Rozprawy doktorskie na temat „Shear wave velocity”
Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: Shear wave velocity.
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 50 najlepszych rozpraw doktorskich naukowych na temat „Shear wave velocity”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.
1
Hepton, Peter. "Shear wave velocity measurements during penetration testing". Thesis, Bangor University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330070.
Pełny tekst źródła
2
Liu, Siyu. "Shear Wave Velocity Analysis by Surface Wave Methods in the Boston Area:". Thesis, Boston College, 2017. http://hdl.handle.net/2345/bc-ir:107367.
Pełny tekst źródłaStreszczenie:
Thesis advisor: John E. EbelThesis advisor: Alan L. Kafka
As the best seismic indicator of shear modulus, shear-wave velocity is an important property in engineering problems in near-surface site characterization. Several surface-wave methods have been developed to obtain the subsurface shear-wave velocity structure. This thesis compared three surface-wave methods, Spectral Analysis of Surface Waves (SASW) (Nazarian et al., 1983), Multichannel Analysis of Surface Waves (MASW) (Park et al., 1999), and Refraction Microtremor (ReMi) (Louie, 2001), to determine which method gives the best estimation of the 1-D shear-wave velocity profile of near-surface soils. We collected seismic data at three sites in the greater Boston area where there are direct measurements of shear-wave velocities for comparison. The three methods were compared in terms of accuracy and precision. Overall, the MASW and the ReMi methods have comparable quality of accuracy, whereas the SASW method is the least accurate method with the highest percentage differences with direct measurements. The MASW method is the most precise method among the three methods with the smallest standard deviations. In general, the MASW method is concluded to be the best surface-wave method in determining the shear-wave velocities of the subsurface structure in the greater Boston area
3
Yung, See Yuen. "Determination of shear wave velocity and anisotropic shear modulus of an unsaturated soil /". View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20YUNG.
Pełny tekst źródła
4
Gang, Liu. "VERIFICATION OF SHEAR WAVE VELOCITY BASED LIQUEFACTION CRITERIA USING CENTRIFUGE MODEL". Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1228274570.
Pełny tekst źródła
5
Zomorodian, Seyed Mohammad Ali. "Shear wave velocity of soils by the spectral analysis of surface waves (SASW) method". Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10395.
Pełny tekst źródłaStreszczenie:
Spectral analysis of surface waves (SASW) method is an in-situ seismic method used for determining the thickness and elastic properties of soil and pavement. The SASW method is fast and economical to perform since no boreholes are required. The method is suitable for sites where the use of large equipment is difficult or where sublayer conditions make it difficult to perform other seismic tests. The SASW method is also ideal for preliminary field investigations to be conducted prior to more detailed site investigation, and for quality control and monitoring of ground improvement. The purpose of this research was to improve the SASW method by incorporating multi-mode propagation in the backcalculation procedure. In order to facilitate the investigation carried out in this study, two computer programs were developed to simulate SASW tests (and also Steady-State surface wave tests) and to calculate theoretical dispersion curves. The program for calculating theoretical dispersion curves was based on the root-searching procedure used in existing backcalculation methods. The computer programs developed in this study were used in a case study to demonstrate difficulties encountered by existing methods in dealing with multi-mode situations. It was shown that: (i) wavelength filtering criteria used by existing methods yield inconsistent (i.e. erroneous) dispersion curves when more than one propagation mode participate in the wave field, and (ii) backcalculation procedures based on root-searching cannot identify predominant propagation modes and hence fail to yield accurate results in the case of multi-mode propagation. Two developments were made in the present study to overcome the above difficulties. First, a new wavelength filtering criterion was adopted. In this criterion, the dispersion data point for a particular frequency is rejected (i.e. filtered out) if the values of phase velocity obtained from two different receiver-to-receiver spacings are not in close agreement. In this manner, inconsistencies that might result in the dispersion due to multi-mode propagation are avoided. Second, a new procedure to calculate the theoretical dispersion curve was developed. This procedure is based on the maximum vertical flexibility coefficient (at each frequency) of the theoretical layered model. Unlike root-searching methods, the maximum vertical flexibility coefficient method easily identifies predominant propagation modes. A computer program was developed in this study for backcalculation of SASW data based on the flexibility coefficient method. Least-squares optimization using the down-hill simplex method was also implemented in this program to automate the backcalculation process. The accuracy of the above proposed procedures was demonstrated using SASW field tests. The shear wave velocity profiles obtained using the procedures developed in this study are in good agreement with those obtained from other in-situ seismic tests. (Abstract shortened by UMI.)
6
Gonsiewski, James P. "Bedrock Mapping Using Shear Wave Velocity Characterization and H/V Analysis". Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1453247272.
Pełny tekst źródła
7
Chan, Chee-Ming. "A laboratory investigation of shear wave velocity in stabilised soft soils". Thesis, University of Sheffield, 2006. http://etheses.whiterose.ac.uk/15165/.
Pełny tekst źródłaStreszczenie:
The stabilisation of soft clay soils is intended to increase their shear strength and to reduce their compressibility. The possibility exists of using geophysical methods to monitor changes in these properties. Laboratory experiments were carried out on stabilised clays to study the relationships between shear wave velocity, and hence small strain shear stiffness, and shear strength or one-dimensional compressibility. One artificial clay, Speswhite kaolin, and two natural clays, from Malaysia and Sweden, were used as the base clays. Either ordinary Portland cement or a 1: 1 mix of the cement with unslaked lime was added to the base clays in order to stabilize them. In the first part of the investigation, samples of stabilised clay were initially subjected to a non-destructive bender element test to obtain the shear wave velocity and then to an unconfined compressive strength test or vane shear strength test. It was evident that small stabiliser amounts (less than 10 % of the dry weight of the base clay) could significantly improve both the strength and stiffness of the originally soft material. In addition, good correlations between the shear strength and the shear wave velocity (or small strain shear stiffness) of the stabilised clays were established. In the second part of the investigation, an instrumented oedometer was used to simultaneously monitor shear wave velocity and one-dimensional compression during tests on samples cured for a set period. Lateral stresses were also measured. Complementary tests were conducted in standard oedometers, to study the effect of the curing period. In these tests yield stresses were identified and corresponded to the onset of changes in shear wave velocity. After yield, the constrained moduli could be correlated with shear wave velocity. Tests were also carried out on samples of clay in which a central stabilised column had been created. Equal strain predictions of the compression of these samples, based on the results of separate tests on the two components, were relatively successful. The results of the research suggest that shear wave velocity measurements could be useful in practice to enable the shear strength and post-yield compressibility of stabilised clay soil to be estimated.
8
McGillivray, Alexander Vamie. "Enhanced Integration of Shear Wave Velocity Profiling in Direct-Push Site Characterization Systems". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19714.
Pełny tekst źródłaStreszczenie:
Enhanced Integration of Shear Wave Velocity Profiling in Direct-Push Site Characterization Systems
Alexander V. McGillivray
370 Pages
Directed by Dr. Paul W. Mayne
Shear wave velocity (VS) is a fundamental property of soils directly related to the shear stiffness at small-strains. Therefore, VS should be a routine measurement made during everyday site characterization. There are several lab and field methods for measuring VS, but the seismic piezocone penetration test (SCPTu) and the seismic dilatometer test (SDMT) are the most efficient means for profiling the small-strain stiffness in addition to evaluating large-strain strength, as well as providing evaluations of the geostratigraphy, stress state, and permeability, all within a single sounding.
Although the CPT and DMT have been in use for over three decades in the USA, they are only recently becoming commonplace on small-, medium-, and large-size projects as more organizations begin to realize their benefits. Regrettably, the SCPTu and the SDMT are lagging slightly behind their non-seismic counterparts in popularity, in part because the geophysics component of the tests has not been updated during the 25 years since the tests were envisioned. The VS measurement component is inefficient and not cost effective for routine use. The purpose of this research is to remove the barriers to seismic testing during direct-push site characterization with SCPTu and SDMT.
A continuous-push seismic system has been developed to improve the integration of VS measurements with SCPTu and SDMT, allowing VS to be measured during penetration without stopping the progress of the probe. A new type of portable automated seismic source, given the name RotoSeis, was created to generate repeated hammer strikes at regularly spaced time intervals. A true-interval biaxial seismic probe and an automated data acquisition system were also developed to capture the shear waves. By not limiting VS measurement to pauses in penetration during rod breaks, it is possible to make overlapping VS interval measurements. This new method, termed frequent-interval, increases the depth resolution of the VS profile to be more compatible with the depth intervals of the near-continuous non-seismic measurements of the SCPTu and the SDMT.
9
Vance, David M. "Shear-wave velocity database and derivative mapping for the upper Mississippi embayment". Lexington, Ky. : [University of Kentucky Libraries], 2006. http://lib.uky.edu/ETD/ukygeol2006t00488/VanceThesis06.pdf.
Pełny tekst źródłaStreszczenie:
Thesis (M.S.)--University of Kentucky, 2006.Title from document title page (viewed on November 1, 2006). Document formatted into pages; contains: ix, 142 p. : ill. (some col.), maps. Includes abstract and vita. Includes bibliographical references (p. 138-141).
10
Li, Jianhua Rosenblad Brent L. "Study of surface wave methods for deep shear wave velocity profiling applied in the upper Mississippi embayment". Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/6619.
Pełny tekst źródłaStreszczenie:
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 25, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Brent L. Rosenblad. Vita. Includes bibliographical references.
11
Gillespie, Donald G. (Donald Gardner). "Evaluating shear wave velocity and pore pressure data from the seismic cone penetration test". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30573.
Pełny tekst źródłaStreszczenie:
Recent developments in cone penetration testing have resulted in the addition of both pore pressure measurements and seismometers. The seismometers allow shear wave velocity testing to be performed at designated intervals. Both of these additions were researched to improve their application and interpretation.
The significant factors effecting the pore pressure generated during cone penetration tests are discussed. The importance of various factors is especially dependent upon permeability, strength, and stiffness. For all sands tested, pore pressures lower than static were recorded behind the tip and higher than static were recorded on the face of the cone. It is believed that the large compressive stresses on the cone face result in positive pore pressures. As the cone tip passes a soil element unloading and continued shearing generate pore pressures lower than static in all sands. The sign of this pore pressure (higher or lower than static) was therefore considered primarily a function of the test equipment.
Pore pressure response and the rate of dissipation of excess pore pressures were found useful in distinguishing fine granular soils and explaining soil stratigraphy. In cohesive soils the details of pore pressure measurement were found to be important only in stiff soils. Pore pressures at all measurement locations were found to increase with soil strength in soft to firm clays but may be negative of static in very stiff clays. Pore pressures behind the cone tip were often negative of static in stiff clays.
