This study evaluates the seismically induced displacements of a slope using the Finite Element Method (FEM) in comparison to the results of twelve empirical predictive approaches. First, the existing methods to analyze the stability of slopes subjected to seismic loads are presented and their capabilities to predict the onset of failure and post-failure behavior are discussed. These methods include the pseudostatic method, the Newmark method, and stress-deformation numerical methods. Whereas the pseudostatic method defines a seismic coefficient for the analysis and provides a safety factor, the Newmark method incorporates a yield coefficient and the actual acceleration time history to estimate permanent displacements. Numerical methods incorporate advanced constitutive models to simulate the coupled stress-strain soil behavior, making the process computationally more costly. In this study, a model slope previously studied at laboratory scale is selected and scaled up to prototype dimensions. Then, the slope is subjected to 88 different input motions, and the seismic displacements obtained from the numerical and empirical approaches are compared statistically. From correlation analyses between seven ground motion parameters and the numerical results, new empirical predictive equations are developed for slope displacements. The results show that overall the FEM displacements are generally in agreement with the numerically developed methods by Fotopoulou and Pitilakis (2015) labelled "Method 2" and "Method 3", and the Newmark-type Makdisi and Seed (1978) and Bray and Travasarou (2007) methods for rigid slopes. Finally, functional forms for seismic slope displacement are proposed as a function of peak ground acceleration (PGA), Arias intensity (Ia), and yield acceleration ratio (Ay/PGA). These functions are expected to be valid for granular slopes such as earth dams, embankments, or landfills built on a rigid base and with low fundamental periods (Ts<0.2). / Master of Science / A landslide is a displacement on a sloped ground that can be triggered by earthquake shaking. Several authors have investigated the failure mechanisms that lead to landslide initiation and subsequent mass displacement and proposed methodologies to assess the stability of slopes subjected to seismic loads. The development of these methodologies has to rely on field data that in most of the cases are difficult to obtain because identifying the location of future earthquakes involves too many uncertainties to justify investments in field instrumentation (Kutter, 1995). Nevertheless, the use of scale models and numerical techniques have helped in the investigation of these geotechnical hazards and has led to development of equations that predict seismic displacements as function of different ground motion parameters. In this study, the capabilities and limitations of the most recognized approaches to assess seismic slope stability are reviewed and explained. In addition, a previous shaking-table model is used for reference and scaled up to realistic proportions to calculate its seismic displacement using different methods, including a Finite Element model in the commercial software Plaxis2D. These displacements are compared statistically and used to develop new predictive equations. This study is relevant to understand the capabilities of newer numerical approaches in comparison to classical empirical methods.

Two experiments were conducted to determine the influence of light on 'Norman' and 'Cresthaven' peach fruit quality characteristics. Of primary interest was the relationship between ground color and flesh firmness. Light levels were manipulated by use of shade cloth, reflective mulch, and aluminum foil. 'Norman' trees, with a randomly chosen half of the canopy covered with 73% shade cloth, had fruit with lower levels of red color, soluble solids concentration (SSC), specific leaf weight, and average photosynthetic photon flux (PPF) than did non-shaded trees. Foil-covered 'Cresthaven' fruit were larger, less firm, and had lower SSC than non-covered fruit. Covered fruit developed yellow but not red color. Position of the fruit within the canopy of the tree also affected fruit quality characteristics. Inside fruit on both 'Norman' and 'Cresthaven' trees were smaller and firmer, had lower SSC, and were less red than fruit from the canopy exterior. The position effect was probably due to the degree of light exposure and not to the distance from the roots. Fruit on the inside of the tree canopies received much lower average PPF than outside fruit. Relationships were evaluated between ground color and firmness for both cultivars. At a given hue angle, fruit developing in high-light environments were firmer than fruit from low-light environments for 'Cresthaven', but the opposite was true for 'Norman'. Therefore, canopy position or the light environment in the vicinity of the developing fruit does not consistently influence the relationship between hue angle on the non-blush side of the fruit, and flesh firmness. / Master of Science

