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1
Satyanaga, Alfrendo, Jong Kim, Sung-Woo Moon e 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.
Testo completoAbstract (sommario):
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 e D. G. Fredlund. "Factors affecting drying and wetting soil-water characteristic curves of sandy soils". Canadian Geotechnical Journal 41, n. 5 (1 settembre 2004): 908–20. http://dx.doi.org/10.1139/t04-042.
Testo completoAbstract (sommario):
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
Yan, Wei, Emanuel Birle e Roberto Cudmani. "A simple approach for predicting soil water characteristic curve of clayey soils using pore size distribution data". MATEC Web of Conferences 337 (2021): 02012. http://dx.doi.org/10.1051/matecconf/202133702012.
Testo completoAbstract (sommario):
The soil water characteristic curve (SWCC) of soils can be derived from the measured pore size distribution (PSD) data by applying capillary models. This method is limited for clayey soils due to the PSD changes during SWCC testing. In this study, a suction-dependent multimodal PSD model based on probability theory is developed and used to derive SWCC. The model is validated by simulating the drying branches of SWCCs of four compacted Lias Clay samples with different initial states. A good consistency between the measured and predicted SWCC is shown.
4
Li, J. H., L. M. Zhang e X. Li. "Soil-water characteristic curve and permeability function for unsaturated cracked soil". Canadian Geotechnical Journal 48, n. 7 (luglio 2011): 1010–31. http://dx.doi.org/10.1139/t11-027.
Testo completoAbstract (sommario):
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.
5
Guo-Quan, Ding, Bian Xia, Yuan Jun-Ping e Zhu Jun-Gao. "Bimodal SWCC and Bimodal PSD of Soils with Dual-Porosity Structure". Mathematical Problems in Engineering 2022 (24 giugno 2022): 1–10. http://dx.doi.org/10.1155/2022/4052956.
Testo completoAbstract (sommario):
The soil–water characteristic curve (SWCC) and pore-size distribution (PSD) are fundamental characteristics of soils that determine many physical and mechanical properties. Recent studies demonstrate that both SWCC and PSD sometimes exhibit a bimodal feature. In this paper, soils with bimodal SWCCs are mainly divided into three categories: gap-graded soils, compacted clayey soils, and natural dual-porosity structural soils, from the perspective of microporosity structure. Based on the Fredlund and Xing unimodal SWCC equation, a bimodal SWCC equation is presented. The bimodal PSD equation d v / d log r for mercury intrusion porosimetry (MIP) is derived theoretically, according to the relationship between the mercury intrusion process in MIP and the water desorption process along the drying SWCC. These two associated equations have the same set of parameters, so the corresponding relationship between the bimodal SWCC and bimodal PSD can be directly shown. Three main presenting forms of PSD in MIP tests are summarized. Regression analysis results show that the proposed PSD equation can well fit bimodal PSD experimental data of various soils in the literature, and the SWCCs are predicted at the same time.
6
Zeng, Ling, Fan Li, Jie Liu, Qianfeng Gao e 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, n. 3 (12 dicembre 2019): 230–40. http://dx.doi.org/10.1093/tse/tdz018.
Testo completoAbstract (sommario):
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.
7
Fredlund, Delwyn G., Daichao Sheng e Jidong Zhao. "Estimation of soil suction from the soil-water characteristic curve". Canadian Geotechnical Journal 48, n. 2 (febbraio 2011): 186–98. http://dx.doi.org/10.1139/t10-060.
Testo completoAbstract (sommario):
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.
8
Al-Mahbashi, Ahmed M., Tamer Elkady e Mosleh Al-Shamrani. "The Role of Stress States on the Hysteric Behavior of Expansive Soil under Multiple Drying-Wetting Cycles". Buildings 13, n. 7 (26 giugno 2023): 1619. http://dx.doi.org/10.3390/buildings13071619.
Testo completoAbstract (sommario):
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.