Measurement techniques were refined to improve the accuracy of downhole shear wave velocity measurements. Comparisons of downhole and crosshole measurements were made at three well documented sites validating the technique. At several sites it was found useful to consider the Gmax values determined from shear wave velocity and density to distinguish soil type. Gmax to cone resistance ratios were shown to vary systematically with cone resistance values in sands. A wide range in Gmax to cone resistance was observed in clays. The dependence of both cone penetration resistance and Gmax to increased stress level or overburden stress is discussed.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
12
Vance, David M. "Shear-Wave Velocities and Derivative Mapping For the Upper Mississippi Embayment". UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_theses/296.
Pełny tekst źródłaStreszczenie:
During the past two decades, University of Kentucky researchers have been acquiring seismic refraction/reflection data, as well as seismic downhole data, for characterizing the seismic velocity models of the soil/sediment overburden in the central United States. The dataset includes densely spaced measurements for urban microzonation studies and coarsely spaced measurements for regional assessments. The 519 measurements and their derivative products often were not in an organized electronic form, however, limiting their accessibility for use by other researchers. In order to make these data more accessible, this project constructed a database using the ArcGIS 9.1 software. The data have been formatted and integrated into a system serving a wider array of users. The seismic shear-wave velocity models collected at various locations are archived with corresponding x-, y-, and z-coordinate information. Flexibility has been included to allow input of additional data in the future (e.g., seismograms, strong ground-motion parameters and time histories, weak-motion waveform data, etc.). Using the completed database, maps of the region showing derivative dynamic site period (DSP) and weighted shear-wave velocity of the upper 30 m of soil (V30) were created using the ArcGIS 9.1 Geostatistical Analyst extension for examination of the distribution of pertinent dynamic properties for seismic hazard assessments. Both geostatistical and deterministic techniques were employed. Interpolation of V30 data yielded inaccurate predictions because of the high lateral variation in soil layer lithology in the Jackson Purchase Region. As a result of the relatively uniform distribution of depths to bedrock, the predictions of DSP values suggested a high degree of accuracy.
13
Jang, Jun-keun. "Study on the Application of Shear-wave Elastography to Thin-layered Media and Tubular Structure: Finite-element Analysis and Experiment Verification". 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/217145.
Pełny tekst źródła
14
AIMAR, MAURO. "Uncertainties in the Estimation of the Shear-Wave Velocity and the Small-Strain Damping Ratio from Surface Wave Analysis". Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2972200.
Pełny tekst źródła
15
Muttashar, Wisam Razzaq. "EFFECTS OF DEPOSITIONAL PROCESSES ON STRENGTH AND COMPRESSIBILITY OF SEDIMENTS USING ELASTIC SHEAR WAVE VELOCITY". UKnowledge, 2019. https://uknowledge.uky.edu/ees_etds/66.
Pełny tekst źródłaStreszczenie:
Depositional processes are the most critical, complicated conditions that govern sediment properties and their variations, which in turn significantly affect the geotechnical behavior of the sediment. The complexity of depositional and post-depositional processes, which results in a variety of depositional environments, makes constructing a plausible model for the consolidation process of sediments difficult. The mutual influence between the temporal and spatial variation of depositional environments with their resultant physical and mechanical properties cause several compression issues, such as consolidation settlement and land subsidence, which mostly occur in estuarine-riverine regions throughout the world.
The first aim of this study is proposing a new grain-size based scheme to classify unconsolidated inorganic sediments that cover a wide range of natural depositional environments with a special emphasis on fine-grained deposits. The proposed classification depends on the linear relationship between percent Fines and the silt fraction. By combining grain size characteristics and plasticity, the proposed scheme provides further characterization of depositional environments. The proposed scheme extends the utility of the scheme beyond simply classifying the sediment class, towards inferring the potential mechanical behavior of sediments having various Grain Size Distribution (GSD) proportions and mineralogy.
Addressing elastic wave properties as a geotechnical parameter, in particular, shear wave velocities to determine the mechanical behavior of sediments is because is strongly influenced by the change in those physical state properties during compression and cementation processes. This study presents a continuous function that explicitly uses shear wave velocity to predict the non-linear function of consolidation process (e -log p'),
This approach also defines factors that describe the depositional environment, such as grain size and plasticity limits. These factors are shown to influence and control the e -log p' relationship. Thus, the resulting function is shown to be applicable to a variety of sedimentary materials.
Also, in this dissertation, elastic shear-wave velocity under critical state framework was employed. A shear wave-based constitutive model was developed that is able to predict the stress-strain behavior of a normally consolidated sediments, under undrained loading. A new power-type relationship that predicts the shear strength behavior and critical stress paths of fine-grained sediments under undrained conditions. Also, it investigates the reliability of the link between input model parameters with the basic properties of a variety of fine-grained sediments. As importance of measuring of elastic wave velocities, a number of soil tests performed during particular construction stages can be reduced and compensated. This reduces the cost of evaluating the stability level, monitoring stress path distributions, and determining undrained shear strength behavior during particular stages of the construction process. The study also provides correlations that can be applied in various fine-grained depositional environments that have weak, fine-grained soil layers, on which the constructions are built.
16
Abbas, Khalid. "Processing of full waveform sonic data for shear wave velocity at the Ketzin CO2 storage site". Thesis, Uppsala universitet, Geofysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-181271.
Pełny tekst źródłaStreszczenie:
The accumulation of carbon dioxide gas (CO2) in the atmosphere is considered be the main cause of global warming effects. These emissions can be reduced substantially by capturing and storing the CO2. The CO2SINK project started in April 2004 in the northeast German Basin (NEGB) at the town of Ketzin near Berlin, Germany. Uppsala University is one of the main participants in the seismic part of the CO2SINK project. Full waveform sonic data were acquired in the Ktzi-201 injection well at the Ketzin CO2 storage site. The mode of logging was monopole logging. The target was the Stuttgart Formation, a saline sandstone aquifer at the depth of 500-700m. A total of 1210 shots were conducted and data were recorded on 13 channels. Receiver spacing was 6 inches (15.24 cm). The focus of the CO2SINK project was to develop the basis for the CCS technique by injecting CO2 into a saline aquifer and monitoring of the injected CO2 in the aquifer as a pilot study for future geological storage of CO2 in Europe. The objective of this study is to calculate P-wave & S-wave velocities from full waveform sonic data recorded in Ktzi-201 injection well. In hard formations, shear wave velocities can be determined directly from full waveform sonic data recorded in monopole logging. However, in slow formations like Stuttgart Formation as in the Ketzin CO2SINK project, shear wave arrivals are absent in full waveform sonic data recorded in monopole logging. In this case, shear wave velocities can be determined from Stoneley wave velocities provided that one knows the P-wave velocity in the borehole fluid. P-wave velocities were calculated by picking the P-wave arrivals on full waveform sonic data. Due to the absence of shear wave arrivals, the shear wave velocities were estimated from the larger amplitude Stoneley waves. The estimated S-wave velocities from Stoneley waves were less than the fluid wave velocity in the borehole, confirming the mode of logging was monopole and the formation is a slow formation. The reliability of shear wave velocities estimated from Stoneley waves also depends on five other parameters such as formation permeability, borehole fluid property, tool diameter, borehole radius etc.
17
Bailey, Jonathan Pqul. "Development of shear wave velocity profiles in the deep sediments of the Mississippi Embayment using surface wave and spectral ratio methods". Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5635.
Pełny tekst źródłaStreszczenie:
Thesis (M.S.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 10, 2009 Includes bibliographical references.
18
Apaza, Marco Aurelio Flores. "Determinação do Gmáx através do método de análise espectral de ondas superficiais". Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3145/tde-21082009-165223/.
Pełny tekst źródłaStreszczenie:
Esta dissertação apresenta o método de análise espectral de ondas superficiais (SASW) para a obtenção das variações do módulo cisalhante (Gmáx) com a profundidade, no domínio das deformações muito pequenas (abaixo de 0,001%). O SASW é um método sísmico in situ, não destrutivo, baseado na geração e detecção de ondas Rayleigh e na natureza dispersiva desta onda. Pela aplicação de um impacto na superfície do solo e detecção da onda em vários pontos, através de dois receptores, é construída uma curva de dispersão (velocidade de fase versus comprimento de onda). Esta curva de dispersão é, então, invertida. A inversão é um processo analítico para a reconstrução do perfil de velocidade de onda de cisalhamento (VS), partindo-se da curva de dispersão experimental de campo. O módulo de cisalhamento máximo de cada camada é facilmente obtido a partir do perfil de VS. No conteúdo teórico da dissertação discutem-se propriedades dinâmicas dos solos e descrevem-se as equações que dominam a propagação das ondas elásticas, tanto em meios homogêneos como em meios estratificados. A metodologia desenvolvida para a obtenção das curvas de dispersão, através da realização de ensaios SASW, apresenta os resultados obtidos em ensaios realizados na Cidade Universitária em São Paulo, sendo esses resultados comparados com estimativas feitas a partir de correlações baseadas em ensaios SPT existentes. Essas comparações permitem concluir que a metodologia SASW é uma boa alternativa para a determinação do perfil de rigidez (Gmáx) do solo, concordando com o nível de deformação envolvido nos ensaios. São desenvolvidos estudos de sensibilidade do método para verificar a influência na mudança dos parâmetros assumidos (peso específico, coeficiente de Poisson e espessuras das camadas) no processo de redução de dados (inversão) sobre o perfil final de VS, concluindo-se que o parâmetro que apresenta maior influência é o coeficiente de Poisson.This dissertation presents the spectral-analysis-of-surface-waves (SASW) method as a tool for obtaining the variations in the modulus shear (Gmax) with depth in the field of very small strains (below 0,001%). The SASW method is a nondestructive in situ seismic method, based on the generation and measurement of Rayleigh wave and on its dispersive characteristic nature. Throughout the implementation of an impact on the soil surface and the detection of the wave at various points by two receptors a dispersion curve is constructed (phase velocity versus wave-length). This dispersion curve is then inverted. Inversion is an analytical process for reconstructing the shear wave velocity profile from the experimental field. The shear modulus of each layer is readily obtained from the shear wave velocity profile. The theoretical content of the dissertation presents dynamic properties of the soils and is described in the equations that dominate the propagation of elastic waves, both in homogeneous media and in stratified media. The methodology developed to obtain the dispersion curves through the implementation of SASW test is defined, and results from tests carried out at the University Campus in São Paulo are presented and compared with values obtained from correlations based on SPT tests. These comparisons indicate that the SASW method is a good alternative to determine the profile of stiffness (Gmax) of the soil, agreeing with the level of deformation involved in the tests. Studies on the methods sensitivity are developed to verify the influence on the changing of the parameters given (natural unit weight, Poisson coefficient and thickness of layers) in reduction of data (inversion) on the final profile of VS. The conclusion is that the Poisson coefficient is the parameter with greater influence.
19
Fairbanks, Cedric D. "Shear-wave velocity model of near-surface sediments, site response, and building damage 1886 Charleston, South Carolina earthquake /". Connect to this title online, 2006. http://etd.lib.clemson.edu/documents/1171901551/.
