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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
381

Experimental in-plane behavior of a generic scale model drag embedment anchor in Kaolinite test beds

McCarthy, Katelyn Barbara 07 July 2011 (has links)
The trajectory and capacity are key components of the design of drag embedment anchor and drag-in vertically loaded anchors. This experimental testing program quantifies two factors that describe the anchor trajectory and capacity: the equilibrium bearing factor (Ne) and the tangential bearing factor (Ne). These factors can aid in the development of a numerical model of anchor behavior. A magnetometer device is used to track the orientation and location of the anchor during drag embedment. The results of the experimental testing program were compared with the results from a predictive model. The experimental program consisted of drag embedment tests with various testing conditions including different anchor line diameters and different initial pitch orientations. The results with the different anchor lines indicated that thinner anchor lines cause the anchor to dive deeper in the soil. The different initial pitch results indicate that regardless of the initial pitch of the anchor, the anchor rotates to a unique pitch trajectory within 2 fluke lengths. / text
382

MOISTURE AND UNIT WEIGHT READINGS FROM A COMPLEX IMPEDANCE MEASURING INSTRUMENT

Jenkins, Kirk Andrew 01 January 2013 (has links)
Complex Impedance Measuring Instruments (CIMI’s) are non-nuclear devices that calculate the dry unit weight and moisture content of soil by means of electromagnetic wave propagation theory. Unlike nuclear based test devices, these devices do not require certification or elaborate maintenance to own and operate. CIMI operation requires a soil specific calibration process where soil moisture and unit weight are correlated to electrical parameters. A new, smaller acrylic mold was developed as an alternative calibration tool to the manufacturer’s recommended mold. Calibrated soil models were generated using manufacturer recommended procedures as well as new procedures involving an acrylic mold. Models were then tested for accuracy. The new procedure outperformed the manufacturer’s procedure. Another small, acrylic mold was used to investigate the relationship between CIMI readings and soil parameters. Using several samples from four soils, the relationship between moisture, unit weight, and some electrical parameters was characterized. This characterization was then used to create a new, accurate calibration procedure.
383

PRESSURE MEASUREMENT AT THE BALLAST-TIE INTERFACE OF RAILROAD TRACK USING MATRIX BASED TACTILE SURFACE SENSORS

McHenry, Michael T. 01 January 2013 (has links)
The pressure distribution at the ballast-tie interface of railroad track plays a key role in overall track support. Failure of the ballast or tie can result from excessive loads that were not designed for, requiring increased maintenance and reducing railroad operating efficiency. Understanding the forces acting on the ballast and tie are required to design higher performance and longer lasting track. To further this understanding, the use of Matrix Based Tactile Surface Sensors (MBTSS) is employed to measure the actual pressure distribution at the ballast-tie interface, characterized by individual ballast particle contact points and non-uniform pressures. The research explores this application of MBTSS including the development of sensor protection and calibration procedures. Results from laboratory ballast box testing conducted at the Transportation Technology Center, Inc. (TTCI) are presented. Conservative estimates of peak pressure under a typical wheel load on new ballast averaged 1450 psi and on fouled ballast averaged 680 psi. Contact areas varied across the range of ballast gradations and are shown to increase under increased applied load. A parameter to describe the "roughness" of the ballast-tie pressure distribution is offered. Results from in-track testing performed at TTCI, including pressure distributions along ten test ties, are also presented.
384

CALIBRATION OF NON-NUCLEAR DEVICES FOR CONSTRUCTION QUALITY CONTROL OF COMPACTED SOILS

Wells, Joshua E. R. 01 January 2014 (has links)
Inadequate compaction of a soil subgrade can lead to detrimental outcomes that are not only costly but dangerous to the general public. To avoid this, quality control (QC) devices such as the nuclear density gauge (NDG) are currently being used to monitor the compaction and moisture content of soil subgrades. However, regulatory concerns associated with the NDG have encouraged federal and state agencies, as well as the heavy civil construction industry to consider non-nuclear devices for QC testing of compacted soils. One such non-nuclear device is the Soil Density Gauge (SDG), which utilizes electromagnetic wave propagation to obtain soil properties such as wet unit weight and moisture content. This research shows that through using soil-specific trend lines, the SDG has the capability of obtaining an equivalent NDG wet unit weight. Alongside the SDG, two dielectric moisture probes were also evaluated and through a calibration process on compacted soils, a general moisture content trend line was developed. This general moisture content trend line related outputted volumetric moisture contents from the moisture probes to gravimetric moisture contents. Field data were then plotted along with the general moisture content trend line to show that these devices have the potential of predicting gravimetric moisture contents. By combining the results of the SDG and moisture probe analyses, graphs were then developed that relate SDG wet unit weights to NDG dry unit weights using soil and moisture-specific trend lines.
385

