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The development of an interactive computer model for managing geologic hazards databases is vital and long overdue. As highway rockslopes continue to age and become more unstable and earthen dams are subjected to ever increasing flood events, a more proactive management system is required in order to provide timely information to planners and emergency personnel on demand. In recent years, deaths have occurred associated with both highway rockslides and earthen dam failures in southwest Virginia. In February 1991, a rockfall event occurred on Route U.S. 11 in the City of Radford, VA, which resulted indirectly in a highway accident and fatality. The incident made all parties aware that rockfalls from aging highway roadcuts within the city limits pose some threat to the motoring public (Watts et al., 1996). Additionally, in June 1995, the Timberlake dam in Lynchburg, VA, failed due to flash flooding from intense summer storms. Two people died on highways downstream of the dam, even though emergency personnel were on the scene. The lack of organized critical information about the dam, its downstream flood inundation zone, and its emergency action plan contributed to the tragedy. The outcome of the ensuing litigation is pending. In the case of the City of Radford, a user-friendly interactive database containing structural stereonet analysis, digital images, hazardous slope conditions, and maintenance records would provide a proactive approach to rockslope maintenance by allowing the slopes to be ranked in terms of geologic and traffic conditions. Appropriate remediation measures can then be taken in the most cost-effective manner. In the case of the Timberlake dam failure, a database containing critical information about the dam, its upstream watershed characteristics, downstream flood inundation zones, and emergency action plan could have been accessed by state geologists and emergency dispatchers. Appropriate measures could have been taken to deal with the event as it was unfolding. / Master of Science

This thesis investigates pressure stimulated voltages (PSVs) in manmade and geological materials using a field capable and commercially viable electric potential sensor (EPS) technology. Sensing technologies are of great importance for the structural health monitoring (SHM) of manmade and geological structures and are critical for improving the health and safety of humans and infrastructure. A wide variety of sensing technologies are needed to assess damage over structures. Work by others involves measuring pressure stimulated electrical emissions (PSEs) (i.e. the study of pressure stimulated voltage, electric field and current) that are related to acoustic emissions (AEs) in rock and cement mortar, and also mechanical properties. Although these studies yield promising results, the measurement tools (laboratory electrometers and electromagnetic emissions (EME) antennas) are not suitable for field use. This is predominantly because of the need of Faraday shielding to reduce noise, plus the impracticalities and high costs associated with using laboratory instruments for SHM. However, the EPS developed at the University of Sussex is capable of measuring PSVs in rocks and is field capable. In this thesis, PSVs in rocks and man-made materials were measured using two EPS variants. An existing capacitively coupled sensor was used to measure high frequency (25.5 mHz to 750 kHz) transient PSVs associated with cracking. In addition, a novel directly coupled smart EPS was developed for monitoring low frequency (DC to 250 Hz) PSVs associated with applied stress. A signal conditioning and data reduction procedure was developed for PSV emissions analogous to methods used for AE. A new robust method for measuring PSV was established in which cylindrical material specimens were instrumented with strain gauges, piezo transducers and EPSs to measure strain, AE and PSV respectively and a force transducer was used to measure the applied load. The results showed that PSVs were detected in a wide range of piezo and non-piezo rocks and for the first time in concrete, in the range of millivolts (0.32 mV – 1180 mV). Faraday shielding the experiments was not necessary as with other PSE monitoring technologies. For oven dried materials there was some degree of correlation between PSV high frequency transient signals and AE (i.e. cracking). Rocks had cross-correlation coefficients ranging from 0.13 to 0.86, and the cross-correlation coefficient for concrete (0.24) was lower than most rock lithologies. Environmental conditions and the stage of uniaxial deformation of materials influence PSV-AE cross-correlations. Water or saline saturation of materials generally reduced the PSV-AE cross correlation coefficients. During the cyclic loading of various rock lithology, a work hardening effect was observed in the PSV emissions analogous to the well-known Kaiser and Felicity effect of AE. A likely reason for the PSV-AE correlations is that PSVs are generated by the movement and separation of fresh charged fracture surfaces. EPS could be a cost effective and more advanced technology for detecting cracking in structures and in combination with piezo transducers, could be used to identify material deformation stages. There was a linear relationship between applied stress and DC/low frequency PSV in piezo rocks (r2 = 0.84) but not non-piezo rocks (r2 = 0.0063). The piezoelectric effect of quartz is the most likely generation mechanism behind the PSV-stress relationship. The novel, directly coupled, smart EPS is a successful design as it has the necessary high input impedance and low noise characteristics for measuring PSVs noninvasively at low frequencies. EPS could be the first non-invasive technology for in-situ stress measurement in quartz bearing rocks; current methods involve disturbing the rock mass and are expensive to implement. In conclusion, the results show that the EPS-PSV measurement technique is viable for the SHM of rocks and concrete. Although, factors such as material composition, environmental condition and type of material deformation influence PSV characteristics and would need to be accounted for in real world applications. Future directions for the research would involve the development of a “real time” PSV event detection system for long term monitoring of structures for SHM applications. Additionally, large scale testing of different material samples in different environmental conditions and the testing of larger structures using arrays of EPS would be necessary before commercialisation. Future commercialisation could result in a restively coupled broadband monolithic semiconductor EPS being developed for SHM to monitor PSVs associated with applied stress and cracking events simultaneously. This would produce a more cost effective and advanced tool than existing technologies, such as piezo transducers for monitoring AE and in-situ stress monitoring techniques.