Pełny tekst źródła
20
MANU-MARFO, DANIEL. "Crust-Uppermost Mantle Shear-wave Velocity Structure and Buoyancy Flow Model beneath the Tyrrhenian Basin and Surrounding Margins". Doctoral thesis, Università degli Studi di Trieste, 2020. http://hdl.handle.net/11368/2961200.
Pełny tekst źródłaStreszczenie:
The Tyrrhenian basin serves as a natural laboratory for back-arc basin studies in the Mediterranean region. Yet, little is known about the crust-uppermost mantle structure beneath the basin and surrounding margins. Here, we present a new 3D shear-wave velocity model and Moho topography map for the Tyrrhenian basin and its margins using ambient noise cross-correlations. We apply a self-parameterized Bayesian inversion of Rayleigh-wave group and phase velocity dispersions to estimate the lateral variation of shear velocity and its uncertainty as a function of depth down to 100 km. We also derived a contemporary 3D density model of the lithosphere beneath the Tyrrhenian region by combining seismic velocity, surface heat flow, gravity and topography. Further, we investigated the contribution of buoyancy forces to the regional dynamics by modelling the lithospheric flow field below the Tyrrhenian basin and margins using as input the 3D lithospheric density structure beneath the study area. In general, our models support present-day geodynamics with a predominant Africa-Eurasia convergence and provide new insights into the geodynamics and magmatism in the Tyrrhenian basin and surrounding margins.
21
Su, Bei. "EFFECTS OF RAILROAD TRACK STRUCTURAL COMPONENTS AND SUBGRADE ON DAMPING AND DISSIPATION OF TRAIN INDUCED VIBRATION". UKnowledge, 2005. http://uknowledge.uky.edu/gradschool_diss/312.
Pełny tekst źródłaStreszczenie:
A method for numerical simulation of train induced track vibration and wave propagation in subgrade has been proposed. The method uses a mass to simulate the bogie of a train and considers the effect of rail roughness. For this method, rail roughness is considered as a randomly generated signal and a filter is used to block the undesired components. The method predicts the particle velocity around the track and can be applied to many kinds of railroad trackbeds including traditional ballast trackbed and modern Hot mix asphalt (HMA) trackbed. Results from ballast and HMA trackbeds are compared and effects of HMA layer on damping track vibration and dissipating wave propagation are presented. To verify the credibility of the method, in-track measurements were also conducted. Site measurements included performing geophysical tests such as spectral analysis of surface wave test and seismic refraction test to determine the subsurface conditions at the test site. Ballast and HMA samples were tested in the laboratory by resonant column test to obtain the material properties. Particle velocities were measured and analyzed in the frequency domain. Results from in-track tests confirm the applicability of the numerical method. The findings and conclusions are summarized and future research topics are suggested.
22
Ku, Taeseo. "Geostatic stress state evaluation by directional shear wave velocities, with application towards geocharacterization at Aiken, SC". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45905.
Pełny tekst źródłaStreszczenie:
Evaluations of stress history and the geostatic state of stress of soils are ascertained on the basis of field geophysical measurements that provide paired complementary types of shear waves. It is well-established that multiple types of shear waves occur in the ground due to their directional and polarization properties. The shear wave velocity (Vs) provides the magnitude of small strain stiffness (G0) which depends on effective stress, void ratio, stress history, and other factors (cementation, age, saturation). Herein, this study examines a hierarchy of shear wave modes with different directions of propagation and particle motion from in-situ geophysical tests (HH, VH, and HV) and laboratory bender element data. A special compiled database from well-documented worldwide sites is assembled where full profiles of stress state, stress history, and several paired modes of Vs profiles have been obtained from crosshole tests (CHT), downhole tests (DHT), and rotary crosshole (RCHT). Reference profiles of the lateral stress coefficient (K0) are available from direct in-situ measurements (self-boring pressuremeter, hydrofracture, and push-in spade cells). Stress history is documented in terms of yield stress ratio (YSR) from consolidation testing and careful engineering geology studies. A methodology is developed that relates both the YSR and K0 to stiffness ratios obtained from directional shear wave velocities. In further efforts, means to extract reliable shear wave profiles from continuous downhole testing via a new GT autosource and seismic piezocone testing are outlined and applied to results from three test sites in Windsor/VA, Norfolk/VA, and Richmond/BC.
A driving impetus to this research involves the geologic conditions at the US Dept. of Energy's Savannah River Site (SRS) in South Carolina. Here, the overburden soils in the upper 60 m depths consist of very old Miocene and Eocene sediments, primarily layered deposits of sands, clayey sands, silty sands, and interbedded clays which exhibit an apparent and unusual stress history profile. Special geologic conditions include the dissolutioning of old calcareous sediments (Santee Formation) at depths of 40 to 50 m below grade, similar to karstic limestone deposits. As a consequence, caves, voids, and infilled soft soil zones occur within the soil matrix at these elevations, probably resulting in localized collapse of the overlying soil column. Based on conventional laboratory and in-situ test data conducted during geotechnical investigations at SRS, available interpretative relationships for assessing the soil stress history and geostatic stress states show scattered and inconsistent results. Complications abound in the systematic assessments of these geomaterials due to effects of very old ageing, cementation, desiccation, and diagenesis, as evidenced by unusual in-situ shear wave velocity profiles that decrease in magnitude with depth, as measured by CHT and DHT. Based on the findings of this study, it is recommended that a new set of shear wave velocity measurements be made at SRS to obtain HH waves (and complementary VH waves) needed for an independent assessment of YSR in the upper soil column.
23
Hao, Gang. "Laboratory study of shear wave velocity and very small stain modulus of Macao marine clay under anisotropic stress condition". Thesis, University of Macau, 2008. http://umaclib3.umac.mo/record=b1783644.
Pełny tekst źródła
24
Curd, Jason M. "Unsaturated Soil Parameters From Field Stiffness Measurements". UKnowledge, 2013. http://uknowledge.uky.edu/ce_etds/11.
Pełny tekst źródłaStreszczenie:
The behavior of unsaturated soils depends heavily on material properties and soil conditions. In Geotechnical Engineering, compacted soils are frequently used as fill material, and quality control is vital to the construction process. There are few methods available to estimate the parameters associated with unsaturated soils based on field measurements, and a relationship between these factors could reduce testing time and lower construction costs. Undrained triaxial tests were performed on four clays representing a range of material properties in an effort to reach the maximum dry density, which provides the highest bearing capacity. Each clay was compacted at optimum moisture content, as well as wet and dry of optimum. Measurements were taken using the GeoGauge and shear wave velocities. An empirical approach was used to estimate the effect of a density gradient on soil suction. A relationship between the normal stress and matric suction produced a strong trend when plotted against a function of stiffness and the void ratio, which represents a density gradient. Another relationship between the GeoGauge and shear wave stiffness measurements was found, but no relationship with the material properties of the samples was observed, indicating that more in-depth research is needed to find a stronger relationship.
25
Lee, Joo-yong. "Hydrate-bearing sediments formation and geophysical properties /". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/24726.
Pełny tekst źródłaStreszczenie:
Thesis (Ph.D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.Committee Chair: J. Carlos Santamarina; Committee Member: Carolyn D. Ruppel; Committee Member: Costas Tsouris; Committee Member: Glenn J. Rix; Committee Member: J. David Frost
26
Pilidou, Sylvana Demetriou. "Upper mantle shear-wave velocity and anisotropy structure beneath the North-Atlantic : a seismic image of the Iceland mantle plume". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615904.
Pełny tekst źródła
27
PASSERI, FEDERICO. "Development of an advanced geostatistical model for shear wave velocity profiles to manage uncertainties and variabilities in Ground Response Analyses". Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2730182.
Pełny tekst źródła
28
Smallwood, Cameron David. "Frequency Response and Recovery of Muscles and Effects of Wrapping the Lower Leg on Surface Velocity Measurements". BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7503.
Pełny tekst źródłaStreszczenie:
This thesis is comprised of two studies. The objective of the first study was to find the frequency response and stiffness of the biceps brachii muscle group during recovery from exercise induced damage and to determine whether these data could be used to track muscle recovery by correlating changes in the frequency response with changes in muscle stiffness. Stiffness moduli were collected using Shear Wave Elastography (SWE) which were then applied to a proportional first mode frequency analysis. Data were collected for the muscle stiffness and frequency response for fifteen subjects (25.6 +- 4.5). By comparing the proportion of the square root of the SWE results, the variation in stiffness showed a less than 2 Hz change in first mode resonance for the control group. Frequency response results for the control group agreed with the modified SWE results and the proportion analysis. SWE results for the damage protocol group showed an average increase of 4 Hz. Frequency response results for the damage protocol group were sorted into three categories: three subjects had a change in frequency of peaks of at least 4 Hz in the positive direction; four subjects had an increase in amplitude, but no change in frequency of peaks; three subjects showed mixed responses like fewer resonance peaks, variable amplitudes, changes in peak bandwidth. This research allowed for the documentation of the in-vivo frequency response of the biceps brachii muscle. We believe that the frequency response of a muscle group may be used in the future to evaluate recovery from exercise induced damage. Lessons learned were also recorded for helping future studies in their efforts using an SLDV with human body testing.The second study focused on finding the effects on the surface velocity of tissue above and below a region of the lower leg wrapped in an elastic band when excited by an external source. Ten male subjects between the ages of 18-25 were seated in a chair with one foot placed on a vibrating platform. Two excitation frequencies were separately applied while three points along the leg were measured. A repeatability analysis, using results without the leg wrap, showed a 6.5%, 2.5%, and 10.5% variance in the x-, y-, and z-directions respectively, applying a 20 Hz frequency. With a 40 Hz frequency, the variations were 24%, 23.8%, and 28.4% respectively. A change in displacement of +38% and +10% occurred above the knee in the x-direction with 40 Hz and in the y-direction with 20 Hz, respectively. A change in displacement of -20% occurred below the knee in the x-direction with 20 Hz. A change in displacement of -24% occurred below the wrap location in the y-direction with 40Hz. With a confidence interval of 93%, surface velocity of the tissue located above the wrap increased, while the surface velocity of the tissue below the wrap decreased.
29
Fallahi, Mohammad Javad. "Surface wave tomography and monitoring of time variations with ambient noise in NW-Bohemia/Vogtland". Doctoral thesis, Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-191196.
Pełny tekst źródłaStreszczenie:
In this study, ambient noise wavefield was used for the first time to image spatial and temporal upper crustal seismic structures in NW-Bohemia/Vogtland region. The data come from 111 stations and were collected from continuous recordings of the permanent station networks of Germany and Czech Academy of Sciences as well as temporary stations of the BOHEMA and PASSEQ experiments. Rayleigh and Love waves travelling between each station-pair are extracted by cross-correlating long time series of ambient noise data recorded at the stations. Group velocity dispersion curves are obtained by time-frequency analysis of cross-correlation functions between 0.1 and 1 Hz, and are tomographically inverted to provide 2-D group velocity maps. At shorter periods Rayleigh wave group velocity maps are in good agreement with surface geology where low velocity anomalies appear along Mariánské Lázně Fault and Eger rift. A low velocity zone is observed at the northern edge of Mariánské Lázně Fault which shifts slightly to the south with increasing period and correlates well with the main focal zone of the earthquake swarms at 5 s period. We invert the 2-D group velocity maps into a 3-D shear wave velocity model. In this step Love waves were excluded from further analysis because of their high level of misfit to modelled dispersion curves. Horizontal and vertical sections through the model reveal a clear low velocity zone above the Nový Kostel seismic focal zone which narrows towards the top of the seismic activity and ends above the shallowest hypocenters at 7 km depth.