Non-linear analysis of jack-up structures subjected to random waves

Cassidy, Mark Jason January 1999 (has links)
There is a steadily increasing demand for the use of jack-up units in deeper water and harsher environments. Confidence in their use in these environments requires jack-up analysis techniques to reflect accurately the physical processes occurring. This thesis is concerned with the models appropriate for the dynamic assessment of jack-ups, an important issue in long-term reliability considerations. The motivation is to achieve a balanced approach in considering the non-linearities in the structure, foundations and wave loading. A work hardening plasticity model is outlined for the combined vertical, moment and horizontal loading of spudcan footings on dense sand. Empirical expressions for the yield surface in combined load space and a flow rule for prediction of footing displacements during yield are given. Theoretical lower bound bearing capacity factors for conical footings in sand have been derived and are used in a strain-hardening law to define the variation in size of the yield surface with the plastic component of vertical penetration. The complete incremental numerical model has been implemented into a plane frame analysis program named JAKUP. The spectral content of wave loading is considered using NewWave theory, and the importance of random wave histories shown by constraining the deterministic NewWave into a completely random surface elevation. Using this technique, a method for determining short-term extreme response statistics for a sea-state is demonstrated. A numerical experiment on an example jack-up and central North Sea location is shown to emphasise the difference in long-term extreme response according to various footing assumptions. The role of sea-state severity in the variation of short-term extreme response statistics is also highlighted. Finally, probabilistic methods are used to develop further understanding of the response behaviour of jack-ups. A sensitivity study of influential variables (with probabilistic formulations as opposed to deterministic values) has been conducted using the response surface methodology.
386

Development of non-linear numerical models appropriate for the analysis of jack-up units

Thompson, Richard Saint George January 1996 (has links)
Jack-up units have considerable economic significance because they are used to carry out a large proportion of the world's oil and gas exploration in water depths less than 90.0m. Due to the increase in use of jack-ups in harsher environments, analysis techniques assuming quasi-static and linear structural behaviour have had to be reassessed. This thesis is concerned with non-linear dynamic analysis methods appropriate for a jack-up assessment. Jack-up modelling requires realistic representation of the structure, the foundations and the environmental loading, together with the implementation of appropriate dynamic analysis algorithms. Techniques for each of these aspects of jack-up analysis are reviewed and the implementation of several of the methods in an advanced plane frame analysis program called JAKUP is described. Geometric non-linearity in the structure and work hardening plasticity at the foundations are accounted for in the program. Test cases are presented to verify the implementation of the methods and then some illustrative plane frame quasi-static and dynamic analyses are described. These simple models highlight the importance of accounting for dynamic motions in a jack-up analysis. For the quasi-static analyses, the assumption of pinned footing behaviour is seen to always result in the most conservative displacement and moment predictions. However, the analyses show that this is not always the case when dynamic amplification is accounted for.
387

Σιδηροδρομική σήραγγα Αιγίου : σχεδίαση τεχνικογεωλογικής μηκοτομής και οριζοντιογραφίας από τη σύνθεση των γεωλογικών αποτυπώσεων των μετώπων εκσκαφής

