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This study evaluates the seismically induced displacements of a slope using the Finite Element Method (FEM) in comparison to the results of twelve empirical predictive approaches. First, the existing methods to analyze the stability of slopes subjected to seismic loads are presented and their capabilities to predict the onset of failure and post-failure behavior are discussed. These methods include the pseudostatic method, the Newmark method, and stress-deformation numerical methods. Whereas the pseudostatic method defines a seismic coefficient for the analysis and provides a safety factor, the Newmark method incorporates a yield coefficient and the actual acceleration time history to estimate permanent displacements. Numerical methods incorporate advanced constitutive models to simulate the coupled stress-strain soil behavior, making the process computationally more costly. In this study, a model slope previously studied at laboratory scale is selected and scaled up to prototype dimensions. Then, the slope is subjected to 88 different input motions, and the seismic displacements obtained from the numerical and empirical approaches are compared statistically. From correlation analyses between seven ground motion parameters and the numerical results, new empirical predictive equations are developed for slope displacements. The results show that overall the FEM displacements are generally in agreement with the numerically developed methods by Fotopoulou and Pitilakis (2015) labelled "Method 2" and "Method 3", and the Newmark-type Makdisi and Seed (1978) and Bray and Travasarou (2007) methods for rigid slopes. Finally, functional forms for seismic slope displacement are proposed as a function of peak ground acceleration (PGA), Arias intensity (Ia), and yield acceleration ratio (Ay/PGA). These functions are expected to be valid for granular slopes such as earth dams, embankments, or landfills built on a rigid base and with low fundamental periods (Ts

The Deep Mixing Method (DMM) is a widely used, in-situ ground improvement technique that modifies and improves the engineering properties of soil by blending the soil with a cementitious binder. Laboratory specimens were prepared to represent soil improved by the wet method of deep mixing, in which the binder is delivered in the form of a cement-water slurry. To study the influence of curing temperature on the strength of the treated soil, specimens were cured in temperature-controlled water baths for the desired curing time. After curing, unconfined compressive strength (UCS) tests were conducted on the specimens. To investigate the optimum mix design for the wet method of deep mixing, UCS tests were performed to measure the strength of cured specimens, and laboratory miniature vane shear tests were conducted on uncured specimens to measure the undrained shear strength (su), which is used to represent the consistency of the mixture right after mixing. The consistency is important for field mixing because a softer mixture is easier to mix thoroughly. Based on the UCS test results, an equation that can provide a good fit to the strength data of the cured binder-treated soil is proposed. When the curing temperature was changed during curing, the UCS of the specimen cured at a low temperature and then cured at a high temperature was greater than the UCS of the specimen cured at a high temperature first. This seems to be due to different effects of elevated curing temperatures at early and late curing times on the cement reaction rates, such that elevating the curing temperature later produces a more constant reaction rate, which contributes to the reaction efficiency. An optimum mix design that minimizes the amount of binder while satisfying both a target strength of the cured mixture and a target consistency of the uncured mixture can be established by using the fitted equations for UCS and su. The amount of binder required for the optimum mix design increases as the plasticity of the base soil increases and the water content of the base soil (wbase soil) decreases. Master of Science The Deep Mixing Method (DMM) is a ground improvement technique widely used to improve the strength and stiffness of loose sands, soft clays, and organic soils. The DMM is useful for both inland and coastal construction. There are two types of deep mixing. The dry method of deep mixing involves adding the binder in the form of dry powder, and the wet method of deep mixing involves mixing binder-water slurry with the soil. The strength of the cured mixture is significantly influenced by the amount of added cement and water, the curing time, and the curing temperature. This research evaluates the influence of curing temperature on the strength of cured cement-treated soil mixture. Mixture proportions and curing conditions also influence the consistency of the mixture right after mixing, which is important because it affects the amount of mixing energy necessary to thoroughly mix the binder slurry with the soil. This research developed and evaluated fitting equations that correlate the cured mixture strength and the uncured mixture consistency with mixture proportions and curing conditions. These fitting equations can then be used to select an economical and practical mix design method that minimizes the amount of binder needed to achieve both the desired cured strength and uncured consistency. The amount of binder required for the optimum mix design increases as the plasticity of the base soil increases and the water content of the base soil (wbase soil) decreases.

