A semi-analytical method of dynamic analysis, capable of predicting both the magnitude and pattern of earthquake induced deformations, is presented. The analysis is based on a modulus reduction approach which uses a reduced modulus to simulate the softening induced in soils during cyclic loading. The effects of the inertia forces developed during dynamic loading on the induced deformations are also included through an appropriate selection of the reduced modulus. The reduced modulus is utilized in a static stress-strain analysis to predict the magnitude and pattern of the deformations induced during earthquake loading. The appropriate modulus reduction is determined from laboratory tests on undisturbed soil samples. Three methods of computing a suitable post-cyclic modulus were investigated but only the cyclic strain approach, in which the modulus is determined from cyclic loading tests that duplicate the field stress conditions, yields reductions of sufficient magnitude to provide realistic estimates of earthquake induced deformations. The modulus reduction analysis was used to predict the deformations occurring during dynamic loading of a model tailings slope in a laboratory shaking table test and of the Upper San Fernando Dam during the earthquake of February, 1971. These studies showed that the modulus reduction analysis is capable of reproducing the dynamically induced deformations and that reductions in the modulus of up to 1000 times may be required. Unfortunately, limitations of the testing equipment and inadequacies in the available data required that the appropriate modulus reductions could not be determined entirely through laboratory and field investigations. Some assumptions were necessary in selecting the reduced modulus values used in the analyses. Although these case studies were, hence, unable to provide full verification of the proposed method, they do demonstrate the reliability and simplicity of the analysis as a method of assessing the performance of soil structures during earthquake loading. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

A hybrid method based on three-dimensional finite element idealization in the near field and a semi-analytic scheme using the principles of wave propagation in multilayered half space in the far field is proposed for dynamic soil-structure interaction analysis. It combines the advantages of both the numerical and analytical techniques. A structure resting on the surface or embedded in a multilayered soil-medium and subjected to vertically propagating plane waves is analyzed by using the method. An important aspect of the soil-structure interaction problem considered is the presence of waves scattered from the soil-structure interface and geometrical irregularities in the soil. The dynamic response of an embedded structure of rectangular cross section to a vertically propagating compressional pulse is solved as an example problem. The proposed method is verified by comparison of its predictions with those from a finite element procedure with absorbing boundaries, and from an analytical solution. The results from the hybrid method compare well with those from the other two, with closer correlation between the hybrid and analytical methods.

Vibratory rollers are commonly used for compaction of embankments and landfills. This task is time consuming and constitutes a significant part of most large construction and infrastructure projects. By improving the compaction efficiency, the construction industry would reduce costs and environmental impact. This research project studies the influence of the vibration frequency of the drum, which is normally a fixed roller property, and whether resonance can be utilized to improve the compaction efficiency. The influence of frequency on roller compaction has not before been studied but the concept of resonance compaction has previously been applied successfully in deep compaction of fills and natural deposits. In order to examine the influence of vibration frequency on the compaction of granular soil, small-scale compaction tests of sand were conducted under varying conditions with a vertically oscillating plate. Subsequently, full-scale tests were conducted using a vibratory soil compaction roller and a test bed of crushed gravel. The results showed that resonance can be utilized in soil compaction by vibratory rollers and plates and that the optimum compaction frequency from an energy perspective is at, or slightly above, the coupled compactor-soil resonant frequency. Since rollers operate far above resonance, the compaction frequency can be significantly reduced, resulting in a considerable reduction in fuel consumption, environmental impact and machine wear. The thesis also presents an iterative equivalent-linear method to calculate the frequency response of a vibrating foundation, such as a compacting plate or the drum of a roller. The method seems promising for predicting the resonant frequency of the roller-soil system and can be used to determine the optimum compaction frequency without site- and roller-specific measurements. / <p>QC 20160613</p>

