No description available.

During the Illinoian glaciation (approximately 180,000 to 125,000 years ago) glacial lobes advancing into Illinois deposited an extensive till sheet (i.e., the Vandalia Member till). However, very little is known about the retreat phase that followed this major ice advance. Erosional events and the heterogeneous sediments associated to the Illinoian deglaciation may also have important hydrogeologic implications. Specifically, the occurrence and emplacement of these heterogeneous deposits, informally referred to as the Glasford deglacial unit, into and overlying the Vandalia Member till, may impact the integrity of this extensive till aquitard, and possibly influence groundwater flow to the deeper and regionally important Mahomet aquifer. Thus, the purpose of this research is to improve knowledge of the heterogeneous character of the Glasford deglacial sediments and their three-dimensional (3-D) hydrostratigraphic architecture. The methodology to study the Glasford deglacial unit relies on the detailed analysis of 7 continuous cores and interpretations of 4 geophysical profiles, which provide key stratigraphic control to estimate unit geometry and establish the vertical succession of facies assemblages in the unit. A 3-D geological model was created using gOcad®, a geomodelling software, across a 2642 square kilometer study area and the deglacial unit having a subsurface volume domain of 5.70E+9 cubic meters. Utilizing all available data sources including 38 continuous cores, 69 downhole geophysical logs, 799 driller’s logs, and 4 near-surface geophysical profiles; triangulated surfaces were interpolated representing the top and bottom of the Glasford deglacial unit and key internal layers. These surfaces provided a framework for a 3-D cellular partition, where descretizing the model allowed for mapping of hydrofacies assemblages that represented mappable heterogeneities of coarse- and fine-grained sediment in the Glasford deglacial unit. Results of the subsurface facies analysis led to the identification of three main facies types that form the Glasford deglacial unit: 1) massive, matrix-supported diamicton; 2) interstratified sand and gravel; and 3) fine-grained massive and/or bedded sediment. Using key seismic reflectors and interpretations based on near-surface seismic profiles as well as geologic logs from numerous boreholes, these facies were assigned to two features of possible regional extent: 1) a broad channelized erosion surface informally named the Champaign valley; and 2) an extensive tabular unit overlying the valley fill and extending across the entire study area. Grouping of facies into distinct facies assemblages was useful to distinguish sediments that in-fill either the Champaign valley or compose the tabular unit. Major heterogeneities have been recognized in these features and mapped at regional scale represented by fine- and coarse-grained sediment assemblages that comprise 46% and 54% respectively of the Glasford deglacial unit volume. Laterally continuous coarse-grained sediment assemblages are primarily located in the Champaign valley and potentially represent local aquifers of limited but usefully productivity for east-central Illinois. These small aquifers are characterized by hydraulic conductivities ranging from 1.07E-3 m/s to 1.78E-6 m/s. Fine-grained sediment assemblages have an average hydraulic conductivity value of 4.38E-8 m/s and thus may represent discontinuous aquitards impeding water flow. However, these fine-grained sediment assemblages cannot be considered homogeneous aquitards because of their textural variability and limited lateral continuity. The geological model developed in this study contributes to better understanding the complex subsurface geology in east-central Illinois. Results of this study confirm the high degree of heterogeneity in the Glasford deglacial unit that includes features of glacial erosion, and these findings question, at least locally, the integrity of the underlying Vandalia Member till as a regional aquitard unit. Overall, the Glasford deglacial unit is a complex subsurface ice-marginal package of sediments, which challenges the aquifer-aquitard concept. It is argued herein that some ice-contact or ice-marginal sediments units may be laterally extensive as a whole, yet internally too heterogeneous to be mapped as an aquifer or aquitard at a regional scale. A new conceptual hydrostratigraphic layer, the hybrid layer (part-aquifer/ part-aquitard), is thus proposed to better describe these units. This new hybrid layer is meant to augment the traditional aquifer/aquitard concept representing hydrostratigraphic bodies that may not form laterally extensive aquifer or aquitard units. These hybrid layers may better represent conceptually the complex ice-marginal deposits that are found across east-central Illinois, and perhaps other similar areas affected by glacial lobe fluctuations during multiple glaciations.

