Recursos de colección

DSpace at MIT (90.784 recursos)

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Civil and Environmental Engineering - Ph.D. / Sc.D.

Mostrando recursos 1 - 20 de 670

  1. Stiffness characterization of mechanically-compressed cohesive soils using wave propagation

    Marjanovic, Jana
    Wave propagation through soils is a non-destructive method used to characterize soil stiffness properties and is the basis for geophysical interpretations. Due to the difficulty of measuring shear waves through soft cohesive soils with ultrasonic transducers, bender elements are typically used, which couple to the soft clay. Unfortunately, the stress limitation of bender elements precludes it from testing above 1.5 MPa. A novel setup using ultrasonic transducers, with electronic conditioning, is developed in order to overcome the difficulties of transmitting a shear wave through a soft material. The successful fabrication of triaxial cell endcaps fitted with ultrasonic piezoceramic elements has...

  2. Indoor navigation for passengers in underground transit stations using smartphones

    Wang, Yin, Ph. D. Massachusetts Institute of Technology
    People are increasingly relying on smartphones to solve a lot of their daily problems, among which navigation is one of the most fundamental tasks. Estimating the locations of pedestrians and tracking them in an indoor environment is a long sought after research goal. This thesis develops a smartphone-based indoor navigation system specifically designed for transit stations, but which also allows easy extension to other navigation scenarios. The thesis' system requires no extra hardware installation in the indoor environment or on the phone and few assumptions are made about the indoor space and the path tile user is taking, unlike previous...

  3. Effective mechanical Properties of material models with random heterogeneities

    Dimas, Leon Sokratis Scheie
    In this thesis we obtain analytical approximations to the probability distribution of the elastic tensor and fracture strengths of material models with random heterogeneities. We start by investigating the effective elastic properties of one-, two-, and three-dimensional rectangular blocks whose Young's modulus varies spatially as a lognormal random field. We decompose the spatial fluctuations of the Young's log-modulus F = In E into first- and higher-order terms and find the joint distribution of the effective elastic tensor by multiplicatively combining the term-specific effects. Through parametric analysis of the analytical solutions, we gain insight into the effective elastic properties of this...

  4. From clay slurries to mudrocks : a cryo-SEM investigation of the development of the porosity and microstructure

    Deirieh, Amer (Amer Mohammad)
    This thesis investigates the microstructure of smectitic and illitic rich mudrocks that are resedimented in the laboratory from the Gulf of Mexico and Boston Blue clay natural sediments. The resedimentation technique consists of mixing clay sediments with saline water to form a slurry, which is then subjected to a wide range of effective stresses. Cryo-SEM and conventional SEM techniques are used to investigate the microstructure of the clay slurry and resedimented mudrocks. Cryo-SEM enables the imaging of samples in their in-situ conditions, while conventional SEM is used to image oven-dried samples. Two techniques are used to prepare the slurry samples...

  5. Biological nutrients and growth in anaerobic digestion

    Speece, Richard Eugene
    by Richard Eugene Speece.

  6. Clustering of motile bacteria around phytoplankton in a turbulent ocean

    Bowen, James Douglas
    by James Douglas Bowen.

  7. A static evaluation of soil plug behavior with application to the pile plugging problem

    Paikowsky, Samuel G
    by Samuel G. Paikowsky.

  8. A stochastic live load model for buildings.

    Peir, Jong-cherng
    Massachusetts Institute of Technology, Dept. of Civil Engineering. Thesis. 1972. Ph. D.

  9. Investigating the evolution and formation of coastlines and the response to sea-level rise

    Ortiz, Alejandra C
    To understand how waves and sea level shape sandy shoreline profiles, I use existing energetics-based equations of cross-shore sediment flux to describe shoreface evolution and equilibrium profiles, utilizing linear Airy wave theory instead of shallow-water wave assumptions. By calculating a depth-dependent characteristic diffusivity timescale, I develop a morphodynamic depth of shoreface closure for a given time envelope, with depth increasing as temporal scale increases. To assess which wave events are most important in shaping the shoreface in terms of occurrence and severity, I calculate the characteristic effective wave conditions for both cross-shore and alongshore shoreline evolution. Extreme events are formative...

  10. An experimental and numerical study on the fracturing processes in Opalinus shale

    Morgan, Stephen Philip
    The extraction of hydrocarbons from unconventional oil and gas reservoirs relies on a detailed understanding of the fracture processes in shale. Also, underground structures designed for nuclear waste repositories are typically constructed in shale due to its characteristic low permeability. To understand the behavior of shale it is important to know how cracks initiate, propagate and coalesce. Although there have been many studies on the cracking processes in rock, cracking in shale is not well understood mainly due to its anisotropy, which is caused by naturally formed bedding planes. Natural bedding planes are weak zones along which cracks can initiate...

