<p> Near surface soils can greatly influence the amplitude, duration, and frequency content of ground motions. The amount of their influence depends on many factors, such as the geometry and engineering properties of the soils and underlying bedrock, as well as the earthquake source mechanism and travel path. Building codes such as the 2012 International Building Code (IBC) define six site categories for seismic design of structures, which are based on the sites defined by the National Earthquake Hazards Reduction Program (NEHRP). Site categories A, B, C, D, and E are defined by the time averaged shear wave velocity over the top 30 meters of the soil deposit. Site category F is defined as sites that include liquefiable or sensitive soils, as well as sites with more than 3 meters (10 ft) of peat or highly organic clays, more than 7.5 meters (25 ft) of soil with PI > 75, and more than 37 meters (120 ft) of soft to medium stiff clays. The IBC specifies simplified procedures to calculate design spectra for NEHRP sites A through E, and requires a site specific investigation for NEHRP F sites. However, established procedures for performing the required site specific investigations for NEHRP F sites are limited. </p><p> The objective of this research is to develop a simplified procedure to estimate design spectra for non-liquefiable NEHRP F sites, specifically sites with organic soils, highly plastic soils, and deep soft soil deposits. The results from this research will directly affect US practice by developing much needed guidelines in this area. </p><p> There is little empirical data on the seismic response of non-liquefiable NEHRP F sites. As a result, this study focused on generating data from site response analyses. To capture the variability of ground motions, this study selected five base case scenarios according to tectonic environments and representative cases encountered in common US practice. Suites of ground motions for each scenario were created by collecting ground motions from online databases. Some of the ground motions were scaled and others were spectrally matched to their respective target response spectra. Fifteen different NEHRP E and F sites were created for the site response analyses. Seven of the sites are based on actual sites from the San Francisco Bay Area, New York City, Ottawa, Canada, Guayaquil, Ecuador, and Hokkaido, Japan. The other eight sites are variations of the seven base case sites. This study conducted a total of 14,541 site response analyses using a well documented site response analysis program. </p><p> This study then developed a simplified model to estimate response spectra for non-liquefiable NEHRP F sites. The simplified model was developed in two stages. In the first stage, the results for each site were regressed separately against the ground motion intensity to estimate the effect of the ground motion scenario. In the second stage, the site specific coefficients calculated from the first stage were regressed against site properties to determine their site dependence. These two parts were then combined to form the final model. The simplified model was validated against a separate database than the one used to develop it. This validation database consisted of 24 effective stress nonlinear site response analyses for three sites and eight ground motion scenarios. </p><p> The simplified model developed in this study does not replace a site response analysis, but rather augments it. It is hoped that the results of this dissertation will help practicing engineers gain a better understanding of their site before conducting site response analyses</p>

abstract: The geotechnical community typically relies on recommendations made from numerical simulations. Commercial software exhibits (local) numerical instabilities in layered soils across soil interfaces. This research work investigates unsaturated moisture flow in layered soils and identifies a possible source of numerical instabilities across soil interfaces and potential improvement in numerical schemes for solving the Richards' equation. The numerical issue at soil interfaces is addressed by a (nonlinear) interface problem. A full analysis of the simplest soil hydraulic model, the Gardner model, identifies the conditions of ill-posedness of the interface problem. Numerical experiments on various (more advanced and practical) soil hydraulic models show that the interface problem can also be ill-posed under certain circumstances. Spurious numerical ponding and/or oscillations around soil interfaces are observed consequently. This work also investigates the impact of different averaging schemes for cell-centered conductivities on the propensity of ill-posedness of the interface problem and concludes that smaller averaging conductivities are more likely to trigger numerical instabilities. In addition, an agent-based stochastic soil model, with hydraulic properties defined at the finite difference cell level, results in a large number of interface problems. This research compares sequences of stochastic realizations in heterogeneous unsaturated soils with the numerical solution using homogenized soil parameters. The mean of stochastic realizations is not identical to the solution obtained from homogenized soil parameters. / Dissertation/Thesis / Doctoral Dissertation Applied Mathematics 2017

