Dissertations / Theses on the topic 'Unsaturated hydraulic conductivity'

Unsaturated hydraulic conductivity was measured using four different methods. Tension permeameters were used to measure unsaturated hydraulic conductivity in the field, using a single disc method, which depends on the measurements of sorptivity, steady state flow rate, initial and final water content (White and Perroux, 1987, 1989). Also, a double disc method was used which utilizes Wooding's (1968) equation for two different disc radii at the same tension for steady state flow rates. Undisturbed and disturbed soil cores were used to measure unsaturated hydraulic conductivity in the lab, using water retention curves with van Genuchten's equations. There were no significant differences in the mean of hydraulic conductivity between single and double disc methods in all the tensions used (0, 5, 10 and 15 cm). There were significant differences between the field methods and undisturbed soil cores in zero cm tension, and disturbed soil cores in 10 and 15 cm tension. The effect of land preparation on the unsaturated hydraulic conductivity was studied using the double disc method. Tilling has significant effects on the unsaturated hydraulic conductivity at all tensions used. The spatial variation of unsaturated hydraulic conductivity and steady state flow in different tensions using the double disc method was studied. We found exponential variogram models for unsaturated hydraulic conductivity at 5, 10 and 15 cm tensions and a random model for zero cm tension. Also, exponential models were best fitted for steady state flow corresponding to pores radii of 0.03 - 0.015 cm, 0.015 - 0.010 cm and steady state flow at 10 cm tension. A Michaelis-Menton model was used for steady state flow at 5 cm and 15 cm tension. Disc permeameters were also used to add 5 cm depth of water, bromide and dye solution at 0, 5, 10 and 15 cm tensions with three replicates. A comparison was made between field data and simulated model under the same boundary and initial conditions as in the field. Results showed that the water and bromide move deeper than the prediction of the simulated model in all tensions used. The differences were larger between simulated model and field data for both water and bromide concentrations in the lower tension and smaller in the higher tension as a result of elimination of some preferential flow paths. An equation was developed for cumulative infiltration valid for both small and large time. The parameters calculated using the developed equation closely matched the measured infiltration, and fit better than a three term series similar to the Philip equation for one-dimensional flow.

Accurate estimates of field-scale hydraulic conductivities of unsaturated heterogeneous soils are very difficult to obtain. In the present study, various approaches to determining effective conductivity values for heterogeneous sands are compared with laboratory measurements. The unsaturated hydraulic conductivity, K(Ψ), of two homogeneous sands and one layered sand composed of the two homogeneous sands was measured using the steady-state flux control method. A van Genuchten model and an exponential model were fitted to the data. Various means of the homogeneous sand fitted K(Ψ) curves were compared with the layered sand K(Ψ) data using a direct averaging approach. The observed suction head variance, effective hydraulic conductivity, and the anisotropy were compared with expressions developed from stochastic theory. The results qualitatively support the stochastic approach. The outcome of the direct averaging approach was inconclusive however. Additional laboratory and field experimentation is needed.

A tension infiltrometer for field use, where both water level changes measurement and tension settings could be automated, was built in-house. Differential pressure transducers were used to automate the water level measurement in the reservoir. The Mariotte bottle was automated by a set of solenoid valves which were connected via tubing to pre-defined depths in the Mariotte bottle. Based on design parameters tested in the laboratory (sensor sensitivity, water reservoir diameter, and bubbling rate) three identical tension infiltrometers connected to a single Mariotte bottle were built. A new reservoir system made of two plexiglass tubes of different diameter slotted in each other was found to reduce the measurement fluctuations caused by the disturbance created to rising bubbles in the reservoir. The new system was tested on a uniform sandy loam profile prepared in the soil bin laboratory and different analytical and numerical data analysis methods were compared. The measured steady state data were used to determine K(h) at different suctions using the analytical method proposed by Reynolds and Elrick (1991). The K(h) points obtained were fitted with the van Genuchten’s equation (van Genuchten, 1980) using the RETC program to calculate the best fit parameters Ks,  and n. These parameters were used as initial estimates of the soil hydraulic parameters in the numerical models HYDRUS 1D and 2D, in which transient cumulative flow data was used to determine the soil hydraulic functions via inverse modelling. The analysis of variance determined significantly higher K(h) values calculated by HYDRUS 1D while the other methods did not differ from each other. Finally, the tension infiltrometer was used in the field on a sandy loam soil to characterise five different tillage treatments (conventional plough, shallow plough, minimum tillage, direct drill, and no-tillage). The effect of wheel traffic was also evaluated by measuring the infiltration rates in the wheel-marks. The fully automated system allowed the measurement of infiltration rates for 8 tensions in triplicate per day with hardly any human intervention apart for refilling the reservoir. The results show that the tillage practices and wheel-traffic have a significant influence on the soil hydraulic function K(h).

Conductivité hydraulique non saturée est un paramètre important pour caractériser le comportement des sols non saturés. Ce paramètre peut être utilisé pour modéliser l'écoulement de l'eau dans les sols. Le défaut de mesure ou d'estimation de ce paramètre avec une précision fiable peut causer des incidents catastrophiques. La mesure de la conductivité hydraulique des sols non saturés peut être longue et coûteuse. Des méthodes directes et indirectes peuvent être utilisées pour établir ce paramètre. Dans cette étude, en vue de réduire le temps et le coût de la mesure de la conductivité hydraulique des sols non saturés nécessaires par les méthodes directes, la modélisation inverse a été utilisée comme une méthode indirecte pour estimer ce paramètre. Des essais de laboratoire ont été effectués pour trouver la courbe de rétention d'eau des différents échantillons de sol étudié. Les résultats expérimentaux obtenus ont été utilisés pour effectuer la modélisation inverse, et la conductivité hydraulique non saturée de chaque échantillon a été estimé.<br>Unsaturated hydraulic conductivity is an important parameter to characterize unsaturated soils behaviour. This parameter can be used to model flow of water in soils. Failure in measuring or estimating this parameter with a reliable precision can cause catastrophic incidents. Measuring unsaturated hydraulic conductivity can be expensive and time consuming. Direct and indirect methods can be used to determine this parameter. In this study, in order to decrease the time and the expense of measuring unsaturated hydraulic conductivity by direct methods, inverse modelling was used as an indirect method to estimate this parameter. Some laboratory tests were performed to find water retention curve of different samples of the studied soil. Obtained experimental results were used to perform inverse modelling, and unsaturated hydraulic conductivity of each sample was estimated.