We investigate temporal variation of seismic velocity within and around the Nový Kostel associated with 2008 and 2011 earthquake swarms by employing Passive Image Interferometry method using 7 continuous seismograms recorded by the WEBNET network. The results reveals stable seismic velocities without a clear post seismic velocity change during earthquake swarms in the Nový Kostel area.
30
Chang, Ouliang. "Numerical Simulation of Ion-Cyclotron Turbulence Generated by Artificial Plasma Cloud Release". Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34018.
Pełny tekst źródłaStreszczenie:
Possibilities of generating plasma turbulence to provide control of space weather processes have been of particular interest in recent years. Such turbulence can be created by chemical released into a magnetized background plasma. The released plasma clouds are heavy ions which have ring velocity distribution and large free energy to drive the turbulence. An electromagnetic hybrid (fluid electrons and particle ions) model incorporating electron inertia is developed to study the generation and nonlinear evolution of this turbulence. Fourier pseudo-spectral methods are combined with finite difference methods to solve the electron momentum equations. Time integration is accomplished by a 4th-order Runge-Kutta scheme or predicator-corrector method. The numerical results show good agreement with theoretical prediction as well as provide further insights on the nonlinear turbulence evolution. Initially the turbulence lies near harmonics of the ring plasma ion cyclotron frequency and propagates nearly perpendicular to the background magnetic field as predicted by the linear theory. If the amplitude of the turbulence is sufficiently large, the quasi-electrostatic short wavelength ion cyclotron waves evolve nonlinearly into electromagnetic obliquely propagating shear Alfven waves with much longer wavelength. The results indicate that ring densities above a few percent of the background plasma density may produce wave amplitudes large enough for such an evolution to occur. The extraction of energy from the ring plasma may be in the range of 10-15% with a generally slight decrease in the magnitude as the ring density is increased from a few percent to several 10's of percent of the background plasma density. Possibilities to model the effects of nonlinear processes on energy extraction by introducing electron anomalous resistivity are also addressed. Suitability of the nonlinearly generated shear Alfven waves for applications to scattering radiation belt particles is discussed.Master of Science
31
Liao, Tianfei. "Post processing of cone penetration data for assessing seismic ground hazards, with application to the New Madrid seismic zone". Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-05042005-133640/.
Pełny tekst źródłaStreszczenie:
Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.Mayne, Paul W., Committee Chair ; Goldsman, David, Committee Member ; Lai, James, Committee Member ; Rix, Glenn J., Committee Member ; Santamarina, J. Carlos, Committee Member.
32
Chao, Tzu-Kai Kevin. "Temporal changes of shear wave velocity and anisotropy in the shallow crust induced by the 10/22/1999 m6.4 Chia-yi, Taiwan earthquake". Thesis, Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28088.
Pełny tekst źródłaStreszczenie:
Temporal changes of seismic velocity and anisotropy in the shallow crust are quantified using local earthquakes recorded at a 200-m-deep borehole station CHY in Taiwan. This station is located directly above the hypocenter of the 10/22/1999, M6.4 Chia-Yi earthquake. Three-component seismograms recorded at this station show clear direct (up-going) and surface-reflected (down-going) P- and S-waves, and S-wave splitting signals. The two-way travel times in the top 200 m is obtained by measuring the time delays between the up-going and down-going waves in the auto-correlation function. The S-wave travel times measured in two horizontal components increase by ~1-2% at the time of Chia-Yi main shock, and followed by a logarithmic recovery, while the temporal changes of S-wave splitting and P-wave are less than 1% and are not statistically significant. We obtain similar results by grouping earthquakes into clusters according to their locations and waveform similarities. This suggests that the observed temporal changes are not very sensitive to the seismic ray path below CHY, but are mostly controlled by the variation of material property in the top 200 m of the crust. We propose that strong ground motions of the Chia-Yi main shock cause transient openings of fluid-filled microcracks and increases the porosity in the near-surface layers, followed by a relatively long healing process. Because we observe no clear changes in the shear wave anisotropy, we infer that the co-seismic damages do not have a preferred orientation. Our results also show a gradual increase of time delays for both the fast and slow S-waves in the previous 7 years before the Chia-Yi main shock. Such changes might be caused by variations of water table, sediment packing or other surficial processes.
33
Choo, Hyunwook. "Engineering behavior and characterization of physical-chemical particulate mixtures using geophysical measurement techniques". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52178.
Pełny tekst źródłaStreszczenie:
Natural geomaterials exhibit a wide range in size, physical properties, chemical properties, and mechanical behaviors. Soils that are composed of mixtures of particles with different physical and chemical properties pose a challenge to characterization and quantification of the engineering properties. This study examined the behavior of particulate mixtures composed of differently sized silica particles, mixtures composed of aluminosilicate and organic carbon particles, and mixtures composed of particles with approximately three orders of magnitude difference in particle size. This experimental investigation used elastic, electromagnetic, and thermal waves to characterize and to quantify the small to intermediate strain behavior of the mixtures.
The mechanical property of stiffness of mixed materials (e.g. binary mixtures of silica particles and fly ashes with various carbon and biomass contents) was evaluated through the stiffness of active grain contacts, and the stiffness of particles which carry applied load, using the physical concepts of intergranular void ratio and interfine void ratio. Additionally, the change in both contact mode/stiffness and electrical property due to the presence of nano-sized particles (i.e., iron oxides) on the surface of soil grains was evaluated according to applied stress, packing density, iron coating density, and substrate sand particle size. Finally, the biomass fraction and total organic carbon content of mixtures was used to quantify the electrical and thermal conductivities when particulate organic was mixed with aluminosilicate particles.
34
Mainsant, Guenolé. "Variation de la vitesse des ondes de cisaillement lors de la transition solide-liquide au sein des argiles. Application aux glissements de terrain". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENU005/document.
Pełny tekst źródłaStreszczenie:
Les glissements de terrain argileux affectent de nombreux versants à travers le monde et menacent régulièrement les activités humaines dans les zones urbanisées montagneuses. Ces glissements sont caractérisés par des cinématiques souvent lentes mais ils peuvent brutalement se liquéfier et accélérer de manière imprévisible. Cette transition solide-liquide a été étudiée sur les argiles de la région du Trièves (Alpes Françaises) à l'aide d'études rhéologiques. Elles ont montré le caractère de fluide à seuil thixotrope avec une bifurcation de viscosité importante lors de la fluidification pouvant expliquer le caractère catastrophique de l'accélération observée sur le terrain. Cette perte de rigidité du matériau peut être observée par une chute de la vitesse des ondes de cisaillement (Vs). Des études réalisées en parallèle à la fois sur un modèle analogique de plan incliné et sur le terrain (glissement de Pont-Bourquin, Suisse) ont permis d'observer une chute de Vs précédent à cette fluidification montrant ainsi que Vs pourrait être un bon proxy pour la surveillance des instabilités de terrain argileuxLandslides affect many clay slopes in the world and regularly threaten people in urban areas mountainous. These landslides are characterized by a slow velocity but they may suddenly liquefy and accelerate unexpectedly. The solid-liquid transition on the clay has been studied of Trièves region (French Alps) using rheological experiments. They have shown the yield stress thixotropic behavior with a viscosity bifurcation which can explain the catastrophic fluidization observed in the field. This loss of material stiffness can be followed by a drop in the shear wave velocity (Vs). Inclined plane test and field experiments (Pont-Bourquin landslides in Switzerland) have both shown a precursor drop of Vs indicating that it could be a good proxy for monitoring unstable clay slope
35
Legendre, Cédric [Verfasser], Wolfgang [Gutachter] Friederich, Thomas [Gutachter] Meier, Jörg [Gutachter] Renner i Michael [Gutachter] Alber. "Shear wave velocity model of the upper mantle beneath Europe and surroundings / Cédric Legendre ; Gutachter: Wolfgang Friederich, Thomas Meier, Jörg Renner, Michael Alber ; Fakultät für Geowissenschaften". Bochum : Ruhr-Universität Bochum, 2013. http://d-nb.info/1238345050/34.
Pełny tekst źródła
36
Julea, Felicia. "Conditions de validité de l'Élastographie par Résonance Magnétique". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS053/document.