Automation of hydraulic earth moving and construction equipment is of prime economic and social importance in today's marketplace. A human operator can be replaced or augmented with a robotic system when the job is too dull, dirty or dangerous. There are a myriad of applications in both Government and Industry that could benefit from augmenting or replacing an operator of hydraulic equipment with an intelligent robotic system. A specific important situation is the removal of unexploded ordnance (UXO). The removal of UXO is a troubling environmental problem that plagues people around the world. This document addresses the danger that UXO pose to military groups in applications such as active range clearance and disposal of unexploded or dud munitions. Disposing of these munitions is a difficult problem, which first begins by determining their location. The process can be aided through the use of teleoperated hydraulic equipment, which allows the operator to be located at a safe distance from these munitions. In the past, converting a large piece of hydraulic construction equipment for teleoperated use has been an expensive task. An important result of this research is demonstrating that through readily available commercial products and existing design methodologies, such robotic tasks can be accomplished at relatively low cost and in a timely, reliable fashion. / Master of Science

The objective of quantitative Performance-Based Earthquake Engineering (PBEE) is designing buildings that meet the specified performance objectives when subjected to an earthquake. One challenge to completely relying upon a PBEE approach in design practice is the open-ended nature of characterizing the earthquake ground motion by selecting appropriate ground motions and Intensity Measures (IM) for seismic analysis. This open-ended nature changes the quantified building performance depending upon the ground motions and IMs selected. So, improper ground motion and IM selection can lead to errors in structural performance prediction and thus to poor designs. Hence, the goal of this dissertation is to propose methods and tools that enable an informed selection of earthquake IMs and ground motions, with the broader goal of contributing toward a robust PBEE analysis. In doing so, the change of perspective and the mechanism to incorporate additional information provided by Bayesian methods will be utilized. Evaluation of the ability of IMs towards predicting the response of a building with precision and accuracy for a future, unknown earthquake is a fundamental problem in PBEE analysis. Whereas current methods for IM quality assessment are subjective and have multiple criteria (hence making IM selection challenging), a unified method is proposed that enables rating the numerous IMs. This is done by proposing the first quantitative metric for assessing IM accuracy in predicting the building response to a future earthquake, and then by investigating the relationship between precision and accuracy. This unified metric is further expected to provide a pathway toward improving PBEE analysis by allowing the consideration of multiple IMs. Similar to IM selection, ground motion selection is important for PBEE analysis. Consensus on the "right" input motions for conducting seismic response analyses is often varied and dependent on the analyst. Hence, a general and flexible tool is proposed to aid ground motion selection. General here means the tool encompasses several structural types by considering their sensitivities to different ground motion characteristics. Flexible here means the tool can consider additional information about the earthquake process when available with the analyst. Additionally, in support of this ground motion selection tool, a simplified method for seismic hazard analysis for a vector of IMs is developed. This dissertation addresses four critical issues in IM and ground motion selection for PBEE by proposing: (1) a simplified method for performing vector hazard analysis given multiple IMs; (2) a Bayesian framework to aid ground motion selection which is flexible and general to incorporate preferences of the analyst; (3) a unified metric to aid IM quality assessment for seismic fragility and demand hazard assessment; (4) Bayesian models for capturing heteroscedasticity (non-constant standard deviation) in seismic response analyses which may further influence IM selection. / Doctor of Philosophy / Earthquake ground shaking is a complex phenomenon since there is no unique way to assess its strength. Yet, the strength of ground motion (shaking) becomes an integral part for predicting the future earthquake performance of buildings using the Performance-Based Earthquake Engineering (PBEE) framework. The PBEE framework predicts building performance in terms of expected financial losses, possible downtime, the potential of the building to collapse under a future earthquake. Much prior research has shown that the predictions made by the PBEE framework are heavily dependent upon how the strength of a future earthquake ground motion is characterized. This dependency leads to uncertainty in the predicted building performance and hence its seismic design. The goal of this dissertation therefore is to employ Bayesian reasoning, which takes into account the alternative explanations or perspectives of a research problem, and