This study uses dynamic centrifuge tests and three-dimensional (3D), nonlinear finite-difference analyses to: (1) evaluate the effect of soil-cement grid reinforcement on the seismic response of a deep soft soil profile, and (2) to examine the dynamic response of structures supported by shallow foundations on soft clay reinforced by soil-cement grids. The soil profile consisted of a 23-m-thick layer of lightly over-consolidated clay, underlain and overlain by thin layers of dense sand. Centrifuge models had two separate zones for a total of four different configurations: a zone without reinforcement, a zone with a "embedded" soil-cement grid which penetrated the lower dense sand layer and had a unit cell area replacement ratio Ar = 24%, a zone with an embedded grid with Ar = 33%, and a zone with a "floating" grid in the upper half of the clay layer with Ar = 33%. Models were subjected to a series of shaking events with peak base accelerations ranging from 0.005 to 0.54g. The results of centrifuge tests indicated that the soil-cement grid significantly stiffened the site compared to the site with no reinforcement, resulting in stronger accelerations at the ground surface for the input motions used in this study. The response of soil-cement grid reinforced soft soil depends on the area replacement ratio, depth of improvement and ground motion characteristics. The recorded responses of the structures and reinforced soil profiles were used to define the dynamic moment-rotation-settlement responses of the shallow foundations across the range of imposed shaking intensities. The results from centrifuge tests indicated that the soil-cement grids were effective at controlling foundation settlements for most cases; onset of more significant foundation settlements did develop for the weakest soil-cement grid configuration under the stronger shaking intensities which produced a rocking response of the structure and caused extensive crushing of the soil-cement near the edges of the shallow foundations. Results from dynamic centrifuge tests and numerical simulations were used to develop alternative analysis methods for predicting the demands imposed on the soil-cement grids by the inertial loads from the overlying structures and the kinematic loading from the soil profile's dynamic response. Ph. D.

Shallow geothermal energy (SGE) systems are becoming increasingly popular due to both their environmental and economic value. By using the ground as a source and sink for thermal energy, SGE systems are able to more efficiently heat and cool structures. However, their utility beyond structural heating and cooling is being realized as their applications now extend to slab and pavement heating, grain and agricultural drying, and swimming pool temperature control. Relatively recently, SGE systems have been combined with deep foundations to create a dual purpose element that can provide both structural support as well as thermal energy exchange with the subsurface. These thermo-active foundations provide the benefits of SGE systems without the additional installation costs. One of the novel applications of thermo-active foundations is in bridge deck deicing. Bridge decks experience two main winter weather related problems. The first of which is preferential icing, where the bridge freezes before the adjacent roadway because the bridge undergoes hastened energy loss due to its exposed nature. The second problem is the accelerated deterioration of concrete bridge decks resulting from the application of salts and other chemicals that are used to prevent accumulation and/or melt the frozen precipitation on roads and bridges. By utilizing the foundation of a bridge as a mechanism by which to access the shallow geothermal energy of the subsurface, energy can be supplied to the deck during the winter to melt and/or prevent frozen precipitation. An experimental ground-source bridge deck deicing system was constructed and the performance is discussed. Numerical models simulating the bridge deck and subsurface system components were also created and validated using the results from the numerical tests. Furthermore, the observed loads that result in a foundation from bridge deck deicing tests are shown. In order to better design for these loads, tools were developed that can predict the temperature change in the subsurface and foundation components during operation. Mechanisms by which to improve the efficiency of these systems without increasing the size of the borehole field were explored. Ultimately this research shows that SGE can effectively be used for bridge deck deicing. Ph. D.

Seismic hazard analyses require an estimate of earthquake ground motions from future events. These predictions are achieved through Ground Motion Prediction Equations, which include a prediction of the median and the standard deviation of ground motion parameters. The differences between observed and predicted ground motions, when normalized by the standard deviation, are referred to as epsilon (𝜖). For spectral accelerations, the correlation structure of normalized residuals across oscillator periods is important for guiding ground motion selection. Correlation structures for large global datasets have been studied extensively. These correlation structures reflect effects that are averaged over the entire dataset underlying the analyses. This paper considers the effects of site response, at given sites, on the correlation structure of normalized residuals. This is achieved by performing site response analyses for two hypothetical soil profiles using a set of 85 rock input motions. Results show that there is no significant difference between correlation coefficients for rock ground motions and correlation coefficients after considering the effects of site response for the chosen sites. Master of Science

