Determination Of Hydraulic Properties Research Articles

Determination of hydraulic properties of shallow aquifer from electrical resistivity and pumping test data in Aragba-Okpe Delta State Nigeria

Determination of hydraulic properties of shallow aquifer from electrical resistivity and pumping test data in Aragba-Okpe Delta State Nigeria

Determination of hydraulic properties of shallow aquifer from electrical resistivity and pumping test data in Aragba-Okpe Delta State Nigeria

Determination of hydraulic properties of shallow aquifer from electrical resistivity and pumping test data in Aragba-Okpe Delta State Nigeria

Estimating Aquifer Hydraulic Properties in Bida Basin, Central Nigeria Using Empirical Methods

An evaluation of the aquifer properties of the inland sedimentary Bida basin, central Nigeria, was conducted using empirical methods derived from particle size distribution curves. The main aquifer properties determined were hydraulic conductivity, porosity, effective porosity and coefficient of uniformity. Samples for analysis were obtained from test water wells drilled to 100m in selected parts of the Basin. The empirical method used was the Hazens method, while porosity was determined in the laboratory. The results show that three levels of aquifers generally exist in the Basin. The aquifer material consist of well sorted medium sand to fine gravel. The upper aquifer occurs at a depth of between 10 – 18m and has a hydraulic conductivity of 18.5m/d and effective porosity of 9.0. The second, or middle, aquifer occurs at a depth of between 45 – 65m and has a hydraulic conductivity of 37m/d and effective porosity of 20. The third, or lower, aquifer occurs between 80 – 100m and has a hydraulic conductivity of 32m/d and effective porosity of 24. Effective porosity generally increases with depth in the basin indicating coarsening up of the sandstone with fewer fine grained cementing material. Mean hydraulic conductivity value is 29.16m/d, porosity 63%, effective porosity of 6.7 and coefficient of uniformity of 2.8. The results have therefore shown that it is possible to obtain quantitative results from particle size distribution curves that are useful for the determination of hydraulic properties of aquifers.

Numerical study of the evaporation process and parameter estimation analysis of an evaporation experiment

Abstract. Evaporation is an important process in soil-atmosphere interaction. The determination of hydraulic properties is one of the crucial parts in the simulation of water transport in porous media. Schneider et al. (2006) developed a new evaporation method to improve the estimation of hydraulic properties in the dry range. In this study we used numerical simulations of the experiment to study the physical dynamics in more detail, to optimise the boundary conditions and to choose the optimal combination of measurements. The physical analysis exposed, in accordance to experimental findings in the literature, two different evaporation regimes: (i) a soil-atmosphere boundary layer dominated regime (regime I) close to saturation and (ii) a hydraulically dominated regime (regime II). During this second regime a drying front (interface between unsaturated and dry zone with very steep gradients) forms which penetrates deeper into the soil as time passes. The sensitivity analysis showed that the result is especially sensitive at the transition between the two regimes. By changing the boundary conditions it is possible to force the system to switch between the two regimes, e.g. from II back to I. Based on this findings a multistep experiment was developed. The response surfaces for all parameter combinations are flat and have a unique, localised minimum. Best parameter estimates are obtained if the evaporation flux and a potential measurement in 2 cm depth are used as target variables. Parameter estimation from simulated experiments with realistic measurement errors with a two-stage Monte-Carlo Levenberg-Marquardt procedure and manual rejection of obvious misfits lead to acceptable results for three different soil textures.

Hydraulic Property Estimation Using Piezocone Results

Governing underground water flow, hydraulic properties such as hydraulic conductivity or coefficient of consolidation are major geotechnical parameters. Determination of hydraulic properties, however, is traditionally time consuming and expensive. This research proposes an easy and economical way of determining the hydraulic properties of soils through piezocone penetration tests. Pore pressure responses of soils from piezocone penetration tests are numerically analyzed herein by the coupled theory of mixtures, which is based on the large strain elastoplasticity. Using the numerical results, the effects of input parameters are evaluated. Simple equations are also derived for a faster estimation of the hydraulic conductivity or the coefficient of consolidation of soils. The hydraulic properties predicted by these derived equations agree reasonably with the measured results.

Reprint of “Multi-step and two-step experiments in heterogeneous porous media to evaluate the relevance of dynamic effects”

The determination of hydraulic properties in non-stationary experiments is suspected to be affected by dynamic effects. This is based on thermodynamic considerations on the pore scale displacement of wetting and non-wetting phase. But also macroscopic heterogeneities at the continuum scale may influence the dynamics of water during drainage and wetting. In this paper we investigate both aspects. Firstly, we present the results of typical multi-step outflow experiments in heterogeneous sand columns which are compared with two-step outflow experiments covering the same pressure range. The discrepancies caused by pressure steps of different size reveal the impact of dynamic effects due to the non-stationarity of the experiments. Secondly, the influence of macroscopic heterogeneities is investigated based on two-dimensional heterogeneous parameter fields where we compare static hydraulic properties with those obtained from simulated dynamic experiments. These analyses are restricted to numerical experiments because the focus is on the effect of heterogeneities and not on the validity of the applied model (i.e. Richards equation). We found that dynamic effects are not critical neither during the non-stationary experiments nor for heterogeneous parameter fields. This is a positive message for the usage of multi-step outflow experiments to estimate hydraulic parameters. A prerequisite for this clear statement was the introduction of a highly flexible parametrization of the pressure-saturation relation ψ( θ) which has the only physical constraint to be monotone.