propose robust quantitative methods that aid IM selection and ground motion selection in PBEE The fact that the local intensity of an earthquake can be characterized in multiple ways using Intensity Measures (IM; e.g., peak ground acceleration) is problematic for PBEE because it leads to different PBEE results for different choices of the IM. While formal procedures for selecting an optimal IM exist, they may be considered as being subjective and have multiple criteria making their use difficult and inconclusive. Bayes rule provides a mechanism called change of perspective using which a problem that is difficult to solve from one perspective could be tackled from a different perspective. This change of perspective mechanism is used to propose a quantitative, unified metric for rating alternative IMs. The immediate application of this metric is aiding the selection of the best IM that would predict the building earthquake performance with least bias. Structural analysis for performance assessment in PBEE is conducted by selecting ground motions which match a target response spectrum (a representation of future ground motions). The definition of a target response spectrum lacks general consensus and is dependent on the analysts’ preferences. To encompass all these preferences and requirements of analysts, a Bayesian target response spectrum which is general and flexible is proposed. While the generality of this Bayesian target response spectrum allow analysts select those ground motions to which their structures are the most sensitive, its flexibility permits the incorporation of additional information (preferences) into the target response spectrum development. This dissertation addresses four critical questions in PBEE: (1) how can we best define ground motion at a site?; (2) if ground motion can only be defined by multiple metrics, how can we easily derive the probability of such shaking at a site?; (3) how do we use these multiple metrics to select a set of ground motion records that best capture the site’s unique seismicity; (4) when those records are used to analyze the response of a structure, how can we be sure that a standard linear regression technique accurately captures the uncertainty in structural response at low and high levels of shaking?

Microwaves heat food rapidly and foods are prepared in less time. However, due to non-uniform heating nature of microwave cooking, there exists a serious concern over complete elimination of pathogens in the food. There has been an increase in interest to accurately understand the behavior of different food materials in a microwave field and microbial inactivation during microwave cooking. Recent research showed that fat content in muscle food plays an important role in microbial inactivation by increasing the inactivation level with an increase in the fat level. It was also demonstrated that muscle food heats up differently than a vegetable food product. Cooking food in a microwave oven either by covering the food container or not results in significantly different temperature profiles. The current research attempts to use modeling techniques to analyze impact of these factors on microwave heating. Mathematical modeling is faster, easier and economically better than actual experiments in determining heating behavior of a microwave-cooked food. Though modeling cannot completely replace actual experiments, it can be used as a tool to understand the effects of various factors influencing the microwave cooking. A factor that is highly important during microwave processing is dielectric properties of the material. The interaction of microwave with the food is mainly based on its dielectric properties, which can change with temperature. Therefore, determination of dielectric properties of food with respect to temperature becomes critical. The current research project has two parts. One to determine the dielectric properties of food being tested and another is to employ mathematical modeling techniques to analyze the effect of fat content, food type and the effect of cooking food by covering the bowl using the lid and not covering bowl. Dielectric properties of ground beef patties at 4%, 9%, 20% fat levels and frozen broccoli were determined using an open-ended, 3.6 mm diameter, semi-rigid coaxial line with copper conductors, connected to a network analyzer. The properties were determined at various temperatures. Foods were measured in triplicate. Results showed that dielectric constant and dielectric loss factor of low fat ground beef were higher than that of high fat level ground beef. In addition, the dielectric properties of florets were lower than that of stem parts for frozen broccoli. A 1,200W, household type microwave oven was used in this study to heat the food. Food was placed in a microwave-safe glass bowl and cooked for 120 seconds. One headspace and three internal temperature measurements were recorded for every 0.6 seconds. Five replications were performed. Finite element method was used as modeling technique and temperatures were predicted. Experimental and predicted temperature values were compared. Results showed that the model used in the study was more suitable for modeling the uncovered cooking than covered cooking process. Modeling results also revealed that high fat ground beef patties reached higher temperature than low fat patties. In high fat meat products, fat content also contributed to increase in temperature during microwave heating. In vegetable products and low fat meat food, moisture content is mainly responsible for microwave heating. A more extensive study on critical fat level above which fat content helps in increasing temperature is needed. In addition, inclusion of steam properties in the headspace for modeling the covered cooking is recommended. / Master of Science