Traditionally, geothermal boreholes have utilized the ground energy for space heating and cooling. In this system, a circulation loop is placed in a small-diameter borehole typically extending to a depth of 200-300 ft. The hole is then backfilled with a mixture of sand, bentonite and/or cement. The loop is connected to a geothermal heat pump and the fluid inside the loop is circulated. The heat energy is fed into the ground for cooling in the summer and withdrawn from the ground for heating in the winter. Geothermal heat pumps work more efficiently for space heating and cooling compared to air-source heat pumps. The reason is ground-source systems use the ground as a constant temperature source which serves as a more favorable baseline compared to the ambient air temperature. A significant cost associated with any deep geothermal borehole is the drilling required for installation. Because Energy Piles perform the dual function of exchanging heat and providing structural support, and are only installed at sites where pile foundations are already required, these systems provide the thermal performance of deep geothermal systems without the additional drilling costs. Low maintenance, long lifetime, less variation in energy supply compared to solar and wind power, and environmental friendliness have been cited as additional Energy Pile advantages. Case studies show that they can significantly lower heating/cooling costs and reduce the carbon footprint. Energy cost savings for typical buildings outfitted with Energy Piles could be as much as 70 percent. The use of Energy Piles has rapidly increased over the last decade, especially in Europe where more than 500 applications are reported. Primary installations have been in Germany, Austria, Switzerland and United Kingdom. Notable projects include the 56-story high Frankfurt Main Tower in Germany, Dock E Terminal Extension at Zurich International Airport in Switzerland and the One New Change building complex in London U.K. Energy piles have seen very little use in the North America, only a handful of completed projects are known; Marine Discovery Center in Ontario, Canada, Lakefront Hotel in Geneva, New York and the Art Stable building in Seattle, Washington. Energy Piles are typically installed with cast-in-place technology (i.e. drilled shafts, continuous flight auger piles, micropiles etc.) while some driven pile applications are also reported. Other types of geotechnical structures in contact with the ground, such as shallow foundations, retaining walls, basement walls, tunnel linings and earth anchors, also offer significant potential for harnessing near-surface geothermal energy. Energy Pile design needs to integrate geotechnical, structural and heat exchange considerations. Geotechnical characteristics of the foundation soils and the level of the structural loads are typically the deciding factors for the selection and dimensioning of the pile foundations. The geothermal heat exchange capacity of an Energy Pile is a key parameter to be considered in design. Thermal characteristics of the ground as well as the heating and cooling loads from the structure need to be considered for the number of piles that will be utilized as heat exchangers. Therefore, the thermal properties of the site need to be evaluated for an Energy Pile application in addition to the traditional geotechnical characterization for foundation design. Energy Piles bring new challenges to geotechnical pile design. During a heat exchange operation, the pile will expand and contract relative to the soil as heat is injected and extracted, respectively. These relative movements have the potential to alter the shear transfer mechanism at the pile-soil interface. Furthermore, the range of temperature increases near the pile surface, though limited by practical operational guidelines, can have a significant effect on pore pressures generation and soil strength. This dissertation provides answers for several research questions including the long-term performance of Energy Piles, the applicability of the thermal conductivity tests to Energy Piles. Furthermore, it presents the results and a detailed discussion about the full scale in-situ thermo-mechanical pile load test conducted at Virginia Tech. Ph. D.

Levees are a significant part of the United States flood protection infrastructure. It is estimated that over 100,000 miles of levees exist in the United States. Most of these levees were designed many years ago to protect farmland and rural areas. As growth continues in the United States, many of these levees are now protecting homes and other important structures. The American Society of Civil Engineers gave the levees in the United States a grade of D- in 2009. To bring flood protection up to modern standards there requires adequate methods of evaluating levees with respect to seepage, erosion, piping and slope instability. Transient seepage analyses provide an effective method of evaluating seepage through levees and its potentially destabilizing effects. Floods against levees usually last for days or weeks. In response to a flood, pore pressures within the levee will change from negative (suction) to positive as the phreatic surface progresses through the levee. These changes can be calculated by finite element transient seepage analyses. In order for the transient seepage analysis to be valid, appropriate soil properties and initial conditions must be used. The research investigation described here provides simple and practical methods for estimating the initial conditions and soil properties required for transient seepage analyses, and illustrates their use through a number of examples. Ph. D.

