Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019 / Cataloged from PDF version of thesis. / Includes bibliographical references. / Submerged outfalls consisting of multiple, closely spaced jets are often used to discharge industrial effluents in coastal waterbodies. Examples of such effluents include heated water from thermal power plants, treated wastewater effluent from sewage treatment plants, and reject brine from desalination plants. At locations with shallow water depth, the interaction between adjacent jets is enhanced and can affect mixing. The mixing of submerged outfalls in shallow water is studied in this thesis with particular emphasis on discharge of dense treated brine from desalination plants. Treatment options for brine involve blending it with less saline effluents or its concentration, and can have significant effect on the design of outfall and its mixing. The effect of shallow water depth on dilution of submerged outfalls is determined first for quiescent conditions, and a unified theory is developed for single and multiple jets discharging in shallow water. / The effect of shallowness is shown to be characterized by a non-dimensional parameter, which depends on the receiving water depth and the effluent momentum and buoyancy fluxes. The effect of brine treatment processes, which affect both discharge momentum and buoyancy, on the dilution of various contaminants is determined next. The effect of brine treatment on outfall design is also explored, and optimum outfall design variables are calculated for a range of conditions. In the presence of a crossflow, the mixing dynamics of multiple port outfalls are quite different, and can give rise to complex jet interactions and even reversing flow close to the upstream jets. Laboratory experiments, in which discharge and ambient parameters are varied, have led to an improved empirical expression for dilution. In addition to the strength of crossflow, outfall length and spacing of jets are also found to significantly affect dilution. / A numerical model, capable of modeling the discharge of multiple jets in a crossflow, is developed and shows significant improvement over existing models. / by Ishita Shrivastava. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering

Thesis: Ph. D. in the field of Geotechnical and Geoenvironmental Engineering, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 165-168). / Overpressure or fluid pressure in excess of hydrostatic pressure has been observed globally in many deep water sedimentary basins. One of the possible mechanisms for overpressure is the smectite-to-illite (S-I) transformation. During the transformation, the basal spacing of the smectite layer reduces. The interlayer water is released into pore space, causing an increase in pore pressure. This thesis investigates the compression and permeability behavior change due to S-I transformation. Uniaxial compression testing was performed on smectitic and illitic mudrocks. The original Gulf of Mexico - Eugene Island (GoM-EI) mudrock sets the baseline for smectitic mudrock in order to compare with illitic mudrocks. Two methods were used to create illitic mudrock from the GoM-EI sediment. / The illitic mudrock A was cooked in a high temperature constant rate of strain (CRS) device with effective stress applied (200 °C and 30 days); the illitic mudrock B was cooked in a hydrothermal cooker in a slurry state (250 °C and 18 days). The multi-functional high temperature CRS device was designed from scratch to tackle the challenge of measuring the mechanical properties of a mudrock and transforming the clay minerals. Although the methods of inducing S-I transformation are different, similar degrees of illitization for the illitic mudrock A and B was achieved by selecting the right temperature and time combination. The mineral transformation does not greatly alter the compressibility of the mudrocks. However, both the illitic mudrock A and B sit higher in porosity space than the smectitic mudrock at low stress level. / As effective stress increases, the illitic mudrock A converges with the smectitic mudrock, while the illitic mudrock B reverses order with the smectitic mudrock at 30 MPa. The permeability of the smectitic mudrock ranges over five orders from 10⁻¹⁶ to 10⁻²⁰ m² from a porosity of 0.58 to 0.23. The permeability of the mudrocks are greatly increased by the mineral transformation. The permeability ratio of the illitic mudrocks over the smectitic mudrock increases from 2 to 12 as porosity decreases. The creep rate (C[subscript alpha]) at room temperature and elevated temperature were measured during the transformation stage of the illitic mudrock A. C[subscript alpha] at elevated temperature increases by 50 % compared with that at room temperature. The increase in rate is caused by mineral transformation. Using the difference in rate, a model is proposed to estimate the effective stress reduction or overpressure generation based on the degree of mineral transformation. / by Chunwei Ge. / Ph. D. in the field of Geotechnical and Geoenvironmental Engineering / Ph.D.inthefieldofGeotechnicalandGeoenvironmentalEngineering Massachusetts Institute of Technology, Department of Civil and Environmental Engineering