Knowledge of unsaturated zone hydraulic properties is critical for many environmental and engineering applications. Various stochastic methods have been developed during the past two decades to estimate the effective unsaturated hydraulic properties. Independent of these stochastic methods, we develop in this paper a practical approach to estimate the three-dimensional (3 -D) effective unsaturated hydraulic conductivity tensor using spatial moments of 3-D snapshots of a moisture plume under transient flow conditions. approach hydraulic hydraulic Application of the new to a field site in southeastern Washington State yields an effective unsaturated conductivity tensor that exhibits moisture- dependent anisotropy. The effective conductivities compare well with laboratory- measured unsaturated hydraulic conductivity data from small core samples; they also reproduce the general behavior of the observed moisture plume at the site. We also define a moisture diffusivity length concept which we use in conjunction with estimated correlation scales of the geological media at the field site to explain deviations between the observed and simulated plumes based on the derived effective hydraulic properties.

Permeable Interlocking Concrete Pavements (PICP) have seen increased popularity in the principles of Water Sensitive Urban Design and Sustainable Drainage Systems in recent years. To address certain design queries that still existed in industry, a two-year experimental study was conducted. It entailed the construction of an Infiltration Table Apparatus and subjecting a representative volume of PICP to hydraulic testing within it. The study aimed at determining the controls of the flow of water into and through these pavements, the effect of variations in construction materials and incline on them, the validity of the hydraulic testing methods currently being applied to them in industry and lastly, to inform on their infiltration rates. A host of permeability data for PICP was gained and it was found that both the choice of materials and the incline on which PICP are constructed, can change their hydraulic properties drastically. In general, the selection of lower permeability materials in the surface portion of the layer works decreased the overall permeability of the pavement, while increases in inclines did the same. In addition, it was found that field investigation techniques require revision and further innovation before they can be effectively applied to PICP.<br>Dissertation (MSc)--University of Pretoria, 2019.<br>Bosun Brick (Pty) Ltd.<br>Geology<br>MSc<br>Unrestricted

The importance of applying unsaturated soil mechanics concepts to geotechnical engineering design has been widely recognized. Soil water characteristic curve (SWCC) and hydraulic conductivity function (HCF) are vital soil properties that govern engineering behavior of unsaturated soils. In this study, a transient water release and imbibitions method (TRIM) is used to measure the SWCC and HCF under drying and wetting states, which accommodates integrated experimental and modeling techniques. The results of saturated hydraulic conductivity tests through flexible wall method are then used as input parameters for simulating experimental data. In general, the model provides a satisfactory fit to experimental data. Soil water characteristic curves (SWCCs) and hydraulic conductivity functions (HCFs) are presented for a variety of soils that were prepared at different molding water contents and compactive efforts. The influences of dry density, molding water content, and hysteresis have been investigated. Dry density affects soil-water characteristic in terms of its air-entry value (AEV), rate of drying, and size of the hysteresis loop. The test results indicate that the SWCC and HCF obtained in terms of volumetric water content is more sensitive to the changes in dry density than molding water content. Based on cohesive soil results, some statistical relations are proposed to estimate wetting-path SWCC and HCF parameters from more easily measured drying curves. Changes in the van Genuchten's fitting parameters and residual volumetric water content are investigated for both drying and wetting conditions, with changes in the kaolin clay content.<br>Master of Science

Hydraulic conductivity of variably-saturated soils is critical to understanding processes at the land surface. Yet measuring it over an area comparable to the resolution of land-surface models is fraught because of its strong spatial and temporal variations, which render point measurements nearly useless. We derived unsaturated hydraulic conductivity at the horizontal scale of hectometers and the vertical scale of decimeters by analyzing trends in soil moisture measured using the cosmic-ray neutron method. The resulting effective hydraulic conductivity remains close to its value at saturation over approximately half of the saturation range and then plummets. It agrees with the aggregate of 36 point measurements near saturation, but becomes progressively higher at lower water contents; the difference is potentially reconcilable by upscaling of point measurements. This study shows the feasibility of the cosmic-ray method, highlights the importance of measurement scale, and provides a route toward better understanding of land-surface processes.

The diploma thesis is focused on issues of measurement and evaluation of hydraulic characteristics of soil. In the literary research, the definitions of hydraulic conductivity and retention curve of soil moisture, their measurements in laboratory and field conditions and the prediction of these characteristics by using of pedotransfer functions. In the practical part of the diploma thesis, an evaluation of the hydraulic conductivity of soil from the experimental areas near the village Bohaté Málkovice. Two-cylindrical and mini-disc infiltration meters were used for field measurements, and a constant-gradient permeameter was used in the laboratory. Physical and empirical equations were used to evaluate the hydraulic conductivity. The results were processed numerically, tabulated and then compared.

A problem common to many studies involving the use of unsaturated flow and chemical models is determining a representative expression for the value of unsaturated hydraulic conductivity K(ψ). A new steady-state inverse methodology called the multi-step steady-state outflow method (MSSOM) is presented here for the determination of unsaturated hydraulic conductivity. The method offers a practical alternative for the estimation of K(ψ) using either the exponential model, three-parameter model, or the van Genuchten formulations for K(ψ), a global-optimization simplex routine (MSSOM.EXE), and simple outflow data from a one-dimensional column experiment. The inverse technique was applied to a coarse sand and both the wetting an drying curves were well within the range of K(ψ) expected. Conductivity data from four other soils in the literature were then fitted using a curve fitting routine (RETC.F77) by van Genuchten, 1985 and compared to the inverse solution from the MSSOM model. The parameters for the K(ψ) expressions from both RETC and the MSSOM inverse model agreed well. Additional refinement of the multi-step steady-state outflow laboratory apparatus and the optimization program MSSOM.EXE are needed however to further improve the method.

This thesis deals with the theoretical description of the infiltration process and field measurements of infiltration in the cadastral territory of Bohaté Málkovice. The research work carried out in 2011 in an experimental area on Haplic Chernozem/FAO, medium-heavy loam soil. The experimental area was divided into two parts, the topsoil layer on these surfaces was processed by both classic and minimization technologies. The plots were sown by spring barley. The applied measurements of water infiltration into the soil were two-cylinder method and MiniDisc. Within the vicinity of the infiltration experiments with intact soil were collected samples for laboratory determination of saturated hydraulic conductivity. From the field measurements and laboratory experiments were determined values of hydraulic conductivity (saturated and unsaturated), and other infiltration characteristics, the cumulative infiltration and infiltration rate. To evaluate the infiltration of the heats was used three-paramether Philp type equation that provides a good estimate of saturated hydraulic conductivity. For the evaluation of the MiniDisc there was used the Zangova method that provides the unsaturated hydraulic conductivity. The laboratory evaluation of the saturated hydraulic conductivity was compared with the estimated values obtained from the field measurements. The values of the saturated hydraulic conductivity from the laboratory measurements are closely comparable with estimates obtained from the steady infiltration rates from the field experiments. The research results also showed that medium-heavy loam soil, when being processed by minimization including modification of the soil surface by digging, have a positive effect on the infiltration of water into the soil. This fact leads to a higher protection plants in the vegetative period and improvement of the retention and storage capacity of soil.

