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

Wastewater generated in the Tucson metropolitan region is conveyed to and treated at the Roger Road Wastewater Reclamation Facility (WRF) and Ina Road WRF. From 2005 to 2012, approximately 15,000 acre-feet per year of effluent was returned to the City of Tucson for additional filtration and reuse in the reclaimed water system. The remaining 48,000+ acre-feet per year of treated effluent was discharged to the Santa Cruz River, where a variable portion of the effluent infiltrates the streambed. The effluent that infiltrates the streambed contributes to recharge credits for participants invested in the Managed Underground Storage Facilities. In the effluent-dependent river, physical, chemical, and biological processes work in combination to develop a clogging layer near the streambed surface, which reduces infiltration. Previous studies have shown that large storm events have the ability to scour away the clogging layer and are the most significant processes contributing to establishing infiltration rates. Without the occurrence of large storm events, other variables such as effluent discharge and effluent concentrations affect infiltration to a lesser degree. Effluent discharge, biochemical oxygen demand, and total suspended solids are monitored and recorded daily at the outfalls of the WRFs. The parameters were investigated individually and in combination using statistical analyses to determine their correlations with streambed infiltration in the Santa Cruz River. The dry spring-early summer seasons from 2005 to 2012 were analyzed. A water balance was constructed for non-stormflow days during each time period. Evapotranspiration was calculated using riparian vegetation surveys and detailed delineations of aerial photography of the surface water and streamside herbaceous vegetation. Infiltration was derived as the residual of the water balance. At the daily time scale, correlations among variables were unobtainable due to the extremely variable characteristics of infiltration. The seasonal time scale analyses demonstrated an inverse relationship between both the effluent concentrations of biochemical oxygen demand and total suspended solids with infiltration and a direct correlation between effluent discharge and infiltration under extreme conditions. Under normal conditions, the distribution of discharge between Roger Road WRF and Ina Road WRF had a critical effect on infiltration as a result of the different deposition and erosive regimes through the Santa Cruz River.

Titanium carbonitride (Ti(C,N)) cermets have become more popular in recent research due to their mix of high hardness, high hot hardness, good ductility, chemical stability, and low densities. These mechanical properties make Ti(C,N)-cermets especially desirable as a replacement for current ‘hardmetals’, such as tungsten carbide cobalt (WCCo), as it is known that WC-Co exhibits poor mechanical behaviour at elevated temperatures. Additional interest and research has been conducted in reference to binders which enhance the cermet’s capability to retain strength at high temperatures while remaining ductile. One such binder, Ni3Al actually increases in yield strength up to a temperature of ~900°C. In this thesis, the production method utilizing melt infiltration for TiC, Ti(C0.7,N0.3), Ti(C0.5,N0.5), and Ti(C0.3,N0.7)-based cermets with Ni3Al binder contents of 20, 30 and 40 vol. % have successfully been developed and utilized. This process produced high density samples at each nitrogen content for all binder contents, excluding Ti(C0.3,N0.7). Ti(C0.3,N0.7)-Ni3Al samples at 20 and 30 vol. % suffered from poor infiltration and could not be tested. The reciprocating wear mechanisms were examined, using a ball-on-flat test, utilizing WC-Co spheres with a diameter of 6.35 mm as a counter-face, and test parameters of 20 Hz, 2 hrs., and applied loads of 20, 40, 60 and 80 N. The wear tracks were examined using optical profilometry, SEM, and EDS to determine the volumetric wear rate, and the dominant wear mechanisms. The wear volume, and wear mechanisms were compared with the effect of binder content, nitrogen content, and applied load.

No description available.

No description available.

Surface mining of the Athabasca Oil Sands of Canada is occurring at an unparalleled rate resulting in large scale disturbances over vast areas. Soil water availability for plants is one of the key issues faced when reclaiming the landscape. A factor which limits the soil water availability is soil water repellency (SWR). Soil water repellency is found on both natural and disturbed sites in this region and can cause reduced infiltration, reduced soil water storage, enhanced runoff, increased preferential flow, and reduced ecosystem productivity. Effective characterization of SWR, determination of the causes of SWR and understanding how it affects soil pores and water flow are important for environmental management. The main objective of this study is to examine the effect of SWR and fungal hydrophobicity on soil water dynamics in Athabasca Oil Sands. This was accomplished by determining the relationship between the measurement of severity and persistence of SWR and the critical water content (CWC) where SWR is greatest between different soils in the region. Examining how the water conducting porosity and soil pores are affected by SWR. Developing methods to quantify fungal strains that cause SWR and testing of these fungal strains for their ability to alter the SWR and infiltration into soil. Results show that a high severity (Contact angle) of repellency does not necessarily denote long persistence (Water Drop Penetration Time) or high CWC in soils from the region. A high severity of SWR in larger diameter pores decreased the water conducting porosity due to the larger pore contribution to the total liquid flux. The modified microscopy approach and the alcohol percentage test (APT) resulted in improved characterization of fungal hydrophobicity. Fungal strains were classified as hydrophilic, hydrophobic and chrono-amphililic based on their surface properties from these measurements. The surface property of selected fungi strains can alter the SWR in both a repellent and wettable soil and can also change the water infiltration rate. This research highlights the importance of characterization of SWR, the effects on water flow, and how fungal hydrophobicity can alter the SWR and infiltration. This will aid in improving our understanding of SWR and improve remediation efforts on water repellent soils in the Athabasca Oil Sands region.

