Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 88-94).

No description available.

Valley Creek, an urbanized stream in Southeastern Pennsylvania, has undergone changes typical of streams in urbanized areas, such as bank erosion, channel redirection, and habitat disruption. One area of disruption that has been little studied is the hyporheic zone, the top layer of the streambed where stream water exchanges with subsurface water and chemical transformations occur. The hyporheic zone of an 18 m reach of Valley Creek in Ecology Park was characterized using a tracer test coupled with a hydrogeophysical survey. Nested wells screened at depths of 20, 35, 50, and 65 cm were placed at four locations along the center of the stream to monitor the passage of the salt tracer through the hyporheic zone. Results from well sampling were compared with time-lapse Electrical Resistivity Tomography (ERT) monitoring of the stream tracer. The streambed was also characterized using temperature probes to calculate the stream water-groundwater flux and freeze core samples to characterize heterogeneities in streambed sediment. Models were created using MODFLOW, MATLAB, and EARTH IMAGER 2-D to understand differences between Ecology Park and Crabby Creek, a tributary within the Valley Creek watershed, where similar studies were performed in 2009 and 2010. Hyporheic exchange and ERT applicability differed between the two study sites. At Ecology Park, tracer was detected only in the 20 cm wells at nests 2 and 4 during the injection period. Noise in the falling limbs of the tracer test breakthrough curves made it difficult to determine whether tracer lingered in the hyporheic zone using well data. ERT surveys were unable to detect tracer lingering after the injection period. At Crabby Creek, tracer was present in all shallow wells, and lingering tracer was detected in the hyporheic zone using ERT during the post-injection period. ERT surveys at Ecology Park were less effective than at Crabby Creek for two reasons: the presence of groundwater discharge (which inhibited hyporheic exchange) and increased stream water depth at Ecology Park. Temperature modeling of heat flux data revealed groundwater discharge at three locations. MODFLOW models predicted that this discharge would diminish the length and residence time of subsurface flow paths. Groundwater discharge likely increased along the contact between the hydraulically conductive Elbrook Formation and the less conductive Ledger Formation. Models created with MATLAB and Earth-Imager 2-D showed ERT sensitivity to tracer in the hyporheic zone depended on stream thickness. With increased water depth, more current propagated through the stream, which reduced sensitivity to changes in the hyporheic zone. A sensitivity analysis showed that the resistivity change in the hyporheic zone at Ecology Park (average water depth 0.36 m) would have to exceed 30% to be detectable, which was greater than the induced change during the tracer test. Deeper water also amplified the confounding effect of changes in the background conductivity of the stream water, though time-lapse ERT detected no lingering tracer even after correcting for this drift. Studies performed at Crabby Creek were able to map lingering tracer in the hyporheic zone because the site had a thin water layer (0.1 m), a large percentage increase of conductivity during the tracer test, and no groundwater discharge. Conversely, at Ecology Park groundwater discharge inhibited hyporheic exchange, and imaging sensitivity was reduced by the thicker water layer, demonstrating the limitations of ERT for hyporheic zone characterization. The modified inversion routines used here demonstrated that, with accurate stream conductivity and depth measurements, ERT can be used in some streams as a method for hyporheic characterization by incorporating site-specific conditions. / Geology

No description available.

Permanent electrode arrays were set up at ten monitoring sites from Whitehorse, Yukon, to Fort St. John, British Columbia, in order to gain a clearer perspective of the effectiveness of electrical resistivity tomography (ERT) monitoring over an annual cycle of freezing and thawing. This research forms part of a longer-term project that is attempting to use ERT to examine changes in permafrost resulting from climate change. Inter-site and intra-site variability were examined by installing and maintaining data-loggers to monitor active layer and shallow permafrost temperatures, air temperatures, and snow depths at each site from August 2010 – August 2011. Additional site information was collected on each ERT survey date, including frost table depths, snow depths, and vegetation heights. Based on nearby community records, the climate in the region has been warming by a rate of 0.3 to 0.5 °C per decade since 1970. The permafrost at all ten sites was characteristic of sporadic discontinuous and isolated patches permafrost zones, and is classified as Ecosystem-protected. Nine of the ten permafrost sites had permafrost that was thinner than the 14 or 7 m penetration depth of the ERT survey (three-layer system consisting of an active layer, permafrost, and sub-permafrost perennially unfrozen zone). The most predictable results were achieved at the two-layer system site (active layer overlying permafrost to the base of the profile) in each of its virtual resistivity boreholes, relative resistivity change comparisons, and mean near-surface apparent resistivity progressions. ERT is an effective method of delineating permafrost boundaries in thin permafrost environments and does show strength when monitoring areas of seasonally frozen ground. Repeat surveys at a site indicate seasonal changes in three-layer conditions, but not as predictably as those in a two-layer system. In order to receive the most accurate information regarding permafrost extent and thickness, it appears ideal to conduct ERT surveys annually, within the same month as the previous year’s survey.