The development of southwest Virginia’s coal mining areas is severely hampered by a lack of building sites and waste disposal facilities. New technologies to reclaim mined lands have the capacity to produce large level expanses of land suitable for building sites by using the minespoil to reshape the land contours. Because these areas are generally too remote for centralized sewer to be economically feasible, the problem of waste disposal remains. Also, the current Virginia Department of Health regulations forbid placement of on-site waste water treatment and dispsoal systems (OSWTDS) in any fill material, including minespoil. The objective of this research is to examine alternative OSWTDS technologies for their applicability to treating wastewater in fill materials with respect to both removal of biological and chemical contaminants and hydraulic performance. In the fall of 1989, topsoil and minespoil materials were transported from southwest Virginia to Blacksburg, Virginia. The soil material was screened, air-dried, and packed into large plastic cylinders. Septic tank effluent and sand filter effluent was applied to the soil columns daily at three different loading rates for a period of 5 months. Wastewater samples were collected after passing through the soil columns and analyzed for several chemical parameters as well as fecal coliforms. Antibiotic-resistant Escherichia Coli and bacteriophage T-1 (virus) were introduced into the columns and analyzed in the filtrate. The soil material in the columns was also characterized for selected physical parameters. The results indicate that the concentration of total inorganic N was reduced 15 to 60% after the effluent was passed through the soil columns. However, the NO₃ - N concentrations were still above the 10 mg/L drinking water standard indicating that housing density should be considered when fill material is used for OSWTDS. The quantity of P emerging from the columns was higher than anticipated in minespoil column effluent which is probably related to the indigenous P present in the minespoil. The P concentration in topsoil column effluent increased with influent application and this relationship could be described by quadratic functions. The numbers of fecal coliforms were reduced (93 to 99%) by passing effluent through the soil columns. The concentration of indicator organisms indicated a gradual decline in viable bacterial cells and viral particles over time, with the indicator virus assays being completely negative by day 11. The tracer organism study also indicates that the survival time of these organisms can be effectively controlled in topsoil by reducing the influent loading rates, and in minespoil by reducing the influent loading rates and using some type of pretreatment, such as a sand filter. This study indicates that OSWTDS can be placed in selected topsoil areas in reclaimed minelands. It further indicates that at least 60 cm of unsaturated topsoil should be available for wastewater renovation. Minespoils were also effective at renovating wastewater, but may require pretreatment before application, a lower loading rate, a deeper unsaturated zone, or perhaps a combination of these factors. / Master of Science

Two shallow-placed low pressure distribution (LPD) systems were evaluated in soils that were marginally suited for a conventional on-site wastewater disposal system (OSWDS) because of low hydraulic conductivity and shallow depth of soil to bedrock. The soils used for this study were Edom (fine, illitic, mesic, Typic Hapludult) and Penn-Bucks soil (fine-loamy, mixed, mesic, ultic Hapludult). In the Edam soil, the LPD system was installed with four subsystem designs operating: a narrow trench design with a design loading rate of 17.5 Lpd/m², and three designs based on Virginia regulations with design loading rates of 9.0 Lpd/m², 4.5 Lpd/m², and 5.7 Lpd/m². In the Penn-Bucks soil, the LPD system was installed with three subsystem designs operating: a narrow trench design with a design loading rate of 30.6 Lpd/m², and two designs based on Virginia regulations with design loading rates of 14.3 Lpd/m², and 7.3 Lpd/m². The evaluation was conducted under different moisture and temperature conditions (summer of 1989, and the winter of 1990), and focused on the fate and transport below each system of two antibiotic resistant <i>Escherichia coli</i> strains and two host-specific bacteriophage strains. The potential loss of N0₃"-N through the biological process of denitrification was also examined. In the Edom soil, a narrow trench design, and designs based on the Virginia regulation