wet Cycles". Advances in Civil Engineering 2021 (11.04.2021): 1–11. http://dx.doi.org/10.1155/2021/6683859.
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The hysteresis characteristics of soil-water characteristic curves (SWCCs) under dry-wet cycling conditions are very important for understanding unsaturated soil properties, so it is crucial to propose an accurate and efficient method for predicting the hysteretic behaviors of SWCCs. To this end, this paper investigates the hysteresis characteristics of SWCCs in the full suction range of seven kinds of Hunan red clay with different initial dry densities by combination of the pressure plate method, the paper filter method, and the saturated salt solution method. It is found that there are, respectively, strong and weak hysteresis zones in the drying and wetting SWCCs under dry-wet cycling conditions. By combining this feature and based on the drying curve, the soil volume and contact angle changes during the drying and wetting processes are employed to predict the hysteretic behaviors of SWCCs. To verify the validity of the prediction method, the predicted curves of the samples with different initial dry densities are compared with the measured curves. The results show that in the strong hysteresis zone, the hysteresis characteristics of the drying and wetting SWCCs are mainly resulted from the changes in the soil pore structure; in the weak hysteresis zone, the hysteresis characteristics are mainly influenced by the changes in the receding and advancing contact angles corresponding to the drying and wetting processes. The Young–Laplace theory is used to transform the changes of contact angle during the drying and wetting processes into the proportional relationship k of matric suction, and the corresponding wetting curve is obtained by smoothing the drying curve. It is found that the prediction effect in the high suction part (the strong hysteresis zone) is better than that in the weak hysteresis zone, which confirms that the hysteresis effect of SWCCs in the high suction part is influenced by the contact angle. Our proposed method can greatly reduce the test period and has a significant practical application value, which provides a new idea for the prediction of SWCCs under dry-wet cycling conditions.
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Naik, Aparimita Priyadarshini, i Sreeja Pekkat. "Determination of wetting soil water characteristics curve from disk infiltrometer measurements". E3S Web of Conferences 382 (2023): 25006. http://dx.doi.org/10.1051/e3sconf/202338225006.
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A wetting soil water characteristic curve (SWCCw) is necessary for understanding and interpreting the re-distribution of infiltrated rainwater, percolation rate, and contaminant transport. Direct determination of SWCCw is tedious and needs destructive sampling and invasive sensor installation. This study demonstrates an indirect method for determining SWCCw based on infiltration measurements using a mini disc infiltrometer (MDI). Under controlled initial conditions, infiltration tests were conducted, coupled with real-time soil moisture and matric potential measurements using sensors. Sensor data facilitated assessment and cross-verification of SWCCw indirectly determined from MDI measurements. The indirect estimation involved inverse analysis and optimization of SWCCw parameters (α and n of the van Genuchten model) based on measured cumulative infiltration (CI) -versus-time response along with the knowledge of final volumetric water content (VWCf). The optimized SWCCw from MDI-infiltration matched the sensor-measured SWCCw reasonably well. The statistical tests using ANOVA proved that the CI measurements from MDI, together with VWCf information, are reliable input for inverse estimation of SWCCw and its parameters. Based on a realistic wetting process in the unsaturated zone beneath the disc infiltrometer, this study demonstrates the utility of a compact MDI for a quick, non-destructive measurement of SWCCw.
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Jayanth, Sneha, Kannan Iyer i D. N. Singh. "Influence of Drying and Wetting Cycles on SWCCs of Fine-Grained Soils". Journal of Testing and Evaluation 40, nr 3 (marzec 2012): 104184. http://dx.doi.org/10.1520/jte104184.
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Khaledialidusti, Rasoul, i Jon Kleppe. "Surface-Charge Alteration at the Carbonate/Brine Interface During Single-Well Chemical-Tracer Tests: Surface-Complexation Model". SPE Journal 23, nr 06 (17.08.2018): 2302–15. http://dx.doi.org/10.2118/191356-pa.
