Railway track stiffness (vertical track load divided by track deflection) is a basic parameter oftrack design which influences the bearing capacity, the dynamic behaviour of passing vehiclesand, in particular, track geometry quality and the life of track components. Track stiffness is abroad topic and in this thesis some aspects are treated comprehensively. In the introductionpart of the thesis, track stiffness and track stiffness measurements are put in their propercontext of track maintenance and condition assessment. The first aspect is measurement of track stiffness. During the course of this project, Banverkethas developed a new device for measurement of dynamic track stiffness called RSMV(Rolling Stiffness Measurement Vehicle). The RSMV is capable of exciting the trackdynamically through two oscillating masses above one wheelset. The dynamic stiffness is acomplex-valued quantity where magnitude is the direct relation between applied load anddeflection (kN/mm) and phase is a measure of deflection-delay by comparison with force. Thephase has partial relationship with damping properties and ground vibration. The RSMVrepeatability is convincing and both overall measurements at higher speeds (up to 50 km/h)and detailed investigations (below 10 km/h) can be performed. The measurement systemdevelopment is described in Paper A and B. The second aspect is evaluation of track stiffness measurements along the track from a trackengineering perspective. Actual values of stiffness as well as variations along the track areimportant, but cannot always answer maintenance and design related questions alone. InPaper D track stiffness is studied in combination with measurements of track geometryquality (longitudinal level) and ground penetrating radar (GPR). The different measurementsare complementary and a more reliable condition assessment is possible by the combinedanalysis. The relation between soft soils and dynamic track stiffness measurements is studiedin Paper C. Soft soils are easily found and quantified by stiffness measurements, in particularif the soft layer is in the upper part of the substructure. There are also possibilities to directlyrelate substructure properties to track stiffness measurements. Environmental vibrations areoften related to soft soils and partly covered in Paper C. One explanation of the excitationmechanism of train induced environmental vibrations is short waved irregular supportconditions. This is described in Paper E, where track stiffness was evinced to have normalvariations of 2 – 10 % between adjacent sleepers and variations up to 30 % were found. Anindicative way of finding irregular support conditions is by means of filtering longitudinallevel, which is also described in the paper. Train-track interaction simulation is used in PaperH to study track stiffness influence on track performance. Various parameters of trackperformance are considered, e.g. rail sectional moment, rail displacement, forces at wheel-railinterface and on sleepers, and vehicle accelerations. Determining optimal track stiffness froman engineering perspective is an important task as it impacts all listed parameters. The third aspect, efficient maintenance, is only partially covered. As track stiffness relates toother condition data when studied from a maintenance perspective, vertical geometricaldefects (longitudinal level and corrugation/roughness) are studied in paper F. The generalmagnitude dependency of wavelength is revealed and ways of handling this in conditionassessment are proposed. Also a methodology for automated analysis of a large set ofcondition data is proposed in Paper G. A case study where dynamic track stiffness,longitudinal level and ground penetrating radar are considered manifests the importance oftrack stiffness measurements, particularly for soil/embankment related issues. / QC 20100623

published_or_final_version / Civil Engineering / Master / Master of Philosophy

Topography effects, the modification of seismic motion by topographic features, have been long recognized to play a key role in elevating seismic risk. Site response, the modification of ground motion by near surface soft soils, has been also shown to strongly affect the amplitude, frequency and duration of seismic motion. Both topography effects and 1-D site response have been extensively studied through field observations, small-scale and field experiments, analytical models and numerical simulations, but each one has been studied independently of the other: studies on topography effects are based on the assumption of a homogeneous elastic halfspace, while 1-D site response studies are almost exclusively formulated for flat earth surface conditions. This thesis investigates the interaction between topographic and soil amplification, focusing on strong ground motions that frequently trigger nonlinear soil response. Recently, a series of centrifuge experiments tested the seismic response of single slopes of various inclination angles at the NEES@UCDavis facility, to investigate the effects of nonlinear soil response on topographic amplification. As part of this collaborative effort, we extended the search space of these experiments using finite element simulations. We first used simulations to determine whether the centrifuge experimental results were representative of free-field conditions. We specifically investigated whether wave reflections caused by the laminar box interfered with mode conversion and wave scattering that govern topographic amplification; and whether this interference was significant enough to qualitatively alter the observed amplification compared to free-field conditions. We found that the laminar box boundaries caused spurious reflections that affected the response near the boundaries; however its effect to the crest-to-free field spectral ratio was found to be insignificant. Most importantly though, we found that the baseplate was instrumental in trapping and amplifying waves scattered and diffracted by the slope, and that in absence of those reflections, topographic amplification would have been negligible. We then used box- and baseplate-free numerical models to study the coupling between topography effects and soil amplification in free-field conditions. Our results showed that the complex wavefield that characterizes the response of topographic features with non-homogeneous soil cannot be predicted by the superposition of topography effects and site response, as is the widespread assumption of engineering and seismological models. We also found that the coupling of soil and topographic amplification occurs both for weak and strong motions, and for pressure-dependent media (Nevada sand), nonlinear soil response further aggravates topographic amplification; we attributed this phenomenon to the reduction of apparent velocity that the low velocity layers suffer during strong ground motion, which intensifies the impedance contrast and accentuates the energy trapping and reverberations in the low strength surficial layers. We finally highlighted the catalytic effects that soil stratigraphy can have in topographic amplification through a case study from the 2010 Haiti Earthquake. Results presented in this thesis imply that topography effects vary significantly with soil stratigraphy, and the two phenomena should be accounted for as a coupled process in seismic code provisions and seismological ground motion predictive models.

