A Comparison of Laboratory Measured and Calculated Hydraulic Conductivity Values of Unsaturated Soils PDF Download

Author: Mitiku Mamo
Publisher:
ISBN:
Category :
Languages : en
Pages : 118

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Author: G. Didier
Publisher:
ISBN:
Category : Borehole
Languages : en
Pages : 22

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Book Description
For waste facilities, field assessment of the hydraulic conductivity of fine- grained soils has been a real challenge for the past decades that has led to several types of test methods. Although standards (ASTM, NF, etc.) have been adopted in many countries, any test method needs careful application for constructing quality-control programs. The type of apparatus, its geometry, and even specimen preparation may be major sources of discrepancy. We compared hydraulic-conductivity values obtained from various field-testing methods (open, sealed, single and double infiltrometers, and borehole methods), and laboratory-testing methods such as oedometer cells or rigid and flexible-wall permeameters. Three materials were tested in this study: a compacted sandbentonite mixture, compacted clayey silt, and natural sandy clay. The field tests were run on soil-test pads whose characteristics were defined beforehand in the laboratory and the field. Comparison of the results shows a large range of hydraulic-conductivity values for a single soil sample. Such variability can commonly be explained by a scale effect, as demonstrated by the use of various types of diameter or geometry for the field or laboratory tests. Soil behavior (swelling or shrinkage) and test-analysis methods (saturated or unsaturated-flow analysis) are other important parameters. In conclusion, we identified the main problems affecting tests with infiltrometers and permeameters, and how they can be reduced or avoided by the improvement of current techniques.

Author: A. Guerra
Publisher:
ISBN:
Category : Field experiments
Languages : en
Pages : 16

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The hydraulic conductivity of a soil was measured in the laboratory and in the field. Although each technique used yielded consistent results, the hydraulic conductivity obtained differed over several orders of magnitude. These differences in hydraulic conductivity can only be attributed to macroscopic features that weigh differently depending on the mass of soil affected by the different tests.

Author: D. S. Ward
Publisher:
ISBN:
Category : Soil moisture
Languages : en
Pages : 46

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Author: Alessandro Tarantino
Publisher: Springer Science & Business Media
ISBN: 1402088191
Category : Science
Languages : en
Pages : 214

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This volume details recent global advances in laboratory and field testing of unsaturated soils. Coverage includes mechanical, hydraulic, and geo-environmental testing and applications of unsaturated soil monitoring to engineering behavior of geo-structures.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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In this project, a new cone penetration test (CPT) method for the determining the hydraulic properties of unsaturated soil was developed. A modified cone penetrometer (cone permeameter) is used to inject water into the soil under constant pressure through a screen and measure movement of the wetting front with tensiometer rings. An inverse methodology is used to analyze the cumulative inflow volume and pressure head readings to obtain estimates of the hydraulic conductivity and soil moisture retention curves for the soil. To accomplish the inversion, a cone permeameter test is numerically simulated with the radially symmetric form of Richard's equation and the van Genuchten hydraulic conductivity and moisture retention functions. An objective function expressing the differences between flow responses measured with the cone permeameter and those predicted using the numerical model with the parameterized soil hydraulic properties is minimized to obtain the hydraulic parameter estimates. Full scale tests in a laboratory aquifer and field tests were performed during the course of this study. Excellent agreement between saturated hydraulic conductivity values obtained with the cone permeameter and values from in-situ Guelph permeameter and laboratory falling head tests was obtained. Soil moisture retention curves were similar to those obtained from multi-step outflow and capillary rise tests.

Author: Dan B. Jaynes
Publisher:
ISBN:
Category : Soil permeability
Languages : en
Pages : 236

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Author: DJ. DeGroot
Publisher:
ISBN:
Category : Dilatometer
Languages : en
Pages : 18

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The measurement of hydraulic conductivity using a variety of field and laboratory techniques was evaluated at a site consisting of medium stiff and soft lacustrine varved clay in western Massachusetts. Field measurements were obtained by conducting "slug" tests in both predrilled and push-in piezometers and also from pore pressure dissipation tests using the piezocone and flat dilatometer. Laboratory hydraulic conductivity values were obtained for both vertical and horizontal flow conditions using a flexible wall permeameter and by indirect estimation from 1-dimensional consolidation tests. Based on a comparison of tests conducted throughout the profile, laboratory flexible wall tests with vertical flow gave the lowest values of hydraulic conductivity whereas the predrilled piezometers yielded the highest values. Of all the field techniques, the push-in piezometers gave the lowest values. Hydraulic conductivity values interpreted from piezocone and flat dilatometer dissipation tests tended to be between those obtained from the predrilled and push-in piezometers. Results from tests in predrilled piezometers show that the hydraulic conductivity increases with increasing screen length, showing the influence of scale effects. The results of this study clearly show that estimation of hydraulic conductivity for this soil is highly dependent on scale effects, the test technique used and on the direction of flow (i.e., parallel versus perpendicular to the orientation of the varves).

Author:
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ISBN:
Category :
Languages : en
Pages :

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This report details some recent field measurements and compares predicted and measured values of hydraulic conductivities for three locations at the Hanford Site. Measurements from small (6-cm-dia) /open quotes/point/close quotes/ and large (2-m by 2-m) /open quotes/plot/close quotes/ areas utilized inflitration and drainage techniques to obtain in situ data for field-saturated and unsaturated hydraulic conductivity. The Guelph permeameter was used for point sampling, and the unsteady drainage-flux method was used on plots for field-saturated and unsaturated hydraulic conductivity measurements. Steady-state techniques were used to measure unsaturated hydraulic conductivities in small columns in the laboratory for one of the three soils tested to provide a comparison with data obtained from the field. Measured unsaturated hydraulic conductivities and those predicted from particle-size distribution and bulk density data agree within one-half to one and one-half orders of magnitude, depending on soil type. To use a particle-size distribution to estimate water retention characteristics and, subsequently, to predict unsaturated hydraulic conductivities, measurements of water-retention characteristics are necessary to determine a parameter value used in one of the models. No single method for measuring or calculating unsaturated hydraulic conductivities was found appropriate for all Hanford Site soils. Ideally, several methods should be used to take advantage of the strengths of each method, considering the data needs and resources available. 45 refs., 24 figs., 19 tabs.

Author: Eduardo E. Alonso
Publisher: CRC Press
ISBN: 0203834011
Category : Technology & Engineering
Languages : en
Pages : 1532

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Book Description
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.