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Although pervious concrete was first used in the nineteenth century, it has only recently begun to increase in popularity. As urban areas expand, the problems associated with runoff management have become more challenging. The focus on the negative environmental effects associated with pavement runoff has also increased. These two issues have spurred the recent interest in pervious concrete pavements.Pervious concrete, however, has deficiencies which limit its application as pavements. These limitations include low compressive strength, flexural strength, clogging, and other durability issues. The overall purpose of this project was to provide tools to evaluate and improve the durability and strength of pervious concrete such that it may be more confidently employed in urban roadways. The specific objectives of this project were to (a) investigate the effect of mixture design on strength of pervious concrete (including the effect of fibers), (b) evaluate effect of clogging materials on coefficient of permeability, (c) and investigate the use of the dynamic pressurization test to evaluate the durability of pervious concrete, (d) develop a simple model for predicting removal of clogging particles from pervious concrete pavement surface pores. This thesis documents the results of the laboratory testing, and presents recommendations for mixture proportioning. In addition, recommendations are provided for optimizing the balance between compressive strength and permeability.

In this thesis, the author hypothesizes that the use of computationally intensive mathematical operations in password authentication protocols can lead to security vulnerabilities in those protocols. In order to test this hypothesis: 1. A generalized algorithm for cryptanalysis was formulated to perform a clogging attack (a formof denial of service) on protocols that use computationally intensive modular exponentiation to guarantee security. 2. This technique was then applied to cryptanalyze four recent password authentication protocols, to determine their susceptibility to the clogging attack. The protocols analyzed in this thesis differ in their usage of factors (smart cards, memory drives, etc.) or their method of communication (encryption, nonces, timestamps, etc.). Their similarity lies in their use of computationally intensivemodular exponentiation as amediumof authentication. It is concluded that the strengths of all the protocols studied in this thesis can be combined tomake each of the protocols secure from the clogging attack. The conclusion is supported by designing countermeasures for each protocol against the clogging attack.

In the continuous casting of steels, clogging of the submerged entry nozzle has long been a persistent and costly issue. Previous modelling attempts have assumed that inclusions of different types exhibit the same degree of adhesion when colliding with the nozzle wall - an assumption not borne out by evidence in the literature. In this thesis, a dynamic clogging model is proposed which accounts for the effects of different degrees of inclusion-wall and inclusion-clog adhesion on clog formation and growth. The overall clogging model consists of several sub-models in order to account for the different physics. The melt flow and inclusion motion are modelled using an Eulerian-Lagrangian approach. The inclusion adhesion behavior is determined by the use of a stochastic model activated when an inclusion collides with a surface. A user defined sticking probability is used to determine if an inclusion sticks to a surface (Swall for wall collision or Sclog for clog collision) or instead bounces off. A macroscopic model is used to determine clog growth, where the volume of clog in a cell is tracked and used to determine when the clog grows into adjacent cells. Finally, a modified Kozeny-Carmen equation is used as a porosity model so that the presence of the clog affects and diverts the melt flow. The modified melt flow then alters subsequent inclusion deposition and clog growth. The model is used to investigate the effects of different degrees of inclusion adhesion on inclusion deposition and clog growth. Three scenarios are examined - 1) Inclusion deposition in a pilot scale nozzle, 2) Inclusion deposition in an industrial scale slide-gate controlled nozzle and 3) Clog formation and growth in a pilot scale nozzle. The deposition studies indicate that in a pilot scale nozzle, only a minority of inclusions ever collide with the nozzle (≈ 10%). In contrast, in the industrial scale nozzle there are far more inclusion collisions with the nozzle wall, ranging from 80% when the slide-gate is 20% open to 30% when the slide-gate is 100% open. Despite the differences in nozzle geometry and flow conditions, a similar effect on inclusion deposition is seen when Swall is varied. The effects of Swall can be divided into two regimes. When 0 ≥ Swall < 0.05 there is a sharp increase in the deposition ratio as Swall increases. When Swall > 0.05 there is a small and linear increase in the deposition ratio as Swall increases. This pattern is also seen in the study of clog formation and growth in a pilot scale nozzle. The effects of Swall or Sclog on clog volume can be divided into two regimes. As Swall or Sclog increases, there is a large increase in clog volume, until the sticking probability increases above 1E-2, then any further increase results in only a small increase in clog volume. In comparison to literature data the model successfully simulates the location of clog formation, the initial jump in clogging factor and the clogging factor growth rate in the later stages of clogging. However, the model underestimates the overall increase in clogging factor, resulting in a clogging factor at the end of the simulation which is half of that seen in the experiment. / Thesis / Doctor of Philosophy (PhD) / One of the ongoing challenges in the continuous casting industry is the occurrence of nozzle clogging. Over time, a buildup of material occurs within the submerged entry nozzle, called a clog. The clog leads to the partial or complete blockage of the nozzle, resulting in increased production costs. Since studying this phenomena experimentally is difficult due to the high temperature and opacity of the molten steel, modelling provides a useful alternative approach. However, previous modelling efforts regarding nozzle clogging have treated all inclusions as exhibiting the same adhesion behavior. This thesis aims to address this issue by presenting a dynamic nozzle clogging model which accounts for the effects of different degrees of inclusion adhesion. The model is used to study both inclusion deposition and clog formation. Results indicate that even a small amount of sticking probability results in a significant degree of inclusion deposition and clogging. The effect of sticking probability on clogging can be divided into two regimes, one where the clogging is very sensitive to the sticking probability and one where it is insensitive. Finally, the model was shown to run adequately even on coarser meshes (meshes with a smaller number of larger cells), indicating its utility in industrial applications, where it can be used to predict the location of clog formation and the clog growth rate.