The cyclic resistance of predominantly fine-grained soils has received considerable attention following ground and foundation failures at sites underlain by silt-rich soils during recent earthquakes. In several cases substantial ground deformation and reduced bearing capacity of silt soils has been attributed to excess pore pressure generation during cyclic loading. These field case studies are significant due to the occurrence of liquefaction related phenomena in soils that would be characterized as not susceptible to liquefaction using current geotechnical screening criteria. The most widely used of these criteria, the "Chinese Criteria" and its derivatives, are based solely on soil composition and they are essentially diagnostic tools that categorize the soil in a binary fashion as either liquefiable or non-liquefiable. The most significant limitations of these screening tools are that they fail to account for the characteristics of the cyclic loading. This investigation was undertaken to elucidate the potential for strain development in silts during cyclic loading, and to develop a practice-oriented procedure for evaluating the seismic performance of silts as a function of material properties, in situ stresses, and the characteristics of the cyclic loading. This dissertation presents the results of a multi-faceted investigation of the potential for seismically induced pore pressures and large strain development in silt soils. The primary focus of the research was on the synthesis of laboratory testing results on fine grained soils. Laboratory data from cyclic tests performed at Oregon State University and other universities formed the basis for enhanced screening criteria for potentially liquefiable silts. This data was supplemented with field data from sites at which excess pore pressure generation, liquefaction, and/or ground failures were observed during recent earthquakes. This investigation specifically addressed the behavior of silts during loading in cyclic triaxial tests due to the relative abundance of data obtained for this test. The data was used in conjunction with standard geotechnical index tests to enhance an existing energy based procedure for estimating excess pore pressure generation in silts. This pore pressure model can be used with the uncoupled, stress-based methods for estimating the post-cyclic loading volumetric strain developed in this investigation. The energy-based excess pore pressure model and empirical volumetric strain relationship were used to calibrate for applications involving silt soils a nonlinear, effective stress model for dynamic soil response (SUMDES). The SUMDES model was employed, along with the equivalent linear total stress model SHAKE, to estimate excess pore pressures generated at un-instrumented field sites that have exhibited evidence of liquefaction during recent earthquakes. A comparison of the SUMDES and SHAKE results highlighted the limitations of the latter model for simulating dynamic soil response at various levels of shaking and pore pressure response. The results of the SUMDES modeling at several well documented case study sites are presented in this dissertation. These comparisons are valuable for demonstrating the uncertainties associated with modeling of the effective stress behavior of silt during seismic loading. / Graduation date: 2005

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.

This study is comprised of three major parts. The first part involved the development of a multi-measurement, confined, free-free resonant column device. This device was developed to improve upon traditional manually excited, vacuum-confined, free-free methods. The device is capable of testing specimens with diameters up to 6-in., under confinements upwards of 50 psi. The device is composed of a seismic-source system, a data acquisition system and a specimen support and confinement system. The seismic source system is used to induce small-strain constrained compression waves, and longitudinal and torsional stress waves in the specimen. The data acquisition system is used to measure: (1) direct travel time of constrained compression waves, (2) longitudinal resonance in unconstrained compression, and (3) torsional resonance. From these measurements, constrained compression wave velocity, Vp, unconstrained compression wave velocity, Vc, and shear wave velocity, Vs, can be determined. With these wave velocities, small-strain, constrained modulus, Mmax, Young’s modulus, Emax, and shear modulus, Gmax can be determined. Poisson’s ratio is also calculated with the wave velocities. Finally, from the resonance measurements, small-strain material damping in unconstrained compression, DCmin, and in shear, DSmin, can be evaluated. The second part of this study involved verification tests with materials of known dynamic properties. The tests were performed with a manufactured aluminum specimen, ASTM graded Ottawa sand, and crushed rock aggregate base. The results compared well with previous results from similar tests. The third part of this study involved testing artificially cemented ASTM graded Ottawa sand. Cement contents (by weight) of 0.0, 0.5, 1.0 and 2.0%, were used to observe the effect of cementation with curing time at a constant confining pressure of 5 psi. The overall effect of cementation was: (1) a large increase in stiffness, and (2) an increase in material damping. The key effects related to cementation versus curing time are: (1) the increase in wave velocities are reasonably proportional to an increase in cement content up to a curing time of about 5 to 7 days, and (2) after a curing time of 5 to 7 days time the velocity increase with time seems to be similar for all cemented specimens. Additionally, the 2% cemented specimen was tested to observe the effect of confining pressure. The stiffness of this specimen was quite insensitive to confining pressure as was the material damping. / text

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Thesis (Ph. D.)--University of Missouri--Rolla, 2007. / "UTC R155." Title from PDF title screen. Includes bibliographical references (p. 130-135). Also available online.

Thesis (Ph. D.)--University of California, Davis, 1998. / Cover title. "September 1998." Includes bibliographical references.