Impact of molding water content on hydraulic conductivity of compacted sand-bentonite

1992 ◽  
Vol 29 (2) ◽  
pp. 253-262 ◽  
Author(s):  
Moir D. Haug ◽  
Lionel C. Wong
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Test Program ◽  
Design Factor ◽  
Ottawa Sand ◽  
Critical Design ◽  
Hydraulic Gradients ◽  
To Come ◽  
The Relationship ◽  
Water Contents

The relationship between molding water content and hydraulic conductivity of a compacted sand-bentonite mixture was examined in a laboratory test program. This program involved triaxial permeability testing of nine specimens of 8% bentonite and Ottawa sand, compacted at standard Proctor density using molding water contents ranging from6 to 19%. The permeability tests were conducted using hydraulic gradients ranging from 19 to 40. The specimens were subjected to an average effective stress during testing of 21 kPa. The tests were conducted using continuous back pressure saturation. Each test was run for a minimum of 40 000 min (approximately 28 days) to enable the flow in and out of the specimen to come to equilibrium with respect to each other. The hydraulic conductivity decreased from 6.5 × 10−9 cm/s for a molding water content of 5.9% to 1.4 × 10−9 cm/s for a molding water content of 15.8%. However, although the hydraulic conductivity was related to the molding water content, the variation in hydraulic conductivity was relatively small. Therefore, the low values reported for all hydraulic conductivity tests suggest that molding water content is not a critical design factor in the construction of a low-permeability sand-bentonite liner. Key words : molding water content, bentonite, liners, hydraulic conductivity, triaxial permeability testing, covers, sand.

Tree/pasture interactions at a range of tree densities in an agroforestry experiment. III. Water uptake in relation to soil hydraulic conductivity and rooting patterns

1990 ◽  
Vol 41 (4) ◽  
pp. 709 ◽  
Author(s):  
J Eastham ◽  
CW Rose ◽  
DM Cameron ◽  
SJ Rance ◽  
T Talsma ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Root Length ◽  
Tree Density ◽  
Soil Hydraulic Conductivity ◽  
Tree Transpiration ◽  
Rooting Patterns ◽  
Soil Hydraulic ◽  
Water Contents

Eucalyptus grandis was planted in a Nelder fan design in November 1983 into a previously established pasture dominated by Setaria sphacelata cv. Kazungula, at the CSIRO Sanford Pasture Research Station, Queensland, Australia. Nine concentric rings of 18 trees were planted at radii of 4.4-61.6 m, giving a range of tree densities which decreased from 3580 to 42 stems/ha. Tree transpiration was studied at three tree densities (2150, 304 and 82 stems/ha, representing high, medium and low densities) over a 'drought' period of approximately 1 yr (Nov. 1985-Sep. 1986) and related to rooting patterns and soil hydraulic properties. Over the range of soil water contents studied, the ratio of tree transpiration rate to equilibrium evaporation rate (T/Esub(eq)) decreased linearly with decreasing mean soil water content at each tree density. To investigate the effects of soil hydraulic conductivity and root length density on the total transpirational flux, overall soil conductances (Ksub(s)) were calculated, with soil conductance in each horizon weighted according to the length of root in that horizon. At each tree density, decreases in the ratio T/Esub(eq) were related to decreases in ln Ksub(s) measured at 1.2 m from the stem. A more rapid decrease in T/Esub(eq) with decrease in water content observed at the low tree density was attributed to a greater decrease in Ksub(s) as mean water contents decreased. The greater decrease in Ksub(s) at low tree densities was associated with a larger proportion of water extracted and a higher proportion of total root length in surface soil horizons, which showed a greater decrease in hydraulic conductivity than subsoil horizons for the same decrease in water content.

Soil texture and salinity effects on calibration of TDR300 dielectric moisture sensor

Soil Research ◽  
2013 ◽  
Vol 51 (4) ◽  
pp. 330 ◽  
Author(s):  
George Kargas ◽  
Nikolaos Ntoulas ◽  
Panayiotis A. Nektarios
Keyword(s):  
Porous Media ◽  
Water Content ◽  
Soil Water ◽  
Time Domain ◽  
Soil Texture ◽  
Time Domain Reflectometry ◽  
Bulk Soil ◽  
The Relationship ◽  
Calibration Equations ◽  
Water Contents