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999. / Includes bibliographical references (leaves 107-111). / by Li Yu. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 178-190). / The Nile basin is an ecosystem under stress due to rapid population growth, urgent needs for more efficient utilization of natural resources, potential impacts of climate change, and persistent conflicts between riparian countries on the limited set of resources. This thesis develops a framework for optimal allocation of land and water resources to agriculture and hydropower production in the upper Blue Nile (UBN) basin, which contributes about 60 percent of the Nile river flow. The framework consists of three optimization models that aim to: (a) provide accurate estimates of the basin water budget components, (b) allocate land and water resources optimally to rain-fed, and irrigated agriculture, and (c) allocate water to agriculture and hydropower production, and investigate trade-offs between them. This thesis makes two methodological contributions. / First, a data assimilation procedure suitable for data-scarce basins is proposed to deal with data limitations and produce estimates of hydrologic components especially evaporation, consistent with the principles of mass and energy conservation while also fitting closely available observations from satellite remote sensing and ground stations. The spatial distribution of evaporation from the UBN basin is poorly known. This thesis provides new spatial maps of the monthly evaporation. Second, the most representative datasets on topography and soil properties are objectively identified, compared to other datasets, and used to delineate the arable land in the basin. Maps of suitable soils are incorporated into a land-water allocation model that allows for enhancement of the soils from one suitability class to another to increase agricultural productivity in return for an investment in soil inputs such as fertilizers. / The assimilated hydrology and the delineated arable lands are used as input to an optimization model that allocates land to rain-fed agriculture while maximizing the total net economic benefits. The same framework is extended to incorporate irrigated agriculture in the basin. Eleven proposed irrigation projects are screened, and only three of them were found economically attractive. This optimal agricultural expansion, including rain-fed and irrigated agriculture, is expected to reduce the basin flow by 7.6 cubic kilometres, impacting countries downstream from the UBN. Cooperation scenarios that limit the magnitude of this reduction are studied and their impact on the net economic benefit is quantified. The optimization framework is expanded further to include hydropower production. Optimal operation rules for the Grand Ethiopian Renaissance dam (GERD) are identified to maximize annual hydropower generation from the dam while achieving a relatively uniform monthly production rate. / Trade-offs between agricultural expansion and hydropower generation are analysed in an attempt to define scenarios for cooperation that would achieve win-win outcomes for all riparian countries of the basin. / by Mariam M. Allam. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 399-408). / The development of constitutive models that can realistically represent the effective stress-strain-strength of the soil properties is essential for making accurate predictions using finite element analysis. Currently, most of the existing constitutive models are based on the framework of incrementally-linearized elasto-plasticity. However, most of these models do not typically consider energy conservation and are also phenomenological. This means that they can only be used to predict the behavior/ loading conditions for which they have been developed and that they often employ artificial mathematical formulations. This research proposes an improved constitutive model for sands based on the framework of Granular Solid Hydrodynamics [GSHJ. The GSH framework considers energy and momentum conservation simultaneously and, by combining them with thermodynamic considerations, develops constitutive relations for a given energy expression. / This thesis offers a detailed study of the element level behavior of the Tsinghua-Thermosoil model [TTSI (Zhang and Cheng, 2016) based on the GSH. Through this study, we identify and propose a series of modifications to the original formulation in order to improve predictions of well-established soil behavior. The proposed formulation, MIT-GH, introduces a new expression of the free energy and modifies the evolution laws and the steady state values for the internal variables. The model can successfully predict phenomena such as a unique compression response at high confining pressures (Limiting Compression Curve [LCC]) and at large shear strain conditions (Critical State Line [CSL]), and a State Boundary Surface [SBS] that limits the peak shear resistance measured in drained shear tests. The LCC and CSL conditions are defined solely from the evolution of elastic strains while the SBS is defined from the free energy expression. / Finally, our work also offers a novel use of the "double" failure mechanism -- inherent in the GSH framework. Using these mechanisms, MIT-GH can model not only Critical State conditions but also localization phenomena. The proposed criterion for the localization is the maximum expected peak friction angle that a specimen can develop at different void ratios and stress levels. This study also includes a detailed parametric analysis of the model and a proposal for the calibration of the model. The proposed MIT-GH model should be considered as a first generation formulation based on the principles of granular solid hydrodynamics and how it ties to classic knowledge of soil behavior and prior elasto-plastic models. Further research is now needed to extend the framework to address more complex features of sand behavior including the cyclic response and liquefaction. / by Andriani-loanna Panagiotidou. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering

For the past several decades the segmental box girder bridge has proven itself to be one of the more efficient bridge types. Using reusable form work, segments are match-cast, ensuring a more perfect connection during the construction phase. These benefits in conjunction with the fact that the costs of startup and form work are absorbed into the total cost of each segment mean that the longer the final bridge is, the less the cost is per segment, making the segmental box girder bridge one of the most popular long bridge types constructed in the U.S. To minimize cost, it is important to design each segment for efficiency in terms of quantity of longitudinal and transverse post-tensioning and reinforcing steel. The inclusion of post-tensioning technology results in an overall compressive state in the longitudinal and transverse directions of the segments, improving structure strength and service life. However, despite the benefits inherent in using post-tensioning technology, the webs still contain standard deformed reinforcement. The goal of this research is to fit a greased and sheathed monostrand within a segment in a way that both webs and bottom flange would be placed in a state of compression, thereby reducing the demand for standard web reinforcement and, hopefully, segment cost. The research objectives include analyzing principal stresses in the webs of the segment, modifying the segment so as to restrain the monostrand within the webs, designing any additional reinforcement that may be necessary, and finally comparing the estimated construction cost of the new design with that of a pre-existing structure. The results from this research have shown that it is indeed possible to place a greased and sheathed monostrand within the webs of a segment with beneficial results and that the demand for standard deformed reinforcement will thus be reduced. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Spring Semester, 2010. / Date of Defense: April 2, 2010. / Segmental, Box girder, Bridges, Monostrand, Post-Tensioning / Includes bibliographical references. / Michelle Rambo-Roddenberry, Professor Directing Thesis; Lisa Spainhour, Committee Member; Kamal Tawfiq, Committee Member.

Sole nutrient removal from wastewater discharges has become an increasing challenge, as regulatory authorities tighten discharge standards to avoid eutrophication problems in receiving waters. Engineers have become aware that there is a need for new engineering design of standard wastewater treatment plants that should include removal of nutrients (nitrogen and phosphorus) in an efficient and cost effective manner. This need led to the development of biological nutrient removal (BNR) process, which is a distinctive modification of the basic activated sludge process. The BNR process is controlled in bioreactor with separate zones that create different biochemical environments, which allow the system to remove a high degree of nitrogen and phosphorus from the wastewater. There are many uncertainties and uncontrollable factors in the BNR process, therefore achieving high reliability depends heavily on knowledgeable operators and engineers. Operators and start-up engineers can help design engineers become more knowledgeable about uniqueness in design by passing on key information that becomes available during operations. This information was collected and used to improve design's layout of BNR bioreactor to accommodate all observed operational deficiencies. The deficiencies found during operations were related to start-up conditions, climate, process related issues and equipment spacing. Start-up conditions, climate and equipment need to be considered more closely during design. Engineers can learn from the process related deficiencies found during operations to improve the process design. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Spring Semester, 2004. / Date of Defense: March 31, 2004. / Nutrient Removal, BioWin / Includes bibliographical references. / Danuta Leszczynska, Professor Directing Thesis; Amy Chan Hilton, Committee Member; Andrew Dzurik, Committee Member.

Hot Mix Asphalt (HMA) is a viscoelastic material and has been broadly used in pavement structures. It is important to understand the mechanism of complex behaviors of HMA mixtures in field for improving pavement mechanical performance. Aggregate gradation and asphalt binder are two key factors that influence the engineering properties of HMA. The asphalt binder plays a significant role in elastic properties of HMA and it is the essential component that determines HMA's viscous behavior. Many research works suggest that Styrene-Butadiene-Styrene (SBS) polymer is a promising modifier to improve the asphalt binder, and hence to benefit the HMA viscoelastic properties. The specific beneficial characteristics and appropriate polymer concentration need to be identified. In addition, aggregate gradation requirements have been defined in Superpave mix design criteria. However, a potentially sound coarse mixture with the gradation curve passing below the coarse size limit may be disqualified from being used. There is a need to evaluate the Superpave gradation requirements by studying mixtures purposely designed exceeding the control limits. Moreover, the mechanical parameters adopted by AASHTO to characterize HMA properties are shifting from indirect diametral tensile (IDT) test to dynamic modulus test (DMT), because the DMT has the ability to simulate real traffic conditions and to record more viscoelastic information of HMA. Thus, the DMT and the IDT test for implementing the AASHTO Mechanistic-Empirical Design Guide (M-E PDG) are needed to be discussed. The primary objective of this research study was to evaluate the fracture mechanics properties of HMA concrete and to study the correlation between the DMT and the IDT test for Superpave mixtures. An experimental program was performed on