9
Syarifudin, Achmad, e Alfrendo Satyanaga. "Variability of Bimodal Soil-Water Characteristic Curves under Different Confining Pressures". Applied and Environmental Soil Science 2021 (5 giugno 2021): 1–10. http://dx.doi.org/10.1155/2021/5569491.
Testo completoAbstract (sommario):
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.
10
Ahmed, Asif, Md Jobair Bin Alam, Pratibha Pandey e 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.
Testo completoAbstract (sommario):
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.
11
Kong, Lingwei, Hossain Md Sayem e 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, n. 2 (febbraio 2018): 208–16. http://dx.doi.org/10.1139/cgj-2016-0614.
Testo completoAbstract (sommario):
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.
12
Oliveira, Alana, Flávia Pelaquim, Renan Zanin, Thadeu Melo, João Tavares Filho, Avacir Andrello e Raquel Teixeira. "The structure of tropical lateritic soils as an impacting factor in the shape of soil-water characteristic curves". Soils and Rocks 45, n. 2 (8 aprile 2022): 1–13. http://dx.doi.org/10.28927/sr.2022.070521.
Testo completoAbstract (sommario):
The presence of unsaturated flow in tropical lateritic soils of unknown hydromechanical behavior may lead to severe geotechnical problems. It is known that soil-water characteristic curves (SWCC) are a valuable tool to define this behavior and facilitate the suction estimation, acting on tests performed with no control of such parameter. This article aimed to determine and model the SWCC for 3 unprecedented tropical soils, in the undisturbed and the compacted conditions, from the Paraná state, located in the south of Brazil. The soils studied are one clay and two sands, all lateritic. The pressure plate and the filter paper methods were used to determine the SWCC. The samples were carved and submitted to the drying paths. Furthermore, Mercury Intrusion Porosimetry (MIP) tests were performed in samples of the studied soils in order to obtain the pore size distribution (PSD), contributing to the bimodal definition of curves and the prediction of SWCC main parameters. Both techniques (pressure plate and filter paper) were combined and the SWCC was adjusted by Gitirana & Fredlund model, which efficiently represents the shape of the traditional curves for tropical soils. Furthermore, the SWCCs were predicted by PSD and obtained satisfactory numerical fits. All SWCC presented air entry values in the macropores that are characteristic of soils as the lateritic, given that its structure was considered a key factor in the shape of the curves.
13
Abbaszadeh, Mohammad M., e Sandra L. Houston. "Influence of Soil Cracking on the Soil-Water Characteristic Curve of Clay Soil". Soils and Rocks 38, n. 1 (1 gennaio 2015): 49–58. http://dx.doi.org/10.28927/sr.381049.
Testo completoAbstract (sommario):
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.
14
NASCIMENTO, ÍCARO VASCONCELOS DO, THIAGO LEITE DE ALENCAR, CARLOS LEVI ANASTÁCIO DOS SANTOS, RAIMUNDO NONATO DE ASSIS JÚNIOR e JAEDSON CLÁUDIO ANUNCIATO MOTA. "EFFECT OF SAMPLE RE-SATURATION ON SOIL-WATER CHARACTERISTIC CURVE". Revista Caatinga 31, n. 2 (giugno 2018): 446–54. http://dx.doi.org/10.1590/1983-21252018v31n221rc.
Testo completoAbstract (sommario):
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.
15
Peranić, Josip, Željko Arbanas, Sabatino Cuomo e Matej Maček. "Soil-Water Characteristic Curve of Residual Soil from a Flysch Rock Mass". Geofluids 2018 (29 luglio 2018): 1–15. http://dx.doi.org/10.1155/2018/6297819.
Testo completoAbstract (sommario):
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.
16
Xie, Xiao, Ping Li, Xiaokun Hou, Tonglu Li e Guowei Zhang. "Microstructure of Compacted Loess and Its Influence on the Soil-Water Characteristic Curve". Advances in Materials Science and Engineering 2020 (8 gennaio 2020): 1–12. http://dx.doi.org/10.1155/2020/3402607.
Testo completoAbstract (sommario):
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.