Pełny tekst źródłaStreszczenie:
L'élastographie par résonance magnétique (ERM) est une technique d'imagerie, reconnue comme une méthode pertinente pour la caractérisation mécanique des tissus humains in vivo. Celle-ci représente un intérêt fondamental en diagnostic clinique car le développement d'un processus pathologique s'accompagne la plupart du temps d'altérations des propriétés mécaniques des tissus atteints. L'ERM consiste à enregistrer le champ de déplacement induit au passage d'une onde de cisaillement généré dans le milieu étudié. Les paramètres mécaniques comme la vitesse, v, et les modules de viscoélasticité de cisaillement, G' et G'', peuvent être cartographiés. La quantification des paramètres mécaniques dépend à la fois de la fréquence mécanique, fexc, de la taille de voxel, a, de l'amplitude des champs de déplacement induits, A, de l'amplitude du rotationnel du champ de déplacement, q, des erreurs de mesure, ΔA et Δq, donc du rapport signal à bruit, RSB, et enfin de la méthode de reconstruction. En inversant les équations différentielles du champ de déplacement acquis selon les trois dimensions de l'espace, ces paramètres ont été considérés pour déterminer la précision et l'exactitude des modules mécaniques obtenus et établir les conditions de validité de l'ERM. Dans cette thèse, nous avons tout d'abord considéré A et A/ΔA afin de définir un premier seuil de validité pour l'ERM. Nous avons étudié l'influence de ces deux paramètres sur un fantôme hétérogène dans un appareil IRM 1,5 T avec deux types d'antennes. Dans une première étude, les champs de déplacement ont été acquis en fonction de A en utilisant deux séquences écho de spin (RFE) et écho de gradient (FFE) sensibilisées au mouvement pour une taille de voxel isotrope de 1 mm. Dans une seconde étude, ils ont été acquis en RFE en fonction de A pour trois résolutions spatiales différentes. Ces études ont révélé l'existence d'un seuil en A/ΔA au-delà duquel les paramètres extraits (G', G'') atteignent un plateau et l'ERM est fiable. Nous avons ensuite considéré le nombre de voxel par longueur d'onde, λ/a, comme paramètre déterminant des conditions de validité de l'ERM et nous avons caractérisé la qualité des données acquises par le rapport q/Δq. Sur des simulaitons dans un milieu élastique, homogène et isotrope avec un RSB variant entre 5 et 30, la précision et l'exactitude des mesures se sont avérées optimales pour 6 à 9 voxels par longueur d'onde. Nous avons reproduit expérimentalement à 2 kHz les conditions des siimulations sur un fantôme de PVA. Les champs de déplacement ont été acquis à 11,7 T en utilisant une séquence RFE sensibilisée au mouvement pour des résolutions spatiales de 150 μm à 300 μm afin de balayer le rapport λ/a de 1 à 20. Les résultats expérimentaux confirment pleinement les prédictions de la simulation. La vitesse de cisaillement diminue et tend vers la vitesse de référence attendue lorsque l'acquisition est réalisée dans le domaine optimal, à savoir ici lorsque a est inférieure ou égale à 200 μm. En outre la dispersion de la vitesse est réduite dans le domaine optimal et des estimations plus précises des paramètres mécaniques ont pu être déduites. Cette thèse montre d'une part que la précision et l'exactitude de l'ERM sont optimales lorsque les acquisitions sont réalisées ou traitées pour un domaine d'échantillonnage de la longueur d'onde déterminé par le RSB. Elle montre d'autre part que la comparaison des résultats obtenus doit être menée dans une gamme similaire de q/Δq. La prise en compte des conditions de validité de l'ERM, déterminées par les rapports λ/a et q/Δq, conduit à une mesure quantitative effective des paramètres mécaniques. Il est ainsi possible d'envisager un diagnostic clinique pertinent au sein d'un même organe, d'un même sujet, entre sujets ou au cours du tempsMagnetic Resonance Elastography (MRE) is a imaging technique, recognized as a pertinent method for the mechanical characterization of human tissue in vivo. It offersa particular interest in clinical diagnosis because the development of a pathological process is often accompanied by modifications of the mechanical properties of diseased tissues. MRE consists of recording, along the three spatial dimensions, the displacement field induced by the propagation of a shear wave generated by excitation of the investigated tissue. Mechanical parameters such as shear wave velocity, v, and shear moduli, G' and G'', can then be mapped. The quantification of the mechanical parameters depends on the frequency of the mechanical excitation, fexc, the spatial resolution, a, the amplitude of the induced displacement field, A and the amplitude of the curl field displacement, q, with associated measurement errors, ΔA and Δq, (related to the signal-to-noise ratio, SNR) and finally the reconstruction method. All these parameters were considered to determine the precision and the accuracy of the estimated mechanical moduli and to establish the conditions of validity of MRE following the inversion of the differential equations of the displacement field. In this work, first A and A/ΔA were considered to define a validity threshold for MRE. The influence of A and A/ΔA was studied on a heterogeneous phantom acquired using a 1.5 T MRI with two different types of coils. In a first study, the displacement fields were acquired as a function of A using motion-sensitized spin-echo (REF) and gradient-echo (FFE) sequences for an isotropic spatial resolution of 1 mm. In a second study, the displacement field was acquired as a function of A using RFE for three different spatial resolutions. These studies revealed the existence of a threshold in A/ΔA beyond which the extracted parameters (G', G'') reach a plateau and the MRE is reliable. Then the number of voxels per wavelength, λ/a was considered as a parameter determining the conditions of validity of MRE. This parameter was studied according to the quality of the acquired data characterized by the ratio q//Δq. Simulations were carried in a homogeneous and isotropic elastic medium with a SNR between 5 and 30. The accuracy and the precision of the measurements were found optimal for 6 to 9 voxels per wavelength. The simulation conditions were experimentally reproduced at 2 kHz on a home-made polyvinyl alcohol phantom. The displacement fields were acquired at 11.7 T using a motion-sensitized RFE sequence with spatial resolutions ranging from 150 μm to 300 μm in order to obtain a λ/a ratio ranging from 1 to 20. The experimental results fully confirm the predictions of the simulation. The shear wave velocity decreases with λ/a. It tends towards the expected reference value when the acquisition is performed in the optimal condition, namely here when a is less than or equal to 200 μm. In addition, the standard deviation of the shear wave velocity is reduced for the optimal conditions. Therefore, accurate estimation of mechanical parameters could be deduced. This thesis first demonstrates that the precision and accuracy of MRE are optimal when the acquisitions are performed or processed for a certain wavelength sampling range determined by the SNR. We also showed that for fair comparison of the results, MRE must be carried out in a similar range of q/Δq. Taking into account the conditions of validity of MRE, determined by the ratios λ/a and q/Δq, leads to an effective quantitative measurement of the mechanical parameters making it possible to establish a relevant clinical diagnosis within the same organ, the same subject, between subjects or over time
37
Sandikkaya, Mustafa Abdullah. "Site Classification Of Turkish National Strong-motion Recording Sites". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609728/index.pdf.
Pełny tekst źródłaStreszczenie:
Since 1976, the General Directorate of Disaster Affairs of Turkey has deployed several strong-motion accelerographs at selected sites. Within the framework of the project entitled Compilation of National Strong Ground Motion Database in Accordance with International Standards, initiated in 2006, site conditions at a total of 153 strong-motion sites were investigated within the uppermost 30 m depth through boreholes including Standard Penetration Testing and surface seismics by means of Multi-channel Analysis of Surface Waves (MASW). In this study, firstly, the assessment of the site characterization was held by making use NEHRP Provisions, EC-8 and Turkish Seismic Design Code. The corrected penetration resistances are calculated and observed how it affects the classification. In addition, the consistency of site classes obtained from either penetration resistance or shear wave velocity criteria is examined. Also the consistency of the boundaries of the site classes in terms of shear wave velocity and penetration resistance data pairs are investigated. Secondly, the liquefaction potential of these sites is examined. Thirdly and finally, the shear wave velocity profiles obtained from MASW technique are contrasted to other seismic tests.
38
Brandmayr, Enrico. "The geodynamics of the Mediterranean in the framework of the global asymmetric Earth: evidences from seismological and geophysical methods". Doctoral thesis, Università degli studi di Trieste, 2013. http://hdl.handle.net/10077/8606.
Pełny tekst źródłaStreszczenie:
2011/2012La tesi presenta l'estensione ed il raffinamento del modello cellulare tridimensionale della crosta e del mantello superiore dell'area centrale mediterranea e propone una interpretazione geodinamica del suddetto modello nel contesto della asimmetria globale della tettonica delle placche. Il modello cellulare è espresso in termini di velocità delle onde di taglio (VS) e di spessore e densità degli strati, fino ad una profondità di 350 chilometri. Tali proprietà caratterizzanti gli strati sono ottenute mediante avanzate tecniche di inversione non lineare, quali l'inversione con il metodo hedgehog di curve di dispersione delle velocità di gruppo e di fase per la determinazione delle VS e l'inversione non lineare di dati gravimetrici mediante il metodo GRAV3D. Il metodo hedgehog consente la definizione di un insieme di modelli strutturali senza fare ricorso ad alcun modello a priori, considerando la VS e lo spessore degli strati come variabili indipendenti. Data la ben nota non unicità del problema inverso, la soluzione rappresentativa di ogni cella è determinata per mezzo dell'applicazione di algoritmi di ottimizzazione ed è inoltre validata alla luce di dati geologici, geofisici e petrologici indipendenti, in particolare la distribuzione della sismicità, sia passata, ottenuta dai bollettini internazionali, sia presente, ottenuta mediante inversione non lineare dei meccanismi focali. Le proprietà delle sorgenti sismiche sono state studiate utilizzando la metodologia INPAR per l'inversione di forme d'onda complete di periodo relativamente corto (fino a 10 s), che permette la determinazione realistica del tensore momento sismico in particolare per eventi poco profondi. Questa metodologia si rivela particolarmente utile nelle aree caratterizzate da eventi di moderata magnitudo, dove le tecniche globali standard non possono in genere venire applicate. Il metodo INPAR fornisce inoltre risultati attendibili anche quando sono disponibili soltanto pochi segnali registrati da un numero limitato di stazioni. L'inversione gravimetrica è stata vincolata alla geometria degli strati definita dal modello VS ottenuto dai dati sismologici. Ai dati gravimetrici di input è applicato un rumore gaussiano con ampiezza di 1,5 mGal. Al fine di non imporre a priori l’esistenza di decrementi della densità al crescere della profondità, il modello di densità di riferimento utilizzato come input dell’inversione consiste, per tutte le celle, in un modello di densità crescente o costante con la profondità, che soddisfa, entro i valori di incertezza, la relazione di Nafe-Drake. Le anomalie ottenute dal processo di inversione gravimetrica vengono poi trasformate in valori assoluti di densità riferiti al modello di riferimento. Il modello tridimensionale così ottenuto, analizzato e discusso lungo sezioni perpendicolari ai complessi orogenetici dell'area di studio (Appennini, Alpi, Dinaridi) conferma l'esistenza di profonde asimmetrie strutturali tra le subduzioni est e ovest-vergenti e la presenza di litosfera sottile nell'area estensiva del bacino Tirrenico, che sovrasta una zona a bassa velocità (LVZ) indicativa della presenza di vaste aree magmatiche o di fusione parziale, probabile sede di un flusso del mantello verso est. Tale flusso è possibile causa dell'asimmetria riscontrata tra la subduzione appenninica, quasi verticale, e la subduzione alpina e dinarica, caratterizzata da un basso angolo di immersione. Ulteriore ed inaspettata caratteristica del modello è rappresentata dal fatto che la litosfera in subduzione risulta essere meno densa del mantello circostante. Tale risultato apre la strada a nuove interpretazioni riguardo alla dinamica delle zone di subduzione, che nella sua descrizione ortodossa vede come fattore determinante il fenomeno dello slab pull. La tesi si articola in un capitolo introduttivo iniziale dove viene esposta l'ipotesi della asimmetria della tettonica delle placche, con particolare riferimento alle evidenze in area mediterranea, mentre nei capitoli successivi vengono presentati i risultati del modello in VS e densità ottenuto a differenti scale risolutive. Tali risultati sono poi discussi, con l'ausilio di sezioni interpretative lungo profili significativi, alla luce di evidenze indipendenti con l'intento di delineare un quadro geodinamico coerente dell'area di studio. In Appendice, unitamente alla presentazione dei risultati tabulati, sono approfondite alcune tematiche particolari.