asphalt mixtures with various types of materials. The laboratory testing program was developed by applying a viscoelastic fracture mechanics-based framework that appeared to be capable of describing the whole mechanical properties of HMA according to past research studies. The goals for these experiments are to evaluate the effect of aggregate type, the effect of gradation adjustment to control mix designs, and the effect of SBS polymer on fracture mechanics properties of HMA mixtures. Two standard coarse mixes were selected as control levels for fracture mechanics tests: one granite mixture and one limestone mixture. Each control mix design was modified to two different gradation levels with the control asphalt binder (PG 67-22) and three SBS polymer content levels (3.0%, 4.5%, and 6.0%) with the original aggregate gradation. The experimental program for dynamic complex modulus test involved 20 Superpave asphalt concrete mixtures commonly used in Florida with a range of aggregates and mix designs. Data evaluation of the test results indicated the increase of nominal maximum size aggregate amount by 5% to 15% to the standard coarse mix designs had negligible effect on HMA fracture mechanics properties. The SBS polymer-modified asphalt binder improved the fracture mechanics behavior of asphalt mixtures comprehensively. The limestone materials hold advantages over granite materials in improving the performance of thermal cracking at low service temperatures and the rutting resistance at high service temperatures. The master curve construction and linear regression analysis indicated that the total resilient modulus increased with an increase in dynamic modulus at a specific loading frequency. The resilient modulus values were comparable with the dynamic modulus values at the loading frequency of 4 Hz. A correlation relationship was developed for predicting the dynamic modulus from existing resilient modulus values of the asphalt concrete mixture in implementing the mechanistic-empirical pavement design. / A Dissertation submitted to the Department of Civil & Environmental Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Spring Semester, 2009. / Date of Defense: January 30, 2009. / Superpave Mix Design, Gradation, SBS Polymer, Resilient Modulus, Creep, Tensile Strength, Fracture Energy, Dynamic Modulus / Includes bibliographical references. / Wei-Chou V. Ping, Professor Directing Dissertation; Xufeng Niu, Outside Committee Member; Tarek Abichou, Committee Member; John Sobanjo, Committee Member.

Understanding the characteristics of probability distribution of extreme water levels is important for coastal flood mitigation and engineering design. In this study, frequency analysis has been conducted to investigate probability distributions along the coast of the U.S. by using three-parameter General Extreme Value (GEV) method. The GEV model combines three types of probability distributions (Type I for Gumbel distribution, Type II for Fretchet, or Type III for Weibull) into one expression. Types of distributions can be clarified by one of the three parameters of the GEV model for the corresponding studied stations. In this study, the whole U.S. coast was divided into four study areas: Pacific Coast, Northeast Atlantic Coast, Southeast Atlantic Coast and Gulf of Mexico Coast. Nine National Oceanic and Atmospheric Administration (NOAA) stations with a long history of data (more than 70 years) in the four study areas were chosen in this study. Parameters of the GEV model were estimated by using the annual maximum water level of studied stations based on the Maximum Likelihood Estimation (MLE) method. T-test was applied in this study to tell if the parameter, , was greater than, less than or equal to 0, which was used to tell the type of the GEV model. Results show that different coastal areas have different probability distribution characteristics. The characteristics of probability distribution in Pacific Coast and Northeast Atlantic Coast are similar with extreme value I and III model. The Southeast Atlantic Coast and Gulf of Mexico Coast were found to have similar probability distribution characteristics. The probability distributions were found to be extreme value I and II model, which are different from those of the Pacific Coast and Northeast Atlantic Coast. The performance of the GEV model was also studied in the four coastal areas. GEV model works well in the five studied stations of both the Pacific Coast and the Northeast Atlantic Coast but does not work well in the Southeast Atlantic Coast and the Gulf of Mexico Coast. Adequate predictions of extreme annual maximum coastal water levels (such as 100-year flood elevation) are also very important for flood hazard mitigation in coastal areas of Florida, USA. In this study, a frequency analysis method has been developed to provide more accurate predictions of 1% annual maximum water levels for the Florida coast waters. Using 82 and 94 years of water level data at Pensacola and Fernandina, performances of traditional frequency analysis methods, including advanced method of Generalized Extreme Value distribution method, have been evaluated. Comparison with observations of annual maximum water levels with 83 and 95 return years indicate that traditional methods are unable to provide satisfactory predictions of 1% annual maximum water levels to account for hurricane-induced extreme water levels. Based on the characteristics of annual maximum water level distribution Pensacola and Fernandina stations, a new probability distribution method has been developed in this study. Comparison with observations indicates that the method presented in this study significantly improves the accuracy of predictions of 1% annual maximum water levels. For