La nécessite de prendre en considération le phénomène de la non-saturation, dont la caractéristique principale est le développement de pression négative ou succion, se fait actuellement principalement ressentir. Dans ce cadre, nous présentons des résultats expérimentaux relatifs à des essais de détermination de la conductivité hydraulique et des essais triaxiaux sur un limon non saturé. Deux méthodes de mesure de la conductivité hydraulique sont exposées. La première, basée sur le suivi du débit sortant lors de l'application d'une pression d'air (succion), permet d'étudier le couplage entre les variations volumétriques de l'échantillon et celles du volume d'eau drainée. Afin de mesurer très précisément ces petites variations, qui, bien évidemment, nécessitent un long temps d'expérience, un système de mesure de haute précision a été utilisé. La seconde méthode repose sur le principe des profils instantanés et permet de couvrir une large gamme de succion. Pour chaque méthode, les essais seront réalisés en drainage et en humidification. Les essais triaxiaux, sur les échantillons non saturés, ont été réalisés dans une cellule triaxiale à succion imposée

Esta tese apresenta um estudo sobre a resistência ao cisalhamento e a condutividade hidráulica de dois solos coluvionares não saturados situados na divisa dos estados do Rio Grande do Sul e Santa Catarina, em um dos trechos do Gasoduto Bolívia-Brasil. Esses solos são constituídos por sedimentos oriundos da Formação Serra Geral (basalto – Solo RO) e da Formação Botucatu (arenito – Solo AV). O trabalho de pesquisa realizado com esses solos tem seu enfoque dividido em duas partes principais: (1) obtenção direta da resistência ao cisalhamento e da função condutividade hidráulica em diferentes níveis de sucção, e (2) previsão indireta dessas propriedades a partir da determinação da curva característica do solo e de parâmetros geotécnicos saturados. As curvas características dos solos AV e RO, nas condições indeformada e remoldada (sem e com secagem prévia do solo), foram obtidas pelo uso combinado do método do papel filtro e da placa de sucção. Para as condições indeformada e remoldada sem secagem prévia, essas curvas exibiram um formato bimodal. A dessaturação é controlada pelos macroporos, para baixas sucções, e pelos microporos, para altas sucções. Para valores de sucção intermediários, praticamente não ocorre remoção de água do solo, devido, provavelmente, à ausência de poros com tamanho intermediário. Já as curvas características das amostras remoldadas com secagem prévia do solo tendem a apresentar um formato mais próximo do unimodal. A influência do índice de vazios inicial e da história de umedecimento e secagem no formato da curva é também discutida. A resistência ao cisalhamento dos solos estudados foi determinada em laboratório através de ensaios de cisalhamento direto convencionais e com sucção controlada. Os resultados, obtidos para amostras indeformadas e remoldadas sem secagem prévia, permitiram a determinação dos parâmetros de resistência ao cisalhamento c’, f’ e fb. Para determinação direta da função condutividade hidráulica do Solo AV foi construído um permeâmetro triaxial com controle de sucção, baseado no modelo apresentado por Huang et al. (1998). Esse equipamento foi utilizado para determinação da função condutividade hidráulica do Solo AV não saturado, em diferentes trajetórias de umedecimento e secagem. Os resultados evidenciaram que as amostras do Solo AV nas três condições de moldagem - indeformada, remoldada sem e com secagem - tendem a reproduzir o comportamento de dessaturação exibido nas curvas características. A função condutividade hidráulica apresenta inicialmente um decréscimo para sucções até 50 kPa, seguido por um valor praticamente constante, para sucções até 90 kPa.<br>This thesis presents a study about the shear strength and hydraulic conductivity of two unsaturated colluvium soils situated at the border between the states of Rio Grande do Sul and Santa Catarina, along one of the Bolivia-Brazil Gas Pipeline stretches. These soils are constituted by sediments originated from Serra Geral (basalt – sample RO) and Botucatu formations (sandstone - sample AV). The research performed with these soils had its focus divided in two main parts: (1) direct measurements of shear strength and hydraulic conductivity function at different suction levels and (2) indirect prediction of these properties from the soil-water characteristic curves and saturated geotechnical parameters. The soilwater characteristic curves of AV and RO Samples, in undisturbed and remolded conditions (without and with previous drying), were determined with both the filter-paper technique and the suction-plate technique. The undisturbed and remolded samples without previous drying showed a bimodal shape. The desaturation is controlled by the macropores for low suction values and by the micropores, for higher values. For intermediary suctions values, practically no removal of water from the sample occurs, possibly due to the lack of intermediate pore sizes. The remolded samples with previous drying tend to present a shape close to unimodal. The influences of void ratio and the drying and wetting history in the shape of the soil-water characteristic curve are also discussed. The shear strength of the studied soils was determined with conventional and suction-controlled direct shear tests. The results obtained for undisturbed and remolded samples without previous drying allowed the determination of shear strength parameters c’, f’ e fb. For the direct measurement of hydraulic conductivity function, a flexible-wall permeameter was built, based on the model presented by Huang et al. (1998). This equipment was used for determining the unsaturated hydraulic conductivity function of Sample AV in different drying and wetting paths. The results showed that Samples AV in the three molding conditions - undisturbed and remolded without and with previous drying – reproduced the desaturation behavior showed by the soil-water characteristic curves. The hydraulic conductivity function presents initially a decrease for suctions up to 50 kPa, followed by a practically constant value, for suctions up to 90 kPa.