This thesis is a study of the effects of lead placement and sample shape in the measurement of electrical resistivity.

Master of Science / Department of Civil Engineering / Stacey Tucker-Kulesza / The erosion rate, or erodibility, of soil depends on many soil characteristics including: plasticity, water content, grain size, percent clay, compaction, and shear strength. Many of these characteristics also influence soil in situ bulk electrical resistivity (ER) measurements. The objective of this study was to characterize soil erosion potential by correlating the in situ ER of soil with erodibility measured in the Kansas State University Erosion Function Apparatus (KSU-EFA). ER surveys were conducted at eleven bridge sites. Soil samples were also collected at each site with a drill rig from the surface to three meters using thin-walled Shelby tubes. Five samples were collected at each site, tested in the KSU-EFA, and classified according to the Unified Soil Classification System. Analysis showed that the rapid in situ data obtained from an ER survey can be used to categorize the level of erodibility. As such, ER surveys may be used to characterize the soils at future bridge sites or prioritize existing bridges for additional testing to measure the scour potential. Moreover, ER surveys may be used to determine which existing bridges should be closed or closely monitored for scour potential during a flood event. Analytical models to predict critical shear stress using ER and other soil parameters were constructed.

Este estudo apresenta a comparação e discussão entre registros de perfilagem geofísica obtidos por três sondas elétricas que medem resistividades de litologias. Uma análise detalhada foi feita para detectar qual destas sondas utilizadas proporciona a melhor opção em termos de identificação das camadas de carvão e resolução vertical. As sondas elétricas utilizadas foram: guard log (GLOG), single point resistance (SPR) e induction log (IND). Para auxiliar na comparação entre esses diferentes perfis, outros dois registros geofísicos importantes foram incluídos: radiação gama natural (GN) e optical televiewer (OPTV), os quais ajudaram a identificar os estratos de carvão. No caso específico do OPTV, quando a situação é favorável, ele permite identificar os estratos de carvão e verificar a resolução vertical dos demais registros, em função da excelente resolução vertical. As imagens produzidas pelo OPTV podem, nas circunstâncias adequadas, servir como testemunho digital, para complementar ou mesmo substituir as amostras de sondagem com recuperação de testemunhos. Neste estudo, foram analisados dados obtidos em 4 depósitos de carvão diferentes: Área B3, Calombo, Cerro e Seival. Todos os depósitos de carvão acima citados situam-se no estado do Rio Grande do Sul (RS) - Brasil. Ao todo, 15 furos foram apresentados e discutidos. Destes, 13 são furos de sondagem com recuperação de testemunhos, enquanto que os dois restantes são furos de desmonte. As descrições geológicas dos 13 furos de sondagens são as informações principais utilizadas como parâmetro de controle nas comparações entre os perfis geofísicos, enquanto que as imagens OPTV serviram como uma alternativa para verificar a resolução vertical dos perfis elétricos. Ao final das análises, verificou-se que o dispositivo guard-log (GLOG) tende a ter o melhor desempenho no aspecto de identificação litológica, demonstrando uma capacidade superior em relação aos demais arranjos em termos de resolução vertical. Estatisticamente, ele apresentou as estimativas de espessuras mais próximas em valor, em relação às espessuras proporcionadas pelas descrições geológicas de testemunhos de sondagem. / This study presents a comparison and discussion between the geophysical logs obtained by three electrical probes that measure resistivity of lithologies. A detailed analysis was carried out to detect which of these probes, provides the best option in terms of identification of coal seams and vertical resolution. The electrical probes used were guard log (GLOG), single point resistance (SPR) and induction log (IND). To aid the comparison between the different logs, two other important geophysical logs were included: natural gamma radiation (GN) and optical televiewer (OPTV), which helped to identify the coal seams. In the specific case of OPTV, when the situation is favorable, it identifies the coal seams and check the vertical resolution of the other logs, in function of its excellent vertical resolution. The images produced by OPTV can serve, in appropriate circumstances, as digital core sample to complement or even replace the diamond drill core samples recovery. In this study, analyzed data were obtained from four different coal deposits, which are: B3 Area, Calombo, Cerro and Seival. All the coal deposits mentioned above are located in the state of Rio Grande do Sul (RS) - Brazil. In all, 15 boreholes were presented and discussed. Out of these, 13 are boreholes with recovered core samples, while the remaining two are blastholes. The geological descriptions of the 13 boreholes are the main information used as a control parameter in comparisons against the geophysical logs, while OPTV images served as an alternative to verify the vertical resolution of the electric logs. At the end of the analysis, it was found that the guard-log probe (GLOG) tends to have better performance in the aspect of lithological identification, demonstrating a greater capacity in comparison with the other in terms of vertical resolution. Statistically, it presented the closest estimated value in relation to the coal seams thickness provided by geological description of the recovered core samples.

