Download or read book Determining the Unsaturated Hydraulic Properties of Cohesionless Soils An Integrated Experimental and Inverse Modeling Approach written by C. S. El Mohtar and published by . This book was released on 2020 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: A simple, inexpensive and quick method for measuring the van Genuchten soil water retention curve (SWRC) model parameters for cohesionless soil is presented. The proposed method is an integration of laboratory testing and numerical modeling. The experimental testing consists of multistage bottom-top water imbibition of a dry sand column while recording pore pressure at the inlet. The experiment is then simulated numerically using Hydrus 1D, and the van Genuchten SWRC model parameters are determined through inverse modeling to match the recorded pore pressures. The soil column flushing includes multiple flow stoppages and resumptions, all before permeating one pore volume of water. The flow stoppage results in a time-dependent redistribution of moisture near the waterfront that is controlled by the unsaturated hydraulic properties of the soil and is reflected by changes in the pore pressure measurements. The uniqueness of this method comes from the simple experimental setup and the multistage flushing that can reduce the testing time by a factor of 30 compared with other methods. The results from testing three different sands with different grain size distributions are presented. The new method generated consistent results from multiple specimens tested at a range of flow rates for the three sands. The hypothesis behind moisture redistribution during flow stoppage was confirmed through a combination of experimental and numerical observations. The van Genuchten SWRC parameters obtained from the new method were comparable to those obtained using the conventional hanging column test for Sands B and C and available data in the literature. Sand A could not be tested using the hanging column test because of its large particle size, which demonstrates the wide range of soils that can be tested using the new proposed method.

Download or read book Inverse Modelling of Desorption Tests to Establish the Hydraulic Conductivity of Unsaturated Sands written by Seyed Mohammad Javad Hosseini Siahdashti and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Unsaturated Soils Experimental Studies written by Tom Schanz and published by Springer Science & Business Media. This book was released on 2006-03-04 with total page 530 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings document the various papers delivered and partially presented at the International Conference “From experimental evidence towards numerical modeling of unsaturated soils,” which was held in Weimar (Germany) during 18-19 September 2003. The conference was organized under the auspices of the International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE) and the National German G- technical Society (DGGT). The need to understand the behavior of unsaturated soils is becoming exclusively - sential for the geotechnical engineers and designers. In the last three decades many - searchers have made significant contribution to the understanding of the unsaturated soil mechanics. Nevertheless, application of the subject to variety of new problems still - quires our attention. This International conference is a mere attempt to unite researchers and engineers in geotechnical engineering and to discuss about the problems associated with the unsaturated soils. Doing so the objectives of these lecture notes are as follows: - to promote unsaturated soil mechanics for practical application, - to exchange experiences in experimental unsaturated soil mechanics and numerical modeling, - to discuss application of unsaturated soil mechanics to variety of problems. In other words, we could also name these two volumes as “From theory to daily pr- tice”. I would like to extend my deep sense of appreciation as the editor and the Head of the organizing committee, to many persons who have contributed either directly or indirectly to organize the International conference and to finalize these proceedings.

Download or read book An Experimental Technique for Determining the Hydraulic Properties of Unsaturated Pyroclastic Soils written by Marco Valerio Nicotera and published by . This book was released on 2010 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: The experimental technique proposed in the paper was designed to rapidly and reliably determine both the water retention curve and the permeability function of undisturbed natural pyroclastic soil samples. The technique was developed in the framework of an experimental research project on mudflows in pyroclastic soils in the southern Italian region of Campania (Italy). Grain-size distribution and void ratio of the particular pyroclastic soils suggested investigation of the hydraulic behavior for matric suction values in the range between 0 and 100 kPa. Our experimental technique consisted of a sequence of testing phases to be conducted on a single undisturbed soil sample: A constant head permeation test, a forced evaporation test, and finally a drying test in a pressure plate apparatus. Interpretation of the experimental data was based on inverse modelling and allowed both water retention curves and permeability functions to be determined. The six parameters of the Mualem-van Genuchten model were adopted to describe the hydraulic behavior of the tested soils. Each testing phase supplied experimental data to be used in the interpretation procedure: The permeation phase provided a matching data point for the permeability function near saturation; the forced evaporation test was related to the hydraulic behavior for matric suction values ranging from a few kPa to less than 80-90 kPa (i.e., mini-tensiometer functioning range); and the drying steps in the pressure plate apparatus provided information about the retention properties for matric suction values up to 1 MPa. The results shown in the paper clearly confirm the goodness of the experimental design and the interpretation procedure.