A função condutividade hidráulica é um dos parâmetros essenciais para o estudo do fluxo em solos não saturados, permitindo abordar, dentre outros, o avanço da frente de umedecimento e questões como a irrigação e drenagem de solos. Para determinar a condutividade hidráulica não saturada de um solo típico da região Centro-Oeste do Estado de São Paulo, utilizou-se o infiltrômetro de disco. Este equipamento permite conduzir a infiltração de água, estando esta sujeita a um potencial negativo. Com os dados de infiltração acumulada e tempo acumulado obtidos em cada ensaio, foi possível determinar os valores da condutividade hidráulica não saturada e sortividade. Os cálculos foram feitos por diferentes métodos para cada ensaio realizado com o infiltrômetro de disco e comparadas com resultados de ensaios utilizando o permeâmetro Guelph. Observou-se que as condutividades hidráulica não saturadas obtidas com o infiltrômetro de disco tenderam a valores próximos das fornecidas indiretamente por meio do permeâmetro Guelph, com dispersão de aproximadamente uma ordem de grandeza para cada sucção. Também se observou que a condutividade hidráulica não saturada tende a diminuir conforme aumenta a sucção imposta ao solo, mesmo considerando a estreita faixa de sucções usadas nos ensaios. Notou-se ainda pequena variação nas condutividades hidráulicas saturadas calculadas por meio do infiltrômetro de disco, por meio de medidas diretas utilizando o permeâmetro Guelph e ensaios de permeabilidade realizados em laboratório.<br>The hydraulic conductivity function is essential to the study of water flow in unsaturated soils. From function there can be derived the advancement of the humidification (saturation) front, among other parameters, which is essential to projects of irrigation and drainage of soils. A disk infiltrometer was used to determine the unsaturated hydraulic conductivity of a sample of typical soil from central São Paulo, Brazil. The disk infiltrometer apparatus conducts the infiltration water, which is held at negative potential. Data for cumulative infiltration and elapsed time for each test was used to determine values of unsaturated hydraulic conductivity and sorptivity. Different methodology was applied in the calculations. Data for each experiment carried out utilizing the disk infiltrometer was compared to data obtained utilizing the permeameter of Guelph. It was observed that the unsaturated hydraulic conductivity obtained through the disk infiltrometer yielded values near those obtained indirectly by the permeameter of Guelph, which showed dispersion approximately within one order of magnitude for each suctioning performed. Furthermore, it was observed that the unsaturated hydraulic conductivity tends to diminish in magnitude in an inverse relation to the suction pressure subjected by the soil, even after considering the narrow band of suction pressures carried out in the tests. It was further observed a small variation in the saturated hydraulic conductivities computed from data obtained directly from the infiltrometer disk, the permeameter of Guelph, and other permeability tests done in laboratory.

A condutividade hidráulica de dois solos não saturados típicos da região de São Carlos, um arenoso e outro argiloso é estudada através de ensaios de campo empregando o permeâmetro Guelph. Duas alternativas de ensaio foram empregadas e os resultados experimentais foram analisados com os modelo teóricos de REYNOLDS e ELRICK (1985) e PHILIP (1985). Paralelamente, obtiveram-se em laboratório curvas de retenção de água dos solos o que possibilitou determinar a função condutividade hidráulica através das fórmulas empíricas de VAN GENUCHTEN, (1980) e de GARDNER (1958). As características e a variação dos valores da condutividade hidráulica não saturada de campo fornecidos pelo permeâmetro Guelph, são discutidos e confrontados com aqueles obtidos a partir dos métodos indiretos provenientes de laboratório. Observou-se que as condutividades hidráulicas saturadas nos solos foram praticamente iguais, quer se considerem os resultados de campo ou laboratório. Os resultados de campo mostraram-se mais consistentes para o solo argiloso qualquer que tenha sido a técnica de ensaio. O parâmetro &#945 da equação de GARDNER (1958) obtido no campo resultou maior que o valor sugerido na literatura ou obtido em laboratório para o solo arenoso. Para o solo argiloso, todas as opções de obtenção do parâmetro tenderam a fornecer valores praticamente iguais.<br>The unsaturated hydraulic conductivity of two typical soils from the region of São Carlos City, sandy and clayey soils, has been studied through field tests using the Guelph permeameter. Two different alternatives of tests have been performed and the experimental data have been analyzed following the theoretical models from REYNOLDS and ELRICK (1985) and PHILIP (1985). However, soil-water characteristic curves were obtained in such a way that the hydraulic conductivity function could be evaluated using the empirical expressions from VAN GENUCHTEN (1980), and GARDNER (1958). The characteristics and the variation of the field unsaturated hydraulic conductivity values from the Guelph permeameter are discussed and compared to those from laboratory indirect methods. The field results showed to be more consistent to the clayey soil independent on the test or calculation method. The &#945 value (GARDNER, 1958) parameter obtained in the fields was Iarger than the values suggested in the literature or obtained in laboratory for the sandy soil. To the clayey soil, all the obtaining options of the parameter tended to supply values quite the same.

Made available in DSpace on 2015-03-26T12:34:15Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3072665 bytes, checksum: 5059ff6769784ba9baead96238de083b (MD5) Previous issue date: 2013-05-27<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>In geotechnical problems of flow, the main variables that characterize the hydraulic behavior in an unsaturated medium, is the water retention curve (WRC) and the hydraulic conductivity function (HCF) of the soil. Experimental determination of these properties is generally time-consuming and costly, leading professionals to use simplifications that may eventually prejudice the projects, increasing costs and compromising safety. In order to help reduce this difficulty, in this thesis, a procedure and equipment adapted into a small centrifuge commonly used in medical applications were developed, allowingto obtain hydraulic properties (WRC and HCF) of soils in a much shorter time. The technique involves exposing soil samples initially saturated to a circular motion, resulting in a centripetal acceleration and a mass force sufficient to overcome capillarity and force fluid drainage. The equipment is able to simultaneously obtain four WRCs and four HCFs. To verify the performance of the new equipment, two soils with different characteristics, one clayey sand (SC) and a high plasticity clay (CH), were tested. The WRCs obtained with the centrifugewere compared with ones obtained by traditional methods offilter paper and pressure plate. Comparisons were appropriate up to suctions of the order of 500 kPa, the current limit of the equipment developed. For soils that require higher suctions, a proposal was made to add to the data obtained with the centrifuge, a point given by the filter paper close to the residual moisture of the soil. The methodology for obtaining the HCF is of the transient type using multiple steps, in which one applies an increase in the matric suction value, and measure the volume of water that flows out of the specimen. The HCFs obtained by centrifugal method were compared with the one given by the theoretical model of van Genuchten- Mualen and points directly measured with a flexible wall permeameter and constant flow application developed by Guimarãeset. al. (2008).Comparisons were good, especially for the thicker texture soil (SC). The maximum times to obtain the WRCs and HCFs were two days for soil SC and three days for soil CH. The methodology is efficient and reduces, significantly, the time required to obtain hydraulic properties of soils.<br>Em problemas geotécnicos de fluxo, as principais variáveis que caracterizam o comportamento hidráulico em um meio não saturado, são a curva de retenção de água (CRA) e a função de condutividade hidráulica (FCH) do solo. A determinação experimental destas propriedades é, geralmente, demorada e onerosa, levando os profissionais a utilizar simplificações que, eventualmente, podem prejudicar osprojetos, aumentando os custos e comprometendo a segurança. No sentido de contribuir para diminuir esta dificuldade, desenvolveu-se nesta tese, um procedimento e aparatos que, adaptados em uma centrifuga de pequeno porte comumente usada em aplicações médicas, permitem obter as propriedades hidráulicas (CRA e FCH) de solos em um tempo bem menor. A técnica consiste em expor amostras de solos inicialmente saturadas a um movimento circular, gerando uma aceleração centrípeta e uma força de massa suficiente para vencer as forças capilares e forçar a drenagem do fluido. O equipamento é capaz de obter simultaneamente quatro CRAs e quatro FCH. Para verificar o funcionamento do novo equipamento, foram utilizados dois solos com características distintas, uma areia argilosa (SC) e uma argila de alta plasticidade (CH). As CRAs obtidas por meio da centrífuga foram comparadas com as CRAs obtidas pelos métodos tradicionais do papel filtro e da placa de pressão. As comparações foram adequadas até sucções da ordem de 500 kPa, atual limite do equipamento desenvolvido. Para solos que necessitem de sucções mais altas, foi apresentada uma proposta de acrescentar aos dados obtidos com a centrífuga, um ponto obtido por meio do papel filtro com umidade próxima da residual. A metodologia para obtenção da FCH é a do regime transiente por passos múltiplos, na qual se aplica um acréscimo no valor da sucção matricial e mede-se o volume de água que sai do corpo de prova. AsFCHs obtidas pelo método centrífugo foram comparadas com ado modelo teórico de van Genuchten-Mualen e com pontos medidos diretamente com um permeâmetro de parede flexível e aplicação de vazão constante desenvolvido por Guimarães et. al. (2008). As comparações ficaram boas, principalmente, para o solo com textura mais grossa (SC). Os tempos máximos para obtenção das CRAs e FCHs foram de dois dias para o solo SC e de três dias para o solo CH. A metodologia desenvolvida se mostrou eficiente, reduzindo substancialmente o tempo necessário para se obter as propriedades hidráulicas de solos.