Mountain Lake in Giles County, Virginia, has a documented history of severe natural lake-level changes involving groundwater seepage [Jansons, 2004] that extend over the past 4200 years [Cawley, 1999], and as of December 2010 the lake was about 2% full by volume. Situated in the Valley and Ridge physiographic province on the axis of a plunging anticline and straddling contacts between three upper Ordovician and lower Silurian formations, the lake is one of two natural lakes in Virginia. A daily water balance, geophysical surveying with dipole-dipole electrical resistivity, and chemical sampling have shed light on the nature of flow to and from the lake, including: 1) the steady nature of net groundwater outflow, 2) the seasonal response to precipitation of a forested first-order drainage system in fractured rock, 3) the influence of a fault not previously discussed in literature regarding the lake, and 4) the possibility of flow pathways through karst features. Results from a water balance indicate steady lake drainage and significant recharge when vegetation is dormant, particularly during rain-on-snow melt events. The resistivity profiles display a highly heterogeneous subsurface and reveal low-resistivity areas that suggest flow pathways to and from the lake. Well logs, satellite images, and outcrop observations appear to confirm the presence of a fault to the east of the lake. Chemical evidence suggests that karst features may be present in the upper Reedsville-Trenton formation underlying the lakebed. Master of Science

This study investigates the February 17th, 2006 massive rockslide that occurred in the island of Leyte, Philippines following heavy rainfall and four minor earthquakes. The rockslide is considered one of the largest and most catastrophic slides in the last few decades as it completely inundated the village of Guinsaugon, taking the lives of approximately 1,400 of the 1,800 residents of the village. The distinct element simulation of the rockslide is performed using 3DEC (Three-Dimensional Distinct Element Code) in order to investigate the underlying triggering mechanism of the slide as well as the behavior of the debris flow. The 3DEC models were established based on field observations from the U.S. Reconnaissance team and material and joint properties based on in-situ and laboratory test results. The possible triggering mechanisms considered in the distinct element analyses were the rainfall-induced hydraulic pressurization of the fault forming part of the main scarp, as well as the seismic acceleration due to the minor earthquakes that occurred the morning of the slide. The results of the analyses and simulations indicate that the rainfall-induced hydraulic pressurization of the fault was potentially the main trigger for the initiation of the slide. The minor earthquakes, which occurred before and around the time of the slide initiation, appeared to have very little effect on the triggering mechanism and the debris flow are comparable to witness accounts and field observations. The results presented in this study are expected to provide better understanding of rockslides such as the one that occurred in the Philippines on February 17, 2006. With further improvements in computational capabilities in the future, distinct element simulations can have the potential to reliably predict the initiation and behavior of slides, and help mitigate their impact. Master of Science

Fractures and fracture networks govern the mechanical and fluid flow behavior of rock masses. Tunneling and other rock mechanics applications therefore require the characterization of rock fractures based on geological data. Field investigations produce only a limited amount of data from boreholes, outcrops, cut slopes, and geophysical surveys. In tunneling, the process of excavation creates a priceless opportunity to gather more data during construction. Typically, however, these data are not utilized due to the impedance of sampling and analysis on the flow of construction, and safety concerns with sampling within unlined tunnel sections. However, the use of this additional data would increase the overall safety, quality, and cost savings of tunneling. This study deals with several aspects of the above, with the goal of creating methods and tools to allow engineers and geologists to gather and analysis fracture data in tunnels without interrupting the excavation and without compromising safety. Distribution-independent trace density and mean trace length estimators are developed using principles of stereology. An optimization technique is developed utilizing Differential Evolution to infer fracture size and shape from trace data obtained on two or more nonparallel sampling planes. A method of producing nearly bias free empirical trace length CDF's is also introduced. These new methods and tools were validated using Monte Carlo simulations. A field study was conducted in an existing tunnel allowing the above methods and tools to be further validated and tested. A relational database was developed to aid in storage, retrieval, and analysis of field data. Fracture models were built and updated using fracture data from within the tunnel. Utilization of state of the art imaging techniques allowed for remote sampling and analysis, which were enhanced by the use of 3d visualization techniques. Ph. D.