Tied-back retaining walls frequently fail during earthquakes. Such failures are usually characterized by large displacements of the retaining wall and subsidence of the backfill. Often these failures result in extensive damage to the tied-back wall system and to adjoining structures and lifeline facilities. Whereas the seismic behavior of gravity retaining walls has been investigated in detail and procedures are now available for the seismic design of gravity retaining walls, very little analytical or experimental work has been reported on the behavior of tied-back retaining walls when they are subjected to seismic loads. In this research, a limit equilibrium method is used to analyze the seismic behavior of tied-back retaining walls. The analytical approach is calibrated against results from shake table tests on aluminium walls retaining a dry cohesionless soil. The shake table experiments were performed at the State University of New York at Buffalo seismic simulator facility. The analytical and the experimental study indicate the tremendous influence of anchorage systems on the performance of tied-back retaining walls during earthquakes. Based on the results of these studies, a procedure is proposed for the design of tied-back retaining walls in seismically active regions. The main thrust of the proposed seismic design procedure is in improving the anchorage capacity of tied-back retaining walls.

The deformability and strength properties of jointed rock masses are two of the fundamental parameters needed for the design and performance estimation of rock structures. Due to the presence of complicated minor discontinuity patterns (joints, bedding planes etc.), jointed rock masses show anisotropic and scale (size) dependent mechanical properties. At present, satisfactory procedures are not available to estimate anisotropic, scale dependent mechanical properties of jointed rock. Because of the statistical nature of joint geometry networks in rock masses, the joint patterns should be characterized statistically. The available joint geometry modeling schemes are reviewed. One of these schemes is used in this dissertation to generate actual joints in rock blocks. Three dimensional distinct element code (3DEC), which is used to perform stress analyses on jointed rock blocks in this study, is introduced and its shortcoming is identified. To overcome the shortcoming of 3DEC, a new technique is developed by introducing fictitious joints into rock blocks. Concerning the introduced fictitious joints, their geometry positions are mathematically determined; the representative mechanical properties for them found at 2D level are reviewed and verified at 3D level. By using the new technique, the deformation and strength properties of the rock blocks with many different joint configurations are found. Then effects of joint geometry parameters on the mechanical properties of jointed rock blocks are investigated. It is found that the joint geometry patterns have significant influences on the mechanical properties of rock blocks. All the joint geometry parameters are then integrated into fracture tensor. The relationships between the mechanical properties of jointed rock blocks and the fracture tensor parameters (its first invariant and directional component) are investigated. The possibility of obtaining the equivalent continuum behavior (REV properties) of jointed rock blocks is explored by using the aforementioned relationships. Finally, based on the research results, a new 3D constitutive model for jointed rock masses is developed to describe their pre-failure behavior. The constitutive model includes the effects of joints in terms of fracture tensor components and it shows the anisotropic and scale dependent natures of jointed rock masses.

This study presents the results of laboratory-scale experimental, analytical and numerical investigations on the sealing performance of crushed tuff concrete plugs in the welded brown unit of the Apache Leap tuff. Included are experimental studies of the bond strength, of the hydraulic conductivity, and of geochemical interactions between cement and the crushed tuff aggregate. The bond strength is measured by means of a total of 37 push-out tests on concrete borehole seals emplaced in hollow cylinders of welded tuff. Lateral stress is applied to 17 rock cylinders during push-out testing. Results are presented of an extensive finite element analysis of the stress distribution during push-out testing. Particular attention is paid to tensile zones in the plug and the host rock. Geochemical interaction analysis includes tests for alkali-silica reaction between the cement and crushed tuff aggregate. ASTM standard tests for the determination of alkali-silica reactivity of aggregates, in addition to uranyl acetate staining test have been performed. Hydraulic conductivity tests include constant head tests on plugged tuff cylinders and falling head tests on fractures induced by push-out testing along the plug/rock interface. The falling head tests have been conducted after the plugs were left to dry for two years in a laboratory environment. The main conclusion from the analysis of push-out tests is that high tensile stresses develop in plugs with a modulus ratio of 1.09 and length-to-diameter ratio of 1. Application of lateral stress to rock cylinders reduces the volume of plug under tension. Results of tests on alkali-silica reactivity indicated that Apache Leap tuff reacts with the alkalies in cement and expand. Replacement of cement 33% by weight with low-calcium Class F fly ash reduces the expansion 50%. Hydraulic conductivity of concrete plug and plug/rock interface interpreted from constant head tests is in the range of 10⁻¹⁰ cm/s. Hydraulic conductivity of fractures along the interface decreased from 10⁻² cm/s to 10⁻⁶ cm/s upon wetting of the concrete, due to the expansion of the cement.