17
Xu, Xu-tang, Dao-qi Liu, Zhen-xing Xian, Feng Yang, Wen-bin Jian, Xiang Xu e Jian-bin Huang. "Influence of Drying–Wetting Cycles on the Water Retention and Microstructure of Residual Soil". Geofluids 2022 (30 agosto 2022): 1–15. http://dx.doi.org/10.1155/2022/9948658.
Testo completoAbstract (sommario):
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.
18
Ng, Charles WW, e Y. W. Pang. "Experimental investigations of the soil-water characteristics of a volcanic soil". Canadian Geotechnical Journal 37, n. 6 (1 dicembre 2000): 1252–64. http://dx.doi.org/10.1139/t00-056.
Testo completoAbstract (sommario):
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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Tran, Thi Phuong An, e Delwyn G. Fredlund. "Verification of the Fredlund (2019) Unsaturated Shear Strength Function". Geosciences 11, n. 4 (26 marzo 2021): 151. http://dx.doi.org/10.3390/geosciences11040151.
Testo completoAbstract (sommario):
There has been a proliferation of equations proposed to describe the unsaturated shear strength envelope going back to the 1970s. However, there have been limited studies to verify the suitability of one unsaturated shear strength equation over another. Most proposed shear strength equations have attempted to relate the shear strength of an unsaturated soil to some aspect(s) of the soil–water characteristic curve (SWCC). Estimation procedures have generally focused on using that of air-entry value (AEV) as defined by the drying (or desorption) branch of the degree of saturation SWCC (S-SWCC). This paper studies the suitability of using two “anchor points” (or reference points) along the drying S-SWCC to estimate the unsaturated soil shear strength function. The anchor points referred to are the air-entry value (AEV) of the soil and the “residual suction point” of the soil defined in terms of the S-SWCC. Shear strength conditions associated with both so-called anchor points are used as “boundary conditions” that should be satisfied when estimating the shear strength function for unsaturated soils. Past research laboratory measurements published in the research literature are used as part of the verification process for this study.
20
Veena, V., Sobha Cyrus, Benny Mathews Abraham e Babu T. Jose. "Soil Water Characteristic Curves of Compacted Marine Clay". Journal of Solid Waste Technology and Management 47, n. 4 (1 novembre 2021): 717–25. http://dx.doi.org/10.5276/jswtm/2021.717.
Testo completoAbstract (sommario):
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.
21
Liu, Ping, Hu Yuan Zhang, Yi Chen, Xian Xian Shao e Xin Yuan Fu. "Research on the Retention Capacity of Ruins Soil under Drying Condition". Applied Mechanics and Materials 580-583 (luglio 2014): 705–10. http://dx.doi.org/10.4028/www.scientific.net/amm.580-583.705.
Testo completoAbstract (sommario):
The soil water characteristic curve (SWCC) has been tested during the drying process. In order to define the relationship between suction, degree of saturation and void ratio, fitting models of SWCC was established. Studies have shown that the shape of SWCC of three kinds of samples (taken from Jiaohe, Gaochang and Jiuzhoutai) was similar to the inverted “S”, the relationship between water content and matric suction was inversely proportional. Under the condition of the same moisture, the matric suction of the Jiaohe and Gaochang samples were greater than the Jiuzhoutai samples, and the changes of pore water pressures showed the same trend. The degree of saturation began to decrease when the water content reduced to the air entry value. When the degree of saturation was greater than 90%, the volume of soil samples contracted significantly, and when saturation is below 80%, volume shrinkage stopped.
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Bashir, Rashid, Jitendra Sharma e Halina Stefaniak. "Effect of hysteresis of soil-water characteristic curves on infiltration under different climatic conditions". Canadian Geotechnical Journal 53, n. 2 (febbraio 2016): 273–84. http://dx.doi.org/10.1139/cgj-2015-0004.
Testo completoAbstract (sommario):
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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Yang, Hong, H. Rahardjo, E. C. Leong e D. G. Fredlund. "A study of infiltration on three sand capillary barriers". Canadian Geotechnical Journal 41, n. 4 (1 agosto 2004): 629–43. http://dx.doi.org/10.1139/t04-021.