Fernandina station, predictions of extreme water level match well with the general trend of observations. With a correlation coefficient of 0.98, the error for the maximum observed extreme water level of 3.11 m (NGVD datum) with 95 return years is 0.92 %. For Pensacola station, the prediction error for the maximum observed extreme water level with a return period of 83 years is 5.5 %, with a correlation value of 0.98. In frequency analysis of 100 year coastal flood (FEMA 2005), annual extreme high water levels are often used. However, in many coastal areas, long history data of water levels are unavailable. In addition, some water level records may be missed due to the damage of measurement instruments during hurricanes. In this study, a method has been developed to employ artificial neural network and harmonic analysis for predicting extreme coastal water levels during hurricanes. The combined water levels were de-composed into tidal signals and storm surge. Tidal signal can be derived by harmonic analysis, while storm surge can be predicted by neural network modeling based on the observed wind speeds and atmospheric pressure. The neural network model employs three-layer feed-forward backgropagation structure with advanced scaled conjugate training algorithm. The method presented in this study has been successfully tested in Panama City Beach and Apalachicola located in Florida coast for Hurricane Dennis and Hurricane Ivan. In both stations, model predicted peak elevations match well with observations in both hurricane events. The decomposed storm surge hydrograph also make it possible for analysis potential extreme water levels if storm surge occurs during spring high tide. / A Dissertation submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Summer Semester, 2007. / Date of Defense: April 6, 2007. / Frequency Analysis, 100 year, Extreme Water Level, Storm Surge / Includes bibliographical references. / Wenrui Huang, Professor Directing Dissertation; Xufeng Niu, Outside Committee Member; Soronnadi Nnaji, Committee Member; Tarek Abichou, Committee Member.

Traffic capacity, queue discharge rates and vehicle speeds at work zones were equally essential in assessment of work zone performance and traffic operation. This study was conducted to analyze the traffic flow characteristics in freeway work zones based on the traffic data collected from CORSIM simulation. A total seven related factors were input into CORSIM software and 129,600 times of CORSIM simulation were run in the designed experiments. In the capacity and queue discharge rate analyses, it was found that capacity could not be obtained definitely on the onset of congested traffic conditions at work zones although the probability to reach the maximum flow rate on the onset of congested traffic conditions was the highest. With analysis of variance, it was found that almost all the levels in each selected factor were statistical significant with respect to the capacity and mean queue discharge rate. The additive regression models of capacity and mean queue discharge rate with the related factors were obtained. The capacity regression models had R-Square 0.903 and 0.726 respectively with or without considering the interaction effects of two factors. However, the models for mean queue discharge rate had R-Square 0.944 and 0.762 respectively with or without considering the interaction effects of two factors. The results showed that consideration of interaction effects of factors would improve the fitness of models greatly. In addition, mean queue discharge rate was more stable to estimate than the capacity. Number of simulation runs required for capacity analyses at work zones was also studied. It was found that 5 times of simulation runs were adequate for capacity analyses with 95% confident level within 5% estimation errors. In speed analyses, under uncongested traffic conditions, the speeds along freeway work zones were controlled mainly by the FFS (or Speed Limit) although there were some minor fluctuations in the traffic flow. However, under congested traffic conditions the speed characteristics were much more complex and the standard deviation of vehicle speeds were much larger. The speed patterns under congested traffic conditions could be divided into seven sections each with different traffic flow characteristics. Since the large standard deviations of the point speeds, only space-mean speed in three sections out of the seven sections was analyzed. Additive regression models of space-mean speed with related factors were developed under both congested and uncongested traffic conditions. The results showed space-mean speed models under uncongested traffic conditions had R-Square 0.902 and 0.870 respectively with or without considering the interaction effects of two factors. However, under congested traffic conditions, space-mean speed models had R-Square 0.801 and 0.742 respectively with or without considering the interaction effects of two factors. It indicated that it was more difficult to estimate speeds under congested traffic flow. In addition, simulation runs were analyzed for space-mean speed estimation at freeway work zones. The results showed 5 times of simulation runs were adequate for speed analyses with 95% confident level within 10% estimation errors under uncongested traffic conditions. However, under congested traffic conditions, 7 or more times of simulation runs were preferred. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Summer Semester, 2004. / Date of Defense: May 20, 2004. / Simulation, Work Zone, Capacity, Speed, CORSIM / Includes bibliographical references. / W. Virgil Ping, Professor Directing Thesis; Renatus Nyakiamo Mussa, Committee Member; Leonard J. Tung, Committee Member.