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Summary Water chemistry has been shown to affect oil recovery by affecting surface charge and rock dissolution. The single-well chemical-tracer (SWCT) test is a field method to measure residual oil saturation (Sor), in which hydrolysis reaction of an ester has been known as a key process that could displace the equilibrium state of a reservoir by changing formation-water (FW) composition. Because oil mobilization during the SWCT tests causes an error in the measurement of Sor, changes in water chemistry might be a concern for the accuracy of Sor measurements. In our previous work, the extent to which different reservoir parameters might change water composition and the effect of water-chemistry changes on the calcite dissolution and the oil liberation from the carbonate-rock surfaces were extensively evaluated. In this study, the effect of water-chemistry changes on surface-charge alteration at the carbonate/brine interface has been studied by constructing and applying a surface-complexation model (SCM) that couples bulk aqueous and surface chemistry. We present how the pH drop induced by the displacement of the equilibrium state and changes in water chemistry in the formation affect surface charge in a pure-calcite carbonate rock during the SWCT tests. The results show that a pH drop during the SWCT tests while calcium concentration is held constant in the FW by ignoring calcite dissolution yields a less-positive/more-negative surface charge so that wettability of carbonate rock might be altered to a less-oil-wetting state, when the oil is negatively charged. In reality, however, calcite dissolves by water-chemistry changes during the SWCT tests, which leads to an increasing calcium concentration in the FW. Consequently, an SWCT test in carbonates is accompanied by increasing calcium concentration while pH drops, which yields an increase in the surface charge of carbonate rocks. Therefore, the pH drop does not directly affect the surface charge of carbonate rock during an SWCT test, and calcium concentration increased from calcite dissolution could control the surface charge more significantly.
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Jadar, Chidanand M., Sathiyamoorthy Rajesh i Suman Roy. "The effect of stress-dependent SWRC on the load carrying capacity of the slope subjected to the drying-wetting path". E3S Web of Conferences 382 (2023): 12004. http://dx.doi.org/10.1051/e3sconf/202338212004.
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The stability and load capacity of structures resting on compacted soil slopes is one of the major concerns in Geotechnical Engineering practice. The mechanically compacted earthen slopes are prone to the dynamic exchange of flux flow, resulting in varying saturation levels across their entire configuration. The soil water retention curve (SWRC) is a property which significantly controls the stability and load capacityof structures resting on these compacted soil slopes. The parameters of a typical SWRC are affected by net stress and climatic changes in field conditions, adding more complexity in evaluating the load capacity and stability of structures resting on these compacted soil slopes. To analyze this issue critically, the load capacity of a footing resting on an unsaturated compacted soil slope under year-long arid climatic conditions has been evaluated numerically in the present study. The effect of net stress has been considered by assessing the stress-dependent SWRC of chosen soil under the wetting and drying cycle at various net confinementsof 10 kPa, 100 kPa, and 200 kPa in the laboratory. Key parameters of the SWRCs under drying and wetting cycles were incorporated to evaluate the load capacity of the footing resting on the unsaturated soil slope.
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Zhang, Tao, Junran Zhang, Tong Jiang, Xincui Wang, Hang Jia i Lijin Wang. "SWCCs of Silt in Yudong Zone and its Prediction Under Different Drying–Wetting Cycle Conditions". Geotechnical and Geological Engineering 37, nr 3 (7.11.2018): 1977–86. http://dx.doi.org/10.1007/s10706-018-0738-x.
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Yan, W. M., i Guanghui Zhang. "Soil-water characteristics of compacted sandy and cemented soils with and without vegetation". Canadian Geotechnical Journal 52, nr 9 (wrzesień 2015): 1331–44. http://dx.doi.org/10.1139/cgj-2014-0334.