This thesis presents the extension and refinement of the 3D cellular model of the crust and upper mantle of the central Mediterranean and offers a geodynamic interpretation of the obtained model in the framework of the global asymmetry of plate tectonics. The cellular model is expressed in terms of shear waves velocity (VS), thickness and density of the layers, to a depth of 350 kilometers. These physical properties are obtained by means of advanced non-linear inversion techniques, such as the hedgehog inversion method of group and phase velocity dispersion curves for the determination of VS and the non-linear inversion of gravity data by means of the method GRAV3D. The hedgehog method allows the definition of a set of structural models without resorting to any a priori model, considering the VS and the thickness of the layers as independent variables. Given the well-known non-uniqueness of the inverse problem, the representative solution of each cell is determined through the application of optimization algorithms and is also validated with the use of independent geological, geophysical and petrological data, e.g. the distribution of historical and recent seismicity, obtained from international bulletins and by non-linear inversion of focal mechanisms. The properties of the seismic sources have been studied using the INPAR methodology for the inversion of complete waveforms at relatively short period (as short as 10 s), that allows the determination of the realistic seismic moment tensor in particular for shallow events. This methodology is very useful in areas of moderate magnitude events, where generally the global standard techniques can not be applied. The INPAR method also provides reliable results even using few signals recorded by a limited number of stations. The gravimetric inversion has been constrained to the geometry of the layers defined by the VS model obtained from the inversion of seismological data. A Gaussian noise with an amplitude of 1.5 mGal has been applied to the gravimetric data input. In order not to impose a priori the existence of the density decreases with increasing depth, the reference density model used in the inversion consists, for all the cells, in a model of increasing or at least constant density with depth, which satisfies, within the range of uncertainty, the Nafe-Drake relation. The density anomalies obtained by the gravimetric inversion process are then transformed into absolute values relative to the reference model. The three-dimensional model thus obtained, analysed and discussed along selected sections perpendicular to the orogenic complexes of the study area (Apennines, Alps, Dinarides) confirms the existence of deep structural asymmetries between E- and W-directed subductions and the presence of a thin lithosphere in the extensional area of the Tyrrhenian basin, which overlies a low velocity zone (LVZ) indicative of the presence of large amount of magma or partial melting, where an eastward mantle flow is likely present. This flow possibly causes the asymmetry found between the almost vertical Apenninic subduction and the Alpine-Dinaric subduction, which is in turn characterized by a low dip angle. Further and unexpected feature of the model is the fact that the subducting lithosphere turns out to be less dense than the surrounding mantle. This result opens the way to new interpretations in subductions dynamics, which in its common description relies on the slab pull phenomenon as a first order acting force. The thesis consists of an introduction where the hypothesis of the global asymmetry of plate tectonics is addressed, with particular attention to the Mediterranean context, while in the Chapters 2, 3 and 4 are presented the VS and density models obtained at different resolution scales. These results are then discussed in the Chapter 5, with the aid of interpretive sections along significant profiles, in the light of the validation though independent data, aiming to establish a coherent geodynamic picture of the study area. In the Appendixes, together with the presentation of the tabulated results, some particular topics are discussed.
XXV Ciclo
1982
39
Chong, Song Hun. "The effect of subsurface mass loss on the response of shallow foundations". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54271.
Pełny tekst źródłaStreszczenie:
Subsurface volume loss takes place in many geotechnical situations, and it is inherently accompanied by complex stress and displacement fields that may influence the performance of engineered geosystems. This research is a deformation-centered analysis, it depends on soil compressibility and it is implemented using finite elements.
Soil stiffness plays a central role in predicting ground deformation. First, an enhanced Terzaghi’s soil compressibility model is proposed to satisfy asymptotic conditions at low and high stress levels with a small number of physically meaningful parameters. Then, the difference between small and large strain stiffness is explored using published small and large-strain stress-strain data. Typically, emphasis is placed on the laboratory-measured stiffness or compressibility; however, there are pronounced differences between laboratory measurements and field values, in part due to seating effects that prevail in small-thickness oedometer specimens. Many geosystems are subjected to repetitive loads; volumetric strains induced by drained repetitive ko-loads are experimentally investigated to identify shakedown and associated terminal density.
The finite element numerical simulation environment is used to explore the effect of localized subsurface mass loss on free-surface deformation and shallow foundations settlement and bearing capacity. A stress relaxation module is developed to reproduce the change in stress associated to dissolution features and soft zone formation. The comprehensive parametric study is summarized in terms of dimensionless ratios that can be readily used for engineering applications.
Field settlement data gathered at the Savannah River Site SRS are back-analyzed to compare measured values with predictions based on in situ shear wave velocity and strain-dependent stiffness reduction. The calibrated model is used to estimate additional settlements due to the pre-existing cavities, new cavities, and potential seismic events during the design life of the facility.
40
Bhamidipati, Raghava A. "Use Of Laboratory Geophysical And Geotechnical Investigation Methods To Characterize Gypsum Rich Soils". UKnowledge, 2016. http://uknowledge.uky.edu/ce_etds/45.
Pełny tekst źródłaStreszczenie:
Gypsum rich soils are found in many parts of the world, particularly in arid and semi-arid regions. Most gypsum occurs in the form of evaporites, which are minerals that precipitate out of water due to a high rate of evaporation and a high mineral concentration. Gypsum rich soils make good foundation material under dry conditions but pose major engineering hazards when exposed to water. Gypsum acts as a weak cementing material and has a moderate solubility of about 2.5 g/liter. The dissolution of gypsum causes the soils to undergo unpredictable collapse settlement leading to severe structural damages. The damages incur heavy financial losses every year.
The objective of this research was to use geophysical methods such as free-free resonant column testing and electrical resistivity testing to characterize gypsum rich soils based on the shear wave velocity and electrical resistivity values. The geophysical testing methods could provide quick, non-intrusive and cost-effective methodologies to screen sites known to contain gypsum deposits. Reconstituted specimens of ground gypsum and quartz sand were prepared in the laboratory with varying amounts of gypsum and tested. Additionally geotechnical tests such as direct shear strength tests and consolidation tests were conducted to estimate the shear strength parameters (drained friction angle and cohesion) and the collapse potential of the soils.
The effect of gypsum content on the geophysical and geotechnical parameters of soil was of particular interest. It was found that gypsum content had an influence on the shear wave velocity but had minimal effect on electrical resistivity. The collapsibility and friction angle of the soil increased with increase in gypsum. The information derived from the geophysical and geotechnical tests was used to develop statistical design equations and correlations to estimate gypsum content and soil collapse potential.
41
Teodorescu, Catalin. "Laboratory investigation of electrostatic ion waves modified by parallel-ion-velocity shear". Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=2901.
Pełny tekst źródłaStreszczenie:
Thesis (Ph. D.)--West Virginia University, 2003.Title from document title page. Document formatted into pages; contains xiv, 215 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 107-113).
42
Soliman, Nancy Ahmed. "Modification et validation de la technique de l'anneau piézoélectrique pour mesurer la prise et le durcissement des matériaux à base de ciment". Mémoire, Université de Sherbrooke, 2010. http://savoirs.usherbrooke.ca/handle/11143/1575.
Pełny tekst źródłaStreszczenie:
A period of cement hydration is one of critical in the life span of concrete structures. One of the reasons of collapse of concrete structural elements during and after construction is the error in determining the concrete characteristics at early age. Recently, non-destructive test emerged as a popular way to evaluate the properties of cement-based materials. This test offers continuous measurements of concrete properties as well as ability to monitor any changes in the current state of structural materials. In the existing research, some of these methods fail to capture well properties of the materials in the plastics stage. A new piezoelectric pulse testing device (Piezoelectric Ring Actuators Technique), (P-RAT ) was initially developed at the University of Sherbrook as a non-destructive test (NDT ) for soil. This technique is considered a completely new, versatile, advanced and accurate. The development of the new technique (P-RAT ) was done on two main bases: the first was the development of piezoelectric ring actuators set-up and the second is the development of the interpretation method. The setup is composed of two main units; emitter and receiver, and is capable of measuring shear and compression wave velocities in specimens. With this technique, many problems of pulse tests, which make interpretation of results difficult and ambiguous, were solved in soil. The P-RAT overcomes wave reflections at boundaries (end-caps and sides), sample disturbance, weak shear coupling between soil and device (interaction) as well as the fixation problems, low resonant frequency and limited input voltage of the existing device. The previous method is exploited forward to measure the hydration properties of cement-based material. To apply this test method, it is necessary to determine how the evolution of shear wave velocity can be related and sensitive to the hydration of cement-based materials. Validation of the P-RAT with four conventional test setups that can be used to monitor early setting and hydration of cement-based materials is carried out. These tests include penetration resistance to monitor initial and final setting respectively, calorimetric to monitor heat of hydration, electrical conductivity to monitor change in continuity of the pore structure and compressive strength at 24 hours. The phase one of this investigation included trial tests to investigate the possibility of employing the original setup used for soil (P-RAT ) to determine setting and hardening properties of cement-based material. Based on the results of the preliminary test, two modifications were conducted to the previous test device to fit with cement based material and to obtain adequate resonant frequency for cement-based materials. These modifications are the design of the container and changing the dimensions of the rings. The resultant version of P-RAT after the modification was referred to be as P-RAT2 . Calibration of the P-RAT2 with water specimen was undertaken using the compression wave velocity and resulted in 99.33% accuracy. One paste mixture was tested three times to determine the experimental error of the P-RAT2 . The repeatability carried out on the P-ART2 proved the ability of this setup to capture accurate results of the shear wave velocity. This relative error is limited to 9 %. A number of series of validation was performed on cement paste and mortar mixtures proportioned with various water cement ratios (w/cm ) as well as chemical admixtures. The w/cm ratio ranged between (0.35 and 0.50). The investigated chemical admixtures comprise of high-range water-reducing agent, viscosity-modifying agent, set-accelerating agent, and set-retarding agent. The presented validations examine the ability of a P-RAT2 to monitor the hydration of the cement-based materials. The hydration is characterized by setting time, heat of hydration, electrical conductivity, and compressive strength at 24 hours. The results obtained using the P-RAT2 was correlated to those obtained using the conventional tests and strength measurement. The results enable to validate the ability of P-RAT2 to accurately detect variations in the hydration of cement-based