This research investigates the difference between indoor and outdoor residential fine particulate matter (PM2.5) and explores the feasibility of predicting residential PM2.5 infiltration for use in exposure assessments. Data were compiled from a previous study conducted in Seattle, Washington, USA and a new monitoring campaign was conducted in Victoria, British Columbia, Canada. Infiltration factors were then calculated from the indoor and outdoor monitoring data using a recursive mass balance model. A geographic information system (GIS) was created to collect data that could be used to predict residential PM2.5 infiltration. Spatial property assessment data (SPAD) were collected and formatted for both study areas, which provided detailed information on housing characteristics. Regression models were created based on SPAD and different meteorological and temporal variables. Results indicate that indoor PM2.5 is poorly correlated to outdoor PM2.5 due to indoor sources and significant variations in residential infiltration. A model based on a heating and non-heating season, and information on specific housing characteristics from SPAD was able to predict a large portion of the variation within residential infiltration. Such models hold promise for improving exposure assessment for ambient PM2.5.

In this study, a two phase investigation of the hydraulic conductivity parameters of silty soils was performed. In the first phase, double-ring infiltrometer tests were used to measure infiltration rates in-situ at two sites in the Piedmont physiographic province of Georgia. The efficacy of predicting saturated hydraulic conductivity for Piedmont soils via published soil surveys from the National Resource Conservation Service and pedotransfer functions was then investigated. Work focused on the development of a consistent test methodology for soils (sandy, to silts and clays) in the Piedmont, and the final test method utilized being the constant head test, using a double-ring infiltrometer with Mariotte tubes to maintain the head. In the second phase of the investigation, laboratory based measurements of the saturated hydraulic conductivity of binary mixtures of fine sand and nonplastic silt were performed to investigate the effects of particle mixtures on hydraulic conductivity. The materials used were ASTM 100/200 sand and Sil-Co-Sil 40 non-plastic silt, chosen based on the ratio of the mean particle diameters. Significant effort was invested in the development and comparison of methodologies to produce uniform specimens of the binary mixtures for hydraulic conductivity testing, with the final being modified dry tubing. Two fixed densities were used to investigate the effects of particle packing on the hydraulic conductivity of binary mixtures, with critical fines contents chosen to ensure the finer particles primarily filled the pore volume of the coarse particles. Incremental fines contents, by mass, up to this theoretical fines content were tested. The measured saturated hydraulic conductivity was evaluated in terms of fines content, global and intergranular void ratio, and confining stress. Models for predicting extreme void ratios and saturated hydraulic conductivity of binary mixtures were also investigated.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23713号 / 理博第4803号 / 新制||理||1687(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 河上 哲生, 教授 田上 高広, 教授 下林 典正 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Between 2004 and early 2006 a large-scale, instrumented, potentially contaminating trial waste rock dump was constructed and monitored at Cadia Hill Mine, in NSW, Australia. The trial waste rock dump was instrumented with lysimeters to measure rainfall infiltration and seepage through its base, and temperature sensors and gas sampling tubes to evaluate oxidation of the waste rock, together with three instrumented trial store and release covers on the surface. This thesis describes the construction and instrumentation of the trial waste rock dump and the monitoring results obtained to date, and applies unsaturated soil mechanics principles to understanding the early performance and predicting the future performance of the trial waste rock dump and trial store and release covers. For a given rainfall regime, the rate and quantity of rainfall infiltration into a waste rock dump of a given height, the wetting up of the dump over time, and the occurrence of base seepage will largely be dictated by the particle size distribution of the waste rock delivered to the dump, and the stratigraphy of the dump. The particle size distribution of the waste rock delivered to the dump will depend on the fragmentation of the rock due to blasting and the degree of weathering and hence breakdown on handling of the rock. A waste rock dump constructed by conventional loose end-dumping from haul trucks from a tip-head, as was the case for the trial waste rock dump, consists of a trafficked surface layer extending to a depth of approximately 1 m, underlain by discontinuous alternating coarse and fine-grained layers raveling at the angle of repose of the waste rock, with a base rubble zone of boulders which ravel to the toe of the dump on end-dumping. Trafficking of the surface of the dump by dozers and haul trucks