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Experiments were undertaken to study the soil-water characteristics of compacted sandy soil (SS) and cemented soil (CS) in field and laboratory conditions. The influence of vegetation and material density on the development of negative pore-water pressure (PWP) and degree of saturation (Sr) in the studied materials was investigated. The field planting experiments demonstrated a promising survival rate of Schefflera heptaphylla in both types of material, while the (SS) promoted better growth of the seedlings than the cemented one. In the field study, PWP and Sr of the compacted SS responded noticeably and promptly to natural drying–wetting cycles. However, the responses in the CS were relatively mild. When subjected to the same drying–wetting cycles, PWP responded more slowly and to a smaller magnitude compared with that of the uncemented counterpart. In addition, Sr changed little in CS. An increase in the density of the SS promoted rapid development of negative PWP, while an opposite trend was observed for CS. Attempts have been made to explain the observations from the perspectives of material permeability and change in water content during a drying period in both soil types. Furthermore, in SS, the development of PWP (with a measurement limit of −90 kPa) was minimally affected by the presence of vegetation, while vegetation noticeably helped the development of negative PWP in CS. Bounds of the soil-water characteristic curve (SWCCs) of the studied materials were presented based on estimates from the drying and wetting scanning curves derived from the field monitoring. A corresponding laboratory study was carried out in an environmental chamber with controllable temperature and humidity. Monitoring results from the laboratory agreed qualitatively with those obtained from the field.
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Bharat, Tadikonda Venkata, i Yagom Gapak. "SOIL WATER CHARCTERISTIC CURVES OF BENTONITES IN ISOCHORIC CONDITIONS DURING WETTING: MEASUREMENT AND PREDICTION". Canadian Geotechnical Journal, 24.07.2020. http://dx.doi.org/10.1139/cgj-2019-0818.
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Determination of soil water characteristic curve (SWCC) of compacted bentonites in the isochoric condition is a prerequisite for unsaturated flow simulations in several geoenvironmental applications. The SWCC data are, however, not readily available for many compacted bentonites over a wide suction range due to difficulties associated with the testing. In this work, wetting SWCCs of four Indian bentonites of different plasticity were established experimentally at compaction dry densities of 1.4, 1.6, and 1.8 Mg/m3 in isochoric conditions using two independent laboratory techniques in different suction ranges. The modified Kovács (MK) model was extended to simulate the SWCC data of the Indian bentonites. Empirical relationships between MK model parameters and compaction dry density for these bentonites were obtained. A theoretical procedure for the estimation of SWCCs of the compacted bentonites based on the basic bentonite properties and proposed correlations was validated on the available wetting SWCC data of compacted GMZ, MX80, and FEBEX bentonites from the literature studies. The proposed model is useful for predicting the the SWCCs of bentonites from basic clay properties in the absence of measured data and in understanding the influence of dry density and plasticity on SWCC.
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Al-Obaidi, Qasim A., i Tom Schanz. "Soil–water characteristic curve of unsaturated collapsible soils". Journal of the Mechanical Behavior of Materials 32, nr 1 (1.01.2023). http://dx.doi.org/10.1515/jmbm-2022-0210.
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Abstract Collapsible soils are almost found in unsaturated states and involved significant engineering problems. Geotechnical challenges of such soils are represented by the hydro-mechanical behaviour during wetting–drying cycles due to the humidity and climate conditions. The main objective of this paper is to investigate the soil–water characteristic curve (SWCC) of unsaturated collapsible soils. In this study, three types of collapsible soils were investigated such as natural soils of sandy gypseous, silty loess, and artificial soil of gypsum–sand mixture. Determination of soil–water characteristic curve represented by wetting and drying paths has been done using a combination of the axis-translation technique (i.e. pressure plate device) and vapour equilibrium technique (i.e. salts solution desiccators) to cover a wide range of applied suction. The test results show that the air-entry value for all soils occurs at a very low suction range. At the boundary effect zone, the coarse grain size of the soil mass cannot hold the water molecules in the pore space, even with a low value of imposed suction. Moreover, the amount of hysteresis varied based on the geological formation and homogeneity of the soil fabric. Furthermore, SWCC has been interpreted by insignificant volume change and a slight reduction in void ratio, especially at high applied suction.