materials. In addition, the initial and final time of setting can be determined from the derivation of velocity vs. time curve. The results show that conductivity, resistivity, has a bilinear relationship to shear wave velocity. The compressive strength at 24 hours was correlated to both the shear wave velocity and shear modulus obtained using the P-RAT2 . Furthermore, analytical model was derived to estimate the w/cm in mortar mixture by measuring the shear wave velocity (V[subscript s] ) and the corresponding time (t )||Résumé : La période d'hydratation du ciment est l'une des périodes clé du cycle de vie des structures en béton. L'une des raisons de l'effondrement d'éléments structuraux en béton pendant et après la construction peut être attribuée à une détermination des caractéristiques au jeune âge erronée. Depuis quelques années, l’auscultation des structures est devenue une méthode très populaire pour évaluer les propriétés des matériaux cimentaires. Cette méthode permet d'obtenir les propriétés du béton en continue et possibilité un suivi de changements dans I'état des matériaux structuraux. Dans I'état actuel de la recherche dans ce domaine, certaines méthodes ne sont pas adéquates pour bien mesurer les propriétés des matériaux à I'état plastique. Un nouvel appareil d'essai à impulsions piezoélectriques (Piezoelectric Ring Actuators technique), (P-RAT) a initialement été développé à l’Université de Sherbrooke comme technique d'auscultation des sols. Cette technique est considérée complètement nouvelle, polyvalente, évoluée et précise. Le développement de cette nouvelle technique (P-RAT) a été effectué en deux volets : la première sole est le développement du dispositif de vérin de commande annulaire piezoélectrique et le deuxième est le développement d'une méthode d'interprétation. Le dispositif d'essai est composé de deux unités principales, un émetteur et un récepteur. Et permet de mesurer la vitesse de propagation des ondes de cisaillement et de compression. Grâce à cette technique, plusieurs des problèmes associés aux dispositifs d'essais par impulsion des ondes, qui rendent les résultats ambigus et difficiles à interpréter, ont été résolu pour les sols. Le dispositif P-RAT surmonte les problèmes de réflexion des ondes aux limites (embouts et côtés), la perturbation de l’échantillon, le couplage de cisaillement faible entre le sol et l'appareil (interaction) ainsi que les problèmes de fixation, la faible résonnance des fréquences et le voltage d'entrée limité du dispositif. La méthode décrite a été utilisée pour mesurer les propriétés d'hydratation des matériaux cimentaires. Pour pouvoir appliquer cette méthode, il faut déterminer comment l’évolution de la propagation des ondes de cisaillement peut être reliée à l'hydratation des matériaux cimentaires et être sensible à ces dernières. La validation de la méthode P-RAT est réalisée, à l'aide de quatre configurations conventionnelles que l’on peut utiliser pour faire le suivi de la prise et de l'hydratation des matériaux cimentaires. Ces essais consistent à la résistance à la pénétration afin de pouvoir déterminer la prise initiale et finale, la calorimétrie pour suivre l’evolution de la chaleur d'hydratation, la conductivité électrique pour effectuer le suivi de la structure des pores et la résistance à la compression à 24 heures. La phase 1 de l'étude comprend des essais pour évaluer la possibilité d'utiliser la configuration originale utilisée pour les sols (P-RAT) pour déterminer les propriétés de prise et de durcissement des matériaux cimentaires. Selon les résultats des essais préliminaires, deux modifications ont été effectuées à l'appareil original pour permettre son utilisation avec des matériaux cimentaires et pour obtenir une fréquence de résonnance raisonnable sur les matériaux cimentaires. Les modifications effectuées sont la conception du contenant et un changement de la dimension des anneaux. La version modifiée du P-RAT est designée P-RAT2. La calibration du P-RAT2 à l'aide d'échantillon liquide sous propagation d'ondes de compression a été menée, avec des résultats d'une précision de 99,33 %. Un mélange a été testé trois fois pour déterminer l'erreur expérimentale du P-RAT2. La répétitivité des essais sur le PART2 a démontré la capacité de cet appareil à produire des résultats de cisaillement de propagation des ondes de cisaillement très précis. L'erreur relative se limite à 9 %. Une série d'essais de validation a été menée sur des mélanges de pâte de ciment et de mortier de rapport eau/ciment variés (e/c) ainsi qu'avec des adjuvants. Le rapport e/c variait entre 0,35 et 0,50. Les adjuvants utilisés étaient des supers plastiflants (réducteur d'eau), des agents de viscosité, des agents accélérateurs de prise et des agents retardateurs de prise. Les validations présentées ont pour but de valider la capacité du P-RAT2 à suivre l'hydratation des matériaux cimentaires. L'hydratation est caractérisée par le temps de prise, la chaleur d'hydratation, la conductivité électrique et la résistance à la compression à 24 heures. Les résultats obtenus à l'aide du P-RAT2 ont été comparés à ceux obtenus à l'aide d'essais de mesure des caractéristiques physiques et de résistance traditionnels. Ces résultats permettent de valider la capacité du P-RAT2 à détecter avec précision les variations dans l'hydratation des matériaux cimentaires. De plus, le dispositif P-RAT2 peut avoir une correction avec mesure obteniez avec les appareils traditionnels. II est aussi possible de déterminer le temps de prise initial et final à l'aide d'une courbe de propagation vs le temps. Les résultats montrent que la conductivité et la résistivité ont une relation bilinéaire à la propagation des ondes de cisaillement. La résistance à la compression à 24 heures a été comparee à la fois à la propagation des ondes de cisaillement et au module de cisaillement obtenus avec le P-RAT2. De plus, un modèle analytique a été établi pour estimer le rapport e/c dans le mélange de mortier en mesurant la propagation des ondes de cisaillement (V) correspondant au temps (t).
43
Wu, Chunquan. "Temporal change of seismic velocity and site response for different scales and implications for nonlinearity". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/24619.
Pełny tekst źródła
44
Boggs, Cheryle Ann. "Glacial Drift Thickness and Vs Characterized Using Three-Component Passive Seismic Data at the Dominion Stark-Summit Gas Storage Field, North Canton, Ohio". Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1420815127.
Pełny tekst źródła
45
Reid, Fiona J. L. "Velocity and attenuation structure of the mantle : constraints from differential properties of shear waves". Thesis, University of Oxford, 1999. http://ora.ox.ac.uk/objects/uuid:83796f01-c45f-4d84-9c4c-04e084ac135f.
Pełny tekst źródłaStreszczenie:
Although much progress has been made in determining the three dimensional distribution of seismic wave velocities in the Earth, substantially less is known about the three dimensional distribution of intrinsic attenuation. In this study variations in attenuation and shear velocity of the Earth's mantle are constrained using measurements of differential travel time and attenuation. The data are broadband displacement SH seismograms filtered to have energy in the period range 8 to 20 s. Broadband data are used as they should allow a more accurate estimation of body wave attenuation to be made. The seismograms are obtained from over 600 globally distributed earthquakes of magnitude, Mw, 5.5 or greater. Two new methods for determining differential travel times and differential t* values from multiple S phases are presented. The first of these, referred to as the "waveform fitting method" is used to analyse approximately 4300 SS and S waveforms and around 1000 SSS and SS waveforms resulting in differential SS-S and SSS-SS travel times, and corresponding values of differential attenuation represented by t*. The second method, referred to as the "spectral ratio method" is used to analyse approximately 3200 SS and S and around 900 SSS and SS waveforms. The differential travel times and t* values are inverted to obtain models of the lateral variation of shear velocity and lateral variation of q(mu) where q(mu) =1/Q(mu). The models explain the data well but have limited depth resolution. The velocity models show good correlation with previous studies, in particular, low velocities are observed underlying spreading ridges and convergent margins and high velocities are observed under continental regions. The q(mu) model shows shield regions to be less attenuating than PREM, with ridges appearing as highly attenuating features. Models of shear velocity and attenuation are also obtained by combining the body wave dataset of this study with the surface wave datasets of Van Heijst (1997) and Selby (1998).
46
Alata, Rodriguez Jair Angelo, i Ninancuro Wilfredo Zevillanos. "Correlación entre el número de golpes N60 del Ensayo de Penetración Estándar y la Velocidad de ondas de corte (Vs) para los suelos arenosos del distrito de Juliaca – Puno". Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2021. http://hdl.handle.net/10757/656163.
Pełny tekst źródłaStreszczenie:
La aplicación del ensayo de penetración estándar (SPT) conlleva a un nivel de detalle alto, así mismo es costosa, requiere de mano de obra calificada para su ejecución y es demorada; su utilización es recomendada en suelos arenosos, restrictiva en suelos finos y plásticos y no recomendada en los demás tipos de suelos. Mientras que en el Análisis multicanal de ondas superficiales (MASW) su ejecución no se restringe, permite abarcar grandes áreas en tiempos cortos, no obstante, es un método indirecto, razón por la cual su aplicación debe ser verificada mediante perforaciones, obtención de muestras, y altos criterios de análisis. En los últimos años la implementación y mejoramiento de las técnicas de prospección de suelos ha permitido investigar la relación de dichos ensayos con diferentes parámetros del suelo.
En la presente se desarrolló una correlación empírica entre los ensayos geotécnicos SPT mediante el número de golpes de resistencia a la penetración (N60) con el valor de las velocidades de ondas de corte (Vs) de los ensayos geofísicos MASW, se realizaron en 30 puntos del distrito de Juliaca para los suelos arenosos. Se contó con un filtro final de 110 pares ordenados de datos (Vs; N60); mediante el análisis de regresión potencial por el método de mínimos cuadrados donde se obtuvo la ecuación: Vs = 81.079*N600.2646; y un coeficiente de determinación R2:0.76. Esta ecuación fue puesta en análisis comparativo con las ecuaciones de las correlaciones de la literatura, en el cual se encontró una tendencia acorde a las mismas, lo que permitirá utilizarla con suelos afines a la región.The application of the standard penetration test (SPT) entails a high level of detail, it is also expensive, requires qualified labor for its execution and is time-consuming; Its use is recommended in sandy soils, restrictive in fine and plastic soils and not recommended in other types of soils. While in the multichannel analysis of surface waves (MASW) its execution is not restricted, it allows covering large areas in short times, however, it is an indirect method, which is why its application must be verified by drilling, obtaining samples, and high analytical criteria. In recent years, the implementation and improvement of soil prospecting techniques has made it possible to carry out studies of the relationship of said tests with different soil parameters. In the present, an empirical correlation was developed between the SPT geotechnical tests by means of the number of penetration resistance blows (N60) with the value of the shear wave velocities (Vs) of the MASW geophysical tests, these tests were carried out in 30 points in the city of Juliaca for sandy soils. There was a final filter of 110 ordered pairs of data (Vs; N60); Through the analysis of potential regression by the method of least squares, the equation was obtained: Vs = 81.079*N600.2646; of the determination coefficient R2:0.76, it was determined that the correlation is acceptable. This equation was put into analysis and comparison with the equations of the correlations of the literature, in which it was found in a trend according to them.
Tesis
47
Goudot, Guillaume. "Applications innovantes des ultrasons en pathologie vasculaire : utilisation de l'imagerie ultrarapide dans l'analyse de la rigidité artérielle et des ultrasons pulsés en thérapie Arterial stiffening assessed by ultrafast ultrasound imaging gives new insight into arterial phenotype of vascular Ehlers–Danlos mouse models Aortic wall elastic properties in case of bicuspid aortic valve Segmental aortic stiffness in bicuspid aortic valve patients compared to first-degree relatives Wall shear stress measurement by ultrafast vector flow imaging for atherosclerotic carotid stenosis Pulsed cavitational therapy using high-frequency ultrasound for the treatment of deep vein thrombosis in an in vitro model of human blood clot". Thesis, Sorbonne Paris Cité, 2018. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=2215&f=13951.
Pełny tekst źródła
48
Mamatsashvili, George. "Dynamics of perturbation modes in protoplanetary discs : new effects of self-gravity and velocity shear". Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5283.