Permeable pavement structures (PPSs) are one of the significant LID systems that have potential positive effect on the ecosystem. Yet, the performance of permeable pavements is still questionable. Further studies on the hydrological performance of the system need to be addressed for better design criteria and maintenance during the operation. The infiltration through the pavement is a crucial parameter that projects the system performance. Several factors affect its deterioration. The entrapment of suspended materials associated with the infiltrated stormwater through the system is one of the major factors that affect its performance. Factors that promote the entrapment of particles were discussed thoroughly through the literature and are explained in this study. Many previous studies were focused on performing experimental work and developing empirical models to study the hydraulic performance of the system. Yet, prediction models on the infiltration deterioration need to be addressed and theoretical analysis needs to be performed in order to determine the empirical coefficients with defined parameters that were introduced in the previous literature. Furthermore, the sensitivity of the pore and particle size distribution and mass loading rate of the suspended materials on the infiltration rate need to be addressed. The study focuses on investigating performance of PPSs with examining the variation effect of pore and particle size distribution on it. A prediction model was made and simulated using Matlab software, in which pore and particle size means and standard deviations are taken as inputs. Further, the variation in these parameters on infiltration is examined. Critical levels, that infiltration decline would reach, were defined based on the introduced mechanisms from the previous literature. Based on the variation of pore and particle size means and standard deviations, these critical levels were studied through the analysis of the obtained results from the simulated model. / Graduate / 2019-12-10

This thesis describes a laboratory investigation of in-situ treatment of synthetic leachate representative of that generated by a municipal solid waste (MSW) landfill. The overall objective is to evaluate alternative designs and operating procedures for effective leachate collection in conjunction with efforts to accelerate waste stabilization (i.e. leachate recirculation). In the investigation five 15 cm (6) diameter PVC columns were packed with pea gravel and concrete of different sizes; geotextiles were also placed between the packed sections as filter-separators and promoters of bacterial growth. Synthetic leachate was continuously input to the top of the columns and circulated at rates representative of operating field conditions. For each column, effluent was discharged to a nitrification reactor before recirculation. The tests were conducted under anaerobic and unsaturated conditions in the columns. Results indicate about a 97% decrease in COD from the synthetic leachate concentration entering the top of the column, and about 98 % conversion of the ammonia to nitrogen gas. COD depletion and methane production were not significantly inhibited by the denitrification process. Optimum Hydraulic Retention Time (HRT) for the nitrification-denitrification system makes it economically viable for its development at a landfill site. Gas production shows low CO2 values, decreasing the potential of clogging in the Leachate Collection System (LCS) and extending the Landfill Gas (LFG) networks life service by generating a less corrosive environment. The use of concrete as an alternative to the most commonly used natural gravel as leachate collection drains may not be a good option. During the experiment, the leachate that permeated the columns packed with crushed concrete, presented a higher pH than the leachate that permeated the natural stone. At the conclusion of the experiment noticeable weathering was observed when the columns where dismantled. Further studies are recommended until more conclusive evidence as to concrete performance is found. The overall results obtained from the experiment show that in situ passive treatment at landfills is viable.