Success in geotechnical analysis, design, and construction invariably requires that we have proper knowledge and understanding of (1) the strength, (2) the fluid flow properties, and (3) the stress-deformation behavior of the earth materials. These important engineering properties are primarily determined by the components and structure of a soil, which also dictate the soil's responses in an electromagnetic field. As a nondestructive technique, the electromagnetic property measurement offers a promising approach to characterize earth materials and identify the effects of changes in environments. However, despite many investigations in the last several decades, the relationship between the frequency-dependent electromagnetic properties of soils and their components and structure are still not well understood. Hence, estimation of engineering properties of a soil in a quantitative way from electromagnetic measurements can be uncertain. In this research several tasks have been accomplished: (1) Development of a physically based model that provides a means of investigating the coupled effects of important polarization mechanisms on soil electromagnetic properties, and a means of relating the electromagnetic properties of a soil to its fines content, clay mineralogy, anisotropy, degree of flocculation and pore fluid chemistry; (2) Proposal of a practically applicable method to determine the volumetric water content, specific surface area and pore fluid salt concentration simultaneously from the dielectric spectrum; (3) Deduction of the wide-frequency electromagnetic properties of a soil by measuring its responses to a step pulse voltage using time domain reflectometry (TDR); (4) Establishment of the relationships between the specific surface area and compressibility, residual shear strength and hydraulic conductivity. This study establishes a framework for quantifying soil engineering properties from their electromagnetic properties. If properly determined and interpreted, the electromagnetic properties can also provide insights into the causes of soil property changes over time and can be very useful in studying the effects of biological factors in geotechnical engineering, a field that may offer great potential for future advances. Ph. D.

A fundamental element of the observational method in geotechnical engineering practice is the utilization of a carefully laid out performance monitoring system which provides rapid insight of critical behavioral trends of the work. Especially in tunnels, this is of paramount importance when the contractual arrangements allow an adaptive tunnel support design during construction such as the NATM approach. Utilization of measurements can reveal important aspects of the ground-support interaction, warning of potential problems, and design optimization and forecasting of future behavior of the underground work. The term back-analysis involves all the necessary procedures so that a predicted simulation yields results as close as possible to the observed behavior. This research aims in a better understanding of the back-analysis methodologies by examining both simplified approaches of tunnel response prediction but also more complex numerical methods. Today a wealth of monitoring techniques is available for tunnel monitoring. Progress has also been recorded in the area of back-analysis in geotechnical engineering by various researchers. One of the most frequently encountered questions in this reverse engineering type of work is the uniqueness of the final solution. When possible errors are incorporated during data acquisition, the back analysis problem becomes formidable. Up to the present, various researchers have presented back-analysis schemes, often coupled with numerical methods such as the Finite Element Method, and in some cases the more general approach of neural networks has been applied. The present research focuses on the application of back-analysis techniques that are applicable to various conditions and are directly coupled with a widely available numerical program. Different methods are discussed and examples are given. The strength and importance of global optimization is introduced for geotechnical engineering applications along with the novel implementation of two global optimization algorithms in geotechnical parameter identification. The techniques developed are applied to the back-analysis of a modern NATM highway tunnel in China and the results are discussed. Ph. D.

The interphase is a localized region adjacent to a manufactured inclusion that is surrounded by granular soil. These regions are ubiquitous in civil infrastructure and often are components of large-scale composite systems. The interphase region influences load-deformation behavior of the entire composite system. However, mechanisms that control the mechanical behavior of the interphase region and, in turn, control the composite structure behavior, are not clearly understood. Few relationships exist for predicting interphase behavior from properties of granular materials and the inclusion surface that can be measured in the laboratory. A two dimensional discrete element model of a general interphase system was developed and validated against laboratory data. Numerical experiments are conducted with varying soil to inclusion relative geometry. A new micromechanics-based approach, which utilizes microscopic quantities to explain the mechanics of granular media from a continuum point view, is adopted to investigate the mechanisms that underlie the interphase behavior. It is shown that the grain to inclusion surface relative geometry controls the degree of granular media strength mobilization by controlling development of fabric and contact force anisotropy inside the interphase region. A unique bilinear relationship exists between the mobilized granular media strength and the principal direction of average contact force anisotropy at the interface between the particles touching the surface and the inclusion. These findings suggest the problem is one of contact and can not be solved using purely geometric correlations, as past research presumed. A fundamental mechanism of behavior, long sought in geomechanics problems, is presented. Publications resulting from this research are significant and original contributions to the geoengineering, material science, geophysics and granular physics literature. Ph. D.