Concrete repair materials are being widely used to restore and extend the service life of structures. While most cement-based repair materials are compatible with concrete structures, their durability properties do not attract much attention which it deserves from researchers. Since repair materials can deteriorate like conventional concrete, the search for reliable, long-lasting concrete repair materials is becoming more intensive. Amongst other factors, concrete permeability and chloride diffusivity within concrete are believed to play a major role in determining the durability and success of the repair. These two parameters determine the penetration rate of aggressive substances into concrete and how fast degradation could take place. A number of test methods have been proposed to study these two factors, and the commonly used test methods are water penetration, surface/bulk electrical resistivity, rapid chloride permeability (RCP), and half-cell potential. However, the relationship between each durability test method and their correlation with compressive strength measurement have not been fully understood. So, in this study, we aim for using multiple testing techniques, destructive and non-destructive, to evaluate the durability of concrete repair materials as well as correlating different test methods. Three types of commercially available cement-based materials are tested and evaluated, and results have indicated that cementitious concrete mortar (termed as Mix M) amongst others has the best durability performance which means low water permeability, high resistivity, and compressive strength. Whereas, the flexural performance of Mix M still needs some improvement in terms of flexural strength and flexural toughness. For various durability testing methods, surface resistivity is found to have a strong linear relation and a polynomial relation to bulk resistivity and water permeability respectively. No relationship is established between concrete resistivity and compressive strength, though high-strength concrete tends to have a high resistivity in our study. RCP test results do not correlate well with resistivity measurements, which requires further study to overcome its heating and binding effect when measurements are being taken. Half-cell potential method is used for validating test results but it reveals no difference for materials with different permeability and resistivity. A model is proposed to counteract temperature’s effect while calculating the coefficient of diffusion, which indicates the concrete to resist chloride diffusion. It is found that this model can shift the RCP measurement slightly closer to its theoretical prediction but the difference between them is still large. Therefore, further research is required for acquiring more raw data from RCP measurements as the regression analysis input. In addition, a more comprehensive model that involves more correction factors for binding effects, etc., is also needed. / Graduate / 2020-04-30

This project addresses the topic of evaluating water movement inside a hillslope using a combination of conventional and advanced geophysical techniques. While slope dynamics have been widely studied, ground water movement in hills is still poorly understood. A combination of piezometers, ground-penetrating radar (GPR), and electrical resistivity (ER) surveys were used in an effort to monitor fluctuations in the subsurface water level in a reengineered slope near Keokuk, Iowa. This information, integrated with rainfall data, formed a picture of rainfall-groundwater response dynamics. There were two hypotheses: 1) that the depth and fluctuation of the water table could be accurately sensed using a combination of monitoring wells, ground-penetrating radar and resistivity surveys; and 2) that the integration of data from the instrumentation array and the geophysical surveys would enable the characterization of water movement in the slope in response to rainfall events. This project also sought to evaluate the utility and limitations of using these techniques in landslide and hydrology studies, advance our understanding of hillslope hydrology, and improve our capacity to better determine when slope failure may occur. Results from monitoring wells, stratigraphy, and resistivity surveys at the study site indicated the presence of a buried swale, channelizing subsurface storm flow and creating variations in groundwater. Although there was some success in defining hydrologic characteristics and response of the slope using this integrated approach, it was determined that GPR was ultimately not well suited to this site. However, the use of GPR as part of an integrated approach to study hillslope hydrology still appears to hold potential, and future work to further evaluate the applicability and potential of this approach would be warranted.