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Chang, Ilhan, Gye-Chun Cho i Thi Phuong An Tran. "Water retention properties of xanthan gum biopolymer-treated soils". Environmental Geotechnics, 30.03.2023, 1–11. http://dx.doi.org/10.1680/jenge.22.00098.
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This study aims to estimate the effects of xanthan gum biopolymer on the wetting and drying processes of soils. Xanthan gum was used to treat jumunjin sand and sand/clay mixture with different content to the mass of dried soil. The wetting and drying soilwater characteristics of xanthan gum biopolymer-treated sand were investigated using capillary rise open tubes and Fredlund-type SWCC device, respectively. The results show that xanthan gum has a significant effect on controlling the movement of water in the soil. Xanthan gum biopolymer shapes the drying soil-water characteristic of the soils and forms the nonlinear relationship between xanthan gum content and soil-water characteristic parameters of the treated soils. Xanthan gum significantly reduces the capillary conductivity of soil down to 10−7 ∼ 10−8 m/s as the soil treated with 1.0% xanthan gum. Xanthan gum affects the capillary equilibrium process of water differently in wetting tests as well. Furthermore, the wetting results show the role of clay particles in the flow controlling performance of xanthan gum.
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Ling, Jianming, Xiang Li, Sheng Lin, Yebo Cen i Chenchen Li. "Laboratory Study on Entire Range Suction Measurement and Microstructure Change of Granite Residual Soil". Transportation Research Record: Journal of the Transportation Research Board, 11.04.2023, 036119812311605. http://dx.doi.org/10.1177/03611981231160546.
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The shear strength of unsaturated granite residual soil (GRS) will decline rapidly when moisture content increases, because of loss of matric suction in the soil. This can lead to slope instability and embankment collapse during rainfall. Determining the matric suction of GRS accurately at different conditions can improve the accuracy of stability analysis. Generally, matric suction can be characterized as the soil–water characteristic curve (SWCC), and it is closely related to soil microstructure. In this study, the entire range of matric suction was measured using a combination of pressure plate method, filter paper method, and vapor equilibrium method. Microstructure change was investigated based on mercury intrusion porosimeter tests, in which the pore size distribution (PSD) curves of GRS samples with different initial densities and moisture content were measured. The PSDs of samples before and after wetting were also measured and compared to investigate the influence of water intrusion. Test results indicate that the combination of measurement methods can cover the entire matric suction range. The microstructure of GRS with different initial conditions presents a clear bimodal PSD. At the same density, the increase in initial moisture content can increase intra-aggregate pores and decrease inter-aggregate pores. When initial density increases, only the volume of inter-aggregate pores decreases. Wetting can decrease inter-aggregate pores and increase intra-aggregate pores. Finally, the Li model is applied in SWCC fitting for tested samples, the result of which performs well with a high correlation coefficient (R2 > 0.95) and is recommended for GRS analysis.
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Wang, Haiman, Wankui Ni, Kangze Yuan, Yongpeng Nie i Lan Li. "Study on SWCC and PSD evolution of compacted loess before and after drying-wetting cycles". Bulletin of Engineering Geology and the Environment 82, nr 5 (20.04.2023). http://dx.doi.org/10.1007/s10064-023-03218-z.
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Hoang, Nguyen Van, Hoang Viet Hung i Pham Van Dung. "Moisture Transfer Finite Element Modeling with Soil-Water Characteristic Curve-Based Parameters and its Application to Nhan Co Red Mud Basin Slope". VNU Journal of Science: Earth and Environmental Sciences 37, nr 1 (7.03.2021). http://dx.doi.org/10.25073/2588-1094/vnuees.4655.