Download or read book Indirect Methods for Estimating the Hydraulic Properties of Unsaturated Soils written by M. Th Van Genuchten and published by . This book was released on 1992 with total page 742 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Analytical Method for the Simultaneous Determination of Soil Hydraulic Properties from Multistep Outflow Data written by Rayan Ribal Bsat and published by . This book was released on 2006 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: Water transport in the vadose zone greatly depends on the hydraulic properties o f soils. The direct determination of those properties in the field or laboratory is tedious, time-consuming, and involves considerable uncertainty for most prac tical applications. Recently, inverse modeling has been introduced to estimate s oil hydraulic properties, using transient flow information of measured time seri es. Inverse methods combine forward soil water flow models with optimization alg orithms to find the best parameter set that minimizes an objective function. Ass uming a linear hydraulic conductivity - moisture content k(theta) relationship a nd an exponential hydraulic conductivity - water pressure k(h) model, the parame ter identification problem is solved with reasonable accuracy and simplicity, th rough the analysis of multistep outflow data. Unsaturated hydraulic properties o f a hypothetical soil are first evaluated by a nonlinear inversion method minimi zing various objective functions, to identify the information content of data re quired for the proper determination of soil hydraulic parameters. Multistep expe riments are then simulated on three soils with different texture characteristics via Hydrus-1D software, to explore the applicability and limitations of applyin g the proposed parameter estimation technique to various soil types. Finally, tr ansient flow data from an actual multistep experiment with inherent measurement errors is used, whereby the proposed optimization method is used along with the Hydrus-1D numerical code to inversely estimate the unsaturated soil hydraulic pr operties. The proposed method does not require a numerical solution of the flow problem, and when tested against numerical and experimental outflow data gives v ery satisfactory results.

Download or read book Experimental Evidence and Theoretical Approaches in Unsaturated Soils written by A. Tarantino and published by CRC Press. This book was released on 2000-01-01 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents the work of postgraduate and postdoctoral researchers on unsaturated soil mechanincs. Topics covered include: innovative experimental techniques; new experimental data on compacted, collapsible and swelling soils; and advances in constitutive modelling.

Download or read book Unsaturated Soil Hydraulic Parameter Studies written by and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Different field and laboratory methods for determining the hydraulic properties of unsaturated soils were studied. Drying moisture retention curves were measured on undisturbed soil samples with a pressure plate apparatus, and wetting soil moisture retention curves were measured on repacked soil columns via a capillary rise experiment Saturated hydraulic conductivities were measured in-situ with a Guelph permeameter, and in the laboratory with falling head tests. Finally, an inverse modeling technique was used to analyze transient flow data from in-situ cone permeameter and laboratory multi-step outflow experiments to simultaneously obtain wetting and drying curves for both the moisture retention and the hydraulic conductivity functions. The retention curves obtained from analysis of the cone permeameter data were consistent with results of the multi-step outflow tests and bounded by the capillary and pressure plate test results, as expected. The retention curves derived from cone permeameter data exhibited more curvature than those obtained from the other methods. The curves obtained from multi-step outflow tests exhibited less hysteresis than those derived from cone permeameter tests and were more repeatable than the pressure plate test results.