Testo completoAbstract (sommario):
The capillary barrier effect was investigated by conducting infiltration tests on three soil columns of fine sand over medium sand, medium sand over gravelly sand, and fine sand over gravelly sand. The barrier effect was verified in the underlying layer of coarser material, and the water-entry values of the coarser layers were confirmed to be nearly equal to the residual matric suctions of the soils. The coarser layer of gravelly sand, which had a lower water-entry value, was more effective in forming a barrier than the coarser layer of medium sand, which had a higher water-entry value. When the capillary barrier was comprised of a coarser layer of gravelly sand, there was more water stored in the finer layer at the end of the drying stage than when the capillary barrier was comprised of a coarser layer of medium sand. Non-equilibrium static conditions of pore-water pressure profiles were observed in the three soil columns, and a generalized ultimate pore-water pressure profile of a capillary barrier system was proposed. In addition, the final volumetric water contents versus matric suctions of the soils as measured from the soil columns were reasonably consistent with the soil-water characteristic curves (SWCCs) of the soils, suggesting that the drying SWCC of a soil could also be obtained from the drying process in a soil column (or a capillary open tube). The drying SWCC could be established from measurements in the soil column up to a height corresponding to two times the residual matric suction head of the soil.Key words: capillary barrier, soil column, soil-water characteristic curve, pore-water pressure, water content, matric suction.
24
Zhang, Liting, Shujun Sun, Mengqi Lin, Kaijun Feng, Yue Zhang, Jinshi Lin, Hongli Ge, Yanhe Huang e Fangshi Jiang. "Study on soil-water characteristic curves in the profiles of collapsing walls of typical granite Benggang in southeast China". PeerJ 10 (1 giugno 2022): e13526. http://dx.doi.org/10.7717/peerj.13526.
Testo completoAbstract (sommario):
Benggang with steep collapsing walls is one of the worst soil erosion problems in South China. The collapse of walls is the most critical process in Benggang development. This is mainly due to the soil water properties. The soil water characteristic curve (SWCC) is a key indicator for analyzing soil moisture, but the SWCC and its mechanism of influence in collapsing walls remain obscure. A pressure plate meter was used for drying experiments to research the SWCCs of undisturbed soils of five layers (from top to bottom: red soil layer, transition layer I, sand soil layer, transition layer II and detrital layer) of two typical collapsing walls. The van Genuchten (VG) model can be fitted to the SWCCs for different layers (NSE ≥ 0.90). With increasing soil depth, the parameters a and θs first decreased and then increased, the parameters n first increased and then decreased, θr declined as the soil depth increased. These findings illustrate that soil water holding capacity decreases with increasing soil depth. The bottom of the soil is weak in water retention and water can easily reach saturation, resulting in a decline in soil stability, thus promoting soil collapse and finally inducing upper soil collapse. Furthermore, gravel content and particle morphology are factors that should not be neglected for SWCCs. The results of this study provide a theoretical basis for understanding the process of wall collapse in Benggang landforms in South China.
25
Li, Xuebo, Tianlun Shen, Ke Xiang, Qian Zhai, Harianto Rahardjo, Alfrendo Satyanaga e Shijun Wang. "Effect of the Wetting Hydraulic Property of Soil on 1-D Water Infiltration". Sustainability 15, n. 3 (18 gennaio 2023): 1822. http://dx.doi.org/10.3390/su15031822.
Testo completoAbstract (sommario):
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.
26
Du, Peng, Xiao Ling Liu e Xiao Ying Li. "The Study of Correction Method for Soil-Water Characteristic Curve of Swelling-Shrinking Soil". Advanced Materials Research 712-715 (giugno 2013): 873–76. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.873.