This thesis consists of two major parts. In the first part, I monitor the temporal change of S-wave velocity in shallow soil layers using seismic data collected in an experiment at Panola Mt. Atlanta, GA, 2006. I use the cross correlation function to find the arrival time differences for different water levels, and then calculate the change of Rayleigh wave phase velocity according to different frequencies in the range 5 to 50 Hz. After that, I find a reference 1-D layered P and S-wave velocity model from the measured Rayleigh wave dispersion curve, and put 6 sets of Gaussian perturbations into the reference velocity structure to invert for the actual temporal change of velocity structure in the experiment. I find a clear increase of S-wave velocity in the water injection area, and the S-wave velocity gradually recovers to the initial value after we stop pumping water. In the second part, I analyze temporal changes in fault zone site response along the Karadere-Düzce branch of the North Anatolian Fault, starting 8 days before and ending 72 days after the 1999 Mw7.1 Düzce, Turkey, earthquake. The analysis involves comparisons of strong motion seismic records at station VO inside the Karadere fault and station FP about 300 m away from the fault. I compare all available seismic waveforms at these stations, including those generated by foreshocks, the mainshock, aftershocks and seismic noise, and cut them into 10 s windows with a 5 s overlap. Fourier amplitude spectra are computed for seismic data in each window, and the average amplitude spectra for the two horizontal components are used to obtain the spectral ratio for each on/off fault pair of seismic records. The spectral ratios are smoothed over every 10 points in the frequency domain (0.5 Hz). The results show a shift of the spectral peak to lower frequencies during the main shock. The peak frequency reduces from 4.3 Hz several days before the main shock to 2.9 Hz (67.4% of the pre mainshock value) right after the mainshock. It quickly recovers to 3.8 Hz (64% recovery of the dropped value) after a day, and then gradually recovers to 4.0 Hz (79% recovery of the dropped value) after 72 days. I also compare the results from all the seismic data including direct S-wave, S coda waves and seismic noise and from coda waves only and find that the results from coda waves which are generally less scattered than those from all the data, and show lower amplitude of spectra ratio with higher peak frequencies. The observations suggest a nonlinear behavior of the fault zone material under strong ground motion of nearby major earthquakes. Finally I attempt to link the two parts by identifying their implications for the nonlinear site effects.

The site investigation phase plays a vital role in any foundation design where inadequate characterisation of the subsurface conditions may lead to either a significantly over designed foundation that is not cost-effective, or an under-designed foundation, which may result in foundation failure. As such, the scope of an investigation should be dependent on the conditions at the site and the importance of the structure. However, it is common for the expense dedicated to the site investigation to be a fraction of the total cost of the project, and is typically determined by budget and time constraints, and the experience and judgement of the geotechnical engineer. However, additional site investigation expenditure or sampling is expected to reduce the financial risk of the design by reducing the uncertainties in the geotechnical system and protecting against possible foundation failures. This research has quantified the relative benefits of undertaking site investigations of increased and differing scope. This has been achieved by simulating the design process to yield a foundation design based on the results of a site investigation. Such a design has been compared to an optimal design that utilises the complete knowledge of the soil, which has only been possible due to the use of simulated soils. Comparisons between these two design types indicate the performance of the site investigation to accurately or adequately characterise the site conditions. Furthermore, the design based on the results of the site investigation have been analysed using the complete knowledge of the soil. This yields a probability of failure and, therefore, has been included in a risk analysis where the costs associated with the site investigation have been measured against the financial risk of the design. As such, potential savings in financial risk for increased site investigation expenditure have been subsequently identified. A Monte Carlo analysis has been used in this research to incorporate the uncertainties in the foundation design process. Uncertainties have been included due to soil variability; sampling errors; measurement and transformation model errors; and errors related to the use of a simplified foundation response prediction method. The Monte Carlo analysis has also provided the means to obtain results in a probabilistic framework to enable reliability and risk analyses. Computer code has been specifically developed with an aim to: generate a simulated soil that conforms to the variability of soil properties; simulate a site investigation to estimate data for a foundation design; simulate the design of a foundation and conduct a reliability and risk analysis of such a design. Results indicate that there are significant benefits to be derived from increasing the scope of a site investigation in terms of the risk and reliability of the foundation design. However, it also appears that an optimal site investigation scope or expenditure exists where additional expenditure leads to a design with a higher financial risk due to the increased cost of the site investigation. The expected savings in terms of financial risk are significant when compared to the increased investigation cost. These results will assist geotechnical engineers in planning a site investigation in a more rational manner with knowledge of the associated risks. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1255275 / Thesis(Ph.D.) -- School of Civil and Environmental Engineering, 2006