Multi-step and two-step experiments in heterogeneous porous media to evaluate the relevance of dynamic effects

The determination of hydraulic properties in non-stationary experiments is suspected to be affected by dynamic effects. This is based on thermodynamic considerations on the pore scale displacement of wetting and non-wetting phase. But also macroscopic heterogeneities at the continuum scale may influence the dynamics of water during drainage and wetting. In this paper we investigate both aspects. Firstly, we present the results of typical multi-step outflow experiments in heterogeneous sand columns which are compared with two-step outflow experiments covering the same pressure range. The discrepancies caused by pressure steps of different size reveal the impact of dynamic effects due to the non-stationarity of the experiments. Secondly, the influence of macroscopic heterogeneities is investigated based on two-dimensional heterogeneous parameter fields where we compare static hydraulic properties with those obtained from simulated dynamic experiments. These analyses are restricted to numerical experiments because the focus is on the effect of heterogeneities and not on the validity of the applied model (i.e. Richards equation). We found that dynamic effects are not critical neither during the non-stationary experiments nor for heterogeneous parameter fields. This is a positive message for the usage of multi-step outflow experiments to estimate hydraulic parameters. A prerequisite for this clear statement was the introduction of a highly flexible parametrization of the pressure-saturation relation ψ( θ) which has the only physical constraint to be monotone.

Determination of Hydraulic Properties in Sloping Landscapes from Tension and Double-Ring Infiltrometers

The majority of landscapes, natural or cultivated, are nonlevel. However, specifically designed instruments are not available for estimation of soil hydraulic properties in sloping landscapes. The objective of this study is to examine if tension and double-ring infiltrometers are suitable for determination of soil hydraulic properties on sloping soil surfaces. A field experiment was conducted in a silt loam soil (Typic Haplustolls) in Saskatchewan, Canada to explore the usefulness of tension and double-ring infiltrometers for the determination of soil hydraulic properties in sloping landscapes. Soil surfaces were created to represent four treatments, 0 (level), 7, 15, and 20% slopes. For each treatment, water infiltration rates were measured using a double-ring infiltrometer and a tension infiltrometer at −3, −6, −10, −13, −17, and −22 cm water pressure heads. In addition, three-dimensional computer simulation studies were performed for a tension infiltrometer with various disc diameters and water pressure heads for different surface slopes. Steady-state infiltration rate, field-saturated hydraulic conductivity, unsaturated hydraulic conductivity as a function of water pressure head, macroscopic capillary length parameter, and water-conducting macro- and mesoporosity were compared for different surface slopes. These parameters were not significantly different (p < 0.05) between level and sloping lands. Experimental and numerical results of this study suggest that both tension and double-ring infiltrometers are suitable for characterization of surface soil hydraulic properties in landscapes with slopes up to 20%.

Determination of Hydraulic Properties in Sloping Landscapes from Tension and Double‐Ring Infiltrometers

The majority of landscapes, natural or cultivated, are nonlevel. However, specifically designed instruments are not available for estimation of soil hydraulic properties in sloping landscapes. The objective of this study is to examine if tension and double‐ring infiltrometers are suitable for determination of soil hydraulic properties on sloping soil surfaces. A field experiment was conducted in a silt loam soil (Typic Haplustolls) in Saskatchewan, Canada to explore the usefulness of tension and double‐ring infiltrometers for the determination of soil hydraulic properties in sloping landscapes. Soil surfaces were created to represent four treatments, 0 (level), 7, 15, and 20% slopes. For each treatment, water infiltration rates were measured using a double‐ring infiltrometer and a tension infiltrometer at −3, −6, −10, −13, −17, and −22 cm water pressure heads. In addition, three‐dimensional computer simulation studies were performed for a tension infiltrometer with various disc diameters and water pressure heads for different surface slopes. Steady‐state infiltration rate, field‐saturated hydraulic conductivity, unsaturated hydraulic conductivity as a function of water pressure head, macroscopic capillary length parameter, and water‐conducting macro‐ and mesoporosity were compared for different surface slopes. These parameters were not significantly different (p &lt; 0.05) between level and sloping lands. Experimental and numerical results of this study suggest that both tension and double‐ring infiltrometers are suitable for characterization of surface soil hydraulic properties in landscapes with slopes up to 20%.

間隙水圧の気圧変動応答,地球潮汐応答を用いた水理特性評価技術の展望

間隙水圧の気圧変動応答,地球潮汐応答を用いた水理特性評価技術の展望

Field measurement of soil hydraulic properties characterizing water movement through swelling clay soils

Determination of hydraulic properties in swelling clay soils is difficult due to seasonal variations in pore geometry and to soil structural heterogeneity, requiring large samples. Large in situ columns are therefore prepared to measure K sat and K unsat near saturation, using the crust test. Soil structure descriptions can be used to estimate optimal sample size. Infiltration into dry or moist clay soil with vertically continuous cracks involves preferential vertical movement of water along the cracks. The resulting irregular moisture distribution does not allow use of many common soil physical techniques, which require homogeneous moisture contents in isotropic soil.