UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
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Item VISUALIZATION, DATA QUALITY, AND SCALE IN COMPOSITE BATHYMETRIC DATA GENERALIZATION(2024) Dyer, Noel Matarazza; De Floriani, Leila; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Contemporary bathymetric data collection techniques are capable of collecting sub-meterresolution data to ensure full seafloor-bottom coverage for safe navigation as well as to support other various scientific uses of the data. Moreover, bathymetry data are becoming increasingly available. Datasets are compiled from these sources and used to update Electronic Navigational Charts (ENCs), the primary medium for visualizing the seafloor for navigation purposes, whose usage is mandatory on Safety Of Life At Sea (SOLAS) regulated vessels. However, these high resolution data must be generalized for products at scale, an active research area in automated cartography. Algorithms that can provide consistent results while reducing production time and costs are increasingly valuable to organizations operating in time-sensitive environments. This is particularly the case in digital nautical cartography, where updates to bathymetry and locations of dangers to navigation need to be disseminated as quickly as possible. Therefore, this dissertation covers the development of cartographic constraint-based generalization algorithms operating on both Digital Surface Model (DSM) and Digital Cartographic Model (DCM) representations of multi-source composite bathymetric data to produce navigationally-ready datasets for use at scale. Similarly, many coastal data analysis applications utilize unstructured meshes for representing terrains due to the adaptability, which allows for better conformity to the shoreline and bathymetry. Finer resolution along narrow geometric features, steep gradients, and submerged channels, and coarser resolution in other areas, reduces the size of the mesh while maintaining a comparable accuracy in subsequent processing. Generally, the mesh is constructed a priori for the given domain and elevations are interpolated to the nodes of the mesh from a predefined digital elevation model. These methods can also include refinement procedures to produce geometrically correct meshes for the application. Mesh simplification is a technique used in computer graphics to reduce the complexity of a mesh or surface model while preserving features such as shape, topology, and geometry. This technique can be used to mitigate issues related to processing performance by reducing the number of elements composing the mesh, thus increasing efficiency. The primary challenge is finding a balance between the level of generalization, preservation of specific characteristics relevant to the intended use of the mesh, and computational efficiency. Despite the potential usefulness of mesh simplification for reducing mesh size and complexity while retaining morphological details, there has been little investigation regarding the application of these techniques specifically to Bathymetric Surface Models (BSMs), where additional information such as vertical uncertainty can help guide the process. Toward this effort, this dissertation also introduces a set of experiments that were designed to explore the effects of BSM mesh simplification on a coastal ocean model forced by tides in New York Harbor. Candidate vertices for elimination are identified using a given local maximum distance between the original vertices of the mesh and the simplified surface. Vertex removal and re-triangulation operations are used to simplify the mesh and are paired with an optional maximum triangle area constraint, which prevents the creation of new triangles over a specified area. A tidal simulation is then performed across the domain of both the original (un-simplified) and simplified meshes, while comparing current velocities, velocity magnitudes, and water levels over time at twelve representative locations in the Harbor. It was demonstrated that the simplified mesh derived from using even the strictest parameters for the mesh simplification was able to reduce the overall mesh size by approximately 26.81%, which resulted in a 26.38% speed improvement percentage compared to the un-simplified mesh. Reduction of the overall mesh size was dependent on the parameters for simplification and the speed improvement percentage was relative to the number of resulting elements composing the simplified mesh.Item Evaluating Performance of Conical Filter Systems Using Numerical and Laboratory Methods(2022) Ryoo, Sung Chun; Aydilek, Ahmet H; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A significant contributor to retaining wall failure occurs due to inadequate drainage in the backfill. Studies showed 33% of retaining wall failures around the world occurred due to missing or inadequate drainage systems. Even though failure caused by drainage is high, very few United States Departments of Transportation are specific about the backfill material allowed. Traditional weep hole design makes use of pipes perpendicular or parallel to the wall to promote filtration; often covered with a geosynthetic for soil retaining purposes. This study seeks to determine the performance of a recent pore pressure mitigation system through the usage of conical geotextile filters and to investigate an alternative numerical method to effectively determine the type of geotextile in these filters.A numerical model based on a computational fluid dynamics and discrete element method (CFD-DEM) coupled approach was developed to simulate particle movement in the graded filter zone and piping through the geotextiles located in retaining wall backfills. The model was used for conventional as well as conical geotextile filter systems that use a series of woven and nonwoven geotextiles filtering backfill soils with varying fines contents. Poisson line processes and image processing techniques were used to study the pore structure of the nonwoven geotextiles. The results indicated that conical filter systems