The site investigation phase plays a vital role in any foundation design where inadequate characterisation of the subsurface conditions may lead to either a significantly over designed foundation that is not cost-effective, or an under-designed foundation, which may result in foundation failure. As such, the scope of an investigation should be dependent on the conditions at the site and the importance of the structure. However, it is common for the expense dedicated to the site investigation to be a fraction of the total cost of the project, and is typically determined by budget and time constraints, and the experience and judgement of the geotechnical engineer. However, additional site investigation expenditure or sampling is expected to reduce the financial risk of the design by reducing the uncertainties in the geotechnical system and protecting against possible foundation failures. This research has quantified the relative benefits of undertaking site investigations of increased and differing scope. This has been achieved by simulating the design process to yield a foundation design based on the results of a site investigation. Such a design has been compared to an optimal design that utilises the complete knowledge of the soil, which has only been possible due to the use of simulated soils. Comparisons between these two design types indicate the performance of the site investigation to accurately or adequately characterise the site conditions. Furthermore, the design based on the results of the site investigation have been analysed using the complete knowledge of the soil. This yields a probability of failure and, therefore, has been included in a risk analysis where the costs associated with the site investigation have been measured against the financial risk of the design. As such, potential savings in financial risk for increased site investigation expenditure have been subsequently identified. A Monte Carlo analysis has been used in this research to incorporate the uncertainties in the foundation design process. Uncertainties have been included due to soil variability; sampling errors; measurement and transformation model errors; and errors related to the use of a simplified foundation response prediction method. The Monte Carlo analysis has also provided the means to obtain results in a probabilistic framework to enable reliability and risk analyses. Computer code has been specifically developed with an aim to: generate a simulated soil that conforms to the variability of soil properties; simulate a site investigation to estimate data for a foundation design; simulate the design of a foundation and conduct a reliability and risk analysis of such a design. Results indicate that there are significant benefits to be derived from increasing the scope of a site investigation in terms of the risk and reliability of the foundation design. However, it also appears that an optimal site investigation scope or expenditure exists where additional expenditure leads to a design with a higher financial risk due to the increased cost of the site investigation. The expected savings in terms of financial risk are significant when compared to the increased investigation cost. These results will assist geotechnical engineers in planning a site investigation in a more rational manner with knowledge of the associated risks. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1255275 / Thesis(Ph.D.) -- School of Civil and Environmental Engineering, 2006

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.

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.

