No description available.

No description available.

On August 15, 2007, Pisco, Peru was hit by an earthquake of Magnitude (Mw) = 8.0 which triggered multiple liquefaction induced lateral spreads. The subduction earthquake lasted for approximately 100 seconds and showed a complex rupture. From the geotechnical perspective, the Pisco earthquake was significant for the amount of soil liquefaction observed. A massive liquefaction induced seaward displacement of a marine terrace was observed in the Canchamana complex. Later analysis using the pre- and post-earthquake images showed that the lateral displacements were concentrated only on some regions. Despite the lateral homogeneity of the marine terrace, some cross-sections showed large displacements while others had minimal displacements. The detailed documentation of this case-history makes it an ideal case-study for the determination of the undrained strength of the liquefied soils; hence, the main objective of this research is to use the extensive data from the Canchamana Slide to estimate the shear strength of the liquefied soils. In engineering practice, the undrained strength of liquefied soil is typically estimated by correlating SPT-N values to: 1) absolute value of residual strength, or 2) residual strength ratio. Our research aims to contribute an important data point that will add to the current understanding of the residual strength of liquefied soils. / Master of Science

In the natural world, animals encounter terrestrial environments that range from stiff to compliant. Terrestrial locomotion across natural surfaces is highly complex, as animals must overcome substrate heterogeneity to maintain locomotor performance essential for survival (e.g., catching prey, escaping predators). Within these environments, natural substrates such as sand, gravel and cobbles, are known as granular media: a collection of discrete particles varying in material properties and behaviors when exposed to forces of different magnitude. On a single step, granular media alternates between solid and fluid-like states with potentially drastic consequences on running performance. Additionally, granular substrates at different inclinations are ubiquitous in natural environments, such as sand dunes in the desert. At the angle of repose—the maximum angle providing sand dunes their typical shape—granular media will fluidize with the slightest stress, rendering running at these angles extremely challenging. Unlike locomotion through fluids (e.g., swimming and flying), governed by the Navier-Stokes equations, how foot kinematics instigate state changes on granular media is still poorly understood, yet it is critically important for survival. The goal of my dissertation is to determine how foot use affects foot-ground interactions on granular media, with a particular focus on incline locomotion. The objectives of my dissertation are threefold: evaluate the effects of granular inclines on 1) performance and above-surface limb and foot kinematics, 2) sub-surface foot kinematics, and 3) the dynamics of foot-ground interactions using computational simulations. To fulfill these objectives, I examined three lizard species: a sand specialist (Callisaurus draconoides), a desert generalist (Crotaphytus bicinctores), and a fluid specialist (Basiliscus vittatus), selected because they have similarly shaped feet, so that differences detected among performance are due to foot kinematics rather than morphology. I ran these lizard species on a level and inclined granular trackway, while videorecording them at 500 fps using a high-speed video camera (light video) and a bi-planar high-speed fluoroscopy system (X-ray video) for the above-surface kinematics and the subsurface kinematics, respectively. Running trials were used to quantify running speed, basic stride, foot impact, and sub-surface foot kinematics, to implement on computational simulations of foot-shaped intruders entering a volume of particles to quantify force response at the particle scale. Sand specialists not only outperformed non-specialists on the incline, but maintained running speed compared to the level despite presenting some foot slip. While no significant differences across species were found for basic stride and impact kinematics, only sand specialists shifted foot intrusion angle into incline granular media to angles close to perpendicular to the substrate. At the subsurface, sand specialists maintained a stiffer foot similar to generalists, and intruded their feet shallower similar to fluid specialists. However, only sand specialists maintained toe spacings close to 6 mm on level and incline, similar to a study on intruder spacings showing peak force generation. The ground force response exhibited by the sand specialist lizard foot model revealed that by hitting the particles fast (0.7 m/s) and shallow, almost perpendicular to the substrate, toe first, with stiff feet, and toe spacings close to 6 mm, sand specialists are likely taking advantage of the inertial behavior of the particles at the angle of repose. Essentially, by paddling through the substrate’s fluid-like behaving surface, sand specialists run significantly faster than fluid specialists and generalists. My dissertation demonstrates the significance of surface and subsurface kinematics strategies to understand foot-ground interactions, especially on angled yielding substrates, contributing with knowledge to the terradynamics field and elucidating significant applications in bioengineering, bioinspiration and robotics. / Biology

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To aid in forest management, various approaches using Geographic Information Systems (GIS) have been used to identify the spatial distributions of relative slope instability. This study presents a systematic evaluation of three common slope instability modeling approaches applied in the Blue Ridge Mountains of Virginia. The modeling approaches include the Qualitative Map Combination, Bivariate Statistical Analysis, and the Shallow Landsliding Stability (SHALSTAB) model. Historically, the qualitative nature of the first model has led to the use of more quantitative statistical models and more deterministic physically-based models such as SHALSTAB. Although numerous studies have been performed utilizing each approach in various regions of the world, only a few comparisons of these approaches have been done in order to assess whether the quantitative and deterministic models result in better identification of instability. The goal of this study is to provide an assessment of relative model behavior and error potential in order to ascertain which model may be the most effective at identifying slope instability in a forest management context. The models are developed using both 10-meter and 30-meter elevation data and outputs are standardized and classified into instability classes (e.g. low instability to high instability). The outputs are compared with cross-tabulation tables based on the area (m²) assigned to each instability class and validated using known locations of debris flows. In addition, an assessment of the effects of varying source data (i.e. 10-meter vs. 30-meter) is performed. Among all models and using either resolution data, the Qualitative Map Combination correctly identifies the most debris flows. In addition, the Qualitative Map Combination is the best model in terms of correctly identifying debris flows while minimizing the classification of high instability in areas not affected by debris flows. The statistical model only performs well when using 10-meter data while SHALSTAB only performs well using 30-meter data. Overall, 30-meter elevation data predicts the location of debris flows better than 10-meter data due to the inclusion of more area into higher instability classes. Of the models, the statistical approach is the least sensitive to variations in source elevation data. / Master of Science

No description available.