Testo completoAbstract (sommario):
The swelling-shrinking soil embodies the features of expanding when absorbing water and shrinking when drying out; its engineering properties are sensitive to water fluctuation. Mainstream test instruments of SWCC cannot accurately get its relationship between matric suction and water volume fraction. So a correction method based on the results of shrinkage test is carried out. The method is accomplished by using the volume deformation which is obtained in shrinkage test to calculate its real water volume fraction and then combining the results of SWCC test and finally constructing the relationship between matric suction and water volume fraction. Through real application, this method is proved to be feasible and essential.
27
Priono, Harianto Rahardjo, Kalyani Chatterjea e Eng-Choon Leong. "Laboratory investigation on hydraulic anisotropy behavior of unsaturated soil". Canadian Geotechnical Journal 54, n. 7 (luglio 2017): 1034–46. http://dx.doi.org/10.1139/cgj-2016-0023.
Testo completoAbstract (sommario):
Hydraulic anisotropy behavior of unsaturated soil has not been fully investigated. Direct laboratory measurement and indirect determination of hydraulic anisotropy under a drying condition were carried out on statically compacted specimens having different initial conditions. Direct measurement of permeability was carried out using an unsaturated triaxial permeameter whereas indirect determination of permeability was performed through statistical estimation via a measured drying soil–water characteristic curve (SWCC). In this research, two orientations — specifically horizontal-layering (HL) and vertical-layering (VL) orientations — were prepared for a given specimen from statically compacted homogeneous sand–kaolin. The results from both direct measurement and indirect determination of hydraulic anisotropy were in good agreement. Hydraulic anisotropy under an unsaturated condition was found to be similar with that in a saturated condition. Moreover, hydraulic anisotropy was reflected in the ratio of transient time during the direct measurements of HL and VL specimens at high matric suctions. In contrast, in the indirect method, hydraulic anisotropy was reflected in the ratio of equalization time during SWCC tests at matric suctions higher than the air-entry value of the soil.
28
Shi, Jianyong, Xun Wu, Yingbo Ai e Zhen Zhang. "Laboratory test investigations on soil water characteristic curve and air permeability of municipal solid waste". Waste Management & Research: The Journal for a Sustainable Circular Economy 36, n. 5 (7 aprile 2018): 463–70. http://dx.doi.org/10.1177/0734242x18766223.
Testo completoAbstract (sommario):
The air permeability coefficient has a high correlation with the water content of municipal solid waste. In this study, continuous drying methodology using a tension meter was employed to construct the soil water characteristic curve of municipal solid waste (M-SWCC). The municipal solid waste air permeability test was conducted by a newly designed apparatus. The measured M-SWCC was well reproduced by the van Genuchten (V-G) model and was used to predict the parameters of typical points in M-SWCC, including saturated water content, field capacity, residual water content and water content at the inflection point. It was found that the M-SWCC was significantly influenced by void ratio. The final evaporation and test period of M-SWCC increase with the increase in void ratio of municipal solid waste. The evolution of air permeability coefficient with water content of municipal solid waste depicted three distinct characteristic stages. It was observed that the water contents that corresponded to the two cut-off points of the three stages were residual water content and water content at the inflection point, respectively. The air permeability coefficient of municipal solid waste decreased with the increase of the water content from zero to the residual water content. The air permeability coefficient was almost invariable when the water content increased from residual water content to the water content at the inflection point. When the water content of municipal solid waste exceeded the water content at the inflection point, the air permeability coefficient sharply decreased with the increase of water content.
29
Witteman, M. L., e P. H. Simms. "Unsaturated flow in hydrating porous media with application to cemented mine backfill". Canadian Geotechnical Journal 54, n. 6 (giugno 2017): 835–45. http://dx.doi.org/10.1139/cgj-2015-0314.
Testo completoAbstract (sommario):
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.
30
Carnavale, Thiago de Souza, Ana Carolina de Campos Viana, Paula Morais Canedo de Magalhães e 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.
Testo completoAbstract (sommario):
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).
31
Ma, Shaokun, Xiao Huang, Zhibo Duan, Min Ma e Yu Shao. "New Prediction Model for SWCC of Expansive Soil Considering Drying and Wetting Cycles". Journal of Mining Science 57, n. 3 (maggio 2021): 393–404. http://dx.doi.org/10.1134/s1062739121030054.