Download or read book Investigation and Modeling of Unsaturated Flow Through Swelling Soils written by Taghi Ebadi and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although the theory of water movement through an unsaturated, swelling soil has been developing for a number of years, the efficiency of the results has been limited, and the developed models have suffered from a lack of a mechanism to reliably define water flow and experimental techniques for measuring the unsaturated soil hydraulic properties. The intent of the present research is to elucidate and to investigate the theory of flow through unsaturated, swelling soil, to develop a three dimensional theoretical model based on a reliable soil swelling and unsaturated flow mechanism and, furthermore, to characterize the relationships between different soil hydraulic and swelling properties. In the first part, based on the water adsorption mechanism by the soil particles and the use of continuum theory principles, a theoretical model of unsaturated flow through swelling soil has been developed. Some new techniques were established to measure the different soil swelling and hydraulic properties and to analyze the effect of the soil's initial conditions. The reliability of the different existing empirical models, to be applied to the results obtained from hydraulics, shrinkage and swelling experiments, were investigated and modified where necessary. A static neural network model was developed to mathematically characterize the experimental results being used in the proposed numerical solution of the mathematical model. The neural network model works based on the back-propagation error method with adaptive learning rules by means of the neural network tool box of MATLAB software. A finite difference numerical model, based on a fully implicit method, was proposed to numerically solve the one dimensional governing equation (simplified form of 3D governing equation). For this part of the study, a computer program in C++ language was developed. Finally, the results of the numerical method were verified using the results obtained from infiltration tests. The tests were conducted for the semi-infinite soil columns having three different confinement conditions: completely confined, semi-confined and free swelling. The results show a clear agreement between the output of the developed numerical model and the experimental data. As one of the conclusions, the results of the numerical analysis of the developed mathematical model agreed reasonably well with those of the experiments. The study also indicated that the static neural network model, as one of the most promising models, can precisely characterize any experimental function related to the soil properties and cooperates with other numerical approaches such as finite difference method to solve a highly nonlinear partial differential equation such as unsaturated flow equation.

Download or read book Unsaturated Soils Research and Applications written by Claudio Mancuso and published by Springer Science & Business Media. This book was released on 2012-06-23 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: These volumes contain the contributions to the Second European Conference on Unsaturated Soils, E-UNSAT 2012, held in Napoli, Italy, in June 2012. The event is the second of a series of European conferences, and follows the first successful one, organised in Durham, UK, in 2008. The conference series is supported by Technical Committee 106 of the International Society of Soil Mechanics and Geotechnical Engineering on Unsaturated Soils. The published contributions were selected after a careful peer-review process. A collection of more than one hundred papers is included, addressing the three thematic areas experimental, including advances in testing techniques and soil behaviour, modelling, covering theoretical and constitutive issues together with numerical and physical modelling, and engineering, focusing on approaches, case histories and geo-environmental themes. The areas of application of the papers embrace most of the geotechnical problems related to unsaturated soils. Increasing interest in geo-environmental problems, including chemical coupling, marks new perspectives in unsaturated soil mechanics. This book will provide a valuable up-to-date reference across the subject for both researchers and practitioners.

Download or read book Unsaturated Soils Research and Applications written by Claudio Mancuso and published by Springer Science & Business Media. This book was released on 2012-06-26 with total page 435 pages. Available in PDF, EPUB and Kindle. Book excerpt: These volumes contain the contributions to the Second European Conference on Unsaturated Soils, E-UNSAT 2012, held in Napoli, Italy, in June 2012. The event is the second of a series of European conferences, and follows the first successful one, organised in Durham, UK, in 2008. The conference series is supported by Technical Committee 106 of the International Society of Soil Mechanics and Geotechnical Engineering on Unsaturated Soils. The published contributions were selected after a careful peer-review process. A collection of more than one hundred papers is included, addressing the three thematic areas experimental, including advances in testing techniques and soil behaviour, modelling, covering theoretical and constitutive issues together with numerical and physical modelling, and engineering, focusing on approaches, case histories and geo-environmental themes. The areas of application of the papers embrace most of the geotechnical problems related to unsaturated soils. Increasing interest in geo-environmental problems, including chemical coupling, marks new perspectives in unsaturated soil mechanics. This book will provide a valuable up-to-date reference across the subject for both researchers and practitioners.

Download or read book Unsaturated Soils Two Volume Set written by Eduardo E. Alonso and published by CRC Press. This book was released on 2010-09-02 with total page 1532 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent decades the development of unsaturated soil mechanics has been remarkable, resulting in momentous advances in fundamental knowledge, testing techniques, computational procedures, prediction methodologies and geotechnical practice. The advances have spanned the full spectrum of theory and practice. In addition, unsaturated materials exhibiting complex behaviour such as residual soils, swelling soils, compacted soils, collapsing soils, tropical soils and solid wastes have been integrated in a common understanding of shared behaviour features. It is also noteworthy that unsaturated soil mechanics has proved surprisingly fruitful in expanding to other neighbouring areas such as swelling rocks, rockfill mechanics, and freezing soils. As a consequence, geotechnical engineering involving unsaturated soils can be now approached from a more rational and systematic perspective leading towards an improved and more effective practice. Unsaturated Soils contains the papers presented at the 5th International Conference on Unsaturated Soil (Barcelona, Spain, 6-8 September 2010). They report significant advances in the areas of unsaturated soil behaviour, testing techniques, constitutive and numerical modelling and applications. The areas of application include soil-atmosphere interaction, foundations, slopes, embankments, pavements, geoenviromental problems and emerging topics. They are complemented by three keynote lectures and three general reports covering general issues of modelling, testing and applications. Unsaturated Soils is a comprehensive record of the state-of-the art in unsaturated soil mechanics and a sound basis for further progress in the future. The two volumes will serve as an essential reference for academics, researchers and practitioners interested in unsaturated soils.

