Analysis of Slug Tests to Determine Hydraulic Conductivity of Vertical Cutoff Walls

291 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2002.The primary contribution made in this research is to develop two new methods to evaluate hydraulic conductivity in a cutoff wall considering the compressibility of the backfill material and the proximity of the wall boundaries to the well. One of the new methods involves a series of type curves that takes into account the compressibility of the backfill, overall effect of narrow wall boundaries, and eccentricity of the well intake section. The second new method is a modified curve fitting method, which employs a linear curve fitting method such as the Bouwer and Rice method, a modified effective radius, and a reduction factor. Both of these new methods provide a more rigorous and accurate estimate of hydraulic conductivity compared to previously available methods. Both new methods are practical and easy to use.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Numerical Investigation on the Effect of Cementing Properties on the Thermal and Mechanical Stability of Geothermal Wells

In this paper, a two-dimensional (2-D) Finite Element (FE) analysis of a geothermal well was performed with respect to five different cross-sections corresponding to the design specifications for the geothermal well that is currently constructed in Pohang, South Korea. Among the essential components (such as ground formation, casing, and cementing) of a geothermal well, the thermal and mechanical stability of the cementing component was discussed based on a series of parametric studies with consideration of the thermal conductivity and Young’s modulus of the cementing component. With increasing number of casing layers, the cementing component experiences less stress concentration. In addition, the lower thermal conductivity of the cementing material is advantageous for effectively controlling radial displacement. Consequently, it should be noted in geothermal well cementing construction that long-term strength degradation of the cementing might cause the severe structural instability of an entire geothermal well

Field Experiments to Evaluate Thermal Performance of Energy Slabs with Different Installation Conditions

The energy slab is a novel type of horizontal Ground Heat Exchanger (GHEX), where heat exchange pipes are encased in building slab structures. The thermal performance of energy slabs is usually inferior to the conventional closed-loop vertical GHEX because its installation depth is relatively shallow and therefore affected by ambient air temperature. In this paper, heat exchange pipes were made of not only conventional high-density polyethylene (HDPE), but also stainless steel (STS), which is expected to enhance the thermal performance of the energy slabs. In addition to a floor slab, a side wall slab was also used as a component of energy slabs to maximize the use of geothermal energy that can be generated from the underground space. Moreover, a thermal insulation layer in the energy slabs was considered in order to reduce thermal interference induced by ambient air temperature. Consequently, two different field-scale energy slabs (i.e., floor-type and wall-type energy slabs) were constructed in a test bed, and two types of heat exchange pipes (i.e., STS pipe and HDPE pipes) were installed in each energy slab. A series of thermal response tests (TRTs) and thermal performance tests (TPTs) were conducted to evaluate the heat exchange performance of the constructed energy slabs. Use of the STS heat exchange pipe enhanced the thermal performance of energy slabs. Additionally, the wall-type energy slab had a similar thermal performance to the floor-type energy slab, which infers the applicability of the additional use of the wall-type energy slab. Note that if an energy slab is not thermally cut off from the building’s interior space with the aid of thermal insulation layers, heat exchange within the energy slabs should be significantly influenced by fluctuations in ambient temperature

Impact of clay particle reattachment on suffusion of sand-clay mixtures

The detached clay particles directly filtrated through the sand-clay mixture lead to suffusion; however, if the detached clay particles are subjected to reattachment, the degree of suffusion may be less significant. This study investigates the impact of clay particle reattachment on suffusion of sand-clay mixtures through laboratory soil-column experiments. The observed breakthrough curves (BTCs) of kaolinite, illite, and montmorillonite for 5 different column lengths (3 in, 6 in, 9 in, 12 in, and 18 in; 1 in = 2.54 cm) indicated that a higher breakthrough concentration was observed as the column length (L) decreased for kaolinite and illite, whereas a reverse trend was observed for montmorillonite. In addition, the increase in the fraction of filtrated clay particles (Me) with an increase in L (Me = 10.42% for L = 3 in and Me = 3.59% for L = 18 in) for the sand-illite mixture indicated that the reattachment effect became more significant as the travel length of detached clay particles increased. The observed BTCs, retention profiles after injection, and fraction of filtrated clay presented herein suggest the need to incorporate the reattachment effect when assessing the suffusion of clay-containing soils