Pełny tekst źródłaStreszczenie:
Protoplanetary discs, composed of gas and dust, usually surround young stellar objects and serve two main purposes: they determine the accretion of matter onto the central object and also represent sites of planet formation. The accretion proceeds through the transport of angular momentum outwards allowing the disc matter to fall towards the centre. A mechanism responsible for the transport can be turbulence, waves or other coherent structures originating from various instabilities in discs that could, in addition, play a role in the planet formation process. For an understanding of these instabilities, it is necessary to study perturbation dynamics in differentially rotating, or sheared media. Thus, this thesis focuses on new aspects in the perturbation dynamics in non-magnetised protoplanetary discs that arise due to their self-gravity and velocity shear associated with the disc’s differential rotation. The analysis is carried out in the framework of the widely employed local shearing box approximation. We start with 2D discs and then move on to 3D ones. In 2D discs, there are two basic perturbation types/modes – spiral density waves and vortices – that are responsible for angular momentum transport and that can also contribute to accelerating planet formation. First, in the linear regime, we demonstrate that the vortical mode undergoes large growth due to self-gravity and in this process generates density waves via shear-induced linear mode coupling phenomenon. This is noteworthy, because commonly only density waves are considered in self-gravitating discs. Then we investigate vortex dynamics in the non-linear regime under the influence of self-gravity by means of numerical simulations. It is shown that vortices are no longer well-organised and long-lived structures, unlike those occurring in non-self-gravitating discs. They undergo recurring phases (lasting for a few disc rotation periods) of formation, growth and eventual destruction. We also discuss the dust trapping capability of such transient vortices. Perturbation dynamics in 3D vertically stratified discs is richer, as there are more mode types. We first consider non-axisymmetric modes in non-self-gravitating discs and then only axisymmetric modes in the more complicated case when self-gravity is present. Specifically, in non-self-gravitating discs with superadiabatic vertical stratification, motivated by the recent results on the transport properties of incompressible convection, we show that when compressibility is taken into account, the non-axisymmetric convective mode excites density waves via the same shear-induced linear mode coupling mechanism mentioned above. These generated density waves transport angular momentum outwards in the trailing phase, and we suggest that they may aid and enhance the transport due solely to convection in the non-linear regime, where the latter becomes outward. In the final part of the thesis, we carry out a linear analysis of axisymmetric vertical normal modes in stratified self-gravitating discs. Although axisymmetric modes do not display shear-induced couplings, their analysis provides insight into how gravitational instabilities develop in the 3D case and their onset criterion. We examine how the structure of dispersion curves and eigenfunctions of 3D modes are influenced by self-gravity, which mode first becomes gravitationally unstable and thus determines the onset criterion and nature of the gravitational instability in stratified discs. We also contrast the more exact instability criterion obtained with our 3D model with that of density waves in 2D discs. Based on these findings, we discuss the origin of 3D behaviour of perturbations involving noticeable disc surface distortions, as seen in some numerical simulations of self-gravitating discs.
49
Louis, Stephen. "Continuer à irriguer quand les lacs-réservoirs de barrage souffrent de taux de sédimentation sévères - Recommandations d'amélioration de la gestion du principal canal d'irrigation alimenté par l'ouvrage répartiteur de Canneau (Haïti)". Doctoral thesis, Universite Libre de Bruxelles, 2019. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/288808.
Pełny tekst źródłaStreszczenie:
L’État haïtien, pour faire face à l’insécurité alimentaire que connaît sa population (à croissance rapide et à faible revenu), s’appuie particulièrement sur la Vallée du département de l’Artibonite qui constitue depuis toujours le véritable grenier agricole du pays, en fournissant, à elle seule, plus de 80% de la production rizicole nationale. Cette production agricole assure non seulement les besoins alimentaires de la population locale, mais également ceux particuliers des départements voisins (Ouest, Nord et Centre).L’irrigation de cette vaste plaine agricole (32400 ha de terres agricoles irrigables) est garantie, à plus de 75%, par le réseau d’irrigation établi en rive Gauche de l'ouvrage-partiteur de Canneau, alimenté par un Canal principal (CMRG) ayant un débit nominal de 40 m3/s.Néanmoins, ce Partiteur, source d’approvisionnement exclusive du CMRG, est lui-même régulé par le Barrage-réservoir de Péligre qui se trouve à 70 km plus en amont sur le fleuve de l’Artibonite. En termes hydrauliques, nos travaux ont d'abord examiné la situation du réservoir de Péligre. Alors qu'au moment de la construction il était initialement prévu d’y stocker 607 Mm3, il ne reste plus aujourd'hui qu'à peine 40% de cette capacité utile, en raison des dépôts sédimentaires qui se sont constitués année après année derrière le barrage.Cette sédimentation spectaculaire (due à l’érosion des bassins versants amont fort dégradés), combinée aux déficits pluviométriques, provoque en période d’étiage une rareté d’eau, des lâchers insuffisants et donc des déficits en eau utile envoyée en amont de ce Partiteur de Canneau. Cela impacte significativement le réseau d’irrigation aval, dont le CMRG. Nos travaux ont montré que la situation est d'autant plus critique que les débits eux-mêmes, en amont comme en aval du Partiteur, sont en fait très mal connus et devraient faire l'objet d'approches méthodologiques plus rigoureuses que celles déployées sur site actuellement.Aussi, face à ces constats, de nouvelles règles de distribution de l’eau s’imposent, pour continuer à irriguer et espérer obtenir un rendement agricole acceptable (souhaitable).Notre travail s'est ainsi donné pour objectif de contribuer à la mise en place des nouvelles règles de gestion de l’eau (répartition) au sein du réseau d’irrigation alimenté par le CMRG, pour continuer à fournir l’eau à l’irrigant en quantité acceptable (et connue). Cette amélioration de gestion a été envisagée à la fois en amont et en aval de ce réseau d’irrigation, particulièrement en ses différents nœuds-clés (Canal principal et Canal secondaire).La démarche méthodologique adoptée pour relever ce défi majeur s’appuie notamment sur un système d’information hydro-morpho-sédimentaire actualisé et de qualité. Il s’agit d’une base de données, riche en observations de hauteurs d’eau (lues aux stations limnimétriques), vitesses de surface au flotteur, champs de vitesse explorés au moyen d’un courantomètre et en données bathymétriques et granulométriques des tronçons des canaux étudiés, appréciées respectivement au moyen d’un GPS différentiel et du tamisage à sec.Les résultats fort encourageants obtenus permettent d'acquérir une meilleure compréhension du système et une amélioration particulière du réseau d’irrigation en rive gauche du Partiteur de Canneau. En s’appuyant sur les historiques de sédimentation du Lac-réservoir de Péligre (de 1960 à 2016), nous présentons un document de synthèse sur la sédimentation du Lac-réservoir de Péligre. Ce document met notamment en exergue le taux de sédimentation sévère de ce dernier (5.47 Mm3/an), qui continue d’augmenter encore aujourd’hui, ainsi que les conséquences de celui-ci sur les débits turbinés et la disponibilité de l’eau en amont du Partiteur de Canneau.Nous mettons également en évidence les formes irrégulières (Lit-non prismatique) des tronçons des canaux étudiés, via une vue axonométrique des profils en travers (issus de l’étude bathymétrique) des canaux d’irrigation en terre battue étudiés. Puis, nous présentons de manière détaillée le caractère très hétérogène des dépôts sédimentaires de ces derniers, à partir d’une analyse des représentations en Log-Probit des résultats du tamisage, construites au moyen du logiciel GrandPlots.En nous appuyant sur les mesures expérimentales des contraintes de Reynolds et des profils instantanés de vitesse (pris à intervalle de 64 ms), tirés de la base de données EPFL, nous avons montré qu’il faut absolument travailler dans les 18% inférieurs de la colonne d’eau (z/h<0.18) et en mode déficitaire, dans un écoulement turbulent comme celui-là, pour extraire de façon représentative et pertinente une pente expérimentale u*/, comme indicateur de u*.À l’issue d’un examen détaillé de la distribution verticale de la vitesse au canal secondaire FNE, nous validons un DMLWL (Dip-Modified-log-wake-law) à la fois en amont et en aval du réseau. Nous montrons que ceci permet de modéliser le Dip-phenomenon observé systématiquement au sein des profils explorés in situ. Nous proposons une relation entre le coefficient d’inégale répartition de la vitesse à la verticale αv (de Prony) et l’aspect ratio (W/h) pour tout le réseau d’irrigation étudié ;ceci afin d’obtenir une vitesse débitante (Ū), simplement à partir d’une prise de vitesse au flotteur, dans l’axe central d’écoulement.À partir des débits quantifiés à la section de référence du CMRG, via l’équation de continuité (Q=AŪ), nous fournissons un Abaque, diagramme à 3 entrées (débit (Qp), charge amont (H0) et ouverture de vanne (hv)), permettant aux vanniers de connaitre les débits au pont de fer correspondant aux différentes ouvertures de vanne et celui pour lequel le trop-plein (retour des eaux excédentaires vers le fleuve de l’Artibonite) commence à fonctionner.À l’égard des opérateurs locaux et gestionnaires du système, nous mettons enfin à disposition, des méthodes/outils simples et efficaces leur permettant de quantifier finement le débit au Canal principal en amont ainsi qu’au canal secondaire en aval, simplement à partir d’une mesure de hauteur d’eau (h) et de vitesse de surface au flotteur (Us).Doctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished
50
Baumgarten, Lars. "Gesteinsmechanische Versuche und petrophysikalische Untersuchungen – Laborergebnisse und numerische Simulationen". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-202612.
Pełny tekst źródłaStreszczenie:
Dreiaxiale Druckprüfungen können als Einstufenversuche, als Mehrstufenversuche oder als Versuche mit kontinuierlichen Bruchzuständen ausgeführt werden. Bei der Anwendung der Mehrstufentechnik ergeben sich insbesondere Fragestellungen hinsichtlich der richtigen Wahl des Umschaltpunktes und des optimalen Verlaufs des Spannungspfades zwischen den einzelnen Versuchsstufen. Fraglich beim Versuch mit kontinuierlichen Bruchzuständen bleibt, ob im Versuchsverlauf tatsächlich Spannungszustände erfasst werden, welche die Höchstfestigkeit des untersuchten Materials repräsentieren. Die Dissertation greift diese Fragestellungen auf, ermöglicht den Einstieg in die beschriebene Thematik und schafft die Voraussetzungen, die zur Lösung der aufgeführten Problemstellungen notwendig sind. Auf der Grundlage einer umfangreichen Datenbasis gesteinsmechanischer und petrophysikalischer Kennwerte wurde ein numerisches Modell entwickelt, welches das Spannungs-Verformungs-, Festigkeits- und Bruchverhalten eines Sandsteins im direkten Zug- und im einaxialen Druckversuch sowie in dreiaxialen Druckprüfungen zufriedenstellend wiedergibt. Das Festigkeitsverhalten des entwickelten Modells wurde in Mehrstufentests mit unterschiedlichen Spannungspfaden analysiert und mit den entsprechenden Laborbefunden verglichen.