contribute to higher soil piping rates but provided higher permeability than conventional geotextile filtration system counterparts. The model predictions compared with the laboratory measurements indicated that the movement of particles (i.e., suffusion) influenced the soil-geotextile contact zone permeabilities and caused a decrease in system permeabilities. A retention ratio, αsl, successfully predicted piping rates for different types of woven and nonwoven geotextiles with a percent error range of 13-30%, and was converted into a performance chart. A machine learning algorithm was implemented to create woven and nonwoven zones within the performance curves. Overall, the model predictions were comparable to the laboratory results, suggesting the applicability of the model. Once validation was complete, a conversion retention ratio, αc, was developed for practical usage of the performance charts.Item Quarry Fines-Amended Chesapeake Bay Dredged Sediments as Potential Highway Embankment Materials(2018) Singh, Atul; Aydilek, Ahmet H; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Several hundred million cubic yards of sediment are dredged from various U.S. ports, harbors, and waterways annually to maintain and improve the nation’s navigation system for commercial, national defense, and recreational purposes. Most of the dredged materials in these facilities typically classify as ML and MH soils. The current study aims to explore the use of sediments dredged from Chesapeake Bay as potential highway embankment materials by amending them with quarry by-products. Geotechnical analysis is coupled with environmental assessment to ensure satisfactory performance of the dredged materials as an embankment fill material. The compaction and shear properties of the dredged sediments improved upon blending with the quarry by-products. The concentrations of all metals released during the batch leach tests from the treated dredged materials were below the water quality limits. Column leach tests yielded generally low or non-detectable metal concentrations. The results of the geochemical modeling indicated that the leaching of the analyzed metals was solubility-controlled.Item Soil-Pile Interaction Under Vertical Dynamic Loading(2018) Sutaih, Ghassan Hassan; Aggour, Mohamed S; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Improper foundation designs for machine vibrations can result in machine failure, severe discomfort to workers around the machine or excessive settlement. The goal of foundation design for machine vibrations is to minimize vibration amplitude. In poor soil conditions, pile foundations are used to support the machine. Soil-pile stiffness and damping must be known at the level of the pile head. Since piles are used mostly in a group, it is also necessary to determine the interaction of the piles within the group. This study uses a 3D finite element method to study the response of pile foundations subjected to vertical dynamic loading. It uses Lysmer’s analog where the pile is replaced by a single degree of freedom dynamic system that provides frequency independent parameters. A parametric study is performed to obtain the value of the stiffness and the damping of a single pile for different soil properties and for both homogeneous and inhomogeneous soils. Floating and end-bearing piles were also studied. Pile group response is influenced by the soil-pile-soil interaction. The interaction is obtained by varying both the spacing and the soil properties around the pile. Interaction between the piles causes reduction in the stiffness and damping of the soil-pile system compared to an isolated pile. The study provided the interaction factors as a function of pile spacing and properties of the soil. Using the interaction factors, the response of a group of piles can be determined from the response of a single pile.Item Geoenvironmental behavior of lime amended dredged materials(2017) Deshmukh, Aditya; Aydilek, Ahmet H; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Several hundred million cubic yards of sediment are dredged from various U.S. ports, harbors, and waterways annually to maintain and improve the nation’s navigation system for commercial, national defense, and recreational purposes. The United States Environmental Protection Agency mandated containment of dredged sediments in designated containment facilities. For several years, the Maryland Environmental Service is building and operating dredged material confinement facilities. Due to high operation and maintenance costs, Maryland Dredged Material Management Program aims to repurpose the material for various uses. The current study aims to explore the use of sediments dredged from Chesapeake Bay as a potential highway embankment material. Geotechnical analysis is coupled with environmental assessment in order to ensure satisfactory performance of the dredged materials as an embankment fill attributed with no potential environmental ramifications. It is essential to quantify performance and environmental impacts before initiating large scale construction using dredged materials and this study aims to explore these requirements.Item DETERMINATION OF DYNAMIC MODULI AND PERMANENT DEFORMATION OF MARYLAND ASPHALT MIXTURES USING AMPT(2017) Haider, Intikhab; Schwartz, Charles W; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Full implementation of the mechanistic-empirical pavement design guide (MEPDG) in Maryland requires Level 1 (measured) material properties to characterize asphalt mixtures commonly used in the state. Specifically, these proprieties are the dynamic modulus (DM) and the repeated load permanent deformation (RLPD) properties. To achieve this goal, 28 asphalt mixtures were collected from construction sites/asphalt plants and tested in the Maryland State Highway Administration Office of Materials Technology Asphalt Technology Division laboratory. The DM and RLPD testing was performed on all 28 asphalt mixtures following the AASHTO PP 60, AASHTO PP 61 and AASHTO TP 79 protocols. In addition to the 28 asphalt mixtures from