Testo completo
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Shaokun, Ma, Huang Xiao, Duan Zhibo, Ma Min e Shao Yu. "New Prediction Model for SWCC of Expansive Soil Considering Drying and Wetting Cycles". Физико-технические проблемы разработки полезных ископаемых, n. 3 (2021): 38–50. http://dx.doi.org/10.15372/ftprpi20210305.
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Chen, Dong Xia, Ma Xiu Zhang, You Qiang Lin e Jian Ni. "Measurement of SWCC of Xiamen Residual Soil by Filter Paper". Applied Mechanics and Materials 256-259 (dicembre 2012): 1046–51. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.1046.
Testo completoAbstract (sommario):
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.
34
Kayser, Timon, Wiebke Baille, Merita Tafili e Torsten Wichtmann. "Coupled hydro-mechanical behaviour of a Kaolin Clay in the context of the geothermal use of geotechnical structures". E3S Web of Conferences 382 (2023): 23002. http://dx.doi.org/10.1051/e3sconf/202338223002.
Testo completoAbstract (sommario):
An experimental study regarding the hydro-mechanical behaviour of a Malaysian Kaolin is presented. Strain rate-controlled oedometer tests have been conducted on compacted samples. The influence of initial water content on the pore-size distribution (PSD) of compacted samples was investigated by Mercury Intrusion Porosimetry (MIP) tests. The drying path of the soil-water characteristic curve was experimentally determined for initially compacted samples and slurry samples. The preconsolidation stress was found to increase with increase in initial dry density and with decrease in initial water content. The compression curves merge into a single line, as soon as they have reached full saturation during loading. Samples at the dry side of Proctor water content showed a bi-modal PSD, whereas a mono-modal PSD was found for Proctor water content and at the wet side. The different initial compaction states of the samples were getting reflected in the drying SWCC until a suction of about 2 MPa, beyond which the drying paths were found to be identical.
35
Nie, Yongpeng, Wankui Ni, Xiangning Li, Haiman Wang, Kangze Yuan, Yexia Guo e Wenxin Tuo. "The Influence of Drying-Wetting Cycles on the Suction Stress of Compacted Loess and the Associated Microscopic Mechanism". Water 13, n. 13 (29 giugno 2021): 1809. http://dx.doi.org/10.3390/w13131809.
Testo completoAbstract (sommario):
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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Zamin, Bakht, Hassan Nasir, Muhammad Ali Sikandar, Waqas Ahmad, Beenish Jehan Khan, Mahmood Ahmad e Muhammad Tariq Bashir. "Comparative Study on the Field- and Lab-Based Soil-Water Characteristic Curves for Expansive Soils". Advances in Civil Engineering 2022 (2 maggio 2022): 1–9. http://dx.doi.org/10.1155/2022/6390442.
Testo completoAbstract (sommario):
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.
37
Shi, Zhen Hua, e Zhao Wan Gao. "A Model for the Soil-Water Characteristic Curve and its Application in Dam Engineering". Applied Mechanics and Materials 94-96 (settembre 2011): 1930–35. http://dx.doi.org/10.4028/www.scientific.net/amm.94-96.1930.
Testo completoAbstract (sommario):
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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Zhang, Feixia, G. Ward Wilson e D. G. Fredlund. "Permeability function for oil sands tailings undergoing volume change during drying". Canadian Geotechnical Journal 55, n. 2 (febbraio 2018): 191–207. http://dx.doi.org/10.1139/cgj-2016-0486.