  11. Microwave remote sensing of water in the soil - plant system

    Konings, Alexandra Georges
    Remotely sensed measurements made by radars or radiometers in the low microwave frequency range are sensitive to soil moisture, soil roughness, and vegetation water content. Measurements made at multiple polarizations can be used to determine additional ancillary parameters alongside the primary variable of interest. However, if an attempt is made to retrieve too many parameters from too few measurements, the resulting retrievals will contain high levels of noise. In this thesis, I introduce a framework to determine an upper bound on the number of geophysical parameters that can be retrieved from remotely sensed measurements such as those made by microwave...

  12. Approximate, analytic performance models of integrated transit system components

    Hendrickson, Chris Thompson
    by Chris T. Hendrickson.

  13. An evaluation of the performance of a braced excavation.

    Jaworski, Walter Edward
    Massachusetts Institute of Technology. Dept. of Civil Engineering. Thesis. 1973. Sc.D.

  14. Physical mechanisms controlling the strength and deformation behavior of frozen sand

    Andersen, Glen R. (Glen Robert)
    by Glen Robert Andersen.

  15. From atoms to cities : A bottom-up analysis of infrastructure materials and systems

    Abdolhosseini Qomi, Mohammad Javad
    Civil infrastructure is and continues to be the backbone of our society to meet our needs in housing, transportation, water and electricity supply, and so on. However, its functions are recently revisited in response to rising concerns about its certain sustainability aspects. These aspects include and are not limited to excessive greenhouse gas emissions, unreasonably high energy footprint, relatively short service life, low durability and poor resilience. This presents us with an exclusive opportunity to take these detrimental aspects seriously and turn them into exciting venues for research in the realm of civil and environmental engineering. These opportunities are disseminated...

  16. Quantitative sustainability assessment of pavement-vehicle interaction : from bench-top experiments to integrated road network analysis

    Akbarian, Mehdi
    The sustainable development of our nation's roadway system requires quantitative means to link infrastructure performance to lifecycle energy use and greenhouse gas (GHG) emissions. Beside surface texture and roughness-induced Pavement-Vehicle Interactions (PVI), we herein recognize that the dissipation of mechanical work provided by the vehicle due to viscous deformation within the pavement structure is a relevant factor contributing to the environmental footprint of pavements. Through a combination of dimensional analysis, experiments and model-based simulations of energy dissipation in pavement structures, the key drivers of deflection-induced PVI are identified. Specifically, a novel experimental setup is developed to study the mechanism of...

  17. Formation and evolution of atmospheric organic matter from radical intermediates

    Carrasquillo, Anthony Joseph
    Atmospheric particulate matter (or "aerosol") has important implications for public health, climate change, and visibility. Our ability to predict its formation and fate is hindered by uncertainties associated with one type in particular, organic aerosol (OA). The study of the chemistry underlying OA formation is complicated by the large number of reaction pathways and oxidation generations for a given precursor species. This thesis describes a series of experiments in which the chemistry is simplified to that of a single alkoxy radical (RO) isomer generated from the direct photolysis of alkyl nitrites (RONO). First, OA was generated from eleven different C10...

  18. Mutable mechanics in biomaterials : a study of trichocyte keratin and Nvjp-1 protein

    Chou, Chia-Ching, Ph. D. Massachusetts Institute of Technology
    Disulfide bonds and metal-coordination bonds serve as flexible connections on account of their variable bond strengths in different chemical environments. Both bonds can act as an effective switch to stabilize or weaken a protein's geometry. These mechanisms are responsible for protein mutability, enabling distinct biological functions. Understanding the bonds' chemistry and mechanics is important for our knowledge of molecular, cellular and tissue level properties of biological materials that contain high ratios of disulfide bonds or metal-coordination bonds, such as hair and Nereis jaws. In this thesis, we develop the first multiscale framework to study the hierarchical structure of trichocyte keratin...

  19. Structural heterogeneity in silk fibers and its effects on failure mechanics and supercontraction

    Giesa, Tristan
    Spider dragline silk is a protein material that has evolved over millions of years to become one of the strongest and toughest natural fibers known. Silk features a heterogeneous structure that comprises [beta]-sheet crystals embedded in an amorphous matrix. However, it is not fully understood how the heterogeneity of silk affects its mechanical properties. First, the origin of the nanoscale heterogeneity during the Nephila Clavipes dragline silk assembly is investigated. Using molecular dynamics simulations, a shear flow at natural pulling speeds is modelled and the secondary structure transitions as well as shear stresses in the silk protein chains are determined....

  20. Prediction and interpretation of ground movements due to tunneling in stiff clay and impacts on adjacent structures

    Ieronymaki, Evangelia S
    Construction of large diameter tunnels is frequently accomplished by closed face tunnel boring machines (TBM) using a combination of face pressure and grouting around the precast lining in order to limit ground movements and potential damage to overlying structures. This thesis analyzes monitoring data from the Crossrail project involving twin tunnels construction using Earth Pressure Balance (EPB) machines in London Clay. The research focuses on the 'greenfield' response during tunnel excavation beneath Hyde Park. Far-field measurements of surface and subsurface ground movements were interpreted using 2D finite element analyses using a range of constitutive models with parameters calibrated to non-linear...

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