<p> Since the late eighties, an ever increasing number of American craft breweries have opened up across the United States. Although the industry has a relatively high success rate, there are still a number of craft breweries that fail. As craft brewing is an inherently location based business, the sites selected for new brewery locations are important to that business&rsquo;s success. This research aims to examine how geodemographic information plays a role in strategic location decisions for craft breweries. By building a consumer profile for Phoenix craft brewery customers and comparing the results to the actual demographics of trade areas surrounding craft breweries, we begin to get a picture of geodemographics role in the site selection process. The research looks specifically at two locations; Bad Water Brewing Company and a site they are interested in acquiring. An analysis is performed to compare the geodemographic and behaviors of craft beer consumers in Phoenix, Arizona and those of the Bad Water Brewing location and their potential new site. This analysis ultimately results in intelligent business information related to location. The information compiled in this study can be used to make informed site selection decisions.</p>

Accurate estimates of soil moisture are necessary to predict evapotranspiration, runoff, infiltration, and groundwater recharge and, through these variables, weather, climate, and fire and flood frequencies. This dissertation is motivated by the need to estimate soil water content from remotely sensed passive microwave emission. Two different approaches are taken: (1) improved modeling of the microwave emission from the land surface; and (2) measurements of the average dielectric properties of the soil media and vegetation canopies. Consequently, the first part of the dissertation describes how a stratified dielectric model of the microwave emission from the soil was extended to take into account the effects of vegetation. The model parameters were calibrated using observed data and a robust optimization routine. However, the availability of measurements of some of these parameters, particularly the profile of dielectric permittivity of the canopy, would facilitate a more complete evaluation of the accuracy of the extended microwave emission model. The second part of this dissertation describes progress towards the development of a technique to measure the dielectric of vegetation canopies. This technique is based on gated time domain transmission measurements through the substance of interest. Preliminary studies carried out using soils with varying salinity and water content and vegetation show (1) an unexpected response of the signal to saline soils, and (2) a possible dielectric signature of the onset of stress in plant stems.

This thesis develops and applies seismic waveform tomography to solve the unique problem of imaging complicated shallow sub-structures with high resolution. Shallow sub-structures are commonly characterized by seismic reflection/refraction imaging, georadar and seismic travel time tomography (e.g., Steeples, 1998; Carcione et al., 2000 and Azaria, 2002). Their resolving power or applicability is often limited. In contrast, waveform tomography, a full wave field inversion technique, resolves sub-structures at a resolution that is a fraction of the illuminating wavelengths. Forward modeling in waveform tomography is based on a finite difference solution to the acoustic wave equation in the space-frequency domain. During inversion for model parameters, the technique efficiently calculates the gradient of a misfit function with respect to model parameters by correlating back-propagated and forward modeled wave fields, avoiding the forbidding task of explicitly computing Frechet kernels. Part of this study compares travel time and waveform tomography in a synthetic cross-well test. The two tomographic approaches are found to be complementary if data contains no significant low frequency spectra. I then apply waveform tomography to two datasets from a ground water contamination site at the Hill Air Force Base (HAFB) to sample formation heterogeneities and to map the 3D geometry of a buried paleo-channel where DNAPLs (Dense Non-Aqueous Phase Liquids) were dumped. The first is a VSP-surface seismic experiment. The final velocity model from waveform tomography applied to the VSP dataset generally correlates well with lithology logs, depth migrated 2D/3D reflection data and a velocity model from 3D travel time tomography. Large velocity variations vertically and laterally (200m/s) occur in a distance as short as &sim;1m. The model is interpreted geologically and petrologically. Scale features down to &sim;1.5m were recovered. I then apply waveform tomography to 45 2D seismic profiles extracted from a 3-D surface seismic experiment at HAFB, and recover the 3D geometry of a buried paleo-channel acting as a trap for DNAPLs. By combining the identified cross-sectional geometry, the 3D geometry of the channel is reconstructed. The subsurface map could be used to plan injection/extraction well placements with good precision and low cost in the on-going ground water remediation program.

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