Testo completoAbstract (sommario):
The coefficient of permeability function is an important unsaturated soil property required when modeling seepage and contaminant transport phenomena. Inaccuracies in the estimation of the permeability function can lead to significant errors in numerical modeling results. Changes in void ratio and degree of saturation are factors that influence the permeability function. Presently available methodologies for estimating the unsaturated permeability function make the assumption that there is no volume change as soil suction is changed. As a result, volume changes are interpreted as changes in degree of saturation. The commonly used estimation techniques for the permeability function are reasonable for soils such as sands that experience little volume change as soil suction is changed. On the other hand, inaccurate results are generated when soils undergo volume change as is the case with oil sands tailings. Revisions to previous methodologies are proposed to render the estimation of the permeability function more suitable for simulating the drying process associated with soils that undergo high volume changes. The revised methodology independently analyzes the effect of volume changes (i.e., changes in void ratio) and degree of saturation changes (i.e., changes in S-SWCC (degree of saturation - soil-water characteristic curve)). Laboratory data on thickened oil sands tailings are presented and interpreted within the context of the proposed methodology.
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Yoka Khail, Bilal, Mathilde Morvan e 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.
Testo completoAbstract (sommario):
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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Cao, Ling, Zhijian Wang e 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.
Testo completoAbstract (sommario):
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 e Qaiser Iqbal. "Field-Obtained Soil-Water Characteristic Curves of KPK Expansive Soil and Their Prediction Correlations". Advances in Civil Engineering 2020 (20 novembre 2020): 1–13. http://dx.doi.org/10.1155/2020/4039134.
Testo completoAbstract (sommario):
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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Wang, Xuan, Zhenyu Li, Yongjun Chen e Yongsheng Yao. "Influence of Vetiver Root Morphology on Soil–Water Characteristics of Plant-Covered Slope Soil in South Central China". Sustainability 15, n. 2 (11 gennaio 2023): 1365. http://dx.doi.org/10.3390/su15021365.
Testo completoAbstract (sommario):
The soil–water characteristic curve is an important tool to evaluate the water-holding capacity of unsaturated soil. Plant roots can affect the matric suction of soil and the water-holding capacity and permeability of the soil. Therefore, the morphological characteristics of plant roots will lead to the difference in soil–water characteristics between soil slope and plant-covered slope. This study aims to investigate the effect of Vetiver root morphology on soil–water characteristic curves of plant-covered slope soil. The hydrological effect of the root distribution on the root–soil system was also discussed. The results showed that: (1) The root surface area index (RAI) and root volume ratio (Rv) of each soil section of the vetiver root system varied with depth in accordance with the Gaussian function distribution; (2) In the process of natural drying, the matric suction generated within the root system is significantly higher than that generated by evaporation of bare soil in the same soil layer. The ability of vegetation soil to enhance soil matrix suction increases with the increase of soil root surface area index; and (3) The α and n values of the SWCC model decreased with the increase of Rv (root volume ratio of soil), while the air entry value increased. Under the same water content, the matric suction corresponding to vegetation soil is significantly greater than bare soil. In addition, the soil–water characteristic curve can be effectively predicted by combining the Rv of vegetated soils.
43
Tao, Gaoliang, Ziyue Li, Lisheng Liu, Yangyang Chen e 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 aprile 2021): 1–11. http://dx.doi.org/10.1155/2021/6683859.
Testo completoAbstract (sommario):
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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Jayanth, Sneha, Kannan Iyer e D. N. Singh. "Continuous determination of drying-path SWRC of fine-grained soils". Geomechanics and Geoengineering 8, n. 1 (marzo 2013): 28–35. http://dx.doi.org/10.1080/17486025.2012.727034.
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Jayanth, Sneha, Kannan Iyer e D. N. Singh. "Influence of Drying and Wetting Cycles on SWCCs of Fine-Grained Soils". Journal of Testing and Evaluation 40, n. 3 (marzo 2012): 104184. http://dx.doi.org/10.1520/jte104184.
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Feng, Juan, Jianping Li e Yun Li. "A Monsoon-Like Southwest Australian Circulation and Its Relation with Rainfall in Southwest Western Australia". Journal of Climate 23, n. 6 (15 marzo 2010): 1334–53. http://dx.doi.org/10.1175/2009jcli2837.1.