The influence of soil water repellency (WR) on vegetation recovery after a fire is poorly understood. This dissertation presents strategies to broaden opportunities for enhanced post-fire rangeland restoration and monitoring of burned piñon and juniper (P-J) woodlands by: 1) mapping the extent and severity of critical and subcritical WR, 2) determining the influence of WR on soil ecohydrologic properties and revegetation success, and 3) evaluating the suitability of a wetting agent composed of alkylpolyglycoside-ethylene oxide/propylene oxide block copolymers as a post-fire restoration tool for ameliorating the effects of soil WR and increasing seedling establishment. Results indicate that: • Post-fire patterns of soil WR were highly correlated to pre-fire P-J woodland canopy structure. Critical soil WR levels occurred under burned tree canopies while sub-critical WR extended out to approximately two times the canopy radius. At sites where critical soil WR was present, infiltration rate, soil moisture, and vegetation cover were significantly less than at non-hydrophobic sites. These parameters were also reduced in soils with subcritical WR relative to non-hydrophobic soils (albeit to a lesser extent). Aerial photography coupled with feature extraction software and geographic information systems (GIS) proved to be an effective tool for mapping P-J cover and density, and for scaling-up field surveys of soil WR to the fire boundary scale. • Soil WR impairs seed germination and seedling establishment by decreasing soil moisture availability by reducing infiltration, decreasing soil moisture storage capacity, and disconnecting soil surface layers from underlying moisture reserves. Consequently, soil WR appears to be acting as a temporal ecological threshold by impairing establishment of desired species within the first few years after a fire. • Wetting agents can significantly improve ecohydrologic properties required for plant growth by overcoming soil WR; thus, increasing the amount and duration of available water for seed germination and seedling establishment. Success of this technology appears to be the result of the wetting agent increasing soil moisture amount and availability by 1) improving soil infiltration and water holding capacity; and 2) allowing seedling roots to connect to underling soil moisture reserves.

Diploma thesis evaluates quality and healthiness of the soil health located close to Bohate Malkovice focusing on changes in both physical and chemical characteristics of the soil in time. The theoretical part describes physical, chemical, and biological parameters of the soil. Selected physical parameters are structure, texture, determination of measured weight, bulk density of the soil, porosity, actual volumetric water content of the soil, aeration, saturated and unsaturated hydraulic conductivity, infiltration, and colour. Chosen chemical parameters are pH, carbonates, soil electrical conductivity, and humus content. Picked biological parameters are microbial biomass, respiration, nitrogen content, and weed infestation. The practical part analyses selected indicators of quality of the soil from the location of the experiment close to Bohate Malkovice. The area under evaluation has been treated using reduced tillage for long term. The practical part is based on the laboratory examination of disturbed and undisturbed soil samples taken between years 2016 and 2018. Based on outcome results we can evaluate the quality of the soil considering plants growth, development, and soil fertility.

L'utilisation, en centres de stockage de dechets, de materiaux deformables partiellement satures comme barrieres etanches rend necessaire la caracterisation de leurs proprietes hydrodynamiques, en particulier leur permeabilite. Ces dernieres sont examinees ici sous trois angles analytique, experimental et numerique. Si l'on suppose applicable la loi de darcy pour des milieux faiblement permeables, le transport de l'eau en milieu deformable peut etre modelise de maniere equivalente en coordonnees spatiales (formalisme eulerien) ou materielles (formalisme lagrangien). Les equations de transferts ainsi etablies relient les trois relations fonctionnelles retention, conductivite hydraulique et courbe de gonflement. L'analyse de l'infiltration en milieu non sature, tenant compte du chemin de deformation, permet alors d'introduire le concept de sorptivite apparente de la phase solide, complementaire de celui de sorptivite capillaire. Des techniques experimentales, de laboratoire (spectrometrie gamma double energie) et de terrain (infiltrometries a disques et a anneaux), sont ensuite appliquees a l'etude en regime transitoire de l'infiltration dans des materiaux compactes naturels (argiles) et artificiels (melange sable-bentonite). Enfin, les phenomenes experimentaux observes sont reproduits numeriquement a l'aide du code informatique wisp developpe pour l'occasion. Celui-ci permet l'etude des facteurs clefs de l'ecoulement en milieu peu permeable. Des differents resultats obtenus selon ces trois approches, on conclut que la capillarite est de loin le principal moteur du transport dans le type de milieux consideres. On montre par ailleurs que la prise en compte du gonflement et la bonne connaissance du chemin de deformation sont indispensables a une estimation correcte des proprietes hydrodynamiques.

Thesis (M.S.)--University of Wisconsin--Madison, 1994.<br>Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 159-167).