The failure of the Kettleman Hills landfill focused attention on the uncertainties associated with the use of limit equilibrium analyses for evaluation of the stability of slopes in which failure occurs along displacement-softening interfaces. Sliding on such interfaces can occur in a progressive manner with the result that the available interface strengths are reduced below their peak values. The amount of strength reduction depends on the magnitude of shear displacement, which varies from one location to another. Because the limit equilibrium method does not provide any information regarding the magnitudes of shear displacements along the sliding interface, it can only provide realistic assessments of stability where progressive failure effects are small, or where the degree of strength reduction due to progressive failure can be estimated independently. The objective of this research study was to develop procedures to study the phenomenon of progressive failure in lined landfills, and to use the results of these studies as a basis to provide guidance for performing limit equilibrium analyses. Progressive failure along liner interfaces was analyzed using the finite element method. Adaptation and application of the finite element method for this type of analysis was a principal focus of this study. Two new plasticity models for interface behavior, a displacement-softening model and a work-softening model, were developed to simulate strength reduction along liner interfaces. The work-softening model performs better than the displacement-softening model when applied to laboratory tests performed under conditions of changing normal stress. However, the differences in performance of the two models were not significant when applied to landfills. The displacement-softening model is computationally more efficient, and it was used in most of the analyses. Progressive failure effects were severe for all the cases that were analyzed in this study. Analyses of the Kettleman Hills failure showed that the average available shearing resistance at failure was only about 10 percent higher than the residual shearing resistance. Analyses of hypothetical Municipal Solid Waste landfills indicated that the average available shearing resistance would be about 6 percent to 14 percent greater than the residual shearing resistance. This means that a limit equilibrium factor of safety of 1.4 based on residual strengths would correspond to a factor of safety of 1.5 if progressive failure was taken into account. / Ph. D.

The survivability of U.S. warships has become a higher priority than ever before. Two ways to improve survivability are to either avoid damage, or to continue to operate after damage has been incurred. This thesis concentrates on the first line of defense, which involves the first of these two approaches. Specifically, this thesis evaluates the extent of threat due to optical contrast with the ocean background. As part of this effort, an MCRT tool was created that allows the user to vary the shape and surface properties of a ship. A reverse MCRT was performed in order to reduce the processing time required to get accurate results. Using this MCRT tool, the user can determine the theoretical contrast with the ocean surface that would be seen at any viewing angle with and without a polarization filter. The contrast due to differential polarization and a change in viewing angle is estimated to determine the extent of threat. These results can be determined for both daytime and nighttime conditions by specifying if the ray trace is in the infrared or visible light range. The location of the sun for daytime conditions, and the temperature of the surfaces for nighttime conditions, can all be adjusted by the user. In order to get an accurate estimation of the signal power coming from the ocean surface, a great deal of time and effort was spent modeling the ocean surface. Many studies have been done concerning the slope statistics of an ocean surface, some more informative than others. This thesis takes two of the most complete studies and brings them together to get accurate slope statistics in both along-wind and crosswind directions. An original idea by the author was used to give a typical shape to the waves of the simulated ocean surface. The surface properties of the ship were determined using Fresnel's equations and the complex index of refraction of water at the particular wavelengths of interest. / Master of Science

Tiltmeters can be used in the mining environment to monitor slope stability by making use of gravitational force to measure angles of inclination relative to horizontal. Tiltmeters typically use accelerometers, which output a voltage measurement that can be related to angle of tilt. Though wireless tiltmeters already exist today, they lack certain ruggedness and sensitivity preventing use in mines. The purpose of this project was to investigate the feasibility of using already existing wireless tiltmeters in the mining setting. Additionally, a new wireless tiltmeter was designed which could be specially tailored for the needs of monitoring hazardous rock bodies in both surface and underground mines. By recording angles of any slope, either in a surface mine or underground, over extended periods of time, changes in readings can infer instabilities in the rock mass underlying the slope being measured. By placing many tiltmeters in a mesh on a surface slope or underground roof, rib, or other face, the entire surface can be monitored. Compared to the measurements of a single point using one instrument, a dense network can be extremely useful in detecting rock movement. Many monitoring techniques are in use already in mines. Traditional methods of monitoring, though undeniably useful, are often time consuming. By utilizing wireless devices that transmit data back to a single location, data acquisition and analysis time can be minimized, saving the mine employee hours as well as down time. As surface mines continue to deepen, and underground mines continue to progress further from the surface, the extent of necessary monitoring continues to increase: this widening range will require greater time for proper monitoring, unless an automated system is implemented. With proper wireless equipment, real time monitoring of an entire mine is possible. / Master of Science