Testo completoAbstract (sommario):
Abstract Using the NCEP–NCAR reanalysis, the 40-yr ECMWF Re-Analysis (ERA-40), and precipitation data from the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) and the Australian Bureau of Meteorology, the variability and circulation features influencing southwest Western Australia (SWWA) winter rainfall are investigated. It is found that the climate of southwest Australia bears a strong seasonality in the annual cycle and exhibits a monsoon-like atmospheric circulation, which is called the southwest Australian circulation (SWAC) because of its several distinct features characterizing a monsoonal circulation: the seasonal reversal of winds, alternate wet and dry seasons, and an evident land–sea thermal contrast. The seasonal march of the SWAC in extended winter (May–October) is demonstrated by pentad data. An index based on the dynamics’ normalized seasonality was introduced to describe the behavior and variation of the winter SWAC. It is found that the winter rainfall over SWWA has a significant positive correlation with the SWAC index in both early (May–July) and late (August–October) winter. In weaker winter SWAC years, there is an anticyclonic anomaly over the southern Indian Ocean resulting in weaker westerlies and northerlies, which are not favorable for more rainfall over SWWA, and the opposite combination is true in the stronger winter SWAC years. The SWAC explains not only a large portion of the interannual variability of SWWA rainfall in both early and late winter but also the long-term drying trend over SWWA in early winter. The well-coupled SWAC–SWWA rainfall relationship seems to be largely independent of the well-known effects of large-scale atmospheric circulations such as the southern annular mode (SAM), El Niño–Southern Oscillation (ENSO), Indian Ocean dipole (IOD), and ENSO Modoki (EM). The result offers qualified support for the argument that the monsoon-like circulation may contribute to the rainfall decline in early winter over SWWA. The external forcing of the SWAC is also explored in this study.
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Tripathy, Snehasis, Mohd Yuhyi M. Tadza e Hywel Rhys Thomas. "Soil-water characteristic curves of clays". Canadian Geotechnical Journal 51, n. 8 (agosto 2014): 869–83. http://dx.doi.org/10.1139/cgj-2013-0089.
Testo completoAbstract (sommario):
The drying suction – water content soil-water characteristic curves (SWCCs) of three clays (MX80 bentonite, yellow bentonite, and Speswhite kaolin) were experimentally determined using axis-translation, vapour equilibrium, and osmotic techniques. The shrinkage paths of the clays were established from Clod tests. The suction – water content SWCCs in conjunction with the Clod test results enabled establishing the suction – degree of saturation SWCCs and further determination of the air-entry values (AEVs) of the clays. Chemical analyses of the polyethylene glycol (PEG) solutions in the osmotic tests revealed an imbalance of the osmotic suctions between the expelled and the retained salts on either side of semi-permeable membranes. A decrease in the water content due to an applied suction for clays with significant osmotic efficiencies was explained by two mechanisms. In mechanism 1, the water content decrease prior to the air entry is controlled by the interparticle repulsive pressure, and in mechanism 2, a decrease in the degree of saturation following the air entry is primarily due to the matric suction. The agreements between the AEVs of the clays determined based on the osmotic suctions corresponding to various applied suctions and that determined from the suction – degree of saturation SWCCs were found to be very good.
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Zhang, Tao, Junran Zhang, Tong Jiang, Xincui Wang, Hang Jia e Lijin Wang. "SWCCs of Silt in Yudong Zone and its Prediction Under Different Drying–Wetting Cycle Conditions". Geotechnical and Geological Engineering 37, n. 3 (7 novembre 2018): 1977–86. http://dx.doi.org/10.1007/s10706-018-0738-x.
Testo completo
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Jadar, Chidanand M., Sathiyamoorthy Rajesh e 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.
Testo completoAbstract (sommario):
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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Yan, W. M., e Guanghui Zhang. "Soil-water characteristics of compacted sandy and cemented soils with and without vegetation". Canadian Geotechnical Journal 52, n. 9 (settembre 2015): 1331–44. http://dx.doi.org/10.1139/cgj-2014-0334.
Testo completoAbstract (sommario):
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.