all removed >99.9% of the bacterial and viral tracers during the summer of 1989, and >99% during the winter of 1990 throughout a 152 cm depth. The potential loss of N0₃"-N in the Edom soil by denitrification was estimated to be 38%. In the Penn-Bucks soil, the narrow trench design failed within six months of installation because the effluent loading rate was too high to permit infiltration through the silty clay loam soil, once biological clogging developed with the subsequent decrease in infiltrative capacity. The lower Virginia loading rate was mlore effective at microbial retention with >99.9% removal throughout a 114 cm depth in both the summer of 1989 and the winter of 1990. The normal Virginia loading rate removed> 99% of the bacterial and viral tracers throughout a 102 cm depth in both the summer of 1989 and the winter of 1990. The overall loss of N0₃"-N in the Penn-Bucks soil through denitrification was estimated at 67%. / Master of Science

Chemical grouting has been used to insure the stability of underground mine openings for more than twenty years. The polyurethane grout, which is currently being used, has a limited range of mechanical properties that restrict its utilization. Polyurethane also poses serious threats to miners' health due to its toxicity and flammability, To overcome many of these problems and limitations, research has been conducted on a newly developed polyester-based grout. The assessment of mechanical properties of polyester grout is the focus of this work. Field experiences and laboratory research have defined properties which an effective grouting material should possess. Experimental results indicate that the polyester grout meets or exceeds these recommended properties and has the potential to expand the applicability of chemical grouting in ground control. By adjusting its formulations, mechanical properties of polyester grout can be engineered to solve specific ground control problems. / Master of Science

The response of an aggregate pier foundation system during seismic loading was investigated. The factors and phenomena governing the performance of the aggregate pier and the improved ground were identified and clarified. The key factors affecting the performance of the aggregate pier include soil density, stiffness modulus, and drainage capacity. The improved ground is influenced by soil stratification, soil properties, pore pressure dissipation, and earthquake time history. Comprehensive numerical modeling using FLAC were performed. The focus of the study in this research was divided into three parts: the studies of the ground acceleration, the excess pore water pressure ratio and the shear stress in soil matrix generated during seismic loading. Two earthquake time histories scaled to different peak acceleration were used in the numerical modeling: the 1989 Loma Prieta earthquake (pga = 0.45g) and the 1988 Saguenay earthquake (pga = 0.05g). The main results of the simulation showed the following effects of aggregate pier on liquefiable soil deposits: 1) The aggregate pier amplifies the peak horizontal acceleration on the ground surface (amax), 2) The aggregate pier reduces the liquefaction potential up to depth where it is installed, 3) Pore pressures are generally lower for soils reinforced with aggregate pier than unreinforced soils except for very strong earthquake, 4) The maximum shear stresses in soil are much smaller for reinforced soils than unreinforced soils. The excess pore water pressure ratio and the shear stress in the soil matrix calculated by FLAC were generally lower than those predicted by available procedures. / Master of Science

The US Food and Drug Administration Food Safety Modernization Act (FSMA) Produce Safety Rule (PSR) prohibits the harvest of dropped fruits and vegetables due to potential microbial contamination. Under the FSMA PSR dropped produce includes (i) produce that has detached from the parent plant and unintentionally contacts the ground and (ii) produce that is attached to the parent plant and unintentionally contacts the ground. Due to the benefits of plant growth and pest management, agricultural ground covers are a common horticultural practice implemented in the fresh produce production environment and produce may come into contact with these ground covers. Thus, this thesis aims to (i) quantify the survival of bacteria on different agricultural ground cover types and in different production environments and (ii) evaluate the cross-contamination risk of mulch to fresh produce from different drop heights and contact times. A seven-strain Salmonella cocktail was spot inoculated on coupons of biodegradable mulch, landscape fabric, and plastic mulch, and held in a growth chamber (23°C, 55% RH). At 0, 0.06, 0.17, 1, 2, 3, 5, 7, 30, 60, 90, and 140 days post-inoculation (dpi), coupons were enumerated for Salmonella. Coupons of plastic mulch were also spot inoculated with a green-fluorescent protein-tagged generic Escherichia coli and held in a growth chamber, greenhouse, and field environment for enumeration at 0, 0.06, 0.17, 0.41, 1, 2, 3, 5, and 7 dpi. Fresh cucumber, jalapeño, and tomato were dropped from 0, 1, 2, 4, and 6 ft using height-modified PVC (polyvinyl