Liquefaction of granular soil deposits can have extremely detrimental effects on the stability of embankment dams, natural soil slopes, and mine tailings. The residual or liquefied shear strength of the liquefiable soils is a very important parameter when evaluating stability and deformation of level and sloping ground. Current procedures for estimating the liquefied shear strength are based on extensive laboratory testing programs or from the back-analysis of failures where liquefaction was involved and in-situ testing data was available. All available procedures utilize deterministic methods for estimation and selection of the liquefied shear strength. Over the past decade, there has been an increasing trend towards analyzing geotechnical problems using probability and reliability. This study presents procedures for assessing the liquefied shear strength of cohesionless soil deposits within a risk-based framework. Probabilistic slope stability procedures using reliability methods and Monte Carlo Simulations are developed to incorporate uncertainties associated with geometrical and material parameters. The probabilistic methods are applied to flow liquefaction case histories from the 1999 Kocaeli/Duzce, Turkey Earthquake, where extensive liquefaction was observed. The methods presented in this paper should aid in making better decisions about the design and rehabilitation of structures constructed of or atop liquefiable soil deposits. Master of Science

The Rockfall Management System developed for Tennessee DOT (TennRMS)integrates a customized rockfall risk rating system, web-based GIS application, and rockfall database to provide a robust single interface for interacting with rock slope information. The system should prove to be a valuable tool for the proactive management of rock slopes. The most important use of the system will be to identify and prioritizing rock slopes with the greatest potential for rockfall in order to provide decision makers with all the necessary information they need to plan remediation efforts. Over time, TennRMS can be used to track costs and effectiveness of different remediation methods used on problem rock slopes. Three papers have been developed for publication in peer reviewed journals. The papers describe the work done in support of developing Tennessee's Rockfall Management System (TennRMS) and its components. The system can be described by its conceptual framework and actual implemented components. Asset management incorporating risk & decision analysis and knowledge management makes up the conceptual framework. The system components include a field data collection system using PDA's, a rockfall database and a web-based GIS interface. The papers articulate the development and implementation of the various components and to provide a detailed review of rockfall management systems as implemented over the past 15 years. Ph. D.

Fracture systems or networks always control the stability, deformability, fluid and gas storage capacity and permeability, and other mechanical and hydraulic behavior of rock masses. The characterization of fracture systems is of great significance for understanding and analyzing the impact of fractures to rock mass behavior. Fracture trace data have long been used by engineers and geologists to character fracture system. For subsurface fractures, however, boreholes, wells, tunnels and other cylindrical samplings of fractures often provide high quality fracture trace data and have not been sufficiently utilized. The research work presented herein is intended to interpret fracture traces on borehole walls and other cylindrical surfaces by using stereology. The relationships between the three-dimension fracture intensity measure, P32, and the lower dimension fracture intensity measures are studied. The analytical results show that the conversion factor between the three-dimension fracture intensity measure and the two-dimension intensity measure on borehole surface is not dependent on fracture size, shape or circular cylinder radius, but is related to the orientation of the cylinder and the orientation distribution of fractures weight by area. The conversion factor between the two intensity measures is determined to be in the range of [1.0, π/2]. The conversion factors are also discussed when sampling in constant sized or unbounded fractures with orientation of Fisher distribution. At last, the author proposed estimators for mean fracture size (length and width) with borehole/shaft samplings in sedimentary rocks based on a probabilistic model. The estimators and the intensity conversion factors are tested and have got satisfactory results by Monte Carlo simulations. Ph. D.