leads to the breaking down, burial and side-casting of the rock to form a well-graded material typically finer than 100 mm in particle size, with a moderate to high water storage capacity. The underlying coarse-grained angle of repose layers serve as air pathways during dry conditions and preferred seepage pathways during and following periods of heavy rainfall resulting in base seepage. The fine-grained angle of repose layers have a moderate to high water storage capacity and largely retain water in storage rather than generating base seepage. The base rubble zone may contain boulders up to 1 m in size, depending on the fragmentation of the rock due to blasting and the degree of weathering and hence breakdown on handling of the rock. It serves largely as a pathway for air during dry conditions, while passing base seepage during and following periods of heavy rainfall. As the dump wets up, partially saturated “fingers” develop and extend into the dump. Partially saturated fine-grained layers, having a medium to high water storage capacity, largely retain their partial saturation, while coarse-grained layers drain resulting, in base seepage. Plugs of water temporarily stored within the dump drain down through the dump, so that the base seepage that emerges is “old” water, not the rainfall infiltration (“new” water) that generated it. The size of the rainfall event required to generate base seepage will decrease as the dump wets up and the partially saturated fingers extend closer to the base of the dump. The residence time of water within the dump that passes along preferred seepage pathways will be relatively short and will become shorter as the dump wets up, while the residence time of water stored within the fine-grained layers will be very long, and possibly indefinite in a dry climate. The ingress of air through the base rubble zone, up the coarse-grained angle of repose layers, through the sides of the dump, and to a lesser extent through the trafficked layer, by the processes of convection, advection and diffusion, respectively, results in the exposure of reactive waste rock to oxidation. The fine-grained reactive waste rock, presenting a far greater surface area per unit volume than the coarse-grained waste rock, and typically having a greater proportion of fresh surfaces, is by far the most reactive. The ingress of air into the fine-grained layers is largely by diffusion from the adjacent coarse-grained layers. The transport of oxidation products from the dump largely occurs during and following periods of heavy rainfall, when preferred pathway flow is mobilised and base seepage occurs. The main exposure to preferred pathway flow is along these pathways, where the surface area per unit volume and hence the proportion of oxidation products are low, with much of the oxidation products formed on the fine-grained particles retained within the dump along with stored water. Due to the discontinuous stratigraphy of a waste rock dump, the preferential pathways for flow are randomly located within the dump. In addition, preferential pathways evolve over time as the waste rock weathers, settles, and as fines are transported with the flow. The trafficked surface of the dump also evolves over time, becoming more heterogeneous as the surface settles differentially, generating internal rainfall runoff and the transport of fines, and the development of “sinkholes” for the preferred entry of ponded rainfall. The principle purpose of cover systems over waste rock dumps is to restrict net percolation into the dump, so that percolation through the reactive waste rock is minimal in the longer term. The approach used to design any cover system is dominated by climate. Semi-arid environments are conducive to store and release cover systems which take advantage of well-graded oxide materials to provide high storage capacities, low percolation and stability. Three trial store and release covers, each comprising a sealing layer overlain by a thick mounded rocky soil mulch layer, were installed at Cadia Hill Mine in 2005-2006 to assess their feasibility to limit net percolation under the climatic conditions encountered at Cadia. This research described in this thesis has demonstrated a number of key issues that should be considered in the management and closure of waste rock dumps: • the initial moisture condition of the end-dumped waste rock will effect its early ability to store incidental rainfall; • the available water storage capacity of the waste rock will affect the size of the triggering rainfall event and the base seepage response time, with the storage capacity being taken up as the dump wets up, reducing both the size of the triggering rainfall event and the response time; • iterative modelling and calculations using HYDRUS-2D suggest that the trial waste rock dump will take between 3 years and 6 years to become sufficiently saturated that it will pass any rainfall infiltration, depending on the extent to which the waste rock weathers over time; and • all three trial store and release covers have demonstrated good performance over the monitoring period, and this has been verified using HYDRUS-2D, , with any net percolation being the result of an initial high placement moisture content of the cover materials.