Newly developed sensors have simplified real-time determination of soil water content (θm). Although the TDR300 is one of the most recent dielectric sensors, little is known with regard to the accuracy and dependency of its measurements of soil type and other environmental factors. In this study, the performance of TDR300 was investigated using liquids of known dielectric properties and a set of porous media with textures ranging from sandy to clayey. The experiments were conducted in the laboratory by mixing different amounts of water with each soil to obtain a sufficient range of soil water contents. For sand, the calculated permittivity values (εr) correlated adequately with Topp’s equation derived for time domain reflectometry. However, for the remaining inorganic porous media, εr values were overestimated compared with those resulting from Topp’s equation, especially for water contents exceeding 0.2 cm3/cm3. The results suggested that the relationship between θm and √εr was strongly linear (0.953< r2 <0.998). The most accurate results were provided by soil-specific calibration equations, which were obtained by the multi-point calibration equation. However, two-point calibration equations determined water content in all tested soils reasonably well, except for clay soil. A linear regression equation was developed that correlated the slope of the relationship θm–√εr with bulk soil electrical conductivity (EC). The regression slope was influenced more by soil EC than by soil texture. Also, TDR300 response was investigated in bi-layered systems (liquid–air and saturated porous media–air). In a bi-layered sensing volume characterised by strongly contrasting dielectric values, the appropriate bulk permittivity values for water and loam soil were determined by arithmetic rather than refractive index averaging, while for butanol and sand these values remained somewhere between the two averaging schemes, indicating that the upward infiltration calibration technique is inappropriate for the TDR300 sensor. Soil solute EC, as determined by measurements conducted in liquids and sand, significantly affected permittivity values at much lower levels than the limit of EC <2 dS/m, as suggested by the manufacturer. However, the relationship θm–√εr remained linear up to EC 2 dS/m, which corresponded to a bulk soil EC value of 0.6 dS/m. By contrast, for EC values >2 dS/m, the relationship θm–√εr was not linear, and, thus the TDR300 device calibration became increasingly difficult. Therefore, rather than operating as a time domain device, TDR300 operates as a water content reflectometer type device.

scholarly journals STUDY ON PERMEABILITY AND ELECTRICAL RESISTIVITY OF RED CLAY CONTAMINATED BY CU2+

2021 ◽  
Vol 30 (1) ◽  
Author(s):  
Rulong Ban ◽  
Xuejun Chen ◽  
Yu Song ◽  
Pengyan Bi ◽  
Xin Yang ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Electrical Resistivity ◽  
Hydraulic Conductivity ◽  
Water Content ◽  
Contaminated Soil ◽  
Initial Water Content ◽  
Red Clay ◽  
Initial Water ◽  
Electrode Method ◽  
The Relationship

In order to study the permeability characteristics of heavy metal ions contaminated red clay and explore the rapid detection of permeability of heavy metal contaminated red clay. Through variable-head permeability test and electrical resistivity test (different voltages and methods), the effects of Cu2+ concentration and initial water content on hydraulic conductivity characteristic and resistivity of contaminated red clay was systematically investigated. The relationship between permeability characteristic and electrical resistivity was further explored by taking Cu2+ concentration and moisture content as the intermediate variable. The obtained results indicate that the different voltage has no obvious effect on the resistivity of the samples. The four-phase electrode method is more accurate than the two-phase electrode method. With increasing Cu2+ concentrations the hydraulic conductivity of specimens increases, however the permeability coefficient of contaminated soil decreases with increasing initial water content. In the resistivity test, with increasing of Cu2+ concentrations and water content, the resistivity of samples presented a downward trend, which is decreased sharply at first and then tended to be gentle. The relationship between hydraulic conductivity and resistivity of contaminated soil showed a good fitting curve no matter in different Cu2+ concentration or in different water content, but the fitting curves of them presented opposite trend.

Analysis of Pitted Courtyard Cave Dwellings Stability in Baishe Village when Rainfall Infiltration

2011 ◽  
Vol 250-253 ◽  
pp. 2468-2472 ◽  
Author(s):  
Jia Ming Han ◽  
San Qing Su
Keyword(s):  
Water Content ◽  
Field Measurements ◽  
Strength Criterion ◽  
Annual Rainfall ◽  
Rock Stress ◽  
Average Annual Rainfall ◽  
The Stability ◽  
The Relationship ◽  
Water Contents

Pitted courtyard cave dwellings were used as a long-term living form in Baishe village. After field measurements, the size of local pitted courtyards and cave dwellings had been mastered, and the variation of average annual rainfall and monthly rainfall had been analyzed. By the experiment, the changes of physical and mechanical indexes could be showed with different water contents. At the same time, based on the literature, the relationship could be established between rainfall and water content. Basis in the expression of room rock stress and the Mohr-Coulomb strength criterion, the stability of the cave dwellings could be analyzed under different water contents, and the definition could be found of safety factor of loess cave. Then, the stability variation of loess cave dwelling could be obtained in different rainfall, and the evaluation results are given.

The nature of changes in bulk density with water content in a cracking clay

Soil Research ◽  
1977 ◽  
Vol 15 (1) ◽  
pp. 27 ◽  
Author(s):  
RD Berndt ◽  
KJ Coughlan
Keyword(s):  
Water Content ◽  
Bulk Density ◽  
Three Dimensional ◽  
Small Diameter ◽  
High Water ◽  
Density Relationship ◽  
Actual Field ◽  
Diameter Core ◽  
The Relationship ◽  
Water Contents

The effect of changing water content on the bulk density of undisturbed cores of a cracking clay was examined in laboratory experiments. The results were compared with the relationship between bulk density and water content established by core sampling the same soil in the field. Over the water content range measured in the field soil, the laboratory cores shrank three-dimensionally and normally. Small departures from normal shrinkage were attributed to the formation of cracks within the cores, and to the occurrence of some structural shrinkage in cores previously wet to high water contents. Swelling of cores was approximately three-dimensional, except for some unconfined swelling which occurred in the core surface. Unidimensional swelling was induced by confining dry cores to reduce the void ratio before wetting. Subsequent shrinkage was three-dimensional, indicating that the soil particles were reoriented during the unidimensional swelling phase. While the laboratory measurements showed that the soil volume changes were essentially three-dimensional and normal, the field data indicated that unidimensional shrinkage occurred at water contents greater than 0.47 g g-1. These field results were attributed to sampling inaccuracies associated with the use of a small-diameter core sampler, the actual field bulk density relationship being considered three-dimensional.