Ensaios de penetração dinâmica são ferramentas de investigação geotécnica de fácil execução e baixo custo. Estas características tornaram o ensaio SPT na técnica de investigação mais utilizada em diversos países como Canadá, Estados Unidos, Japão e principalmente, no Brasil. Em contrapartida, a penetração dinâmica de amostradores produz um complexo mecanismo de reação do solo, função da energia entregue ao sistema e da capacidade de absorção desta energia pelo próprio solo. Na prática de engenharia, este mecanismo é simplificado através do uso de abordagens empíricas. Pesquisas na década de 1970, realizadas por Schmeertmmann & Palacius (1979) e Schmertmmann (1979), avaliaram a energia inserida no sistema haste-amostrador objetivando a padronização do ensaio SPT para diferentes equipamentos e procedimentos. Pesquisas recentes de interpretação do ensaio utilizam conceitos de conservação de energia e trabalho realizado pelo amostrador ao penetrar no solo, visando equacionar a resistência mobilizada (eg. Oderebrecht, 2003; Odebrecht et al, 2005; Schnaid, 2005). Na presente pesquisa, são utilizados os conceitos de conservação de energia, associados com equações de equilíbrio dinâmico e com a teoria de expansão de cavidades (Vésic, 1972) para desenvolver uma rotina de simulação numérica capaz de modelar os principais mecanismos de reação do solo devido cravação de um amostrador. A partir da validação da rotina de simulação numérica para ensaios dinâmicos de distintas geometrias (ensaios SPT, ILPT, NALPT e RLPT), avalia-se a variabilidade da energia entregue ao solo devido às diferenças de compacidade do solo, eficiência do golpe, geometria do martelo, tipo e comprimento da composição de hastes. Destas simulações, é possível observar as diferenças de resultados entre ensaios de distintas geometrias de martelo e composição de hastes, concluindo-se que pequenas variações geométricas produzem diferenças no índice de resistência à penetração. Como conseqüência, sugere-se que a interpretação dos resultados depende de um método racional de análise capaz de incorporar estes efeitos à estimativa de propriedades de comportamento de solos. Na identificação dos mecanismos de ruptura para solos de diferentes compacidades foram desenvolvidas duas metodologias que permitem estimar a resistência ao cisalhamento de solos granulares a partir do índice de resistência à penetração medida em ensaios de penetração dinâmica. A primeira metodologia utiliza a rotina de simulação numérica desenvolvida através de uma análise do Problema do valor inverso, enquanto a segunda proposta utiliza os pressupostos do Teorema de Buckingham no estabelecimento de uma solução analítica que permita estimar o ângulo de atrito de pico de materiais granulares. As duas alternativas foram validadas através de estudo de casos, permitindo concluir que as soluções produzem estimativas de ângulo de atrito realistas, de mesma ordem de magnitude que outras abordagens difundidas no meio técnico e compatíveis com resultados de ensaios de campo e laboratório. / Dynamic penetration tests are simple, economic and easily performed geotechnical investigation tools. Due to these general characteristics, the test has been used systematically in many countries such as Canada, United States, Japan and Brazil. Despite the attractive conditions of performing a simple test, dynamic penetration of a any tool into a soil mass produces a complex soil reaction mechanism that depends on the energy delivered to the soil, as well as the capability of the soil to absorb this energy. Given this complexity a simple approach of interpreting the test by using empirical correlations has prevailed. In 1970, Schmeertmmann & Palacius (1979) and Schmertmmann (1979) develop the first rational methodology to compute the energy delivered to the rod-sampler system that has been incorporated to engineering practice by normalizing different practices in terms of a reference energy. Most recent researches of SPT test interpretation make uses of energy concepts and work to compute the mobilized soil-resistance due to the sampler penetration (e.g. Oderebrecht, 2003; Odebrecht et al, 2005; Schnaid, 2005). In present research these recent approaches are extended through the use of energy concepts associated with dynamic equilibrium equations and cavity expansion theory (Vésic, 1972). Constitutive equations have been incorporated to a numerical simulation routine able to reproduce the some of the most important processes of soil reaction during dynamic in cohesionless soil. The model validation for different dynamic penetration test geometries (SPT, ILPT, NALPT and RLPT) enabled the energy delivered to soil to be evaluated and the effects of soil density, blow efficiency, hammer geometry, rod type and length to be assessed. From a number of simulations, it was possible to describe the differences related typical geometrical changes (i.e. hammer length, rod cross section and length). Conclusions from the analysis are that small geometrical changes in hammer and rod characteristics - typically observed in different SPT practices - produce differences into the measured blow count. As consequence, it is suggested that interpretation of dynamic penetration test results will depend on a model capable of incorporating all these effects when attempting to derive soil constitutive parameters. This is one of the outputs of the present study that lead to the development of two rational methodologies to assess the internal friction angle of cohesionless soils from dynamic penetration blow count. The first one uses the numerical simulation routine as a Inverse Boundary Value problem while the second one uses the Buckingham’s Theorem to develop an analytical equations that correlates the N-SPT with the soil shear strength. Both methodologies have been validated by a series of case studies designed to demonstrate that the proposed solution produces friction angle values of the same order of magnitude of other approaches and compatible to measurements produced by laboratory and in situ tests.

