scholarly journals Influence of Degree of Saturation in the Electric Resistivity-Hydraulic Conductivity Relationship

10.5772/15667 ◽  
2011 ◽  
Author(s):  
Mohamed Ahmed ◽  
Fernando A. Monterio Santos
Keyword(s):  
Hydraulic Conductivity ◽  
Electric Resistivity ◽  
Degree Of Saturation

Controls on induced polarization in sandy unconsolidated sediments and application to aquifer characterization

Geophysics ◽  
2003 ◽  
Vol 68 (5) ◽  
pp. 1547-1558 ◽  
Author(s):  
L. D. Slater ◽  
D. R. Glaser
Keyword(s):  
Grain Size ◽  
Hydraulic Conductivity ◽  
Internal Surface ◽  
Ionic Mobility ◽  
Induced Polarization ◽  
Hysteretic Behavior ◽  
Degree Of Saturation ◽  
Unconsolidated Sediments ◽  
Fluid Conductivity ◽  
Grain Diameter

Resistivity and induced polarization (IP) measurements (0.1–1000 Hz) were made on clay‐free unconsolidated sediments from a sandy, alluvial aquifer in the Kansas River floodplain. The sensitivity of imaginary conductivity σ″, a fundamental IP measurement, to lithological parameters, fluid conductivity, and degree of saturation was assessed. The previously reported power law dependence of IP on surface area and grain size is clearly observed despite the narrow lithologic range encountered in this unconsolidated sedimentary sequence. The grain‐size σ″ relationship is effectively frequency independent between 0.1 and 100 Hz but depends on the representative grain diameter used. For the sediments examined here, d90, the grain diameter of the coarsest sediments in a sample, is well correlated with σ″. The distribution of the internal surface in the well‐sorted, sandy sediments investigated here is such that most of the sample weight is likely required to account for the majority of the internal surface. We find the predictive capability of the Börner model for hydraulic conductivity (K)estimation from IP measurements is limited when applied to this narrow lithologic range. The relatively weak dependence of σ″ on fluid conductivity (σw) observed for these sediments when saturated with an NaCl solution (0.06–10 S/m) is consistent with competing effects of surface charge density and surface ionic mobility on σ″ as previously inferred for sandstone. Importantly, IP parameters are a function of saturation and exhibit hysteretic behavior over a drainage and imbibition cycle. However, σ″ is less dependent than the real conductivity σ′ on saturation. In the case of evaporative drying, the σ″ saturation exponent is approximately half of the σ′ exponent. Crosshole IP imaging illustrates the potential for lithologic discrimination of unconsolidated sediments. A fining‐upward sequence correlates with an upward increase in normalized chargeability Mn, a field IP parameter proportional to σ″. The hydraulic conductivity distribution obtained from the Börner model discriminates a hydraulically conductive sand–gravel from overlying medium sand.

scholarly journals Determining hydraulic properties of concrete and mortar by inverse modelling

2012 ◽  
Vol 1475 ◽  
Author(s):  
Sébastien Schneider ◽  
Dirk Mallants ◽  
Diederik Jacques
Keyword(s):  
Hydraulic Conductivity ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Inverse Modelling ◽  
Degree Of Saturation ◽  
Water Retention Curve ◽  
Retention Data ◽  
Capillary Suction ◽  
Near Surface ◽  
Van Genuchten Model

ABSTRACTThis paper presents a methodology and results on estimating hydraulic properties of the concrete and mortar considered for the near surface disposal facility in Dessel, Belgium, currently in development by ONDRAF/NIRAS. In a first part, we estimated the van parameters for the water retention curve for concrete and mortar obtained by calibration (i.e. inverse modelling) of the van Genuchten model [1] to experimental water retention data [2]. Data consisted of the degree of saturation measured at different values of relative humidity. In the second part, water retention data and data from a capillary suction experiment on concrete and mortar cores was used jointly to successfully determine the van Genuchten retention parameters and the Mualem hydraulic conductivity parameters (including saturated hydraulic conductivity) by inverse modelling.

scholarly journals Controls of macropore network characteristics on preferential solute transport

2014 ◽  
Vol 11 (8) ◽  
pp. 9551-9588 ◽  
Author(s):  
M. Larsbo ◽  
J. Koestel ◽  
N. Jarvis
Keyword(s):  
Hydraulic Conductivity ◽  
Solute Transport ◽  
Flow Rate ◽  
Saturated Hydraulic Conductivity ◽  
Degree Of Saturation ◽  
State Variables ◽  
Local Connectivity ◽  
Soil Matrix ◽  
Network Characteristics ◽  
Preferential Transport