Determination of Tensile Strength of Compacted Loess by Double Punch Test

2011 ◽  
Vol 194-196 ◽  
pp. 1176-1179 ◽  
Author(s):  
Xiao Jun Li ◽  
Ying Ran Liu ◽  
Li Hua Jiang ◽  
Yi Chuan Tang
Keyword(s):  
Tensile Strength ◽  
Water Content ◽  
Dry Weight ◽  
Brazilian Test ◽  
Punch Test ◽  
Weight Density ◽  
The Relationship ◽  
Water Contents ◽  
Compacted Loess

Through double punch test, the tensile strength of compacted loess is determined under different water contents and different dry densities, the relationship between tensile strength, water content and the dry weight density is discussed, and their relationship is established. Comparing with Brazilian test, it proved the feasibility of determining tensile strength of compacted loess with double punch tests.

A sensitivity analysis of the Jackson method of predicting unsaturated hydraulic conductivity

Soil Research ◽  
1992 ◽  
Vol 30 (3) ◽  
pp. 285 ◽  
Author(s):  
HP Cresswell
Keyword(s):  
Sensitivity Analysis ◽  
Hydraulic Conductivity ◽  
Water Content ◽  
Volumetric Water Content ◽  
Small Range ◽  
Matric Potential ◽  
Unsaturated Hydraulic Conductivity ◽  
Moisture Characteristic ◽  
Intended Use ◽  
Water Contents

An assessment is made of the sensitivity of the unsaturated hydraulic conductivity predictions from the Jackson model to changes in the measured moisture characteristic and matching factor hydraulic conductivity inputs. The model is shown to be sensitive to the volumetric water content corresponding to the matching factor hydraulic conductivity as well as to the 0 to -1.0 kPa matric potential section of the moisture characteristic input. The significance of this sensitivity is dependent on intended use of the data. Where accurate conductivity prediction is required over a small range of water contents near saturation, the moisture characteristic input used with this model should include measured points between 0 and 1.0 kPa matric potential.

On the validity of the theory of flow in saturated swelling materials

Soil Research ◽  
1976 ◽  
Vol 14 (3) ◽  
pp. 389 ◽  
Author(s):  
DE Smiles
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Transient Flow ◽  
Initial Water Content ◽  
Approximate Theory ◽  
Initial Water ◽  
One Dimensional ◽  
Physically Based ◽  
Conductivity Water ◽  
The Relationship

Recently there has been concern that the reorientation of particles during transient flow of water in a saturated swelling material might result in the hydraulic conductivity and capillary potential not being well-defined functions of the water content. If this were the case, the conventional theory of one-dimensional liquid flow in these materials would be invalid. This paper shows that the hydraulic-conductivity/water-content relationship calculated using physically based approximate theory applied to outflow data obtained from red mud, is single-valued and independent of initial water content. Furthermore, the relationship permits recalculation, using a correct iterative procedure, of the data from which it was derived. It is concluded that the data provide no evidence to reject the theory, and that particle reorientation, if it occurs, is parametrized by the water content.

scholarly journals Effects of Breccia and Water Contents on the Mechanical Properties of Fault-core-zone Materials: an Experimental Investigation Using Artificial Specimens

2022 ◽  
Author(s):  
Hyun-Seok Yun ◽  
Seong-Woo Moon ◽  
Yong-Seok Seo
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Penetration Resistance ◽  
Specimen Preparation ◽  
Field Sampling ◽  
Core Zone ◽  
Relationship Of ◽  
The Relationship ◽  
Resistance Value ◽  
Water Contents

Abstract Determining the mechanical properties of fault-core-zone materials is challenging because of the low strength of such materials, which affects field sampling, specimen preparation, and laboratory testing. We overcame this problem by preparing and testing mechanical properties of 132 artificial fault-core-zone specimens consisting of mixtures of breccia, sand, clay, and water. The unconfined compressive strength (UCS), elastic modulus (E), and penetration resistance value (PRV) of these fault-core-zone materials were measured, and the effects of breccia content and water content on mechanical properties were assessed. Results show that UCS is inversely proportional to breccia content and water content, and that E is inversely proportional to water content. Furthermore, the inverse relationship of UCS with water content varies with breccia content. UCS is proportional to both PRV and E, and the relationship for each varies with breccia content. High coefficients of determination (R2 = 0.62–0.88) between the parameters suggest that breccia content, water content, and PRV are potentially useful parameters for estimating the mechanical properties of fault core zones.

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