碩士<br>中興大學<br>水土保持學系所<br>95<br>The experimental system of hydraulic conductivity in the laboratory were setup, and the water characteristic curves were measured by pressure plate. Water characteristic curves and unsaturated hydraulic conductivity of different soil texture (sandy loam, clayey loam, loam) were obtained. The parameters of van Genuchten Model were obtained by curve fitting technique and then to calculate hydraulic conductivity. In order to understand whether this experiment could substitute for the pressure plate, and discusses the usable parameter of these three soils. The result shows that our experiment can obtain the best water characteristic curve in the clayey loam, next is the sandy loam, latter is the loam. The result of the unsaturated conductivity experiment shows that the most correct experiment is in the clayey loam, next is the loam, latter is the sandy loam. The parameters of the van Genuchten Model are α=0.00194, n=2.455; α=0.00168, n=2.695; α=0.00137, n=3.151 for sandy loam, loam and clayey loam respectively in this study.

碩士<br>國立中央大學<br>土木工程研究所<br>96<br>Deep geological disposal is considered by many countries as a feasible way for the final disposal of high-level radioactive wastes. Buffer material plays a major role for the isolation of radioactive wastes in an underground repository. This research investigates the unsaturated hydraulic conductivity and resaturation behavior of buffer material, with emphasis on the effects of soil suction of buffer material on the groundwater intrusion processes and the temperature effect. Soil suction of Zhisin clay and Black Hill (BH) bentoite were determined using vapor equilibrium technique on clay specimens so as to determine the relationship between soil suction and water content. Soil-water characteristic curve was fitted with the Fredlund model such that the hydraulic conductivity of clays in unsaturated conditions can be estimated. The finite element program ABAQUS was then employed to carry out the numerical simulation of the resaturation process in the near field of a repository. The results show that soil suction of BH behtonite is higher than Zhisin clay, and soil suction was found to decrease as the temperature increases. At a dry state, the soil suction will reach a maximum suction of 106 kPa. Results of the numerical simulation were validated using the degree of saturation profile obtained from the water uptake test on the two clays. The unsaturated behavior of highly plastic bentonite material shows important effects on the saturation behavior of the material.

碩士<br>國立臺灣大學<br>森林學研究所<br>92<br>This study applied on the hydraulic conductivity of the unsaturated forest soil in the Lien-Hwa-Chi area, and compared the deviation in hydraulic conductivity among different locations and depths. It’s helpful to understand the effective of water contain, soil pores, rough pores and roots of plants. The study area was located on the eastern slope in Lienhwachi watershed No.5. Measure the forest soil saturated hydraulic conductivity in different gradient, and choose 4 points, 3 depths on ridge, hillslope and valley. The study used the Tension Infiltrometer to measure the hydraulic conductivity and excavated undisturbed soil for physical test. It could tell the effectives of hydraulic conductivity by compared both of the results. These results show that there was no deviation in hydraulic conductivity among different locations but depths. The surface soil is loose and the pores are less in deeper soil, so the hydraulic conductivity becomes smaller within the increasing of depth. The hydraulic conductivity decrease if part of soil pores filled with air, and the gradient become smaller. This situation usually happened in the surface soil. There was no significant difference in deeper soil because the water movement here depended on micro pores.

abstract: In geotechnical engineering, measuring the unsaturated hydraulic conductivity of fine grained soils can be time consuming and tedious. The various applications that require knowledge of the unsaturated hydraulic conductivity function are great, and in geotechnical engineering, they range from modeling seepage through landfill covers to determining infiltration of water under a building slab. The unsaturated hydraulic conductivity function can be measured using various direct and indirect techniques. The instantaneous profile method has been found to be the most promising unsteady state method for measuring the unsaturated hydraulic conductivity function for fine grained soils over a wide range of suction values. The instantaneous profile method can be modified by using different techniques to measure suction and water content and also through the way water is introduced or removed from the soil profile. In this study, the instantaneous profile method was modified by creating duplicate soil samples compacted into cylindrical tubes at two different water contents. The techniques used in the duplicate method to measure the water content and matric suction included volumetric moisture probes, manual water content measurements, and filter paper tests. The experimental testing conducted in this study provided insight into determining the unsaturated hydraulic conductivity using the instantaneous profile method for a sandy clay soil and recommendations are provided for further evaluation. Overall, this study has demonstrated that the presence of cracks has no significant impact on the hydraulic behavior of soil in high suction ranges. The results of this study do not examine the behavior of cracked soil unsaturated hydraulic conductivity at low suction and at moisture contents near saturation.<br>Dissertation/Thesis<br>M.S. Civil and Environmental Engineering 2011

碩士<br>國立屏東科技大學<br>土木工程系所<br>105<br>Clayey soils are used as buffer material in an engineered barrier system for isolation of high-level radioactive wastes (HLW) in a repository. In the current proposal for deep geological disposal of the high-level radioactive wastes in Taiwan, compacted bentonite is used to contain the metallic waste canisters and separate the waste from the host rock and backfill materials. The major roles of the buffer material are used to reduce the groundwater flow, to protect the overpack from degradation, and to minimizee the migration of radionuclides. The resaturation of the buffer considered as a hydro-process occurring at elevated temperatures in the near-field of a repository affects the migration of radionuclides. Hydraulic conductivity properties of buffer material affects this resaturation process. To evaluate the influence of temperature and dry density on hydraulic conductivity properties of buffer material, an equipment was designed to simulate the near-field environment of a repository and to measure the hydraulic conductivity at unsaturated condition.

博士<br>國立中興大學<br>水土保持學系所<br>96<br>There is inseparable relation between moisture movement in soil and pore size distribution of porous media. Therefore, this study developed two one-dimensional vertical flow hydraulic conductivity functions which are based on Arya and Kosugi model. The functions were developed by applying pore radius to present the influence of pore radius (r) on unsaturated hydraulic conductivity (K). (公式略) Where K(θi) is the hydraulic conductivity (L T-1) corresponding with water content θi (L3 L-3); ΔΨm is matric potentials (L); Δz is depth (L); rj is the mean pore radius (L) for the jth pore fraction; wi is the mass ratio (M M-1) for the jth pore fraction from particle-size fraction; ψ is total porosity (L3 L-3); c and x are parameters. K is unsaturated hydraulic conductivity (L T-1); Ks is saturated hydraulic conductivity (L T-1); Se represents the effective saturation (L3 L-3); r is the pore radius (L); rg is the geometric mean pore radius (L); rmax is the maximal pore radius (L); andσis the standard deviation of ln(r). The calculated hydraulic conductivity from these two functions and observed hydraulic conductivity from instantaneous profile method are tested by root mean square error (RMSE). The RMSE of these two functions are 0.508 and 0.553 respectively, all are better than the RMSE of van Genuchten’s hydraulic conductivity function (RMSE = 0.766). The result showed that the relationship between pore radius and hydraulic conductivity can be expressed reasonably by physical function and their empirical parameters. Four soil samples with different texture were collected and analyzed. The soil texture for four soil samples are clay loam, loam, sandy loam and quartz sand. The soil physical properties and required parameters for developing function were measured by the experiments. The measured data sets include basic properties, particle size distribution, water characteristic curve and hydraulic conductivity of soil samples. The parameters which computed from models or regression analysis have pore radius (r), maximal pore radius (rmax), geometric mean pore radius (rg), standard deviation (σ) of ln(r). Furthermore, the dimensionless parameters x and c of volumetric flow rate for a single pore (qsi) can be calculated. These data sets and parameters are applied to develop two functions that was mentioned before. The relevant functions expressed by pore radius and hydraulic conductivity of four soil samples were obtained. And that smaller pore radius has lower hydraulic conductivity, otherwise, larger pore radius has higher hydraulic conductivity. The hydraulic conductivity data which observed by instantaneous profile method on sandbox experiment in the laboratory, were substituted into two functions. Equivalent pore radius (re) can be determined from hydraulic conductivity data according to two functions. The distribution of any amount of equivalent pore radius presented pore-size distribution in soil profile. Finally, pore radius distribution of different depth which at two soil profile depth 5 cm (z5) and 13 cm (z13) were displayed.

Chapters 1 and 2 identify the aims and objectives of the study, as well as the hypotheses and assumptions required. The relevant literature on soil water availability and plant response to water stress is explored. In particular these two chapters explain that plants extract water from soils by regulating a host of physiological mechanisms at their disposal – some plants are more efficient than others at doing this. As soil dries out, plants must ‘sense’ and gradually integrate the net effect of many soil conditions including: increasing soil aeration, as well as matric and osmotic suctions and soil strength, but also diminishing soil hydraulic conductivity. Plants, therefore, gradually take up water more slowly as the soil dries, depending on environmental conditions and other factors, all of which vary enormously on an hourly basis and which are difficult to predict let alone measure. Groenevelt et al. (2001; 2004) proposed a model, the Integral Water Capacity (IWC) to predict the effects of soil physical and chemical restrictions on water availability, but this model has not yet been tested against the performance of realplants. Evaluation of this model forms the primary focus of this study. The IWC uses the soil water retention curve, θ(h), to produce a differential water capacity, C(h)= dθ/dh, which is then reduced using various weighting functions, ω(h),to account for the above limiting physical and chemical properties, then integrated to produce a total amount of water that can be extracted from the soil by plants. The key, of course, is to identify robust weighting functions for each of the limiting soilconditions, yet this is no easy task because the limiting soil conditions often interact.For example, as the soil dries out, the hydraulic conductivity drops while aeration,strength and salinity all increase to varying extents – this makes it difficult to quantify the effect of any one limitation. In the present study it was therefore decided to focus solely on the unsaturated soil hydraulic conductivity as the major limiting soil condition. A significant drop in the soil hydraulic conductivity during a dry period after rainfall or irrigation can make the difference between crop success and failure, particularly in Mediterranean and arid environments. The aims of the study were to: 1) Evaluate the effect of declining soil hydraulic conductivity on soil water availability in the absence of all other known soil physical limitations. 2) Evaluate the link between real plant response to water stress and that predicted using the IWC model of Groenevelt et al. (2001) for a range of different plant species, planting densities, soil types and environmental conditions. 3) Evaluate the utility of the hydraulic conductivity function of Grant et al. (2010) in weighting the water capacity. Chapter 3 identifies the main methods used in the study. It explains that two different, light-textured soils were selected (Very fine sand and Loamy sand), for some pot experiments designed to compare the predicted and measured amounts of water that two contrasting plants (maize v. sorghum) could extract from the soil under different environmental conditions (low and high evaporative demand). In the first instance, the water retention curves were measured on soil samples packed to the same bulk densities used in the plant experiments. The water retention curves were then modelled to produce the differential water capacities and the relative hydraulic conductivities for the two soils. The IWC was then calculated based upon experimental data describing plant responses to environmental conditions (see below). A large number of pots holding 5 kg soil and different numbers of maize or sorghum seeds were well watered until plants reached a critical stage, after which half the pots were no longer supplied with water while the other half were maintained at ideal water contents. An identical set of control pots containing no plants was monitored to separate evaporation from plant transpiration, and to thus determine the soil matric suction at which the rate of water loss from the planted pots declined to the rate of natural evaporation – indicating the point at which transpiration effectively stopped. Stomatal conductance, g (mmol m⁻² s⁻¹), and soil water content, θ (m³ /m³ ) were measured first thing each morning every day until this was no longer possible. When stomatal conductance on the stressed plants could no longer be measured (ranging between 5 and 21 days depending on conditions) the experiments were terminated and the fresh weights of roots and shoots measured. Chapter 4 describes how the stomatal conductance of the stressed plants, g, was expressed as a fraction of that for the well-watered control plants, g[subscript]c, and plotted as afunction of the soil water suction, h (cm). At a certain stage the decline in relative stomatal conductance, g/g[subscript]c, changed from a curved to a linear form and continued in thisway until it was no longer possible to take measurements, at which point g/g[subscript]c wasjudged to be zero. The transition between the curved and linear decline in g/g[subscript]c was considered to mark the soil matric suction, h[subscript]t, at which plants began to experienceterminal water stress. When plants finally stopped transpiring, the soil matric suction, hw, was noted as the end point of the experiments. The stressed plants stopped transpiring across a large range of soil matric suctions, demonstrating that plant-response is strongly influenced by soil texture, plant species, root-length density, and environmental conditions. By far the most important factor, however, was soil texture; plants grown in the Very fine sand (coarser-textured) perished at suctions much smaller than the classical wilting point of 15,000 cm, while plants grown in the finer Loamy sand persisted to matric suctions of nearly 27,000 cm in some cases. The other variables appeared to be less important and somewhat complicated by interactions. For example, when averaged across soil texture (and in most cases, regardless), sorghum extracted water to greater matric suctions at all planting densities than did maize; however at higher planting densities and under higher evaporative demand, maize extracted water to greater matric suctions than sorghum. The large difference in behaviour of plants between the two soils demonstrated that a primary cause of water stress was a limitation in the unsaturated hydraulic conductivity. This highlighted the importance of hydrodynamics in controlling water-availability to plants and indicated the potential usefulness of the unsaturated hydraulic conductivity function in weighting the differential water capacity. Chapter 5 explores the extent to which dynamic plant responses to water stress can be used to calculate the IWC. The best function for weighting the soil water capacity was found to be a modified quadratic relation that incorporated the critical soil matric suctions at the onset and end of hydraulic stress, as well as the root-length density. The onset of hydraulic stress shifted toward lower matric suctions as temperature and evaporative demand increased, and transpiration stopped at lower matric suctions as well – particularly in the Very fine sand (well before the classical permanent wilting point of 15,000 cm). The effects were more modest in Loamy sand where plants (particularly sorghum) survived well beyond the classical wilting point. Both sorghum and maize extracted greater amounts of water from the Loamy sand than from the Very fine sand, and sorghum extracted more water from both soil types than did maize.Chapter 6 explores how soil properties combined with plant response can be used to calculate the IWC. In the first instance, the model of Grant et al. (2010) was applied to obtain the relative hydraulic conductivity of the two soils, which provided useful parameters to develop a simple weighting function for the water capacity. The functional form was based on two factors: the shape of the unsaturated hydraulic conductivity and the soil matric suctions at which plants experienced the onset of water stress and then cessation of transpiration. The IWC’s predicted by applying this weighting function were closer to the actual amounts of water extracted by the plants than were the IWC’s produced in Chapter 5, and were more accurate in the coarser of the two soils, the Very fine sand. The combination of soil and plant factors in predicting IWC appears to produce superior estimates than either soil or plant factors alone. Chapter 7 draws some general conclusions, highlights the implications of the work conducted in this study and identifies potentially fruitful lines of future research.<br>Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2010

博士<br>國立臺灣大學<br>土木工程學研究所<br>94<br>Based on the framework of hydraulic equivalent Unit-Pore-Throat Ensemble Model (UPTEM), this study proposed an approach to qualitatively analyze the wetting phase fluid unsaturated hydraulic conductivity for a two-phase flow system. In order to take the contact angle and the rheology of fluid interface into consideration, the method is composed of the following three issues: 1. According to the capillary pressure thresholds, design a set of proto-Pore-Throat-Units (proto-PTUs) comprised all the possible mechanisms of fluid displacement within a pore-throat unit (PTU). 2. Given several capillary pressures, numerically simulate the static equilibrium capillary surfaces within each proto-PTU and analyze the Laminar flow of the wetting phase fluid to calculate the conductance. 3. Based on the hydraulic equivalent UPTEM, ensemble the proto-PTUs to analyze the unsaturated hydraulic conductivity. Although the PTU provides the elements of cube and equilateral triangular prism to depict the characteristics of the real soil pore structure better, the static equilibrium capillary surface cannot be described with the analytical geometry shapes due to the geometrical singular points. The shape of static equilibrium capillary surfaces within a PTU can be simulated numerically with the aid of Surface Evolver. The Surface Evolver is an interactive program that minimizes the energy of a surface subject to constraints, such as prescribed fluid volume and contact angle on the walls. According to the Surface Evolver graphical output, this study verified the critical conditions and the capillary pressure thresholds of 2 immiscible fluids displacement mechanisms within a PTU. The results revealed that the threshold of piston-type motion occurred at the intersection of cubic pore and equilateral triangular prism should be modified. Moreover, there should be another displacement mechanism, which snaps off the non-wetting phase in the pore body due to the thickening of wetting phase fluid. For contact angle , the study designed 25 proto-PTUs and applied the no-stress boundary condition on the fluid interface to simulate the flow field. With the criteria of Reynolds number less than 0.1, the Laminar flow field of wetting phase fluid are analyzed and the variation of conductance are fitted. Results show that the function of conductance and dimensionless area of capillary surface is the exponential type for the none-full-throat configuration; meanwhile, it could be the exponential type, power type or exponential semi-variogram type for the one-full-throat configuration depends on the throat size ratio. Furthermore, the conductance in drainage process is larger than the one in imbibition process for a given capillary pressure due to the change of the fluid configuration. To analyze the unsaturated hydraulic conductivity of a virtual wetting phase fluid based on the hydraulic equivalent UPTEM, which is deducted from the water-air soil column infiltration experiment, the study ensemble the 25 proto-PTUs by two ways and both can qualitatively depict the hysteresis phenomena. The first way employed the linear programming scheme to calculate the probability of each proto-PTU. Because the relation between probability and throat size deviated from the one of hydraulic equivalent UPTEM significantly, it overestimated the expected total pore volume, and therefore, the unsaturated hydraulic conductivity. On the other hand, the second way categorized the hydraulic equivalent UPTEM into 25 proto-PTUs based on the aspect ratio and the throat size ratio. It successfully revealed the reduction of unsaturated hydraulic conductivity due to non-wetting phase trapped during the imbibition process and simulated the scanning loops well.

Chemical dynamics in the vadose zone are poorly understood due to the transient nature of chemical and hydrologic conditions, but are nonetheless critical to understanding contaminant fate and transport. This work explored the effects of soil structure (i.e. layers, lenses) on linked geochemical, hydrological, and microbiological processes under changing hydrologic conditions (e.g. rainfall, introduction of groundwater, and fluctuating water table heights). A homogenized medium-grained sand, homogenized organic-rich loam and a sand-over-loam layered column were constructed for the first series of experiments. The second series of experiments employed two soil columns with lenses that were packed identically with sterilized and untreated sediments. Each consisted of two lenses of organic-rich loam in a medium-grained sand matrix. Lenses were located at different vertical depths and were horizontally offset. In-situ collocated probes collected soil hydrologic and chemical data. In the layered column, enhanced biogeochemical cycling was observed over the texturally homogeneous soil columns. Enumerations of Fe(III) and SO42- reducing microorganisms also show 1-2 orders of magnitude greater community numbers in the layered column. The greatest concentrations of aqueous FeS clusters (FeSaq) were observed in close proximity to the soil interface. To our knowledge, this was the first documentation of FeSaq in partially saturated sediments. Mineral and soil aggregate composite layers were also most abundant near the soil layer interface; the presence of which, likely contributed to an order of magnitude decrease of hydraulic conductivity. In the live lens column, Fe-oxide bands formed at the fringes of the lenses that retarded water flow rates by an order of magnitude compared to the sterilized column. Microbial activity also produced insoluble gases and that led to the creation of a separate gas phase that reduced hydraulic conductivity. This limited the interaction between groundwater with soil-pore waters that led to the formation of geochemically distinct water masses in relatively close proximity to one another. No such changes were observed in the sterilized column. When compared to homogenous columns, the presence of soil heterogeneities altered biogeochemical and hydrologic processes considerably which highlights the need to consider soil heterogeneity in contaminant fate and transport models. These findings suggest that quantifying coupled hydrologic-biogeochemical processes occurring at small scale soil interfaces is critical to accurately describing and predicting chemical changes at the larger system scale.