Δημητρίου, Μυρσίνη 11 June 2012 (has links)
Η πτυχιακή εργασία αποτελείται από δύο μέρη. Το πρώτο είναι μια τεχνικογεωλογική περιγραφή της σήραγγας του Αιγίου, η οποία αποτελεί μέρος της καινούργιας σιδηροδρομικής γραμμής που ξεκινάει δυτικά του σιδηροδρομικού σταθμού του Διακοπτού και τελειώνει δυτικά της πόλης του Αιγίου, στη Δυτική Ελλάδα. Η σύραγγα έχει συνολικό μήκος 3518 μέτρα, από Χ.Θ. 85+538,67 έως Χ.Θ. 89+246,40, κατασκευάστηκε σε Νεογενείς-Τεταρτογενείς σχηματισμούς, όπως κροκαλοπαγή, ψαμμίτες και μάργες. Το δεύτερο μέρος αφορά τη σχεδίαση της τεχνικογεωλογικής μηκοτομής και οριζοντιογραφίας από τη σύνθεση των γεωλογικών αποτυπώσεων των μετώπων εκσκαφής. / This thesis has two parts, the first part is the geotechnical description of the construction of the tunnel, which is part of the new railway line that starts at the west of the old railway station of the city of Diakopto and ends at the west of the city of Aigio, in western Greece. The tunnel has a total length of 3518m; from kilometric position 85+538,57 to kilometric position 89+246,40, it was built in Neocene’s – Quaternary formations, such as conglomerate, sandstone and marl. The second part is a geotechnical general plan on the horizontal plane and an alignment of the tunnel from kilometric position 85+953,95 to kilometric position 86+936,70, from the composition of the geological mappings of the fronts of the excavations.
388

Uranium Sequestration by pH Manipulation using NH3 Injection in the Vadose Zone of Hanford Site 200 Area

Cardona, Claudia 27 April 2017 (has links)
Past nuclear weapon production activities have left a significant legacy of uranium (U) contamination in the vadose zone (VZ) of the Department of Energy (DOE) Hanford Site. This U is a source of groundwater (GW) contamination. There is a concern that elevated U concentration would slowly infiltrate through the VZ, reach the GW water table, and then end up in nearby rivers and lakes. Remediation of U-contaminated low moisture content soil is a challenging task considering the VZ depth, where contamination is found between 70 and 100 m below the ground surface, and the formation of highly soluble and stable CaUO2CO3 complexes is influenced by Hanford’s soil rich in carbonate. Injection of reactive gasses (e.g., NH3) is a promising technology to decrease U migration in through the VZ. The NH3 injection creates alkaline conditions that would alter the pore water chemistry (e.g., dissolving some aluminosilicates). Over time as the pH neutralizes, U(VI) could precipitate as uranyl mineral (e.g., Na-boltwoodite). Also, the dissolved U(VI) could be incorporated into the structure of some mineral phases or be coated by non-U minerals. These chemical reactions could control the U(VI) mobility to the GW. However, there is a lack of knowledge on how the VZ pore water constituents (e.g., Si, Al3+, HCO3-, and Ca2+) would affect U(VI) removal/precipitation in alkaline conditions. This study quantified the role of the major pore water constituents on the U(VI) removal and evaluated the uranyl minerals that could precipitate from a variety of SPW solutions. Results showed that the percentage of U(VI) removal was controlled by Si/Al ratios and Ca2+ concentration regardless of HCO3- concentration tested. XRD revealed the presence of uranyl minerals by analyzing precipitates formed from SPW solutions, but none of them were identified as uranyl silicates as expected from speciation modeling. The SEM images displayed dense amorphous regions high in silica content, where EDS elemental analysis unveiled higher U atomic percentage in some samples. U(VI) silicate and carbonate minerals were predicted by the speciation modeling.
389

Distinct element modelling of pipe-soil interaction for offshore pipelines on granular soils