Manual fracture mapping in tunnels, caverns, mines or other underground spaces is a time intensive and sometimes dangerous process. A system that can automate this task could minimize human exposure to rockfalls, rockbursts or instabilities and facilitate the use of new methods of data visualization such as virtual environments. This research was undertaken to develop VTtrace; a semi-automatic fracture mapping algorithm based on image processing and analysis techniques. Images of a rock exposure surface are made using a "prosumer" grade digital camera. The grayscale images are preprocessed to remove color information and any noise or distortion. The smoothed images are converted into binary images. The binary images are then thinned to extract the fracture map. The fractures are then separated and stored as different images. Fracture properties such as the length, width, orientation and large-scale roughness are determined using photogrammetric techniques. Results from test images shows the VTtrace is effective in extracting rock discontinuity traces. Additional enhancements to the program are proposed to allow feature attributes from the three-dimensional surface to be determined. Master of Science

Petroleum reservoirs located in the Norwegian sector of the North Sea have undergone unexpected subsidence of great magnitude (> 10 m) during more than 30 years of petroleum recovery operations. Historical laboratory investigations have shown that the subsidence is due to the mechanical behavior and mechanical properties of chalk. Chalk behavior is characterized by elastoplasticity, including pore collapse, shear failure, and tensile failure mechanisms; rate-dependence; and pore fluid dependence. The research described in this dissertation was performed with the objectives to formulate a constitutive model which describes all aspects of chalk and soft rock mechanical behavior, develop and/or implement methods to integrate the equations which form the constitutive model, and to apply the model to finite element simulations of engineering problems encountered in chalk and soft rock. A new rate-dependent constitutive model is developed based on a three-dimensional extension of a volumetric time-lines model, similar to that of Bjerrum (1967). Shear and tensile failure surfaces are also included to reflect these failure mechanisms observed in chalk. Twelve model parameters are required to fully describe chalk behavior. Procedures to determine values for each of these parameters from laboratory test results are described. Correlations of model parameter values with index parameters are given for North Sea chalks, to allow reasonable values to be obtained in the absence of an extensive laboratory testing program. Comparisons between observed behavior and model simulations indicate that the new model is able to reproduce and predict the behavior of chalk quite well. A new integration method for critical state cap plasticity models is presented. This new method may be used for rate-independent or rate-dependent constitutive models which are formulated with elliptical cap yield surfaces, including the chalk model. The new method gives results that compare favorably to integration methods used currently, in terms of accuracy and computational effort. The effects of pore fluid composition on chalk behavior are included in the constitutive model. It is shown that the variability in constitutive behavior with pore fluid composition is due to dependence of model parameter values on pore fluid composition. This variability in model parameters with pore fluid composition has been quantified and implemented into the model for the complete spectrum of oil-water mixtures in chalk. Finite element simulations are presented to demonstrate performance of the model in analyzing problems at several different scales, including laboratory, borehole, and full-field scales. A new algorithm called "equivalent uniform water saturation" has been developed to determine the average mechanical properties of finite chalk masses with non-uniform pore fluid compositions, which are frequently encountered during finite element simulations. Results of the laboratory-scale simulations indicate that the constitutive model can reproduce the inhomogeneous deformation patterns which occur in chalk during waterflooding tests, and that use of the new algorithm utilizing "equivalent uniform water saturation" produces consistent results for chalk masses with inhomogeneous pore fluid distributions when used with different finite element mesh discretizations. Results of the larger-scale simulations indicate that changes in pore fluid composition and pore fluid pressure have different effects on macro-scale chalk mechanical behavior, and that both must be considered during analysis. Ph. D.

Rockfall from rock slopes adjacent to roadways is a major hazard and poses a problem for transportation agencies across the country. The state of Tennessee has implemented the Tennessee Rockfall Management System (RMS) as a means of reducing the liabilities associated with rockfall hazard. It utilizes digital data acquisition via PDAs coupled with distribution via an expandable web-based GIS database. The Tennessee Rockfall Hazard Rating System (RHRS) is part of the Tennessee RMS and assigns a numeric hazard rating according relative hazard for all slopes identified as having a high potential for delivering rock blocks onto Tennessee Department of Transportation maintained roadways. The Tennessee RHRS uses standard rock slope failure mechanisms (planar failure, wedge failure, topple failure, differential weathering, and raveling) along with the site and roadway geometry to assess the rockfall hazard of an individual slope. This study suggests methods that will expedite fieldwork, including an informational guide on how to properly identify individual failure mechanisms in the field. Also, the study examines the current method of scoring abundance and suggests an alternative, multiplicative approach. The alternative of using a multiplicative abundance is considered and its results summarized. Master of Science