Abstract. In this study we examined the relationships between macropore network characteristics, hydraulic properties and state variables and measures of preferential transport in undisturbed columns sampled from four agricultural topsoils of contrasting texture and structure. Macropore network characteristics were computed from 3-dimensional X-ray tomography images of the soil pore system. Non-reactive solute transport experiments were carried out at five steady-state water flow rates from 2 to 12 mm h−1. The degree of preferential transport was evaluated by the normalised 5% solute arrival time and the apparent dispersivity calculated from the resulting breakthrough curves. Near-saturated hydraulic conductivities were measured on the same samples using a tension disk infiltrometer placed on top of the columns. Results showed that many of the macropore network characteristics were inter-correlated. For example, large macroporosities were associated with larger specific macropore surface areas and better local connectivity of the macropore network. Generally, an increased flow rate resulted in earlier solute breakthrough and a shifting of the peak concentration towards smaller drained volumes. Columns with smaller macroporosities, poorer local connectivity of the macropore network and smaller near-saturated hydraulic conductivities exhibited a greater degree of preferential transport. This can be explained by the fact that, with only two exceptions, global (i.e. sample-scale) continuity of the macropore network was still preserved at low macroporosities. Thus, for any given flow rate pores of larger diameter were actively conducting solute in soils of smaller near-saturated hydraulic conductivity. With less time for equilibration between the macropores and the surrounding matrix the transport became more preferential. Conversely, the large specific macropore surface area and well-connected macropore networks associated with columns with large macroporosities limit the degree of preferential transport because they increase the diffusive flux between macropores and the soil matrix and they increase the near-saturated hydraulic conductivity. The normalised 5% arrival times were most strongly related with the estimated hydraulic state variables (e.g. with the degree of saturation in the macropores R2 = 0.589), since these combine into one measure the effects of irrigation rate and the near-saturated hydraulic conductivity function, which in turn implicitly depends on the volume, size distribution, global continuity, local connectivity and tortuosity of the macropore network.

Influence of compaction conditions on pore-size distribution and saturated hydraulic conductivity of a glacial till

2000 ◽  
Vol 37 (6) ◽  
pp. 1184-1194 ◽  
Author(s):  
Y Watabe ◽  
S Leroueil ◽  
J -P Le Bihan
Keyword(s):  
Hydraulic Conductivity ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Void Ratio ◽  
Glacial Till ◽  
Degree Of Saturation ◽  
Size Distributions ◽  
Pore Size Distributions ◽  
Compaction Degree

The paper examines the hydraulic conductivity of a nonplastic till from northern Quebec. It is shown that the hydraulic conductivity is strongly influenced by the compaction degree of saturation, and the variation of hydraulic conductivity with void ratio is influenced by compaction conditions. Determination of pore-size distributions and microphotographs provide evidence that changes in hydraulic conductivity are related to the fabric of the compacted specimens and macroporosity developing when the soil is compacted at degrees of saturation less than that at the optimum.Key words: till, hydraulic conductivity, microfabric.

Suction Stress in Unsaturated Soils Considering Hydraulic Hysteresis

2020 ◽  
pp. 110-123
Author(s):  
J. Ramírez Jiménez ◽  
J. M. Horta Rangel ◽  
M. L. Pérez Rea ◽  
E. Rojas González ◽  
T. Lopez Lara ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Unsaturated Soils ◽  
Time Lag ◽  
Degree Of Saturation ◽  
Soil Suction ◽  
Two Dimensional ◽  
Suction Stress ◽  
Hydraulic Hysteresis ◽  
Transient Thermal ◽  
Over Time

Aims: To develop a flow-moisture model that allows determining the variation of suction over time, as well as the suction stresses, using the finite element method in a two-dimensional model of unsaturated soil through an analogy with a transient thermal problem. Study Design: The variables used in this study were soil suction, hydraulic conductivity, diffusivity and degree of saturation which was represented as the  parameter of the Bishop’s effective stress equation. Place and Duration of Study: Graduate Engineering Department, Universidad Autónoma de Querétaro, between November 2019 and August 2020. Methodology: To establish the model, experimental Soil-Water Retention Curve was taken from Galaviz (2016). With this information, the curves of hydraulic conductivity and diffusivity were calculated with the methods of Fredlund et al. (2012) and Li (1996). In ANSYS 19.2, an analogous transient thermal analysis was run to determine suction changes over time in a 12 x 2.4 meters two-dimensional medium with an impermeable membrane at the center of its surface which was 4.8 meters long. Through these suction changes, the hydraulic hysteresis algorithm presented by Zhou et al. (2012) was used to calculate the respective degrees of saturation, which were considered as the  parameter to obtain the suction stresses. Results: The changes in soil suction, degree of saturation and suction stress were properly modeled. Conclusion: When considering the hydraulic hysteresis cycles, both spatial and temporal variations behaved in a similar way in the  parameters as well as in the suction stresses. Such stresses depended on the analysis period, increasing in the dry season, according to the precipitation-evapotranspiration model, and decreasing in the wetting season. A time lag was observed between the maximum and minimum stresses as greater depths were studied. Along the horizontal axis, considering the same depth, the stresses varied more in the areas adjacent to the impermeable membrane, while at the center this variation was practically null.