This thesis describes a laboratory investigation of in-situ treatment of synthetic leachate representative of that generated by a municipal solid waste (MSW) landfill. The overall objective is to evaluate alternative designs and operating procedures for effective leachate collection in conjunction with efforts to accelerate waste stabilization (i.e. leachate recirculation). In the investigation five 15 cm (6) diameter PVC columns were packed with pea gravel and concrete of different sizes; geotextiles were also placed between the packed sections as filter-separators and promoters of bacterial growth. Synthetic leachate was continuously input to the top of the columns and circulated at rates representative of operating field conditions. For each column, effluent was discharged to a nitrification reactor before recirculation. The tests were conducted under anaerobic and unsaturated conditions in the columns. Results indicate about a 97% decrease in COD from the synthetic leachate concentration entering the top of the column, and about 98 % conversion of the ammonia to nitrogen gas. COD depletion and methane production were not significantly inhibited by the denitrification process. Optimum Hydraulic Retention Time (HRT) for the nitrification-denitrification system makes it economically viable for its development at a landfill site. Gas production shows low CO2 values, decreasing the potential of clogging in the Leachate Collection System (LCS) and extending the Landfill Gas (LFG) networks life service by generating a less corrosive environment. The use of concrete as an alternative to the most commonly used natural gravel as leachate collection drains may not be a good option. During the experiment, the leachate that permeated the columns packed with crushed concrete, presented a higher pH than the leachate that permeated the natural stone. At the conclusion of the experiment noticeable weathering was observed when the columns where dismantled. Further studies are recommended until more conclusive evidence as to concrete performance is found. The overall results obtained from the experiment show that in situ passive treatment at landfills is viable.

A sports field construction method that uses a geotextile to support the root zone atop a synthetic drainage structure is an alternative to the common design that uses gravel drainage material to support the root zone. A study was conducted to address the concern that fine particles in the root zone may migrate under the influence of percolating water, clog geotextile pores, and restrict the amount of water drained from a sports field. In test columns, six root zone mixtures with different particle size distributions were combined with ten geotextiles with different opening sizes to produce 60 replicated treatments. Water flow through the root zone mixture-geotextile combinations in the test columns was evaluated over a six-month period. Change in permeability was assessed by monitoring the temporal distribution of drainage from a 25-mm pulse of water applied to 300-mm deep root zone mixture in the test column. Particles in drainage water were analyzed for size distribution. The study revealed that drainage rates were affected more by drainage trough the root zone mixture than through the geotextile. The amount and particle size distribution of particles in drainage water were influenced more by root zone mixture than by geotextile. It appeared that in the establishment phase of a sports field that fine particles in the root zone may present more of a problem to clogging of the root zone pores than clogging of the geotextile pores.

abstract: The Santa Cruz River, in southern Arizona, receives steady inputs of nutrient-enriched treated wastewater (effluent). Previous studies have documented reduced infiltration of surface water in the river. This disruption of hydrologic connectivity, or clogging, can have consequences for groundwater recharge, flows of wastewater in unwanted locations, and potentially even survivorship of floodplain riparian vegetation. Clogging can result from biotic processes (microbial or algal growth), abiotic processes (siltation of interstitial spaces), or both. Little is known about clogging in rivers and the environmental factors that regulate their dynamics, so natural field experiments along the Santa Cruz and San Pedro Rivers were used to answer: 1) Are there spatial patterns of hydraulic conductivity in the riverbed downstream from the effluent point-source? 2) Is there temporal variability in hydraulic conductivity and microbial abundance associated with flooding? 3) Are there environmental variables, such as nutrients or stream flow, related to differences in hydraulic conductivity and microbial abundance? To address these questions, a series of sites at increasing distance from two municipal effluent discharge points with differing water quality were selected on the Santa Cruz River and compared with non-effluent control reaches of the San Pedro River. Physical, chemical, and biological parameters were monitored over one year to capture seasonal changes and flood cycles. / Dissertation/Thesis / M.S. Biology 2012

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第17131号 / 工博第3621号 / 新制||工||1550(附属図書館) / 29870 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査）教授 松岡 俊文, 教授 大津 宏康, 准教授 水戸 義忠 / 学位規則第4条第1項該当