Download or read book A Transient Water Release and Imbibitions Method for Rapidly Measuring Wetting and Drying Soil Water Retention and Hydraulic Conductivity Functions written by Alexandra Wayllace and published by . This book was released on 2012 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: A transient water release and imbibitions (TWRI) method for measuring the soil water retention curve (SWRC) and hydraulic conductivity function (HCF) under drying and wetting states is presented. The intellectual merit of the TWRI method is its integration of physical and numerical experiments: it employs the simple and reliable measurement of transient water content by electronic balance to record the signature of transient unsaturated flow in soil sample, and it takes advantage of the robust inverse modeling capability to simulate the physical process. The TWRI method; therefore, has two integrated components: testing and modeling. The testing consists of water release upon two-steps increase in matric suction and water imbibitions upon one-step decrease in matric suction. Each process lasts sufficient time in order to obtain transient water content. The data is then used as an objective function in an inverse numerical modeling process to obtain the unsaturated hydrologic parameters that fully define the SWRC and HCF of the soil. A novel feature of the TWRI method is its capability to measure SWRC and HCF under wetting state. The apparatus can accommodate both undisturbed and remolded samples. The testing time required for completing a full drying and wetting loop is approximately one week for most soils. Validation of the technique has been performed both experimentally and numerically. Comparisons between data obtained with the TWRI method and the independent Tempe cell method verify the reliability, applicability, and accuracy of the TWRI method. Results from three different soils are presented to illustrate the procedure and performance of the TWRI method for different soils from fine sand to clayey silt. The TWRI method provides a fast, accurate, and simple testing tool for obtaining SWRC and HCF of various types of soils under both wetting and drying states with high range of matric suction several orders of magnitude above the air-entry pressure of the ceramic stone used in the experimental setup.

Download or read book Identification of Soil Hydraulic Properties on Different Scales Using Inverse Modeling written by Henrike Schelle and published by . This book was released on 2012 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soil Hydraulic Properties written by Nabil Ibrahim Mina and published by . This book was released on 1994 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unsaturated flow through porous media has gained a lot of attention in recent decades in many fields of agriculture and hydrology. Examples are many, of which are deficit irrigation and contaminants transport. Several models simulating unsaturated flow processes require as input the diffusivity -water content relation (D-0) and/or the hydraulic conductivity-water content relation (K-0). Several techniques for measuring or predicting these relations were developed throughout the literature. Most of these techniques involve either analytical and quasi-analytical solutions of the governing non-linear partial differential equation, or laboratory experiments, which are both expensive and time consuming. In this research, an experimental model was developed based on the field capacity concept and requires only measurements of the wetting depth with time. The laboratory setup is simple and inexpensive, consisting of uniformly packed soil columns. Three replicates of three different soil textures were used. Water was added to the columns and measurements of the wetting depths were taken after infiltration has virtually ceased; these measurements were then used to get the D-0 relation. With the aid of the soil moisture characteristic curves developed by the pressure plate method, the K-0 relation was determined. Results produced by this model showed trends that were in good agreement with some empirical relations in the literature, especially for fine textured soils. The best fitted relations for clay and sandy clay loam soils were of the power function and the exponential function types. For coarse textured soils (sand) the data were scattered and the developed model was not valid, - this was due to neglecting the gravity term in the model. The values of the fitted experimental parameters were too high as compared with those in the literature.

Download or read book Souvenir Picture Book of the Bruce Museum written by and published by . This book was released on with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Estimation of Unsaturated Soil Hydraulic Properties from Transient Laboratory and Field Experiments written by Simon Oyaro Eching and published by . This book was released on 1993 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt: