Dissertations / Theses on the topic 'Hydric soils'

Restoring longleaf pine ecosystems is essential for managing rare plant and animal species and protecting biological diversity in the southeastern Coastal Plain of the United States. Natural longleaf pine ecosystems range from xeric uplands to poorly-drained flatwoods and savannas. Most existing stands, however, occur on xeric to dry-mesic sites and approaches to restoring longleaf pine to wetter sites traditionally utilize intensive practices. There is little information available on the efficacy of these practices to establish longleaf pine seedlings on poorly-drained sites and their impacts on soil properties, seedling survival and growth, and the understory plant community. A research project was established at Marine Corps Base Camp Lejeune, NC to evaluate the effects of site preparation methods for returning longleaf pine on hydric soils with no natural seed source. Various site preparation treatments were evaluated in a field experiment, and results revealed greater growth and earlier emergence from the grass stage with more intensive site preparation. There was a marginal increase in soil nutrients, and a slight increase in foliar nutrients found with the more intensive treatments. Site preparation influenced seedling growth in the short-term and this was likely due to the cumulative effects of controlling competition and modifying the planting site. Marine Corps Base Camp Lejeune and other Department of Defense installations include both former and remnant longleaf pine ecosystems that support federally protected plants and animals such as the red-cockaded woodpecker - and thus face the challenge of restoring former, poorly-drained longleaf pine ecosystems. A land use history revealed that, largely due to its poorly-drained status and inaccessibility, the majority of disturbance on the research area occurred after the 1920âs and was largely due to forestry activities. Since purchasing the land area of the project in 1996, the Marine Corpsâ challenge has been to balance the mission of training and readiness with the need for restoration and long-term management of longleaf pine ecosystems. The results of this work provide natural resource managers with a scientific foundation for assessing choices to assist in this restoration and management effort.

Thesis (M.S.)--West Virginia University, 2003.
Title from document title page. Document formatted into pages; contains vi, 131 p. : ill. (some col.), col. map. Vita. Includes abstract. Includes bibliographical references (p. 69-74).

In recent years, the success of wetland mitigation projects and their ability to function as natural systems has been questioned. This study was conducted (i) to characterize and examine differences between mitigation and natural wetlands, (ii) to examine differences in soil morphology along a wetness gradient in mitigation and natural wetlands, and (iii) to observe changes in mitigation wetlands with time. Site characteristics, including soil properties, hydrology, and vegetation, were analyzed for three mitigation-reference wetland pairs located in the Virginia Coastal Plain. Hydrologic regimes of mitigation areas, when compared to reference areas, generally showed larger differentials between seasonal high and low watertables. Mitigation areas, dominated by herbaceous vegetation, tended to be lower in C and N levels and higher in soil pH, and much higher in bulk density than the mature forested reference wetland. Initially low levels of C and N did not increase significantly over the five-year study period. Soils in the mitigation area were more uniform and considerably less differentiated when compared to those of the reference area. Testing for Fe(II) with alpha-alpha, dipyridyl dye solution produced mixed results, obtaining both positive and negative reactions to saturated samples. Oxidized rhizospheres, associated with active root channels in surface horizons, formed in less than ten years under the current hydrologic conditions. These features were more abundant and more prominent in areas saturated at or above the surface for longer periods of time. Overall, site differences between mitigation and reference areas are mainly due to construction practices and a lack of organic matter accumulation. Better design methods should incorporate the addition of organic amendments, with attempts to minimize soil compaction.
Master of Science

In 1998, the Virginia Department of Transportation (VDOT) adopted standards for soil handling and amendments to improve created non-tidal wetland soil conditions. This study was conducted in sites where these new reconstruction practices were supposedly being implemented. Specific objectives were (i) to determine the relative effects of soil reconstruction practices on mitigation site soils, (ii) to assess the degree to which hydric soil indicators were present, and (iii) to evaluate the relative edaphic potential of mitigation site soils. Soil physical, chemical and morphological properties were analyzed in ten mitigation wetlands located in Virginiaâ s Piedmont and Coastal Plain. Surface soil pH was high due to liming, although some sites demonstrated low subsoil pH, indicating the presence of sulfidic materials. Nutrient levels varied, while C:N ratios were low (<25:1), suggesting a high quality organic matter complex. Organic amendments were generally applied at a rate of 4% soil organic matter content. Actual measured carbon content was <2.6% (<50 Mg ha-1). Sites not receiving organic materials and associated tillage had root-limiting bulk densities at the surface, while the majority of sites had root-limiting subsoil (30 cm) bulk densities due to weakly developed soil structure and a lack of deep ripping practices. Many sites also contained high sand content (>50%), which may negatively affect other soil properties. Nine sites had confirmed Hydric Soil Indicators, with their occurrence in a site as high as 70%. Soil reconstruction methods need to incorporate higher organic amendment rates and/or routine disking/ripping practices to improve mitigation wetland soil conditions.
Master of Science

Past research indicates that created non-tidal wetlands in the mid-Atlantic region are considerably lower in soil organic matter than native forested hydric soils. However, optimal loading rates for created wetland soil reconstruction have not been rigorously established. Our objective was to determine appropriate organic amendment loading rates for a Coastal Plain mitigation wetland based on 1) soil properties reflective of hydric soil development, 2) the formation of redoximorphic features, and 3) the growth and vigor of hydrophytic vegetation. The study contained wet (CCW-Wet) and dry (CCW-Dry) experiments, each receiving 6 compost treatments (0 Mg/ha untilled and 0, 56, 112, 224, and 336 Mg/ha tilled). Over the 1.5-year monitoring period, redox potential decreased and redoximorphic feature formation increased with compost loadings up to 112 Mg/ha. Surface bulk density decreased with loadings up to 224 Mg/ha, while no treatment differences were noted in sub-surface bulk density. In the CCW-Dry experiment, soil moisture peaked in the 224 Mg/ha treatment, while soil moisture in CCW-Wet increased consistently across all loadings. Total biomass in CCW-Wet and Betula nigra L. growth in both experiments increased with loading rate. Total biomass in CCW-Dry and Quercus palustris Muench. growth in both experiments peaked at 112 Mg/ha, although differences were not significant. Collectively, these findings indicate that 112 Mg/ha of high quality organic amendment was optimal for inducing hydric soil conditions and positive hydrophytic vegetation response. Incorporating compost at rates exceeding 112 Mg/ha is challenging and leads to higher surface elevations and redox levels in the initial growing season.
Master of Science

Groundwater affects the development of soil in many ways. Due to the natural relationship between soil and groundwater this study was aimed at determining whether soils affect the water table depth, episaturation occurs, and hydric soils exist at the study site. The three soils studied include Pewamo (poorly drained), Blount (somewhat poorly drained) and Glynwood (moderately well drained).Water table data were collected in 1994 and 1995 at the Hults Environmental Learning Center in Albany, Indiana. Soil, by itself, was not found to be significant in affecting water table depth whereas position (horizon), soil by position and Julian date were all found to be highly significant. Soils were affected by existing drainage tile found in Pewamo that acted to lower the water table. Blount and Glynwood were found to have a period of episaturation whereas Pewamo was found to be endosaturated. The soils were not found to be hydric based on the depth to the water table only.
Department of Natural Resources and Environmental Management

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
PROGRAMA DE EXCELENCIA ACADEMICA
BOLSA NOTA 10
Esta tese apresenta um estudo relacionado a dois importantes aspectos da mecânica dos solos não saturados: a caracterização físico-hídrico-estrutural e o efeito do aumento súbito da pressão de ar em solos tropicais não saturados do Rio de Janeiro. A primeira contribuição aborda uma avaliação ampla de parâmetros físicos, químicos, mineralógicos e do efeito da estrutura destes solos em características estruturais, mecânicas, hidráulicas e de deformabilidade. O segundo aspecto, relacionado à avaliação do efeito do aumento da pressão de ar, foi realizado através de ensaios triaxiais não saturados, do tipo CW, com medidas de velocidade da onda cisalhante. Para atingir este último objetivo, um equipamento triaxial servocontrolado não saturado, com instrumentação interna de bender elements, foi implementado. Todos os ensaios foram realizados em amostras indeformadas e reconstituídas, com mesmo teor de umidade e índice de vazios, em dois solos residuais jovens e em um solo coluvionar coletados em Nova Friburgo e Tinguá, RJ. Os resultados obtidos permitiram avaliar que apesar de alguns solos possuírem características físicas semelhantes, estes apresentaram comportamentos mecânicos, hidráulicos e estruturais diferentes. Com relação aos ensaios triaxiais não saturados CW, não foi possível observar um comportamento característico e conclusivo do efeito do incremento de ar nos solos. A verificação individual do pulso de ar em cada amostra estudada indicou, para a maioria dos ensaios, diminuição das velocidades das ondas cisalhantes (Vs) após o aumento.
This thesis presents a study related to two important aspects of unsaturated soil mechanics: a physical-hydric-structural charaterization and the effects of increase of air pressure on the strength of unsaturated tropical soils from Rio de Janeiro. The first contribution exhibits an extensive experimental program aiming to evaluate effcts of physical, chemical, mineralogical and soil structure in the mechanical, hydraulic and deformability characteristics of the soils. The second contribution, related to the effects of increase of air pressure, was performed through constant water content triaxial tests with measurements of shear wave velocities. In order to achieve this last objective, an unsaturated triaxial apparatus with bender elements was implemented. The tests were carried out on undisturbed and reconstituted samples, with the same moisture content and void ratio, in two young residual soils and a colluvial soil from Nova Friburgo and Tinguá, RJ. The results showed that although some soils had similar physical characteristics, they had different mechanical, hydraulic and structural behaviors. Regarding the unsaturated triaxial tests, it was not possible to observe a characteristic and conclusive behavior of the effect of increase of air pressure in soils. The individual evaluation in each sample studied indicated that, for most tests, the increase in air pressure caused decrease in shear wave velocities (Vs).

Vernal pools are small seasonally-ponded wetlands that provide crucial habitat for amphibian reproduction and support trophic levels beyond their boundaries. The Ridge and Valley physiographic province in Pennsylvania is known to have vernal pools, but a regional inventory and geomorphology assessment is needed. My research is split into two independent parts focusing on the higher elevation areas of this region to determine vernal pool distribution and characteristics. Vernal pools were mapped using a LiDAR based suitability model and leaf-off aerial imagery interpretation. Four terrain rasters derived from a 1-meter DEM (modified wind modified wind exposure, terrain surface convexity, topographic position index, and a multiresolution index of valley bottom flatness) were used in the suitability model. An analysis of variance (ANOVA) and Tukey's HSD test found a significant difference using the model between terrestrial (non-wetland) habitat and vernal pools. Photo interpretation and field surveying lead to an inventory of 1011 vernal pools. Geomorphology was assessed from 13 variables to determine the best for vernal pool prediction. Three variables were significant for the occurrence and frequency of vernal pools; saddles with higher surface area, 0.6 to 1.5 kilometers between the summits of parallel ridgelines, and the presence of periglacial related solifluction. Vernal pool distribution is greater than previously known and they occur in predictable settings. Further research should focus on how and where vernal pools form, their impact on water quality, role in forest ecology, and ways to legally protect them at the state level.
Master of Science
Vernal pools are seasonally-ponded wetlands that are very important for amphibian reproduction. The Appalachian Mountains of Pennsylvania are known to have vernal pools, but comprehensive inventory is lacking. My research consists of two parts that focus on the higher elevation areas and assess the distribution and qualities of the vernal pools. Vernal pools were mapped using a LiDAR based suitability model and leaf-off aerial imagery interpretation. Statistical analysis was completed to prove that there was a significant difference in terrain morphology between non-wetland habitat and vernal pools. This research resulted in a total inventory of 1011 vernal pools. Results found that vernal pools were likely occur in landscape positions with higher surface area, 0.6 to 1.5 kilometers between the summits of parallel ridgelines, and the presence of topographic features indicative of glacial processes. Vernal pools are much more abundant than previously known and they occur in predictable settings. Further research could focus on the formation of vernal pools, impact on water quality, role in forest ecology, and ways to legally protect them at the state level.

Made available in DSpace on 2014-07-29T16:24:21Z (GMT). No. of bitstreams: 1 RICARDO FERNANDES.pdf: 1993075 bytes, checksum: 9fd3eb6ccef6337fadda8d38b2a10ec3 (MD5) Previous issue date: 2009-07-15
The objective of this work was to study the soil of wetlands situated in conserved and altered environments (in agricultural and cattle areas), by determining the chemical attributes and texture of the soil. The study was carried through in the central region of Cerrado biome, in the state of Goiás, in wetlands situated in the City of Bela Vista de Goiás. There have been selected three wetlands for soil sampling: one conserved wetland, surrounded by natural vegetation (cerrado); one altered area, with occurrence of pasture in its adjacent areas; and another wetland, also altered, with the occurrence of agriculture in its adjacent areas. The samplings were taken in the months of April and May of 2008, through the use of lines of reference, according to their positions in the relief, in upper, average and lower position, following approximately the direction of the line of draining of the wetland. It has been collected samples in three depths: 0-10 cm; 10-20 cm and 20-40 cm. The variables studied have been: texture, pH in CaCl2 0.01 M; micronutrients (Cu, Fe, Mn, Zn and B), macronutrients (P, K, Ca, Mg and S), concentration of Al and potential acidity (H+Al), and soil organic matter content (SOM). It was verified that the clay percentages in the lower region of the relief are higher in altered environments and the percentage of silt are higher in the wetland adjacent to the agricultural area. In lower position of the relief, the concentrations of SOM are lesser in wetlands adjacent to the agricultural areas and pastures. In the conserved wetland the base saturation is higher in lower position of relief and, in this same position, the acidity (pH) and the aluminum concentration is lesser than that in the average and upper positions, occurring the inverse in farming landscapes.
Este trabalho objetivou estudar os solos de áreas úmidas (veredas) situadas em ambientes conservados e antropizados (em áreas agrícolas e de pecuária), por meio da determinação de atributos químicos e textura do solo. O estudo foi realizado na região nuclear do bioma Cerrado, no estado de Goiás, em veredas situadas no município de Bela Vista de Goiás. Foram selecionadas três veredas para amostragem de solo, sendo: uma vereda conservada, circundada por vegetação natural (cerrado); uma área antropizada, com ocorrência de pastagem em seu entorno; e uma outra vereda, também antropizada, com a ocorrência de culturas anuais (agricultura) em seu entorno. As coletas foram feitas nos meses de abril e maio de 2008, ao longo de linhas de referência dispostas, segundo sua posição no relevo, nos terços superior, médio e inferior de uma das vertentes, acompanhando de modo aproximado o sentido da linha de drenagem da vereda. Foram colhidas amostras em três profundidades: 0-10 cm; 10-20 cm e 20-40 cm. As variáveis estudadas foram: textura, pH em CaCl2 0,01 M; micronutrientes (Cu, Fe, Mn, Zn e B), macronutrientes (P, K, Ca, Mg e S), teor de Al e acidez potencial (H+Al) e teor de matéria orgânica do solo (MOS). Verifica-se que os teores de argila na região inferior do relevo são maiores em ambientes antropizados e os teores de silte são maiores na vereda adjacente à área agrícola. No terço inferior do relevo, os teores de MOS são menores em veredas adjacentes a pastagens e áreas agrícolas. Na vereda conservada a saturação por bases é maior no terço inferior e, nessa mesma posição, a acidez e o teor de alumínio são menores do que nos terços médio e superior, ocorrendo o inverso em ambientes agropecuários.

A thermo-elastic-plastic model for unsaturated soils has been presented based on the effective stress principle considering the thermo-mechanical and suction coupling effects. The thermo-elastic-plastic constitutive equations for stress-strain relations of the solid skeleton and changes in fluid content and entropy for unsaturated soils have been established. A plasticity model is derived from energy considerations. The model derived covers both associative and non-associative flow behaviours and the modified Cam-Clay is considered as a special case. All model coefficients are identified in terms of measurable parameters. To verify the proposed model, an experimental program has been developed. A series of controlled laboratory tests were carried out on a compacted silt sample using a triaxial equipment modified for testing unsaturated soils at elevated temperatures. Imageprocessing technique was used for measuring the volume change of the samples subjected to mechanical, thermal and hydric loading. It is shown that the effective critical state parameters M, ???? and ???? are independent of temperature and matric suction. Nevertheless, the shape of loading collapse (LC) curve was affected by temperature and suction. Furthermore, the temperature change affected the soil water characteristic curve and an increase in temperature caused a decrease in the air entry suction. The simulations from the proposed model are compared with the experimental results. The model calibration was performed to extract the model parameters from the experimental results. Good agreement between the results predicted using the proposed model and the experimental results was obtained in all cases.

The National Technical Committee for Hydric Soils developed the Hydric Soil Technical Standard (HSTS) to identify a functioning wetland (hydric) soil using quantitative measurements of saturation and anaerobic conditions. We used the HSTS to assess wetland restoration success and to compare surface treatments designed to replicate microtopographic relief found in forested wetlands. Experiments were conducted on a wetland restored from agricultural fields in eastern NC where monitoring stations were installed across three surface treatments in the restored wetland: 1) a microtopography (MT) treatment created by roughing the soil surface to mimic the uneven surface of forested wetlands, 2) a crown removal treatment imposed by grading the field flat, and 3) a control treatment that had no surface alteration. Monitoring stations were also installed in a nearby nonriverine swamp forest as a reference wetland. Weekly measurements of water table depth and redox potential were collected for 15 months. Soil at all monitoring stations met the HSTS, indicating that functioning hydric soils were restored. Although a significant difference between surface treatments was not detected, the MT treatment resulted in anaerobic conditions most similar to the reference wetland, signifying that this type of surface treatment should be considered for wetland restoration of areas with smooth surfaces. The HSTS proved to be a useful tool in evaluating wetland restoration success and microtopographic effects. Microtopographic relief did not create nonhydric areas as measured by HSTS; however, microtopographic relief is likely to influence plant establishment.

Cette these etudie les effets de la conversion de la foret tropicale en parcelles agricoles, sur les emissions de n2o par les sols. Ce travail est realise a l’echelle du cycle cultural sur le dispositif experimental de combi (littoral guyanais), a l’aide de mesures in situ et de simulations (modele noe) des flux de n2o. La foret tropicale a ete comparee a des parcelles de foret converties en terres agricoles par la methode ‘chop-and-mulch’. La methode de deforestation ‘chop-and-mulch’ associe coupe mecanique de la vegetation, broyage puis enfouissement des residus forestiers dans le sol. Les terres agricoles etaient soient des parcelles de prairie non paturee soient des parcelles cultivees (maïs fertilise/soja) conduites en semis conventionnel (semis apres travail du sol, sans plante de couverture) ou en semis direct (sans travail du sol, avec plantes de couverture).Les principaux resultats de cette etude sont : le sol de la foret tropicale de combi est un faible emetteur de n2o ; la conversion par la methode ‘chop-and-mulch’ de cette foret en prairie ne conduit pas a une augmentation significative des emissions de n2o entre le 19eme et le 31eme mois suivant la conversion ; la conversion de la foret en parcelles cultivees induit une augmentation significative des emissions de n2o due a la fertilisation et a la modification des parametres edaphiques (densite apparente, temperature, humidite volumique) ; la technique sans travail du sol n’engendre pas de flux de n2o significativement plus eleves que la technique avec travail du sol ; l’introduction du phenomene d’hysterese hydrique dans le modele noe presente un reel potentiel pour l’estimation des emissions de n2o in situ
This study investigates the effects of the conversion of tropical forest to cultivation on soil n2o emissions. The study was carried out over a complete crop cycle at the experimental site combi (french guianese coast). Nitrous oxide fluxes were obtained in the field and by conducting simulations with the noe model. Undisturbed tropical rainforest was compared to rainforest that had been converted to agricultural land using the ‘chop-and-mulch’ method. The ‘chop-and-mulch’ method is a fire-free method used for vegetation clearing combining the mechanical felling of trees with the mulching of small vegetation. Agricultural land included either mowed grassland or soybean/fertilised maize crop rotation. For croplands the two cultivation practices employed were: conventional seeding (using an offset disc harrow, without cover plants) or direct seeding (no till, with cover plants).The main results of this study are: rainforest soil at combi produced low n2o emissions; rainforest converted to mowed grassland using the 'chop-and-mulch’ method did not lead to a significant increase in n2o emissions between the 19th and 31st months after conversion; the conversion of rainforest to croplands induced a significant increase in soil n2o emissions due to the application of fertiliser and the modification of soil parameters (bulk density, temperature, volumetric moisture); n2o emissions from agricultural practices with no-till were no higher than those produced by conventional agricultural practices using an offset disc harrow; and, the introduction of an hydric hysteresis into the noe model constitutes a promising improvement to estimate in situ n2o emissions

In urban areas, trees are often planted in bare soil sidewalk openings (tree pits) which recently are being covered with permeable pavements. Pavements are known to alter soil moisture and temperature, and may have implications for tree growth, root development and depth, drought resilience, and sidewalk lifting. Furthermore, tree pits are often the only unsealed soil surface and are important for water exchange between soil and atmosphere. Therefore, covering tree pits with pavement, even permeable, may have implications for the urban water balance and stormwater management. A better understanding of permeable pavement on tree pavement soil system functioning can inform improved tree pit and street design for greater sustainability of urban environments. We conducted experiments at two sites in Virginia, USA (Mountains and Coastal Plain) with different climate and soil. At each location, we constructed 24 tree pits in a completely randomized experiment with two factors: paved with resin-bound porous-permeable pavement versus unpaved, and planted with Platanus x acerifolia 'Bloodgood' versus unplanted (n = 6). We measured tree stem diameter, root growth and depth, and soil water content and temperature over two growing seasons. We also monitored tree sap flow one week in June 2017 at the Mountains. In addition, we calibrated and validated a soil water flow model, HYDRUS-1D, to predict soil water distribution for different rooting depths, soil textures and pavement thicknesses. Trees in paved tree pits grew larger, with stem diameters 29% (Mountains) and 51% (Coastal Plain) greater. Roots developed faster under pavement, possibly due to the increased soil water content and the extended root growing season (14 more days). Tree transpiration was 33% of unpaved and planted pit water outputs, while it was 64% for paved and planted pits. In June 2016, planted pits had decreased root-zone water storage, while unplanted pits showed increased storage. A water balance of the entire experimental site showed overall decreased soil water storage due to tree water extraction becoming the dominant factor. HYDRUS-1D provided overall best results for model validation at 10 cm depth from soil surface (NSE = 0.447 for planted and paved tree pits), compared to 30- and 60 cm depths. HYDRUS-1D simulations with greater pavement thickness resulted in changes in predicted soil water content at the Coastal Plain, with higher values at 10- and 30-cm depths, but lower values at 60-cm depth. At the Mountains, virtually no difference was observed, possibly due to different soil texture (sandy vs clayey). Tree pits with permeable pavement accelerated tree establishment, but promoted shallower roots, possibly increasing root-pavement conflicts and tree drought susceptibility. Paved tree pits resulted in larger trees, increasing tree transpiration, but reduced soil evaporation compared to unpaved pits. Larger bare soil pits surrounded by permeable pavement might yield the best results to improve urban stormwater retention. Also, HYDRUS 1D was successful at simulating soil water content at 10-cm depth and may be valuable to inform streetscape design and planning.
PHD

The accuracy of the growing season used by regulators in hydric soil and wetland hydrology and the validity of ignoring land use in these definitions is questionable. This study compared measured air and soil temperature with various growing season dates and indicators, and determined the relationships between the hydrology, air and soil temperature. Water table depths, air temperature at 1-m height, soil temperature at 15-, 30-, and 50-cm depths, and CO₂ efflux were measured at 12 plots representing three landuse treatments (forest, field, and bare ground) at two restored wet flats in the thermic Great Dismal Swamp ecosystem. The forest was driest treatment. The forest air was the warmest in winter and coldest in summer, opposite of the bare ground. The forest soil at 50 cm was the warmest in winter and coolest in summer, opposite of the bare ground. Land use affected hydrology, air, and soil temperatures through the presence of surface litter and differences in shading, albedo, and ET. The regulatory frost-free period fell in between the measured frost-free period and the measured 5°C soil temperature period. Based on CO₂ efflux and soil temperature at 50 cm, the biological growing season of native plants and microbes should be year-round for forested areas, one week shorter for early-successional fields, and two weeks shorter for active cropland rather than March to November for all land uses. Changing the growing season definition of forested, thermic wet flats to year-round designation must be considered and studied carefully to avoid jeopardizing wetland hydrology qualifications.
Master of Science

La thèse présente un ensemble de résultats expérimentaux sur des sols fins très plastiques compactés au voisinage de l’optimum Proctor normal (OPN). Elle est réalisée dans le cadre du projet ANR TerreDurable qui traite de la conception des ouvrages en terre en sols fins. Après l’étude de l’effet de compactage sur des chemins de drainage-humidification, la fissuration induite par la dessiccation est mise en évidence et analysée. Par ailleurs, des relations entre différents paramètres mécaniques (module, IPI, Résistance à la compression) et hydriques (succion, perméabilité, ..) en fonction de l’énergie de compactage et du mode de préparation sont présentées. Le comportement mécanique des sols fins compactés est étudié sur des chemins œdométriques et triaxiaux saturés et non saturés, drainés et non drainés. Dans ce dernier cas, l’évolution des paramètres de pression interstitielle de Skempton est analysée sur des chemins isotropes et déviatoires. Ceci a nécessité la mise au point d’une cellule triaxiale équipée de psychromètres à effet Peltier, de tensiomètre et de jauges de déformations
The thesis presents an experimental study on very high plasticity soils compacted near of the standard Proctor optimum (SPO). It is performed as part of the ANR TerreDurable project which is devoted on the design of earthworks with fine soils. After the study of the effect of compaction on drying-wetting paths, induced cracking of drying is highlighted and analyzed. Furthermore, relationships between different mechanical parameters (modulus, IPI, compressive strength) and water (suction, permeability) according to the energy of compaction and method of preparation are shown. The mechanical behavior of soils compacted fine soils is studied on saturated and unsaturated, drained and undrained oedometer and triaxial. For the unsaturated undrained triaxial, the change in Skempton parameters pore pressure is analyzed on isotropic and deviatoric paths. This required the development of a triaxial cell equipped with psychrometers, tensiometer and strain gauges

Thesis (M.S.)--University of Florida, 2002.
Title from title page of source document. Document formatted into pages; contains xii, 104 p.; also contains graphics. Includes vita. Includes bibliographical references.

The hydro-mechanical behaviour of soils during freezing and thawing is a coupled multi-physics process that has important practical applications. To cite but a few examples, on artificial ground freezing –to provide structural support and exclude the groundwater from underground constructions–, on seasonal variations of permafrost soils and their consequences on infrastructures, on geocomposite capillary barriers used to reduce frost heave in soils, and on engineered barriers subjected to freezing and thawing processes. Despite this importance, ice content and its migration process, as well as the coupled hydro-mechanical behaviour have not been extensively studied in partially saturated frozen soils. In these soils, ice formation increases the number of phases and the complexity of the experimental studies. In this thesis, the unfrozen liquid saturation and the hydro-mechanical behaviour of two frozen soils (Barcelona clayey silt and fine sand) have been investigated at different initial degrees of saturation. A series of experimental setups have been designed and built to perform the tests (oedometer cell installed in a freezing/thawing chamber to control the temperature up to -15°C; setup for freezing cylindrical samples in an electrical resistivity tomography ERT cell with 16 lateral electrodes). Different methods have been considered and several models proposed in the thesis to indirectly determine the unfrozen liquid saturation of compacted soils at different temperatures, porosities and initial degrees of saturation. The methods rely on measurements during transient freezing of the bulk electrical conductivity EC, relative dielectric permittivity, and thermal conductivity. In the case of EC tests, the unfrozen liquid saturation results have been interpreted with a modified Archie’s law and compared to the electrical conductivity of the pore liquid. The soil freezing retention curve (unfrozen liquid saturation vs temperature) has been also estimated by combining the Clausius-Clapeyron equation with water retention data on drying, as well as with a capillary bundle model with mercury intrusion porosimetry MIP results. A very good agreement has been found between the proposed approach using bulk EC measurements and the water retention and porosimetry results, which validated the proposed models. The EC model has been used to interpret the transient freezing of cylindrical homogeneous samples that have been exposed to very low temperatures at its central axis (-15°C) and with adiabatic conditions imposed at the external boundaries. A 2D ERT setup is used to monitor the phase change and the migration of pore liquid. Reconstructed maps of EC have been translated into images of temperature and unfrozen liquid saturation at different elapsed times. The reconstructed temperature field showed good agreement with direct temperature measurements using inserted thermocouples. The ERT tests have been also performed on homogeneous samples with inclusions (low electrical conductive or high electrical conductive zones), which indicated that the ERT system could perfectly detect the effects of these anomalies on a transient freezing process. The volume change behaviour on freezing/thawing has been investigated on saturated samples using temperature controlled oedometer cells under different constant vertical stresses. A small irreversible compression has been systematically detected after a freezing/thawing cycle on different soils, which depended on the current stress state. The microstructural changes of the compacted samples after freezing/thawing paths have been also explored using MIP and field emission scanning electron microscopy FESEM observations, which have been analysed using PCAS image processing software. MIP results have indicated that the freezing/thawing process might have decreased the macropore volume (between aggregates) and enlarge some micropore volume.
El comportamiento hidromecánico de los suelos durante la congelación y descongelación es un proceso multifísico acoplado que tiene importantes aplicaciones prácticas. Por ejemplo, en la congelamiento artificial del terreno -para dar soporte estructural y evitar el agua en construcciones subterráneas-, en las variaciones estacionales de suelos permafrost y sus efectos sobre las infraestructuras, en las barreras capilares utilizadas para reducir los efectos de heladas, y en barreras de ingeniería sometidas a ciclos de congelación/descongelación. A pesar de esta importancia, el contenido de hielo y su proceso de migración, así como el comportamiento hidromecánico acoplado, no se han estudiado en forma extensa en los suelos parcialmente saturados. En estos suelos, la formación de hielo aumenta el número de fases y la complejidad de los estudios experimentales. Se han estudiado el grado de saturación de líquido descongelado y el comportamiento hidromecánico de dos suelos congelados (limo arcilloso de Barcelona y arena fina) a diferentes grados de saturación iniciales. Se han diseñado y construido una serie de equipos experimentales para realizar los ensayos (célula edométrica en una cámara de congelación/descongelación para controlar la temperatura hasta -15 °C; equipo para congelar muestras cilíndricas en una célula de tomografía de resistividad eléctrica ERT con 16 electrodos laterales). Se han utilizado diferentes métodos y se han propuesto modelos para determinar indirectamente la saturación de líquido descongelado en suelos compactados a diferentes temperaturas, porosidades y grados de saturación iniciales. Los métodos se basan en mediciones de la conductividad eléctrica del suelo EC, la permitividad dieléctrica relativa y la conductividad térmica. En el caso de los ensayos de EC, los resultados se han interpretado con una ley de Archie modificada y se han comparado con la conductividad eléctrica del líquido intersticial. La curva de retención de congelación del suelo (grado de saturación de líquido descongelado frente a temperatura) se estimó combinando la ecuación de Clausius-Clapeyron con los datos de retención al agua durante el secado, así como con un modelo capilar utilizando porosimetría de intrusión de mercurio MIP. Los resultados de las mediciones de EC, así como de retención al agua y porosimetría, han sido muy consistentes lo que ha permitido validar al modelo. El modelo EC se ha utilizado para interpretar la etapa transitoria de congelación de muestras cilíndricas, que han estado expuestas a temperaturas muy bajas en su eje central (-15 °C) y con condiciones adiabáticas en los contornos. Se utiliza ERT 2D para controlar el cambio de fase y la migración del líquido de poro. Los mapas reconstruidos de EC se han convertido en mapas de temperatura y de saturación de líquido descongelado a lo largo del tiempo. El dominio reconstruido de temperatura resultó ser consistente con las medidas directas de temperatura con termopares. Los ensayos ERT también se realizaron sobre muestras con inclusiones (zonas de alta o baja conductividad eléctrica), que han evidenciado la utilidad de este método para detectar los efectos de estas anomalías durante una congelación. Los cambios de volumen durante un ciclo de congelación/descongelación se han investigado sobre muestras saturadas a diferentes tensiones verticales constantes utilizando células edométricas de temperatura controlada. Se ha detectado una pequeña compresión irreversible después de la congelación/descongelación, que depende del estado tensional. También se han estudiado los cambios microestructurales generados después de un ciclo de congelación/descongelación utilizando MIP e imágenes de microscopía electrónica FESEM analizadas mediante tratamiento de imágenes PCAS. Los resultados de MIP han indicado que el ciclo de congelación/descongelación podría haber disminuido el volumen de macro

Les marais de l'Ouest ont été gagnés sur les sédiments fluvio-marins par poldérisation débutée dès le moyen âge. Les aménagements hydrauliques avaient, initialement, des objectifs sanitaires et d'élevage. A partir des endiguements, ils ont divisé les territoires en marais mouillés et marais desséchés. Depuis les années 1970 le développement des cultures intensives de céréales a nécessité un rabaissement complémentaire de la nappe par drainage en partie pour augmenter la désalinisation de surface et limiter l’engorgement des sols. Néanmoins, ces territoires restent caractérisés par des nappes proches de la surface. En conséquence les profils hydriques vont être gouvernés par les conditions météorologiques y compris l'évapotranspiration, la pluviométrie, mais également par les remontées capillaires issues d'une nappe salée. D'autre par la nature argileuse des sols et ses propriétés de retrait conditionnent énormément le fonctionnement hydrodynamique et les évolutions de structure.La première partie du travail a été de suivre les évolutions des profils hydriques et de salinité en parcelles non drainées (prairies) et en parcelles drainées (Maïs, Blé, Tournesol). Ces suivis ont été complétés par les mesures des niveaux de nappes et par des mesures tensiométriques via des bougies poreuses implantées à différentes profondeurs. L'objectif final a été de calculer et modéliser les profils de réserve utile (RU) et de RU "résiduelle" utilisable par les plantes. Dans ces systèmes alimentés par les remontées capillaires, le réseau racinaire puise l'eau dans la zone non saturée de surface (vadose) puis dans la zone saturée sous-jacente. La teneur en eau caractéristique de l'interface zone non saturée - zone saturée a été déterminée par analogie entre les chemins d'état de la matrice argileuse le long de sa courbe de retrait et du sol le long de sa courbe de compaction. Les profils de RU résiduelle utilisable par les plantes ont été calculés à partir des profils de teneurs en eau puis comparés aux profils de RU obtenus via les données de station météorologique. Ces profils de RU résiduelle ont pu être écrits sous forme d'équation polynomiale du second degré puis modélisés. Dans cet environnement alimenté par les remontées capillaires, ces profils de RU résiduelles peuvent être modélisés à partir d'un paramètre facilement mesurable en surface qui prend en compte la structure du sol et les conditions météorologique : soit la teneur en eau à 10 cm de profondeur. Cette modélisation reste suffisamment réaliste pour être utilisée comme un outil prédictif face à la pédodiversité et/ou les rendements de culture.A ce travail s'ajoute deux études préliminaires : - les mesures des conductivités thermiques effectives de ces sols par la méthode du fil chaud et leurs modélisations dans les systèmes biphasés : eau - argile et air - argile, mais également pour les systèmes triphasés non saturés : eau - air - argile. Les perspectives sont la modélisation des transferts thermiques et hydriques dans le sol à partir de la surface, - et l'élaboration d'un protocole d'imprégnation-polymérisation des sols argileux humides par des résines de type HEMA. Cette imprégnation permet d'envisager la confection de lames minces dans le matériau argileux induré avec conservation de sa structure initiale humide. Les perspectives sont la pétrographie quantitative à l'interface racine - sol le long de profils verticaux dans les environnements argileux à degrés de saturation et structure évolutives
The coastal marshlands are territories generally reclaimed on primary fluvio-marine sediments. They result from hydraulic managements and/or polderization which may date from the Middle Ages. Historically these hydraulic managements were built for goals of wholesomeness, breeding and farming. They isolate two territories: the dried marshes and the wet marshes. For the intensive cereal crops the slow drying caused by land reclamation was recently improved by the drainage, in part for increase the depth of desalinization and decrease waterlogging. Nevertheless, these territories remain characterized by shallow ground water of initial salt water. Consequently, the hydric profiles are governed by the meteoric conditions including the Evapotranspiration, the rainfall, but also the capillarity rises from the salt groundwater. Moreover, the clay dominated nature of the soils and their drastic shrinkage properties govern the hydrodynamic functioning and the soil structure behavior.The first part of the work was the monitoring of the water content and salinity profiles in drained cereal crops and in undrained grasslands. These measurements have been completed by the ground water level and tensiometric monitoring. The final goal was the calculation and modeling of the available water capacity (AWC) and plant available water (PAW) profiles. In these systems mainly supplied by the capillarity rises, the root network gets water in the subsurface vadose zone and then in the deeper saturated groundwater zone. The water content characteristic of the interface between the vadose and saturated zone was determined by comparison between the clay material state paths along its shrinkage curve and along its compaction curve. The PAW profiles were calculated from the water content profiles and then compared to the AWC profiles. The PAW profiles have been equated as polynomial second degree equations. In these shallow groundwater environments the PAW profiles have been modeled taking into account an easy measurable surface parameter which includes the soil structure behavior and the meteoric conditions: i.e. the water content measured at 10 cm depth. The PAW modelling remains sufficiently realistic to be used as a tool for farming management. Two preliminary studies were added to this work: - the measurement of effective thermal conductivity of the clayey soils by the transient hot wire method, and the modeling of the effective thermal conductivity of biphasic air-clay and water-clay media, but also triphasic unsaturated air-water-clay media. The prospect is the modeling of thermal and hydric transfer from the surface to the depth. - and the elaboration of a protocol of impregnation - hardening for wet clay dominated soils by HEMA resins. This impregnation allows the making of thin sections in these clay materials with conservation of their initial wet structures. The prospective is the quantitative petrography at the root - clay matrix interface along vertical profiles in clayey soils at different degrees of saturation and different structures

Les sols argileux peuvent présenter des variations importantes de volume lors d’un changement hydrique, tel une période de sécheresse. Ce phénomène de retrait-gonflement des sols argileux est à l’origine de nombreux préjudices aux bâtis ce qui le situe, après les inondations, au second rang des aléas naturels français en matière de coût des dommages : 5 milliard d’euros entre 1988 et 2007. Les maisons individuelles sont les plus touchées par ce phénomène qui provoque un tassement différentiel du bâti à l’origine de sa dégradation (fissures dans les éléments de maçonnerie non armée en particulier). L’objectif de cette thèse est d’étudier la vulnérabilité des bâtis vis-à-vis de l’aléa retrait-gonflement à travers une analyse de l’interaction sol-structure. Ce travail s’est porté sur les trois grands volets suivants : 1 - le comportement hydromécanique des sols argileux, 2 - l’interaction sol-structure, 3 - l’évaluation des dommages structuraux. Le comportement hydromécanique des sols argileux a été modélisé par le concept de surface d’état et intégré dans un modèle d’interaction sol-structure inspiré du modèle de Winkler, avec des approches de plus en plus complexes : cas unidimensionnel tout d’abord, 2D ensuite en assimilant la structure à une poutre, puis en 3D en représentant la structure par une plaque. Ces modèles d’interaction sol-structure permettent de calculer la déflexion relative d’un bâti, en fonction d’une valeur de succion imposée et des propriétés mécaniques ou hydromécaniques de la structure et du sol d’assise. La déflexion relative du bâti est alors comparée à des valeurs seuils afin d’évaluer le dommage.La dernière partie de cette thèse consiste en une étude de faisabilité pour le développement de courbes de vulnérabilités adaptées à la problématique du retrait gonflement. Ces courbes représentent la moyenne des dommages d’un type de bâti conçu sur un type de sol gonflant pour une valeur de succion imposée. Ces courbes ont été développées à partir d’une typologie des sols gonflants et d’une typologie des bâtis issue des bases de données des maisons sinistrées. La moyenne des dommages est calculée par la méthode de Monte-Carlo, en prenant en compte la variabilité des paramètres du bâti
Clayey soils can present large volumetric deformations in response of water content change. This phenomenon of shrinkage and swelling of clayey soils is recognized as a costly natural hazard throughout the world. In France, this cost is reported between 1988 and 2007 to 5 million Euros, ranking in second class of the French natural hazards in terms of cost of damage after the floods. The individual masonry buildings with shallow foundations are the most affected by this phenomenon that causes a differential settlement of the building leading to cracks in facades and structural elements, especially in unreinforced masonry elements.The objective of this thesis was to study the vulnerability of the building, against the shrink-swell hazard through an analysis of soil-structure interaction. This work was focused on three major points: - Hydro-mechanical behavior of clay soils - Soil-structure interaction - Evaluation of structural damage.The hydro-mechanical behavior of clay soils was considered by the concept of state surface and integrated into a soil-structure interaction model, based on the Winkler model, with increasingly complex approaches: 1D, 2D and 3D by modeling the building behavior respectively by a spring system, the beam element and the plate element. These models of soil-structure interaction are able to calculate the relative deflection of the building, according to the values of imposed suction, mechanical properties of the structure and hydro-mechanical properties of the soil. The relative deflection of the building is then compared to threshold values of the classical damage categories to assess the building damage.Finally a feasibility study was conducted on the development of vulnerability curves adapted to the problem of shrinkage – swelling of clayey soils. These curves represent the average of structural damage versus suction, for each type of building. These curves were developed based on a classification of expansive soils and a building typology outcome from databases of affected buildings. The average damage is calculated by the Monte-Carlo method, taking into account the variability of the building parameters

The present thesis is composed of two parts. The first part presents the chemo-mechanical effect on the volumetric and shearing behaviour of saturated soil as a continuum. The second part presents the chemo-mechanical effect on the shearing behaviour of a discontinuity. Following Gajo and Loret, 2003, saturated soil is considered as a two-phase deformable porous medium, namely solid and fluid phase consisting of different species. There are clay particles, adsorbed water and ion in the solid phase. The fluid phase includes pore water and salt which may diffuse through the porous medium. In addition, water may be exchanged between solid and fluid phases while the mass of clay particles and ions in the solid phase remains constant. Thus, the balance equations are momentum balance, the mass balance of pore water and salt in the fluid phase, the mass balance of absorbed water. A two-dimensional element is proposed to approximate the solution of the balance equations which has been implemented in a user-defined subroutine (UEL) of the commercial code ABAQUS. This element has taken into account the 2D displacement of the soil skeleton, multidimensional flow of water, osmotic effect, advection and diffusion of salt. A new hyperelastic law is presented by extending the chemo-mechanical model proposed by Loret et al., 2002. The innovative aspects of the proposed model are the following: 1) both the tangent shear stiffness and bulk stiffness depend on the applied stress state and pore water solution, 2) the anisotropy of fabric tensor is introduced in the elasticity law. Moreover, the yield function has been modified to obtain smaller peak strength for highly overconsolidated samples to have better agreement with experimental results. The proposed 2D model is validated with experimental results on natural bentonite (a very active clay) and the soil extracted from low activity clay of Costa della Gaveta slope in Southern Italy. The swelling and swelling pressure of these two types of soil have been computed and compared with the experimental data to show the accuracy and reliability of the proposed model. Furthermore, the effects of elastic anisotropy are investigated on the soil behaviour such as swelling, swelling pressure, stress paths and horizontal stress. Furthermore, a simplified analysis has been performed to show the effect of swelling pressure on slope stability. In the second part, a contact element is proposed to account for the flow of water and diffusion of salt in addition to displacement in the simulation of interface behaviour. This element has been implemented in a user-defined subroutine (UEL) of ABAQUS. Moreover, a nonlinear elasticity law is proposed in which traction in the contact region has been taken into account. The Mohr-Columb yield criterion is used for the plastic regime in which it is assumed that the friction angle is a function of salt concentration and displacement rate based on the experimental data. Some preliminary results are shown for the flux of salt and water through the element. In addition, the effects of salt concentration and displacement rate are presented on the shearing behaviour of the contact element.

Climate change poses real threats to the sustainability of slopes, particularly in the tropical region of the world. Its effects have caused a greater occurrence of extreme climate events that are reflected in a greater occurrence of slope failure incidents for this region. The hydro-mechanical characteristics of soils linked with climate variation are factors that can explain deterioration in slope stability. Therefore, the ability to analyse the hydro-mechanical behaviour properly is worthy of investigation and this can be done by the use of experimental investigation and numerical modelling using both saturated and unsaturated soil properties. In this thesis, the description of the important effects of climate impacts on slope stability has been made for a failed tropical residual soil slope located in Precinct 9, Putrajaya, Malaysia. Part of the work involved soil sampling for the acquisition of undisturbed soil samples from the slope. Series of advanced saturated and unsaturated laboratory testing for both hydrological and mechanical properties have also been implemented and were used in transient, unsaturated numerical modelling of slope stability analysis (using Plaxis 2D). The results demonstrate that within a slope the mobilised shear strength drops quickly during a rainfall event (due to rainfall infiltration) but recovers much more slowly during drying. This shows how a series of regular rain storms with short periods of drying in between can cause a ratcheting effect, with rapid loss of strength during each period of rain that is not recovered during the intermediate drying periods. In addition, the results also show that the adoption of critical state soil parameters is more suitable to match the observed failure. The failure was due to a very extreme amount of rainwater infiltration in the two days before the incident, including the largest daily rainfall in 2007 of 140mm.

Experimental investigation of the behaviour of unsaturated soils is a key component in the analysis and design of a wide range of geoenvironmental problems. Furthermore, in some circumstances the influence of temperature variation needs to be considered in addition to the hydraulic and mechanical behaviour. Notwithstanding the significant theoretical and numerical developments, experimental determination of Thermo-Hydro- Mechanical (THM) soil properties remains a challenge. Consequently, in order to address these problems this thesis presents the design and development of two Temperature and Suction controlled Oedometer (TSO) cells with operational support. The new cells permit parallel testing of unsaturated soil over a temperature range of room temperature to 90°C. Suction control is achieved using the axis translation technique and is currently limited to 1.5 MPa. Vertical stress is applied via an air pressure controlled loading ram, operating up to a maximum stress of 2.5 MPa. The new apparatus has been calibrated in response to variations in temperature, suction and net stress. Subsequently, an experimental methodology for sample preparation and testing has been established. Speswhite kaolin has been used throughout this study due to its moderate swelling properties and the abundance of independently obtained data available. Basic geotechnical properties of kaolin have been determined via standard experimental techniques. Stress-path, temperature-path and suction-path tests have been successfully carried out using the new equipment. The results obtained have been validated in comparison to independently obtained data. From the work undertaken it is clear that temperature effects on the behaviour of kaolin are significant. Further work is now necessary to explore the behaviour of other soil types

This thesis presents the design details of an automated modified ring shear apparatus for the testing of unsaturated soils using the axis translation technique. The system is fully automated and it can be used for conducting Constant Load and constant Suction (CLS) shear tests, Constant Volume and constant Suction (CVS) shear tests, Constant Load and constant Water content (CLW) shear tests as well as Constant Volume and constant Water content (CVW) shear tests. In addition to shear tests, the soil-water retention curve (SWRC) can also be generated for the same specimen in the same testing device. The principal advantages of the device include its ability to shear unsaturated soils to very large deformations as well as conducting tests under constant volume conditions. Analysis of the experimental data using these characteristics suggests that the volumetric changes of the sheared specimen are not the only factor affecting the changes of its water content under constant matric suction conditions. In addition, the experimental evidence suggests that shear deformations much greater than those typically used in the testing of unsaturated soils are required if an ultimate water content equilibrium condition is to be reached. Such an equilibrium condition is required if critical state data is to be determined for unsaturated soils. The thesis also presents the design and use of additional equipment utilised for testing unsaturated soils. This includes the use of an electronic balance to measure the change in water volume of the specimen, and provides details on how the readings of the balance can be stabilized to remove the noise caused by the connection of the tubes to the overflow jar. A simple technique relying solely on the measurement of the water volume change to determine the volume of diffused air removed by the flushing operations is also presented. The other pieces of equipment described include a volume gauge/air trap that can be used to measure the water volume changes of unsaturated soil specimens, and a simple, robust, and precise pressure gauge.

The effect of temperature on the behaviour of soils is a crucial problem in geothermal engineering as soils are subjected to the action of temperature variation in many diverse conditions. It is observed in both laboratory experiments and in situ tests that temperature variations can induce interaction between the thermal, hydraulic and mechanical behaviour of soils, which is known as thermo-hydro-mechanical (THM) coupling. In order to simulate the THM coupling, it is necessary to combine the equations governing heat transfer through the soil mass with the equations governing pore fluid flow through the soil skeleton, and the equations governing the stress-strain behaviour of the soil. Due to the complexities of the governing equations, the finite element (FE) method has been regarded as an appropriate numerical tool to solve THM coupled problems. In this thesis, all of the research has been carried out using the Imperial College Finite Element Program (ICFEP), which has been developed specifically for geotechnical engineering analysis. This thesis develops the governing equations for THM coupled analysis. It then describes the implementation of these equations for fully saturated soils in ICFEP. This theory has been applied to all types of elements in ICFEP, such as solid, beam, bar, joint, membrane and shell elements. Thermal boundary conditions relevant to geotechnical engineering have also been developed and implemented into ICFEP. A series of validation tests on the new facilities has been performed, and the results have been compared to those obtained using analytical and finite difference methods. To avoid numerical oscillations, the time-step constraints in coupled transient FE analyses, as well as an adequate mesh discretisation in highly convective coupled analysis, have been investigated. The findings from the analytical and numerical studies have been applied to a simulation of an open-loop ground source energy system, and the results show an excellent agreement with the available approximate solution.

Les sols et les sous-sols urbains peuvent être contaminés par des polluants divers. En effet, leur mobilité est régie par différents processus physico-chimiques de transport et de rétention/libération (la rétention tend à freiner la propagation des particules tandis que la libération accélère le transport des particules). Ainsi, il est nécessaire de comprendre les mécanismes du transport des polluants dans des sols et de prédire cette migration à long terme. Tout d’abord, nous détaillerons un modèle de transport et d’écoulement en milieu poreux saturé, qui est basé sur les EDPs. De plus, ces équations se réfèrent au transport de masse en milieu poreux saturé qui est régi en général par la classique équation de type convection-dispersion-diffusion. En bref, les équations de l'écoulement et du transport avec des effets de viscosité et la densité sont mises en œuvre dans les codes de différences et éléments finis en utilisant la Librairie d’éléments finis Diffpack. Ensuite, nous proposons de coupler le modèle de transport avec l’érosion interne. Pour atteindre ce but, nous avons proposé un modèle mathématique de l’érosion interne et nous l’avons validé par des tests expérimentaux. De même, nous avons montré que l’érosion influe directement sur le transport des particules. Ceci nous a amené à définir un couplage entre le transport, l’érosion et le transfert de polluants. En outre, le modèle développé est basé sur le transport réactif qui tente de simuler les processus d’écoulement-transport, les réactions physico-chimiques. Enfin, nous avons introduit le comportement des milieux déformables dans le modèle pour ainsi étudier le rôle de la déformation du sol dans le transport
Soil and urban basement may be affected by various pollutants. Indeed, their mobility is governed by different physical and chemical processes of transport and retention / release. The retention tends to reduce the spread of the particles while the release accelerates the transport of particles. Thus, it is necessary to understand the mechanisms of pollutants transport in the soil and to predict the long-term migration. First, we will describe a model of transport and flow in porous and saturated media which is based on PDEs. In addition, these equations refer to the mass transport in saturated and porous medium which is governed generally by the classical convection-dispersion-diffusion equation. Briefly, the equations of flow and transport with effects of viscosity and density are implemented in the codes of differences and finite elements using the software Diffpack. Then, we propose to couple the transport model with internal erosion. Thus, we proposed a mathematical model of internal erosion and we validated it by experimental tests. Similarly, we have shown that erosion has a direct influence on particle transport. This led us to define a coupling between the transport, erosion and pollutants. In addition, the developed model is based on reactive transport that attempts to simulate the process of flow-transportation, physical and chemical reactions. Finally, we attempt to model the effect of the transport of eroded particles on deformable media, with respect to the role of the deformation of the ground

The thesis is aimed at characterising the multi-scale and hydro-mechanical behaviour of lightly compacted silty sand penetrated by a turf-grass (Cynodon Dactilon). The study will allow better assessing the impact of vegetation on this compacted soil that has been used in an experimental and fully-instrumented embankment. The literature agrees that roots are enhancing soil shear strength properties while contrasting results have been found in terms of soil hydraulic behaviour. Moreover, there is a lack of information on how roots affect soil microstructure and its consequences at the macroscopic scale (soil hydraulic behaviour, volume change and shear strength properties). A protocol for soil compaction and roots growth was followed for preparing all the tested samples. The soil was lightly compacted, wetted under unconfined conditions to favour plant growth, and then dried up to different hydraulic states. The same soil, plant and seeding density used in the monitored embankment were adopted. Several techniques were exploited to characterise roots geometrical and mechanical features. Large cell triaxial and direct shear tests were performed under saturated and partially saturated conditions. Different stress-strain responses were observed in the vegetated soil at different hydraulic states, due to different roots failure mechanisms and to the combination of water availability and the suction within the soil. Results were interpreted with several constitutive stress expressions for partially saturated soils to consider these state and stress variables. Larger compression deformations on shearing were systematically observed on rooted samples. Roots slightly affected the friction angle but generated an increase in soil cohesion. These observations were confirmed by direct tensile tests performed at different roots growth stages and hydraulic states. A constitutive expression was proposed to predict the increase in cohesion knowing the properties of roots and the soil hydraulic state. Concerning the hydraulic behaviour, roots induced a systematic increase in soil water-saturated permeability. Water retention properties were also affected, with a decrease in the retention capacity as roots volume increased. Micro-CT tomography and mercury intrusion porosimetry were carried out at different soil hydraulic states on samples including plant individuals to obtain information about changes in soil microstructure. Reconstructed information from the two techniques showed that roots were generally increasing macropores (larger than 100 micrometres) due to fissuring and soil-root interface phenomena while reducing smaller pores (below 5 micrometres) due to mucilage clogging. The opening of fissures was enhanced on concurrent soil and roots shrinkage upon drying. The alterations generated by roots growth on the soil structure allowed explaining not only the different soil hydraulic responses but also the soil volume change behaviour. A good agreement between the volume of fissures and the volume of roots was found and allowed calibrating and validating a model able to predict the soil water retention properties and permeability values based on the microstructural changes observed. Results were used to simulate the effect of different periods of plants growth on the hydro-mechanical behaviour of the monitored embankment during a rainfall event. The vegetated slopes remained stable throughout the simulation, even when completely saturated, thanks to the mechanical reinforcement of the roots. Nevertheless, the higher permeability within the vegetated soil had a negative consequence, which was evidenced by a drastic drop in the slope stability safety factor at the early stages of the hydraulic event.
La tesis tiene como objetivo caracterizar el comportamiento hidromecánico de una arena limosa compactada y con raíces (Cynodon Dactilon). El estudio ha permitido evaluar el impacto de la vegetación en este suelo, que ha sido utilizado en un terraplén experimental. El estado de arte indica que las raíces mejoran las propiedades de resistencia al corte de un suelo, mientras que hay resultados contrastantes en términos del comportamiento hidráulico. Además, se carece de información sobre cómo las raíces afectan a la microestructura del suelo y sus consecuencias a escala macroscópica. Se siguió un protocolo para la compactación del suelo y el crecimiento de las raíces para la preparación de todas las muestras estudiadas. El suelo se compactó ligeramente, se humedeció en condiciones no confinadas para favorecer el crecimiento de la planta, y luego se secó a diferentes estados hidráulicos. Se utilizaron varias técnicas para caracterizar las propiedades geométricas y mecánicas de las raíces. Se realizaron ensayos de corte directo, edométricos y triaxiales con equipos de grandes dimensiones. Se observaron diferentes respuestas de tensión-deformación en el suelo con vegetación debido a los diferentes mecanismos de rotura de las raíces y a la combinación de humedad y de succión en el suelo. Los resultados se interpretaron con leyes constitutivas en términos de tensiones efectivas para suelos parcialmente saturados. En las muestras con raíces se observaron sistemáticamente deformaciones mayores de compresión durante el desarrollo del corte. Las raíces afectaron ligeramente el ángulo de fricción y desarrollaron un aumento en la cohesión del suelo. Estas observaciones también se confirmaron mediante ensayos de tracción, que se realizaron a diferentes estados de crecimiento de las raíces. Se propuso una expresión constitutiva para predecir el aumento de la cohesión en función de las propiedades de las raíces y el estado hidráulico del suelo. En cuanto al comportamiento hidráulico, las raíces inducen un aumento de la permeabilidad saturada del suelo y una disminución en la capacidad de retención al agua a medida que aumenta el volumen de las raíces en el suelo. Se realizaron ensayos de micro-tomografía de rayos X y de porosimetría de intrusión de mercurio sobre muestras con raíces. La información reconstruida de las dos técnicas ha indicado que las raíces han inducido el aumento de los poros de más de 100 micrómetros debido a la generación de fisuras y a fenómenos de interfase suelo-raíz, a la vez que han ocluido los poros más pequeños (menores de 5 micrómetros) debido a la producción de mucílago. Las fisuras también se han abierto por la retracción simultánea del suelo y de las raíces durante el secado. Estas alteraciones inducidas sobre la microestructura han permitido explicar mejor los cambios en las propiedades hidráulicas y de cambio de volumen del suelo. Se ha encontrado una relación entre el volumen de fisuras y el volumen de raíces, lo que ha permitido desarrollar y calibrar un modelo capaz de predecir las propiedades de retención al agua y los valores de permeabilidad del suelo. Los resultados experimentales se han utilizado para simular el efecto que tiene los diferentes crecimientos de las plantas sobre el comportamiento hidromecánico del terraplén instrumentado durante un episodio de lluvia. Los taludes con raíces se mantuvieron estables a lo largo de la simulación, incluso cuando estaban completamente saturados, gracias al refuerzo mecánico de las raíces. Sin embargo, la mayor permeabilidad del suelo vegetado tuvo una consecuencia negativa, que se evidenció con una drástica caída en el factor de seguridad del talud en las primeras etapas del episodio de lluvia.
La thèse vise à caractériser le comportement multi-échelles et hydro-mécanique du sable silteux pénétré par des racines de Cynodon Dactilon. L'étude permettra d’évaluer l'impact de la végétation sur ce sol compacté utilisé dans un remblai expérimental en extérieur. La littérature s'accorde à dire que les racines améliorent les propriétés de résistance au cisaillement du sol, tandis que des résultats contrastés ont été obtenus en ce qui concerne leur effet sur le comportement hydraulique. De plus il existe peu d'information sur la façon dont les racines affectent la microstructure du sol et leurs conséquences à l'échelle macroscopique. Un protocole de compactage du sol et de croissance de racines a été suivi pour la préparation de tous les échantillons testés. Le sol a été légèrement compacté, mouillé pour favoriser la croissance des plantes, puis séché jusqu'à différents états hydrauliques. Les plantes et la densité d'ensemencement ont été les mêmes que ceux utilisés dans le remblai. Plusieurs techniques ont été exploitées pour évaluer les caractéristiques géométriques et mécaniques des racines. Des essais de cisaillement triaxial et direct ont été effectués avec des équipements de grande dimension dans des conditions saturées et partiellement saturées. Différentes réponses de contraintedéformation ont été observées pour le sol végétalisé à différents états hydrauliques, en raison de différents mécanismes de rupture des racines. Les résultats ont été interprétés à l'aide de plusieurs lois de comportement pour les sols partiellement saturés afin de tenir compte des variables d'état et de stress. Des déformations de compression plus importantes lors du cisaillement ont été observées sur des échantillons avec racines. Les racines ont généré une augmentation de la cohésion du sol. Ces observations ont été confirmées par des essais de traction directe effectués à différents stades de croissance des racines. Une loi de comportement a été proposée pour prédire l'augmentation de la cohésion en connaissant les propriétés des racines et l'état hydraulique du sol. En ce qui concerne le comportement hydraulique, les racines ont induit une augmentation de la perméabilité saturée en eau du sol et une diminution de la capacité de rétention à mesure que le volume des racines augmentait. La tomographie microCT et la porosimétrie par intrusion de mercure ont été effectuées à différents états hydrauliques du sol sur des échantillons avec racines pour obtenir des informations sur les changements de la microstructure du sol. L'information reconstruite à partir des deux techniques a montré que les racines augmentaient généralement les macropores (plus de 100 micromètres) en raison de phénomènes de fissuration et des interfaces sol-racine tout en réduisant les pores plus petits (moins de 5 micromètres) en raison du colmatage dû au mucilage. L'ouverture des fissures a été augmentée par le retrait simultané du sol et des racines lors du séchage. Les altérations générées par la croissance des racines sur la structure du sol ont permis d'expliquer les différentes réponses hydrauliques du sol et aussi son changement de volume. Un bon accord entre le volume des fissures et le volume des racines a été trouvé et a permis de calibrer et de valider un modèle capable de prédire les propriétés de rétention d'eau et les valeurs de perméabilité du sol à partir des changements microstructurels observés. Les résultats ont été utilisés pour simuler l'effet de différentes périodes de croissance des plantes sur le comportement hydro-mécanique du remblai lors d'une chute de pluie. Les pentes végétalisées sont restées stables tout au long de la simulation, même complètement saturées, grâce au renforcement mécanique des racines. Néanmoins, la perméabilité plus élevée dans le sol végétalisé a eu une conséquence négative, qui a été mise en évidence par une baisse drastique du facteur de sécurité de stabilité de la pente aux premiers stades de l'événement hydraulique.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第22491号
農博第2395号
新制||農||1076(附属図書館)
学位論文||R2||N5271(農学部図書室)
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 村上 章, 教授 藤原 正幸, 教授 白岩 立彦
学位規則第4条第1項該当

Ce travail s’inscrit dans le cadre du projet ANR Terredurable qui regroupe 4 thèses à vocation expérimentale et 2 thèses à vocation théorique, et peut être rangé dans la deuxième catégorie.Cette thèse est consacrée à l’étude du comportement hydro-mécanique des sols fins dans les ouvrages en terre. Ces sols se caractérisent par une saturation proche de 1 avec une présence d’air occlus apportant une forte compressibilité au fluide interstitiel. Ces sols ont un comportement qui diffère de celui des sols désaturés au-delà de l’entrée d’air et des sols parfaitement saturés.Le travail réalisé peut-être décomposé en plusieurs parties :Tout d’abord, la notion de compactage est étudiée dans le but de mieux comprendre l’importance que joue l’air de part et d’autre de l’optimum Proctor. Un travail sur la caractérisation de l’état de contrainte dans le sol à la fin du compactage et de l’évolution de sa contrainte de préconsolidation est apporté.Un modèle théorique permettant de prédire le comportement hydro-mécanique des sols proches de la saturation est présenté. Il permet de répondre à des problématiques telles que la montée des pressions interstitielles dans les noyaux de barrage pendant la construction ou encore le déconfinement de déblais après travaux de terrassement. Le modèle développé se basant sur la quantité d’air occlus au sein du fluide interstitiel a été implémenté dans un code de calcul aux différences finies et comparé aux mesures expérimentales d’essais de laboratoire et ouvrages en terre. L’instrumentation et le suivi au cours du temps du gonflement d’un déblai marneux ont été réalisés dans le cadre de cette thèse
The research presented is funded by the French National Project “TerreDurable” which is dedicated to the constitutive relations of soils in quasi-saturated conditions (close to saturation).This thesis is devoted to the study of hydro-mechanical behavior of fine soils in earthworks. These soils are closed to saturation with the presence of occluded air providing high compressibility in interstitial fluid. These soils have a behavior that differs from non-saturated soil (after air entry) and fully saturated soils.The work may be divided into several parts:• Study of compaction of fine soils and evolution of soil physical characteristics in order to characterize the initial state for a numerical modeling.• Development of a theoretical model and its implementation in a finite differences code in order to predict the evolution of pore pressure and deformation of soil near to saturation. Comparison with experimental measurements (laboratory tests and earthworks). The instrumentation and the monitoring of a marl earthwork excavation were made in the context of this thesis

Les sols agricoles représentent près de 66 % des émissions anthropiques de protoxyde d’azote (N₂O), 3ème gaz responsable de l’effet de serre additionnel. La variabilité des émissions mesurées au champ est élevée. La structure du sol impacte à la fois la production et le transport du N₂O dans le profil de sol. L’objectif de cette thèse était de comprendre le rôle de l’état structural du sol sur la variabilité spatiale des émissions de N₂O. La démarche utilisée associe deux types d’expérimentations en laboratoire - à l’échelle d’un bac de 0,3 m² x 0,1 m et sur une maquette de parcelle agricole de 10 m² x 0,3 m en sol nu - à un travail de modélisation intégrant des processus physiques, chimiques et biologiques dans le profil de sol et le ruissellement, le tout à une résolution temporelle fine. Ce travail a mis en évidence une hiérarchie entre les processus de production et de transport, qui évolue avec le temps et les conditions environnementales : dans des conditions favorables à la dénitrification, la production de N₂O augmente avec la masse volumique en lien avec une augmentation de la part de porosité remplie d’eau, jusqu’à une certaine limite. Le modèle déterministe a montré que la dynamique de la pluie et du ruissellement associé modifie l’intensité et la dynamique des émissions de N₂O, celles-ci étant plus tardives dans les zones avales recevant du ruissellement. Enfin, ce travail a confirmé la complexité du déterminisme des émissions de N₂O et a permis de souligner l’intérêt de caractériser la structure du sol et les émissions à une haute résolution spatiale pour améliorer la qualité des modèles prédictifs
Agricultural soils account for 66 % of anthropogenic nitrous oxide emissions (N₂O), the 3rd greenhouse gas emitted from anthropogenic activities. N₂O emissions variability measured in-situ is quite high. Soil structure affects both N₂O production processes and N₂O movements through the soil profile. The main goal of this work was to understand the part of soil structure in soil N₂O spatial variability. Two kinds of laboratory experiments were designed: rainfall experiments on soil trays of 0.3 m² x 0.1 m and on a 10 m² x 0.3 m box with a slope. A modelling approach with a short time step was combined, involving representation of physical, chemical and biological soil processes as well as a representation of surface runoff.This work highlighted a hierarchy between N₂O production and N₂O transportation processes, which evolve with time and environmental conditions: under conditions that favor denitrification, N₂O production increases with soil bulk density due to an increase in the water-filled pore space, until a threshold limit. The deterministic modelling approach showed that rainfall dynamic and resulting runoff affect soil N₂O emissions, those emissions occurring later downslope. Finally, this work highlighted the complexity of soil N₂O emissions determinism and we pointed out that the description of soil structure at a high spatial resolution would be useful to improve modelling quality

Traditional soil classification methods invoke physical differences based on particle size to group soils into textural classes. Resulting groupings are used to make predictions about soil attributes and processes of interest including hydrologic response. My hypothesis is that more useful classification schemes will be created by starting with response and applying an inverse approach to generate soil groupings. I propose an alternative classification scheme based on these hypotheses, using techniques of cluster analysis. The resulting system has high predictive capacity with simplicity comparable to the U.S. Dept. of Agriculture soil textural triangle or other similar classification diagrams. I conclude that: classification is most appropriate when carried out on process and objective specific bases; there is a physical meaning to cluster-based groupings, which allows for more appropriate segregation of response as compared to textural groupings; using clusters, a small number of samples can be used to characterize the range of response.

La modelisation quantitative du transfert de l'eau et des solutes dans la zone non saturee des sols necessite la mesure in situ des parametres hydro-dispersifs. L'infiltrometrie sous pression controlee couplee a l'utilisation de traceurs de l'ecoulement de l'eau est pour cela un outil efficace et simple a mettre en uvre sur le terrain. La modelisation des transferts et l'analyse des resultats des calculs conduit a une methode simplifiee de caracterisation hydro-dispersive par infiltrometrie. La conductivite hydraulique k et la sorptivite s sont estimees a partir de l'analyse aux temps courts ou aux temps longs de l'infiltration cumulee. La methode mono-tracage est utilisee pour le calcul de la fraction d'eau mobile f. Une nouvelle methode d'estimation du coefficient de dispersion d est proposee. Elle est telle que d reste l'unique parametre a ajuster sur les donnees issues de l'echantillonnage du sol a la fin de l'infiltration. L'incertitude d'estimation est de plus definie pour chacun des parametres. Le domaine de validite des methodes est precise a partir de donnees generees numeriquement. Pour le calcul de k, s et f, il est defini a partir des temps caracteristiques de l'ecoulement de l'eau, de la lame de solution infiltree et de la dispersivite du milieu. La validite du mode de determination de d depend du nombre adimensionnel pext. Trois sols sont caracterises in situ. La porosite bimodale des deux premiers induit une forte augmentation des parametres hydrodynamiques a l'approche de la saturation, et de f avec la taille moyenne de pores hydrauliquement fonctionnels. Le troisieme est soumis a l'encroutement de surface. Les resultats de la caracterisation hydro-dispersive renforces par l'observation du reseau poral sur lames minces montre que le role des croutes de surface sur l'infiltrabilite est minimise par rapport a celui du sol sous-jacent. De plus, le sol sous-jacent semble protege de la coalescence par les croutes de surface.

Wetlands serve important ecosystem functions such as carbon sequestration but are often affected by disturbances like urban development, agriculture, and road building. For wetlands created to mitigate losses, it is important that the ecosystem functions successfully replicate those of natural wetlands. Created wetlands have frequently not provided these functions due to issues including low organic carbon (OC), high soil bulk density (BD), lost topsoil, incorrect hydrology, and failure of targeted vegetation establishment. Organic matter (OM) amendments help created wetlands attain these functions quicker, but, their long-term effects are seldom reported. This research's purpose was to measure the long-term effects of treatments at a sandy tidal freshwater wetland created in 2003 (WWE) and a fine-textured, non-tidal wetland created in 2002 (CCW). We tested OM treatments, topsoil amendment, and microtopography effects on soil and vegetation properties at WWE and OM treatments at CCW. Pedogenic changes in soil morphology, physical and chemical properties were detected by comparing data to previous studies at these sites. At both sites, litter and biomass parameters were measured to estimate total mass C. Herbaceous biomass was measured at WWE. At WWE, no long-term OM treatment effects from 78 or 156 Mg ha-1 were observed. Soils in pits had higher OC, lower BD, and lower chroma than soils on mounds. Sandy and loamy HSFI's developed at WWE within four years, but there were fewer sandy indicators after 12 years. Loamy HSFI's were lost at CCW from 2003 to 2016. Plots at WWE that were amended with topsoil had higher soil mass C than the sandy soil due to a finer texture, but total mass C did not vary. At CCW, long-term OM treatment effects were observed, including lower BD, higher soil mass C, and higher tree mass C with increasing compost rates up to 224 Mg ha-1. Overall, the ideal compost loading rate for constructed wetlands varied with wetland type and mitigation goals. Compost rates of 112 Mg ha-1 are sufficient for short term establishment of wetland vegetation and hydric soil properties, but higher rates near 224 Mg ha-1 may be required for effects that last over 10 years.
Ph. D.

Drought indices based on monthly precipitation and sometimes temperature are widely used due to their simple calculation with readily available climate data. The portrayal of drought through simple precipitation anomalies or water balances when accounting for temperature may not capture the potentially complex evolution of drought events due to the timing, intensity, and frequency of precipitation events at the daily scale. In this study, we present a new drought index that incorporates a deterministic soil model, HYDRUS-1D, and daily climate data to assess how representative simple drought indices are of soil moisture status in the Southwest. Specifically, we compare our drought index with two widely used drought indices: the Standardized Precipitation Index (SPI) and the Standardized Perception-Evapotranspiration Index (SPEI). Modeled soil moisture output was summed into monthly values for direct comparison between indices. SPI and SPEI proved to be representative of soil moisture status at shallow depths, correlating best at a two-month window. SPI correlated higher with our modeled drought index than SPEI in shallow settings across all study sites. Intense drought events were controlled by the magnitude and frequency of precipitation, with large events creating water surplus and then a slow decay in soil moisture until the next large event. Furthermore, heat map correlations indicate that monitoring drought at depth is dependent upon the previous years monsoon, with the best correlating window growing with distance from monsoon onset. Modeled soil moisture showed volumetric water content increased during monsoon season and remained high through the fall and into the winter months. Higher moisture content increased hydraulic conductivity, priming the soil profile for winter recharge. We believe that the addition of a soil physics based drought index greatly improves drought monitoring conditions for the southwest.

Le stockage de chaleur dans des géostructures énergétiques telles que des remblais est réalisable en installant des échangeurs horizontaux au sein des différentes couches de sol compacté. Dans ce système, l'énergie thermique qui est injectée en été via un fluide caloporteur circulant dans les échangeurs de chaleur, peut être extraite en période hivernale. Dans ces conditions, lors de la mise en service, le sol compacté est soumis à des variations de température quotidiennes et saisonnières. Ces variations pourraient modifier les performances thermo-hydro-mécaniques du sol compacté. Ainsi, le but de cette étude est d'étudier les performances thermiques et mécaniques d'un sol compacté lorsqu'il est soumis à des variations de température monotones et cycliques. Le sol étudié est un limon fréquemment utilisé dans les constructions de remblais en France. Le comportement thermique et mécanique du sol est étudié à un état de compactage correspondant aux propriétés thermiques optimales. Dans cet état, le sol compacté est non saturé ce qui complexifie l'estimation de ses propriétés thermiques. Pour pallier à ces difficultés, dans cette étude, un modèle inverse est proposé pour estimer les propriétés thermiques du sol compacté. L’efficacité du modèle est testée sur un jeu de données acquises dans la gamme de 20 à 50 °C dans un modèle réduit en laboratoire. Les valeurs obtenues sont ensuite comparées à des mesures classiques en laboratoire (méthodes en régime transitoire et en régime permanent). Cette méthode pourrait permettre de suivre l’évolution des propriétés thermiques du stockage et ainsi assurer son efficacité tout au long de sa durée de vie. La question de la stabilité à long terme de ces structures soumises à des variations thermiques monotones (5, 20 et 50 °C) et cycliques (5 à 50 °C) est ensuite abordée à l'aide d'essais oedomètriques et d’essais de cisaillement direct à température contrôlée. Les résultats des essais de compressibilité ont montré que l'effet de la variation de température est plus prononcé sous une contrainte verticale supérieure à la pression de préconsolidation. Les indices de compression et de gonflement peuvent être considérés comme indépendants des variations de température. Donc le tassement global du remblai dû aux variations thermiques pourrait être considéré comme négligeable. Les résultats des essais de cisaillement direct ont montré que les variations de température (monotones ou cycliques) augmentent la cohésion ce qui est avantageux pour la capacité portante et la stabilité des pentes des remblais. Dans la phase de conception d'un remblai de stockage, ces résultats seraient utiles au dimensionnement du système si des trajectoires thermomécaniques similaires à celles de cette étude sont respectées. Dans une dernière partie, une simulation numérique prenant en compte l'interaction sol-atmosphère est réalisée afin d’évaluer la performance thermique de ce sol compacté en conditions naturelles. Différentes profondeurs d'installation de boucles d'échangeurs de chaleur sont testéss ainsi que différents scénarios de stockage. Les résultats ont montré que le sol compacté augmente de 8.5% les performances du système par rapport à l'installation d'une boucle horizontale dans le sol naturel (non compacté). Les résultats de deux scénarios différents ont montré qu’en été avec un fluide ayant une température d'entrée de 50 °C augmente significativement la performance du système. De plus, une installation plus profonde des boucles horizontales améliore également la performance du système. Il convient de noter que le remblai est en interaction avec l'atmosphère depuis ses surfaces supérieure et latérale, l'efficacité thermique de la structure pourrait être affectée en raison des pertes de chaleur. Par conséquent, il est préférable de placer les échangeurs de chaleur loin des surfaces supérieures et latérales
Nowadays, thermal energy storage in geostructures like embankments can be possible by installing the horizontal heat exchangers in different layers of compacted soil. In this system, the thermal energy is stored in summer via a fluid, circulating in the heat exchangers, to be extracted in the demand period. When the serviceability of embankment as a medium to store the thermal energy starts, the compacted soil will be subjected to the daily and seasonally temperature variations. These seasonal temperature variations could modify the thermo-hydro-mechanical performance of the compacted soil. Thus, the aim of this study is to investigate the thermal and mechanical performances of a compacted soil when it is subjected to monotonic and cyclic temperature variations. The studied soil is a sandy lean clay that is frequently used in embankment constructions in France. The thermal and mechanical behavior of the soil are investigated at a compaction state corresponding to the optimal thermal properties. However, this compacted soil is unsaturated and the estimation of its thermal properties is complex. In this study, an inverse analytical model is proposed to estimate the thermal properties of the soil using temperature monitoring in the range of 20 to 50 °C in a soil compacted in a large container. The estimated thermal parameters were compared to classical laboratory measurements (transient and steady-state methods). The comparison showed that the estimated values were close to the results obtained in transient laboratory method. Using this method, the thermal efficiency of the compacted soil can be verified in the lifetime of the storage system. To ensure the structure stability, long-term mechanical response of these systems subjected to monotonic and cyclic temperature variations should be investigated. To achieve this aim, using temperature-controlled oedometric and direct shear devices, consolidation and shear parameters of the studied soil at different monotonic (5, 20, and 50 °C) and cyclic (5 to 50 °C) temperatures were investigated. The results of temperature-controlled oedometric tests showed that the effect of the temperature variation is more pronounced under vertical pressures higher than the preconsolidation pressure. The compression and swelling indexes could be considered independent of temperature variations. Therefore, the overall settlement of the embankment due to thermal variation near the heat exchangers could be considered negligible. The results of temperature-controlled direct shear tests showed that the temperature variations (monotonic heating or cooling, or temperature cycles) increased the cohesion which is beneficial for the bearing capacity and slope stability of embankments. These results can be directly used in the design of embankments to store thermal energy exposed to similar thermo-mechanical paths. Finally, the thermal performance of the compacted soil is verified using a numerical simulation considering the soil atmosphere interaction. Different depths installation of heat exchanger loops and different heat storage scenarios were simulated. The results showed that the compacted soil increases 8.5% the systems performance compared to the horizontal loop installation in the local soil. The results of two different scenarios show that an inlet fluid temperature of 50 °C in summer increases highly the system performance (13.7% to 41.4%) while the improvement is less significant (0% to 4.8%) for the ambient inlet temperature. Moreover, a deeper installation of horizontal loops increases the system performance. From the numerical simulation results can be concealed that the embankment is in interaction with the atmosphere from its upper and lateral surfaces, the thermal efficiency of the structure could be affected due to heat losses. Therefore, it is preferable to place the heat exchangers away from the top and side surfaces

A preocupação com o destino de produtos químicos e água, aplicados ao solo, tem motivado vários pesquisadores a desenvolverem e aplicarem modelos teóricos, objetivando descrever os processos físicos envolvidos no transporte desses produtos no perfil do solo. Nesse sentido, a presente pesquisa teve como objetivo a aplicação do modelo Hydrus-1D para simulação do movimento da água e dos íons nitrato e potássio, em condições de laboratório, utilizando-se para tal colunas segmentadas preenchidas com dois tipos de solo não-saturado (Latossolo Vermelho Amarelo e Nitossolo Vermelho), bem como avaliar o desempenho e sensibilidade do referido modelo. Para a obtenção dos parâmetros de transporte de cada soluto, foram elaboradas as curvas de distribuição de efluentes (Breakthrough Curves BTC). Os parâmetros de transporte obtidos e as condições de contorno de cada ensaio foram inseridos no modelo Hydrus- 1D para realização das simulações. O desempenho do modelo foi avaliado com base nos parâmetros estatísticos: erro máximo, erro absoluto médio, raiz quadrada do erro médio normalizado, coeficiente de massa residual, coeficiente de determinação, eficiência e índice de concordância de Willmott. A sensibilidade do modelo foi avaliada conforme o método proposto por McCuen e Snyder (1986) e a análise foi aplicada aos parâmetros: fluxo de entrada, condutividade hidráulica do solo saturado, teor de água na saturação, alfa e n (parâmetros de ajuste da curva de retenção), coeficiente de distribuição e dispersividade. Os resultados experimentais mostraram que o deslocamento do íon nitrato acompanhou a frente de molhamento e em relação ao potássio, observou-se uma maior retenção nas camadas superficiais da coluna de solo, para ambos os solos. Pôde-se concluir que o modelo Hydrus-1D foi eficiente para simulações de deslocamento de potássio e água para ambos os solos estudados e mediante a utilização do modelo de equilíbrio para o transporte de solutos no solo, o modelo Hydrus-1D não foi eficiente para simular o deslocamento de nitrato, para ambos os solos. Os procedimentos experimentais para estimativa de parâmetros de transporte, como as curvas de distribuição de efluentes, foram suficientes para descrever a movimentação de potássio no solo, gerando informações de entrada precisas para os modelos de simulação. Para a simulação do deslocamento do íon nitrato, concluiu-se que o modelo Hydrus-1D requer um processo experimental mais detalhado, sendo necessária a estimativa de um maior número de parâmetros de transporte. Em relação à análise de sensibilidade, ao simular os teores de potássio e água no solo, o modelo apresentou maior sensibilidade aos parâmetros teor de água na saturação e fluxo de entrada da solução. Tais parâmetros, portanto, precisam ser determinados com maior precisão. Houve baixa sensibilidade aos parâmetros condutividade hidráulica do solo saturado e dispersividade, para ambos os solos estudados.
The concern about the fate of chemical products and water, applied to the soil, has been motivating several researchers to develop and apply theoretical models, aiming to describe the physical processes involved in the transport of those products in soil profile. The present research had as objective the application of the model Hydrus- 1D for water and solute (nitrate and potassium) simulation profile, in laboratory conditions, using soil columns filled with two types of unsaturated soil (Oxisol (Haplustox) and Hapludox), as well to evaluate the acting and sensitivity of the model. The transport parameters were obtained for each solute by breakthrough curves (BTCs). The transport parameters obtained and the boundary conditions were inserted in the Hydrus-1D model to realize the simulations. The acting of the Hydrus-1D model was evaluated using the statistical indicators: maximum error, mean absolute error, normalized root mean-square error, coefficient of residual mass, determination coefficient, efficiency and Willmott concordance index. The model sensitivity was evaluated by the method proposed by McCuen and Snyder (1986) and applied to the parameters: input flow, soil saturated hydraulic conductivity, water content (saturation point), alpha and n (soil water retention curve parameters), distribution coefficient and dispersivity. The obtained results, experimentally, showed the nitrate displacement following the wetting front and, in relation to the potassium ion, a larger retention was observed at the superficial soil columns layers. Therefore, was possible to conclude that Hydrus-1D model was efficient for both water and potassium displacement simulations, for both studied soils and by the balance model for solute transport in soil, the Hydrus- 1D model was not efficient to simulate the nitrate displacement in both soils. The experimental procedures to estimate transport parameters, by the BTCs, were enough to describe the potassium movement in soil, generating input information necessary to the model simulation. To the simulation of the nitrate displacement, was possible to conclude that the model Hydrus-1D requests a more detailed experimental process, being necessary the estimate of a larger number of transport parameters. In relation to the sensitivity analysis of the Hydrus-1D model, when simulated the content of potassium and water at the soil columns, was observed that the model shows more sensitivity about to the parameters: water content (saturation point) and input flow. This parameters need to be estimated with more precision. There was a low sensitivity to the parameters soil saturated hydraulic conductivity and dispersivity for both studied soils.

Les objectifs de la thèse sont de (i) modéliser le transport de l’eau, d’un traceur et des polluants dans les sols contaminés, (ii) étudier l’estimabilité des paramètres et les corrélations entre les paramètres, (iii) optimiser les paramètres. Les différents modèles implantés dans le logiciel HYDRUS qui permettent de rendre compte ou pas de l’écoulement préférentiel et du transport hors équilibre physique et chimique sont choisis. Les études concernant le transport d’eau dans un lysimètre de terrain ont montré que les données quotidiennes de pressions et de teneurs en eau volumique contiennent plus d’information que les données horaires, que les pressions ont plus d’information que les teneurs en eau volumique, et que les corrélations des paramètres ont fait perturber les résultats de l’optimisation. Sur le même lysimètre, l’étude d’estimabilité des paramètres caractéristiques pour le transport du traceur (bromure) a montré que les concentrations dans les solutions de percolation ne sont pas suffisantes pour estimer le paramètre de transfert de l’eau entre les zones mobile et immobile car ce paramètre est fortement corrélé avec le paramètre de transfert de soluté. Pour le transport des hydrocarbures aromatiques polycycliques (HAP) dans les colonnes de laboratoire sous différentes conditions de saturation en eau, quand le degré de transport hors équilibre chimique des HAP est élevé, les concentrations en HAP dans les solutions de percolation de la colonne non saturée contiennent plus d’information que celles dans la colonne saturée
Preferential flow and nonequilibrium transport are probably the most frustrating in terms of hampering accurate predictions of contaminant transport through the vadose zone. The mathematical description of preferential flow and nonequilibrium transport needs many parameters that are not measurable. Therefore, the inverse method is a promising way to estimate model parameters. The main objectives of this work are to (i) study the water flow using the uniform flow and dual-porosity models, tracer and contaminant transport using the uniform transport model and/or physical and chemical nonequilibrium transport models, (ii) investigate parameter estimability and correlations between different parameters, and (iii) optimize the hydraulic properties and solute transport parameters. The results concerning the water flow in the bare field lysimeter show that daily data contained much more information than hourly data, daily pressure heads contained more information than daily water contents; the correlations between different parameters hamper the optimization results strongly. Basing on the tracer concentrations in the leaching solution of the lysimeter, the first-order rate water transfer coefficient was not estimable since this parameter was highly correlated with the solute transfer coefficient. PAH concentrations in the leaching solution of the contaminated soil column under saturated and nonsaturated flow conditions show that when the degree of chemical nonequilibirum transport is high, the solute leaching of the nonsaturated column contained more information than those of the saturated column. In addition, the fraction of sites with instantaneous sorption and the linear adsorption distribution coefficient always showed a very strong correlation, they were impossible to optimize simultaneously

Inadequate compaction of a soil subgrade can lead to detrimental outcomes that are not only costly but dangerous to the general public. To avoid this, quality control (QC) devices such as the nuclear density gauge (NDG) are currently being used to monitor the compaction and moisture content of soil subgrades. However, regulatory concerns associated with the NDG have encouraged federal and state agencies, as well as the heavy civil construction industry to consider non-nuclear devices for QC testing of compacted soils. One such non-nuclear device is the Soil Density Gauge (SDG), which utilizes electromagnetic wave propagation to obtain soil properties such as wet unit weight and moisture content. This research shows that through using soil-specific trend lines, the SDG has the capability of obtaining an equivalent NDG wet unit weight. Alongside the SDG, two dielectric moisture probes were also evaluated and through a calibration process on compacted soils, a general moisture content trend line was developed. This general moisture content trend line related outputted volumetric moisture contents from the moisture probes to gravimetric moisture contents. Field data were then plotted along with the general moisture content trend line to show that these devices have the potential of predicting gravimetric moisture contents. By combining the results of the SDG and moisture probe analyses, graphs were then developed that relate SDG wet unit weights to NDG dry unit weights using soil and moisture-specific trend lines.

Le tassement des sols agricoles est l'un des problèmes se posant à l'agriculture moderne dans beaucoup de région du monde: on estime que le tassement lié au passage d'engins concerne 33 millions d'ha en Europe. Du fait des modifications importantes de la structure du sol qu'il engendre (au niveau des couches travaillées et des couches sous-jacentes), le tassement peut avoir des conséquences importantes à la fois sur la production végétales et l'environnement. L'intensité du tassement est déterminée d'une part par les contraintes mécaniques exercées à la surface du sol lors du passage de l'engin agricole (charge, pression des pneumatiques ...) et transmises dans le sol, et d'autre part par la résistance mécanique du sol à ces contraintes. Le travail proposé est constitué de deux parties: la première s'attache à modéliser les contraintes verticales exercées par un engin à la surface du sol. Ce travail numérique réalisé avec le code de calcul PLAXIS montre que les propriétés mécaniques du sol influence fortement la distribution de ces contraintes en surface. Nous proposons une méthode pour les générer numériquement à l'aide d'une plaque de rigidité de flexion variable. La seconde partie concerne la résistance mécanique du sol en interaction avec son état hydrique. Elle s'appuie sur deux dispositifs expérimentaux de laboratoire qui permettent de contrôler ou d'imposer l'état hydrique du sol (succion) au cours de la compression. Cette étude nous a permis de montrer l'importance relative de la structure du sol (granulométrie, masse volumique) et de la succion sur la courbe de compression du sol. Nous avons proposé une typologie de comportement selon la succion et les contraintes appliquées qu'il faudrait généraliser à d'autres sols.