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Since the year of 2017 landslides at the red mud basins in Nhan Co alumina factory, Dak Nong province have been occurring during the rainy seasons. The change of the soil physical and mechanical parameters due to rainwater infiltration has been considered as the main factor of the slope instability. The soil cohesion and angle of internal friction depend very much on the soil moisture: soil with a lower moisture content has a higher shearing strength than that with higher moisture content. The finite element modeling of moisture transfer in unsaturated soils through the relationship between soil moisture, soil suction, unsaturated permeability and soil-moisture dispersivity is capable of accurately predicting the wetting front development. The element sizes and time steps have been selected based on detailed analysis of analytical error estimation and on the numerical simulations with different element sizes numerical simulation errors. Soil samples had been taken and the soil different suctions and corresponding soil moisture values have been determined in the laboratory. The soil water characteristic curve (SWCC) parameters (a, n and m) have been determined by the best fitting using the least squared error method. The hydraulic conductivity of the saturated soil, one of the key input parameters was also determined. The results of the application to the study area's slope has shown that the wetting front depth can be up to 8 meters for 90 days of moisture transfer due to the rainwater infiltration The wetting front depth and the length of the intermediate part of the moisture distribution curve have increased with the infiltration time. The soil moisture distribution with a depth is an essential information to have soil strength parameters for the slope stability analyses. The slope stability analysis with the soil shear strength parameters which are strictly corresponding with the moisture change would provide the most accurate and reliable slope stability results and provide more reliable slope stabilization solutions.
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Kholghifard, Mehrdad. "Effective Stress and Compressibility of Unsaturated Clayey Soil under Drying and Wetting Cycles". Periodica Polytechnica Civil Engineering, 27.07.2020. http://dx.doi.org/10.3311/ppci.16166.
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Naturally, soil moisture reduces during dry seasons when the soil is in drying state; while it increases during wet seasons when the soil is in wetting state. Previous studies have shown that for an unsaturated soil sample, soil-water characteristic curves (SWCCs) do not match in wetting and drying paths. The differences between wetting and drying paths are called the hydraulic hysteresis. The hydraulic hysteresis plays an important role in mechanical properties of soil such as shear strength, volume change, and settlement. The objective of this research is to study the effects of drying and wetting on the effective stress and compressibility of unsaturated clayey fine-grained soils. To this end, saturated and unsaturated triaxial tests were performed on the soil samples under various normal mean stresses, and matrix suctions in drying and wetting paths. It was found that soil samples bear higher levels of effective stress in the drying path than the wetting path under a same level of suction. The attained values of effective stress parameter (χ) showed that the Bishop’s effective stress parameter (χ = Sr) is not properly applicable for the clayey soil. Moreover, the resulting loading-collapse curve (LC) revealed that the effective pre-consolidation pressure in the drying and wetting stages changed even with same degrees of matrix suction.
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Gu, Chuan, Xuan He, Miaomiao Ge i Yuanyuan Liu. "Microstructure evolution of a compacted lateritic silt upon drying-wetting and loading". Canadian Geotechnical Journal, 5.04.2023. http://dx.doi.org/10.1139/cgj-2022-0352.
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In this study, the microstructure properties of a lateritic silt under drying-wetting and one-dimensional compression were investigated using MIP and SEM. Test results show that large-sized aggregates are formed in the compacted lateritic silt with 10% of hematite. These aggregates induce a bi-modal PSD including micropore and macropore peaks. The different macropore distributions under various dry densities lead to scattered SWCCs in a suction range less than 20 MPa. Changes in volume and pore structure mainly occur in the suction path within the "transition zone". Drying causes an increase in macropores due to the decreased volume of aggregates, while has limited effect on micropores. Whereas wetting weakens the bonding between aggregates, and induces a reduction in macropores. The compacted lateritic silt shows obvious collapse upon soaking, in which the collapse grows up to a peak and then turns to decrease with increasing stress level. Both loading and soaking lead to the collapse of macropores, whereas soaking tends to affect a broader range of pore sizes. It is inferred that, the strong particle cementation produced by hematite leads to a strong micropore structure, which is almost unaffected by the suction change under both confined and unconfined conditions. The microstructure reponse to suction change verifies the effects of special mineral composition (iron and aluminium) on soil microstructure and further on the hydro-mechanical behaviour of lateritic soil.