Hydrogeotechnical characterization of a metallurgical waste

2006 ◽  
Vol 43 (10) ◽  
pp. 1042-1060 ◽  
Author(s):  
R Rodríguez
Keyword(s):  
Tensile Strength ◽  
Hydraulic Conductivity ◽  
Cyclic Load ◽  
Water Pressure ◽  
Degree Of Saturation ◽  
Water Retention Curve ◽  
Triaxial Tests ◽  
Drying Process ◽  
Metallurgical Waste

This paper presents the results of hydrogeotechnical characterization tests carried out on the metallurgical waste (MW) from a tailings impoundment located on the terraces of the Moa River, Cuba. Characterization of the MW includes chemical and mineralogical analysis, oedometer tests, triaxial tests, tensile strength tests, determination of the water retention curve, and shrinkage and permeability tests. The MW, which has a grain-size distribution similar to that of a silt, mainly contains iron and heavy metals minerals and has low plasticity. Consolidated undrained triaxial tests on remoulded samples indicate a dilative behaviour, with a decrease in pore-water pressure near failure. The material is susceptible to liquefaction when subjected to a cyclic load in the triaxial test. Hydraulic conductivity, soil stiffness, and compressive and tensile strength of the MW have an important dependence on the degree of saturation and vary significantly during the drying process. The results indicate that, during the drying process, cracks in the MW initiate in quasi-saturated conditions. The cracks increase the hydraulic conductivity by more than one order of magnitude compared with that of intact samples of MW. The main environmental risk with this MW is the possibility of liquefaction under a cyclic load due to an earthquake and the increase in saturated hydraulic conductivity due to desiccation cracks.Key words: desiccation cracks, hydrogeotechnical properties, liquefaction, metallurgical waste, characterization.

scholarly journals Effect of hydraulic conductivity of unsaturated soil on the earth dam performance

2018 ◽  
Vol 162 ◽  
pp. 01008
Author(s):  
Mohammed Fattah ◽  
Mahmood Ahmed ◽  
Nawar Ali
Keyword(s):  
Hydraulic Conductivity ◽  
Water Level ◽  
Water Levels ◽  
Degree Of Saturation ◽  
Earth Dam ◽  
Core Material ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Partially Saturated ◽  
The Core

In this paper, the finite element method is uzed to solve the governing equations of flow through earth dams. The computer program Geo-Slope is used in the analysis through its sub-program named SEEP/W. A case study is considered to be Al-Adhaim dam which consists of zoned embankment with a total length of 3.1 km. The dam in its actual design is analyzed. Then, an attempt is made to study the seepage in unsaturated zone of the dam through studying the effect of several parameters including the effect of changing the unsaturated hydraulic conductivity with the degree of saturation of the core soil and changing of water level in the reservoir. A procedure is proposed to define the hydraulic conductivity function from the soil water characteristic curve which is measured by the filter paper method. Fitting methods are applied through the program SoilVision. A parametric study was carried out and different parameters were changed to study their effects on the behavior of partially saturated soil. The study reveals that the rate of flow is decreased by about 20 - 27% when the degree of saturation of the core material is decreased from 100% to 50% at water level 115.75 m, while the exit gradient of flow is decreased by about 13 -15%. This decrease in flow rate becomes 13-15% and 8-9.5% when the reservoir water level is 131.5 m and 143.5 m, respectively, while the exit gradient of flow is increased by about 23-29.5% and 29-29.5% when the reservoir water level is 131.5 m and 143.5 m, respectively. When the state of soil changes from fully saturated S= 100% to partially saturated S= 90%, a rapid increase in head gradient and pore water takes place at the embankment base for different water levels in the reservoir. This decrease plateaus out on further decrease in the degree of saturation.

Hydraulic conductivity of clays in confined tests under low hydraulic gradients

1999 ◽  
Vol 36 (5) ◽  
pp. 815-825 ◽  
Author(s):  
D A Dixon ◽  
J Graham ◽  
M N Gray
Keyword(s):  
Hydraulic Conductivity ◽  
Reasonable Agreement ◽  
Initial Density ◽  
Degree Of Saturation ◽  
Low Flow ◽  
Flow Rates ◽  
Initial Degree ◽  
Hydraulic Gradients ◽  
Clay Barriers ◽  
Conductivity Gradient

Clay barriers normally function at hydraulic gradients much lower than are commonly used in laboratory tests for hydraulic conductivity. This paper describes low-gradient tests on compacted illite, Na-bentonite, and sand-bentonite specimens at a range of dry densities. The tests examined the effects of deionized or saline pore fluid, the initial degree of saturation at the time of compaction, and back-pressuring to achieve saturation during permeation. No "critical" or "threshold" gradients were observed. In low-density materials, "transitional" gradients defined two separate regions of Darcian flow. Low flow rates and low hydraulic conductivities were associated with hydraulic gradients below the transitional gradient. Higher conductivities were associated with gradients above the transitional gradient. Hydraulic conductivities decreased with increasing initial density. They appeared independent of initial degree of saturation or back-pressuring. Tests on Na-rich bentonite showed that deionized and saline permeants produced similar hydraulic conductivities. Measured hydraulic conductivities were in reasonable agreement with values computed using the Poiseuille and Kozeny-Carman equations. Key words: hydraulic conductivity, gradient, Darcian, illite, bentonite.

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