Maryland, DM and RLPD data for 18 asphalt mixtures tested in NCHRP Project 9-30A were also included in parts of this study. In addition to developing a catalog of typical Level 1 material properties for common Maryland asphalt mixtures, this study produced several other important results and findings. These include: (1) The L-1 inputs (measured E* and G* and recalibrated coefficients of rut model, K1, K2, K3) consistently give lesser predicted distresses than L-3 inputs (predicted E* values, default G* values, and default coefficients of rut model) in MEPDG software. (2) The average percentage differences for each predicted distress at all levels of traffic are highest for L-1 versus L-3 inputs and lowest for L-1 versus L-1A (measured E* and G* data and default coefficients of rut model) inputs. (3) The recalibration of Witczak E* model removes the bias toward underprediction in the original Witczak model. The distresses predicted using L-3 (CWM-Calibrated Witczak Model based on Maryland mixes) inputs are closest to the distresses predicted using the measured L-1 inputs. (4) The total number of samples required for complete characterization of one asphalt mixtures as per AASHTO PP 61 and AASHTO TP 79 can be reduced from 12 to 3. The reduction in total specimen preparation (from 60 to 15 hours) and testing time (from 30 to 10 hours) represents substantial economies in structural characterization of asphalt mixtures and motivates state agencies to perform DM and RLPD testing on routine basis to develop performance based specification.Item The application of soil mechanics to highway engineering(1951) Barber, Edward S.; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Item OPTIMIZATION OF THE INFRARED ASPHALT REPAIR PROCESS(2015) Leininger, Christopher William; Schwartz, Charles W; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Infrared asphalt repair is an alternative technology that potentially allows for year round pavement patching that can be more durable, less expensive, and longer lasting than conventional techniques. Although infrared repair has been used for over 10 years by state and local agencies and commercial property owners in several areas of the country, some continuing resistance to this technique still remains. The principal reasons for this resistance are the largely unknown engineering properties of the patch material as compared to the native in situ pavement and the lack of standardized methods, specifications and quality assurance procedures. The following is a preliminary assessment of these engineering properties and current QA/QC procedures. A proposed specification for adoption is included in addition to recommendations for improving current practice.Item Soil Slope Failure Investigation Management Systems(2012) Ramanathan, Raghav Sarathy; Aydilek, Ahmet H; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Highway slopes are exposed to environmental and climatic conditions, such as deforestation, cycles of freezing and thawing weather, heavy storms etc. Over time these climatic conditions can influence slope stability in combination with other factors such as geological formations, slope angle and groundwater conditions. These factors contribute towards causing slope failures that are hazards to highway structures and the traveling public. Consequently, it is crucial to have a soil slope failure investigation management system to track, record, evaluate, analyze and review the soil slope failure data and soil slope remediation data so that cost effective and statistically efficient remedial plans may be developed. This paper presents the framework for developing such a system for The State of Maryland, using a GIS database and a collective overlay of maps to indicate potentially unstable highway slopes through spatial and statistical analysis.Item Improving the Estimation of Leaf Area Index from Multispectral Remotely Sensed Data(2003-10-27) Fang, Hongliang; Liang, Shunlin; Prince, Stephen D.; Townshend, John R.; Weismiller, Richard; GeographyLeaf Area Index (LAI) is an important structural property of surface vegetation. Many algorithms use LAI in regional and global biogeochemical, ecological, and meteorological applications. This dissertation reports several new, improved methods to estimate LAI from remotely sensed data. To improve LAI estimation, a new atmospheric correction algorithm was developed for the Enhanced Thematic Mapper Plus (ETM+) imagery. It can effectively estimate the spatial distribution of atmospheric aerosols and retrieve surface reflectance under general atmospheric and surface conditions. This method was validated using ground measurements at Beltsville, Maryland. Several examples are given to correct AVIRIS (Airborne Visible/Infrared Imaging Spectrometer), MODIS (Moderate Resolution Imaging Spectroradiometer) and SeaWiFS (Sea-viewing Wide Field-of-view Sensor) data using the new algorithm. Next, a genetic algorithm (GA) was incorporated into the optimization process of radiative transfer (RT) model inversion for LAI retrieval. Different ETM+ band combinations and the number of "genes" employed in the GA were examined to evaluate their effectiveness. The LAI estimates from ETM+ using this method were reasonably accurate when compared with field measured LAI. A new hybrid method, which integrates both the RT model simulation and the non-parametric statistical methods, was developed to estimate LAI. Two non-parametric methods were applied, the neural network ((NN) algorithms and the projection pursuit regression (PPR) algorithms. A soil reflectance index (SRI) was proposed to account for variable soil background reflectances. Both atmospherically corrected surface reflectances and raw top-of-atmosphere (TOA) radiances from ETM+ were tested. It was found that the best way to estimate LAI was to use the red and near infrared band combination of surface reflectance. In an application of this hybrid method to MODIS, the PPR and NN methods were compared. MODIS LAI standard products (MOD15) were found to have larger values than my results in the study area.