In the present research a highway twin tunnel project completed in Japan in 1998 is used as a case study to verify results of numerical analyses with measurement data. Each of the tunnels had approximately 1.1 km of length. For this project a wide geometry of approximately 18.0 m was selected by the designers to facilitate three lanes per tunnel. A sequential tunneling technique known in Japan as the "TBM pilot and enlargement method" was used along with NATM principles. The tunnel was used as a reference project, involving performance testing and extensive monitoring in order to verify and standardize support requirements for other tunnels excavated under similar geologic conditions in the Tomei II expressway. The tunnel was excavated in a region consisting mainly of soft sedimentary rocks, such as locally weathered sandstone, underlain by interbedded sandstone and mudstone. Due to observed non symmetric deformations and loads in the tunnel, the distinct element and the convergence-confinement methods were used during the numerical simulations. A parametric analysis was performed initially in a pseudo-continuum approach to study the behavior of the wide tunnel geometry under various conditions. The effects of rock mass elastic modulus, in situ Ko ratio and boundary conditions are discussed. More complex parametric studies were performed in a stochastically generated model by using joint spatial data from geotechnical investigations. The Barton-Bandis constitutive law was assumed for the behavior of the joints. The sensitivity of the ground "characteristic curves" was examined by statistical variation of the joint shear strength parameters. A final simulation using the code UDEC and the convergence-confinement method yields interesting results which are comparable to the monitored data. Master of Science

Oxidation of pyrite can significantly affect properties and the behavior of soil and rock in civil construction. Problems with pyritic rock and soil extend globally and across many disciplines. Consequences of pyrite oxidation include heave, concrete degradation, steel corrosion, environmental damage, acid mine drainage, and accelerated weathering of rock with concomitant effects on strength and stability. Affected disciplines include soil science, mining, engineering geology, geochemistry, environmental engineering, and geotechnical engineering. While pyrite problems may be well known in their respective disciplines, there has been to date relatively little cross-disciplinary communication regarding problems with pyritic geomaterials. Thus, there is a need to establish an inter-disciplinary and inter-regional awareness regarding the effects of pyrite oxidation and their prevention or mitigation. This engineering research is a compilation of information about geotechnical problems and engineering behavior of pyritic rock and soil, the underlying physicochemical processes, site investigation strategies, and known problematic formations. Several case histories documenting consequences of pyrite oxidation are provided. The results of chemical analyses performed on pyritic shale samples from a formation with acknowledged heave problems are presented. Digital data and ESRI's ArcGIS digital mapping program were used to create maps showing results of sampling and testing performed during this study. Appendices include mitigation options, results of a practitioner survey, chemical test procedures, a glossary, a visual identification key for sulfidic geomaterials, and a summary table of the literature review for this research. Master of Science

Energy piles are deep foundation elements designed to utilize near-surface geothermal energy, while at the same time serve as foundations for buildings. The use of energy piles for geothermal heat exchange has been steadily increasing during the last decade, yet there are still pending questions on their thermo-mechanical behavior. The change in temperature along energy piles, resulting from their employment in heat exchange operations, causes axial displacements, thermally induced axial stresses and changes in mobilized shaft resistance which may have possible effects on their behavior. In order to investigate these effects, an extensive field test program, including conventional pile load tests and application of heating-cooling cycles was conducted on three energy piles during a period of six weeks. Temperature changes were applied to the test piles with and without maintained mechanical loads to investigate the effects of structural loads on energy piles. Moreover, the lengths of the test piles were determined to represent different end-restraining conditions at the toe. Various sensors were installed to monitor the strain and temperature changes along the test piles. Axial stress and shaft resistance profiles inferred from the field test data along with the driven conclusions are presented herein for all three test piles. It is inferred from the field test results that changes in temperature results in thermally induced compressive or tensile axial stresses along energy piles, the magnitude of which increases with higher restrictions such as structural load on top or higher toe resistance. Moreover, lower change in shaft resistance is observed with increasing restrictions along the energy piles. In addition to the design, deployment, and execution of the field test, a thermo-mechanical cyclic numerical model was developed as a part of this research. In this numerical model, load-transfer approach was coupled with the Masing's Rule in order to simulate the two-way cyclic axial displacement of energy piles during temperature changes. The numerical model was validated using the field test results for cyclic thermal load and thermo-mechanical load applications. It is concluded that the use of load-transfer approach coupled with the Masing's Rule is capable of simulating the cyclic thermo-mechanical behavior of energy piles. Ph. D.