Ensaios de penetração dinâmica são ferramentas de investigação geotécnica de fácil execução e baixo custo. Estas características tornaram o ensaio SPT na técnica de investigação mais utilizada em diversos países como Canadá, Estados Unidos, Japão e principalmente, no Brasil. Em contrapartida, a penetração dinâmica de amostradores produz um complexo mecanismo de reação do solo, função da energia entregue ao sistema e da capacidade de absorção desta energia pelo próprio solo. Na prática de engenharia, este mecanismo é simplificado através do uso de abordagens empíricas. Pesquisas na década de 1970, realizadas por Schmeertmmann & Palacius (1979) e Schmertmmann (1979), avaliaram a energia inserida no sistema haste-amostrador objetivando a padronização do ensaio SPT para diferentes equipamentos e procedimentos. Pesquisas recentes de interpretação do ensaio utilizam conceitos de conservação de energia e trabalho realizado pelo amostrador ao penetrar no solo, visando equacionar a resistência mobilizada (eg. Oderebrecht, 2003; Odebrecht et al, 2005; Schnaid, 2005). Na presente pesquisa, são utilizados os conceitos de conservação de energia, associados com equações de equilíbrio dinâmico e com a teoria de expansão de cavidades (Vésic, 1972) para desenvolver uma rotina de simulação numérica capaz de modelar os principais mecanismos de reação do solo devido cravação de um amostrador. A partir da validação da rotina de simulação numérica para ensaios dinâmicos de distintas geometrias (ensaios SPT, ILPT, NALPT e RLPT), avalia-se a variabilidade da energia entregue ao solo devido às diferenças de compacidade do solo, eficiência do golpe, geometria do martelo, tipo e comprimento da composição de hastes. Destas simulações, é possível observar as diferenças de resultados entre ensaios de distintas geometrias de martelo e composição de hastes, concluindo-se que pequenas variações geométricas produzem diferenças no índice de resistência à penetração. Como conseqüência, sugere-se que a interpretação dos resultados depende de um método racional de análise capaz de incorporar estes efeitos à estimativa de propriedades de comportamento de solos. Na identificação dos mecanismos de ruptura para solos de diferentes compacidades foram desenvolvidas duas metodologias que permitem estimar a resistência ao cisalhamento de solos granulares a partir do índice de resistência à penetração medida em ensaios de penetração dinâmica. A primeira metodologia utiliza a rotina de simulação numérica desenvolvida através de uma análise do Problema do valor inverso, enquanto a segunda proposta utiliza os pressupostos do Teorema de Buckingham no estabelecimento de uma solução analítica que permita estimar o ângulo de atrito de pico de materiais granulares. As duas alternativas foram validadas através de estudo de casos, permitindo concluir que as soluções produzem estimativas de ângulo de atrito realistas, de mesma ordem de magnitude que outras abordagens difundidas no meio técnico e compatíveis com resultados de ensaios de campo e laboratório. / Dynamic penetration tests are simple, economic and easily performed geotechnical investigation tools. Due to these general characteristics, the test has been used systematically in many countries such as Canada, United States, Japan and Brazil. Despite the attractive conditions of performing a simple test, dynamic penetration of a any tool into a soil mass produces a complex soil reaction mechanism that depends on the energy delivered to the soil, as well as the capability of the soil to absorb this energy. Given this complexity a simple approach of interpreting the test by using empirical correlations has prevailed. In 1970, Schmeertmmann & Palacius (1979) and Schmertmmann (1979) develop the first rational methodology to compute the energy delivered to the rod-sampler system that has been incorporated to engineering practice by normalizing different practices in terms of a reference energy. Most recent researches of SPT test interpretation make uses of energy concepts and work to compute the mobilized soil-resistance due to the sampler penetration (e.g. Oderebrecht, 2003; Odebrecht et al, 2005; Schnaid, 2005). In present research these recent approaches are extended through the use of energy concepts associated with dynamic equilibrium equations and cavity expansion theory (Vésic, 1972). Constitutive equations have been incorporated to a numerical simulation routine able to reproduce the some of the most important processes of soil reaction during dynamic in cohesionless soil. The model validation for different dynamic penetration test geometries (SPT, ILPT, NALPT and RLPT) enabled the energy delivered to soil to be evaluated and the effects of soil density, blow efficiency, hammer geometry, rod type and length to be assessed. From a number of simulations, it was possible to describe the differences related typical geometrical changes (i.e. hammer length, rod cross section and length). Conclusions from the analysis are that small geometrical changes in hammer and rod characteristics - typically observed in different SPT practices - produce differences into the measured blow count. As consequence, it is suggested that interpretation of dynamic penetration test results will depend on a model capable of incorporating all these effects when attempting to derive soil constitutive parameters. This is one of the outputs of the present study that lead to the development of two rational methodologies to assess the internal friction angle of cohesionless soils from dynamic penetration blow count. The first one uses the numerical simulation routine as a Inverse Boundary Value problem while the second one uses the Buckingham’s Theorem to develop an analytical equations that correlates the N-SPT with the soil shear strength. Both methodologies have been validated by a series of case studies designed to demonstrate that the proposed solution produces friction angle values of the same order of magnitude of other approaches and compatible to measurements produced by laboratory and in situ tests.