Evaluation of gluing of CFRP onto concrete structures by infrared thermography coupled with thermal impedance

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Hydraulic characteristics of bentonite cake fabricated on cutoff walls

Bentonite cake is usually formed on the excavated trench surface that is supported by the bentonite slurry during construction of slurry cutoff walls. The lower hydraulic conductivity of bentonite cakes formed during construction of slurry cutoff walls in comparison to backfill materials provides an additional benefit. In the present study, the hydraulic conductivities of bentonite cakes made using three different bentonites were estimated using the modified fluid-loss test under various pressures. Both the hydraulic conductivities of bentonite cakes and cutoff-wall backfill are important in evaluating the in situ hydraulic performance of slurry cutoff-wall construction. Three bentonite slurry concentrations of 4, 6, and 8% were used to fabricate bentonite cakes that represent common field conditions. X-ray diffraction, cation exchange capacity, and swell-index data were collected to characterize the bentonites. Two modified methods for analyzing fluid-loss test results were used to estimate bentonite cake hydraulic conductivities. In addition, the viscosity as a function of time was measured to explain the sealing capacities of the bentonite slurries. The bentonite-cake hydraulic conductivities ranged from 2.15×10 m/s to 2.88×10 m/s, which were 10 to 500 times lower than the cutoff wall backfill design. Experimental results for 4 and 6% bentonite slurries were relatively similar, but the 8% slurries were noticeably different. Calculated bentonite-cake thickness and stress distribution indicated that the local void ratio and hydraulic conductivity may vary across the cake thickness. The considerably lower bentonite-cake hydraulic conductivities compared to the cutoff wall backfill design show its significance in slurry cutoff-wall construction practices

Impact of Particle Size Distribution of Colloidal Particles on Contaminant Transport in Porous Media

The presence of retained colloidal particles causes the retardation of contaminant transport when the contaminant is favorably adsorbed to colloidal particles. Although the particle size distribution affects the retention behavior of colloidal particles, the impact of particle size distribution on contaminant transport has not been reported to date. This study investigates the impact of the particle size distribution of the colloidal particles on contaminant transport through numerical simulation by representing the particle size distribution as a lognormal distribution function. In addition, the bed efficiency and contaminant saturation of simulated breakthrough curves were calculated, and a contaminant transport model with the Langmuir isotherm for the reaction between the contaminant–sand and contaminant–colloidal particle was introduced and validated with experimental data. The simulated breakthrough curves, bed efficiency, and contaminant saturation indicated that an increase in the mean and standard deviation of the particle size distribution causes the retardation of contaminant transport

Medical expenses and its determinants in female patients with urological disorder

Abstract Background The rising older adult population has led to an increase in the prevalence of chronic diseases and medical expenses. Women tend to have a longer healthy life expectancy than men and are more likely to be exposed to urological disorders around the age of 50, resulting in substantial healthcare expenses throughout their lifetime. Urological disorders often require continuous treatment owing to their high risk of recurrence, contributing to an increased financial burden from medical costs. This study aimed to identify factors influencing medical expense in female patients with urological disorders and propose strategies to alleviate the associated financial burden. Methods We used data from the Korea Health Panel Survey conducted from 2011 to 2016. The final sample comprised 2,932 patients who visited hospitals for urological disorders. To identify the factors influencing medical expense among female patients with urological disorders, we employed a generalized estimating equation model. Results The results indicated that younger people and patients with middle-income levels tended to incur higher medical expenses. Furthermore, patients receiving treatment at tertiary hospitals and those enrolled in National Health Insurance also incurred higher health expenses. Conclusions This study suggests that effective management of medical expenses related to urological disorders in women requires improvements in healthcare accessibility to facilitate early detection and continuous disease management. In addition, the findings highlight the potential benefits of digital health and non-face-to-face treatments in addressing these needs