Macaro, Giulia January 2015 (has links)
Offshore on-bottom pipelines are subjected to cycles of thermal and pressure-induced axial expansion, which can cause them to buckle laterally. For an elegant and cost-effective solution, lateral buckling is allowed in a controlled manner. Of the various design parameters, the soil resistance has the greatest associated uncertainty. Previous studies of lateral pipe-soil interaction have used laboratory model tests and continuum-based numerical methods. However, they are economically and computationally expensive, and have mostly been restricted to pipes on undrained clay. To overcome this limitation, this thesis introduces the distinct element method (DEM) as a novel numerical tool for the study of lateral pipe-soil interaction for partially embedded offshore pipelines on sandy seabeds. The DEM directly models the particulate nature of sandy soils, allowing large displacements of discrete bodies and providing insights into the mechanics of the soil at a particle level. Pipe{soil interaction is studied by DEM analyses through four separate research stages: (i) mechanical characterisation of the soil, (ii) specimen preparation and pipeline implementation, (iii) small displacement pipe loading tests and (iv) large displacement pipe loading tests. The soil is modelled as an assembly of spherical particles exchanging contact forces, energy and momentum when they interact. At the microscopic scale, a novel moment-relative rotation contact law is introduced to account for the irregular shape of real sand grains. At a macroscopic scale, the mechanical behaviour of the sand is calibrated using experimental triaxial test data. Additional work includes the numerical preparation of a soil assembly and the implementation of a pipeline object in the open-source DEM code Yade. A novel specimen preparation technique is developed to assemble a homogeneous sample at a desired relative density. The pipeline is implemented as a cylindrical body with a continuously curved surface and a specific mass. Small displacement loading tests are performed, with a segment of the pipeline interacting with a 3D prismatic soil domain, replicating plane strain conditions. The influence of particle size, domain thickness, loading velocity and damping are investigated. The findings provide valuable recommendations for performing DEM simulations of this problem, balancing numerical accuracy and computational effort. Large displacement loading tests are performed to validate the DEM approach and to obtain detailed insights into the nature of the pipe-soil interaction. Monotonic vertical and lateral loading simulations are quantitatively compared with laboratory results. To replicate realistic loading conditions of the pipeline on the seabed, cyclic large displacement tests are also performed. Both the monotonic and the cyclic tests show a good level of agreement with experimental results obtained in previous research. Moreover, the numerical analyses provide insights into the evolution of particle motion and the failure mechanism within the soil.
390

Influencia de la ingeniería geotécnica en la intervención y resultados por niveles de servicio en la carretera Huancavelica – Lircay – Huallapampa – La Mejorada – Acobamba – Puente Allccomachay

Calizaya Vivanco, Juan Alejandro, Lluncor Gallo, Rodrigo Alonso January 2015 (has links)
El objetivo de la tesis es poner en conocimiento la efectividad que tiene la ingeniería Geotécnica para la aprobación de los niveles de servicios en contratos de conservación vial y así poder conllevar un pavimento básico trabajando de forma satisfactoria. En esta investigación se empleo datos proporcionados por la empresa encargada de la carretera “CORREDOR HUANCAVELICA – LIRCAY –EMP-3S (HUALLAPAMPA) Y EMP. PE 3S (LAMEJORADA)-ACOBAMBA –EMP PE-3S (PUENTE ALCOMACHAY)” y de los resultados de los ensayos realizados en la misma carretera. La tesis tiene un Diseño de Investigación Experimental, Longitudinal y Retrospectivo; así mismo, en el Tipo de Investigación es Cuantitativo, Explicativo y Descriptivo. Para comprobar tal situación se analizan los resultados de la evaluación por niveles de servicio del mantenimiento de la carretera y se comparan con los ensayos geotécnicos de la calidad de los materiales usados, proporcionados por la empresa encargada del mantenimiento del corredor vial, para así llegar a la conclusión que mantener una eficiente ingeniería geotécnica conlleva a tener un pavimento básico trabajando adecuadamente. The aim of the thesis is to inform the effectiveness Geotechnical Engineering has to approve the Service Level in Road Maintenance Contracts and so to lead UN Working basic pavement so yes satisfactoria.En esta Employment Research Data provided by Responsible company's "RB Huancavelica. - Lircay -EMP-3S (Huallapampa) and EMP PE 3S (LAMEJORADA) -ACOBAMBA -EMP PE-3S (BRIDGE ALCOMACHAY)" road and the results of tests carried out on the same road. The thesis has a design of Experimental, longitudinal and retrospective research; Even so, in the kind of research it is quantitative explanatory and descriptive. V To check this situation the evaluation results are analyzed by levels of service and road maintenance compared with geotechnical quality testing of used materials provided by the Company that the maintenance of the corridor, Asi para Arrive concluded that maintaining efficient Geotechnical Engineering involves a pavement Having a basic working properly.

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