chloride) pipes onto generic E. coli inoculated plastic mulch, as well as tomato onto inoculated biodegradable mulch. Produce samples were enumerated after 3 s of mulch contact. Fresh cucumber, jalapeño, and tomato were also grown in contact with generic E. coli inoculated plastic mulch for 0, 1, 3, 5, and 7 days post-placement in the field. Salmonella survived on all ground covers for up to 140 dpi in the growth chamber. From 0 to 30 dpi, biodegradable mulch had the lowest Salmonella reduction, followed by landscape fabric and then plastic mulch (P < 0.05). No significant differences in ground cover type and Salmonella reduction were observed at 90 dpi (P > 0.05). Plastic mulch had the highest reduction of generic E. coli in the field followed by the greenhouse and growth chamber over 7 dpi (P < 0.05) with field and greenhouse coupons achieving approximately a 6-log reduction by 0.17 and 7 dpi, respectively. Ground cover type and environment impacted bacterial survival and highlighted the importance of growing location in risk management. Cucumber and tomato samples dropped from 4 (33%; 17%) and 6 (100%; 43%) ft were damaged, respectively. In general, generic E. coli transferred to the tested commodities regardless of drop height or contact time. These findings support that dropped produce should not be harvested due to potential damage and when surfaces were contaminated, transfer was likely to occur. Similarly, if surfaces were contaminated, regardless of contact time (0, 1, 3, 5, and 7 d), transfer was likely to occur indicating cross-contamination poses a food safety risk despite unintentional or intentional ground contact. Food safety efforts should focus on minimizing visible contamination, as outlined in the FSMA PSR, that may contaminate fresh produce in the production environment. Growing produce in contact with the ground alone may not be the sole factor in the contamination of fresh produce, as a contamination event is needed. / Master of Science in Life Sciences / The US Food and Drug Administration Food Safety Modernization Act (FSMA) Produce Safety Rule (PSR) is a federal regulation that sets science-based standards for the safe production, harvest, and handling of fresh fruits and vegetables. Within the harvesting requirements of the PSR, produce that drops to the ground cannot be harvested because of potential microbial contamination. Dropped produce includes (i) detached from the plant and touching the ground and (ii) attached to the plant and touching the ground. The ground can include different surfaces including agricultural ground covers, a common horticultural practice that increases plant growth and decreases pests. This thesis aims to evaluate the food safety risk of (i) bacteria on different ground covers and in different growing environments and (ii) fresh produce contacting the ground while detached (i.e., drop) and attached to the plant. Three ground cover types, biodegradable mulch, landscape fabric, and plastic mulch, were inoculated with Salmonella and held in a growth chamber with moderate conditions (23°C, 55% RH). At 0, 0.06, 0.17, 1, 2, 3, 5, 7, 30, 60, 90, and 140 days, sample coupons were evaluated for Salmonella counts. Plastic mulch was inoculated with green-fluorescent protein-tagged generic Escherichia coli (E. coli) and placed in a growth chamber, greenhouse, and field for 0, 0.06, 0.17, 0.41, 1, 2, 3, 5, and 7 days to investigate survival. At the selected time-points, generic E. coli counts were evaluated on plastic mulch. Fresh cucumber, jalapeño, and tomato were either dropped through height-modified PVC (polyvinyl chloride) pipes at 0, 1, 2, 4, and 6 ft onto generic E. coli inoculated plastic mulch and only tomato onto generic E. coli inoculated biodegradable mulch (detached produce), or grown in contact with generic E. coli inoculated plastic mulch in the field (attached produce) for 0, 1, 3, 5, and 7 days. Salmonella was present on all ground covers for up to 140 d in the growth chamber. From 0 to 30 d, biodegradable mulch had the highest concentration of Salmonella, followed by landscape fabric and then plastic mulch; however, no differences in material were observed at 90 d. Plastic mulch had the lowest concentration of generic E. coli in the field followed by the greenhouse and growth chamber over 7 d. Ground cover types (biodegradable mulch, landscape fabric, and plastic mulch) and growing environment (field, greenhouse, and growth chamber) influenced bacterial survival and should be considered in food safety management and assessment of preharvest contamination risks. Cucumber and tomato samples dropped from 4 and 6 ft were often damaged, compared to lower drop heights. Bacteria transferred to cucumber, jalapeño, and tomato regardless of drop height and contact time. Dropped produce should not be harvested due to damage and likelihood of cross-contamination. Contamination was not influenced by contact time confirming fresh produce in contact with a contaminated source is likely to become contaminated despite unintentional or intentional ground contact. Thus, food safety efforts should focus on minimizing visible contamination on surfaces that may contact fresh produce in the growing environment.