During the Illinoian glaciation (approximately 180,000 to 125,000 years ago) glacial lobes advancing into Illinois deposited an extensive till sheet (i.e., the Vandalia Member till). However, very little is known about the retreat phase that followed this major ice advance. Erosional events and the heterogeneous sediments associated to the Illinoian deglaciation may also have important hydrogeologic implications. Specifically, the occurrence and emplacement of these heterogeneous deposits, informally referred to as the Glasford deglacial unit, into and overlying the Vandalia Member till, may impact the integrity of this extensive till aquitard, and possibly influence groundwater flow to the deeper and regionally important Mahomet aquifer. Thus, the purpose of this research is to improve knowledge of the heterogeneous character of the Glasford deglacial sediments and their three-dimensional (3-D) hydrostratigraphic architecture. The methodology to study the Glasford deglacial unit relies on the detailed analysis of 7 continuous cores and interpretations of 4 geophysical profiles, which provide key stratigraphic control to estimate unit geometry and establish the vertical succession of facies assemblages in the unit. A 3-D geological model was created using gOcad®, a geomodelling software, across a 2642 square kilometer study area and the deglacial unit having a subsurface volume domain of 5.70E+9 cubic meters. Utilizing all available data sources including 38 continuous cores, 69 downhole geophysical logs, 799 driller’s logs, and 4 near-surface geophysical profiles; triangulated surfaces were interpolated representing the top and bottom of the Glasford deglacial unit and key internal layers. These surfaces provided a framework for a 3-D cellular partition, where descretizing the model allowed for mapping of hydrofacies assemblages that represented mappable heterogeneities of coarse- and fine-grained sediment in the Glasford deglacial unit. Results of the subsurface facies analysis led to the identification of three main facies types that form the Glasford deglacial unit: 1) massive, matrix-supported diamicton; 2) interstratified sand and gravel; and 3) fine-grained massive and/or bedded sediment. Using key seismic reflectors and interpretations based on near-surface seismic profiles as well as geologic logs from numerous boreholes, these facies were assigned to two features of possible regional extent: 1) a broad channelized erosion surface informally named the Champaign valley; and 2) an extensive tabular unit overlying the valley fill and extending across the entire study area. Grouping of facies into distinct facies assemblages was useful to distinguish sediments that in-fill either the Champaign valley or compose the tabular unit. Major heterogeneities have been recognized in these features and mapped at regional scale represented by fine- and coarse-grained sediment assemblages that comprise 46% and 54% respectively of the Glasford deglacial unit volume. Laterally continuous coarse-grained sediment assemblages are primarily located in the Champaign valley and potentially represent local aquifers of limited but usefully productivity for east-central Illinois. These small aquifers are characterized by hydraulic conductivities ranging from 1.07E-3 m/s to 1.78E-6 m/s. Fine-grained sediment assemblages have an average hydraulic conductivity value of 4.38E-8 m/s and thus may represent discontinuous aquitards impeding water flow. However, these fine-grained sediment assemblages cannot be considered homogeneous aquitards because of their textural variability and limited lateral continuity. The geological model developed in this study contributes to better understanding the complex subsurface geology in east-central Illinois. Results of this study confirm the high degree of heterogeneity in the Glasford deglacial unit that includes features of glacial erosion, and these findings question, at least locally, the integrity of the underlying Vandalia Member till as a regional aquitard unit. Overall, the Glasford deglacial unit is a complex subsurface ice-marginal package of sediments, which challenges the aquifer-aquitard concept. It is argued herein that some ice-contact or ice-marginal sediments units may be laterally extensive as a whole, yet internally too heterogeneous to be mapped as an aquifer or aquitard at a regional scale. A new conceptual hydrostratigraphic layer, the hybrid layer (part-aquifer/ part-aquitard), is thus proposed to better describe these units. This new hybrid layer is meant to augment the traditional aquifer/aquitard concept representing hydrostratigraphic bodies that may not form laterally extensive aquifer or aquitard units. These hybrid layers may better represent conceptually the complex ice-marginal deposits that are found across east-central Illinois, and perhaps other similar areas affected by glacial lobe fluctuations during multiple glaciations.

No description available.

No description available.

A Y-branch optical power splitter based on the buried waveguide and the micro-prism waveguide bends is presented. The 132 splitter consists of a beam expanding region, a conventional Y-branch region, and two micro prisms providing large angle waveguide bends of device. The 132 splitter are fabricated by first depositing a 10-£gm-thick PECVD oxide (SiO2) on Si s ubstrates. The guiding core of the device was fabricated by etching trenches in SiO2 cladding, and filled with Benzocyclobutene (BCB) polymer. After etch-back process, the thin layer of spin on glass (SOG) is used to further planarized the surface of the device. The propagation loss of the waveguide is 0.47dB/cm at £f=1.3£gm. The normalized power transmission efficiency of the 132 splitter as large as 3.7dB was obtained. Simulation results based on beam propagation method (BPM) of the splitter is also presented.

PIPE5 is a two-dimensional finite element analysis program for buried structure analysis. The program has gone through several changes over the years. Some of the features that were added in the latest revision are stress stiffening, corotational formulation, bandwidth minimization, residual monitoring, and dynamic memory allocation. Some parts of the program were also rewritten to make them clearer and improve their performance. After the modifications several comparisons were made to other programs and earlier versions of the program to test the accuracy of the program in its latest form.

This work explores the impact of burying a short term thermal storage (STTS) tank within a borehole thermal energy storage (BTES, or borehole field). There is motivation to bury tanks in order to save space on ground level, as well as to improve the overall efficiency of the system by reducing heat losses from the tank. This work mainly looks to understand the impact of the lack of boreholes under the buried tank, as well as the thermal interactions between the tank and boreholes. Computational Fluid Dynamics was used to predict the transient temperature throughout the domain. The long-term performance was assessed by simulation a five year period. Examination of factors that influence the tank-borehole interactions was studied and it was determined that radial stratification of the borehole field as well as the soil properties have the largest influence in terms of increasing the efficiency of the BTES. Other factors, such as tank stratification and tank insulation have little impact and the remainder (tank aspect ratio, and alternate geometries) have some impact. / Thesis / Master of Applied Science (MASc)

No description available.

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