In mining industry, waste storage is a very prominent issue / in this respect, safety of storage structures is one of the leading problems in the industry. Most of the tailings dams require remedial measures, throughout their lifespan to increase their reliability. The objective of the study is to investigate stability problems of formerly constructed but newly raised Eti Copper Mine tailings dam and alternative dam geometries for future raises. Plenty of methods were developed to analyze the reliability of structures / limit equilibrium methods, finite element methods and finite difference methods are among them. In this case, stability of the dam was analyzed with finite element method under static loading conditions. In order to determine input parameters properly, disturbed samples obtained at the field investigations were used. For this purpose, several laboratory experiments were conducted to determine natural moisture content, grain size distribution, specific gravity, Atterberg limits, maximum dry density and shear strength parameters of tailings and embankment material.

With the developments in computer technology, the numerical methods are used widely in geotechnical engineering. Finite element and finite difference are the most common methods used to simulate the behavior of soil and rock. Although the reliability of these methods are proven in several fields of application over the years, they are not equally satisfactory in every case and require sophisticated constitutive relations to model the discontinuous behavior of geomaterials since they assume the material is continuum or the location of discontinuum is predictable. The Discrete Element Method (DEM) has an intensive advantage to simulate discontinuity. This method is relatively new and still under development, yet it is estimated that it will replace of the continuum methods largely in geomechanics in the near feature. In this thesis, the theory and background of discrete element method are introduced, and its applicability in bearing capacity calculation of shallow foundations is investigated. The results obtained from discrete element simulation of bearing capacity are compared with finite element analysis and analytical methods. It is concluded that the DEM is a promising numerical analysis method but still have some shortcomings in geomechanical applications.

Dynamic behaviour of gravity and cantilever retaining walls is investigated by finite element method, incorporating the nonlinear elasto-plastic material properties of soil and seperation of the wall and backfill. Two dimensional finite element models are developed employing the finite element software ANSYS. The wall is modelled to rest on a soil layer allowing translational and rotational movements of the wall. Soil-wall systems are subjected to harmonic and real earthquake motions with different magnitude and frequency characteristics at the base. The maximum lateral force and its application point durinG dynamic loading are determined for each case. It is observed that the frequency content of the base motion has a significant influence on the dynamic lateral soil pressures and the lateral forces considerably increase as the base motion frequency approaches the fundamental frequency of the soil layer. The maximum lateral thrusts calculated by finite element analyses are generally found to be greater than those suggested by Mononobe-Okabe method and experimental findings. Nevertheless, the locations of the application point obtained by finite element method are found to be in good agreement with the results of experimental studies.

In this study, settlement and seepage behavior of Muratli Dam, which is the first asphalt faced rockfill dam in Turkey, is investigated for the &ldquo / end of construction&rdquo / and &ldquo / reservoir impoundment&rdquo / loading conditions. Two dimensional plane strain finite element analyses are carried out in order to determine the total stresses, displacements and pore water pressures. Hardening soil model is used in order to represent the non-linear, inelastic and stress dependent behavior of rockfill material. Material model parameters are selected mainly referring to the previous studies on the dams consisting of similar materials and then back analyses are done to find the best fit. Calculated stresses, displacements and pore water pressures are compared with the observed values for both end of construction and reservoir filling conditions.

Foundation uplift is the partial separation of a shallow foundation from soil due to excessive load eccentricity. Foundation uplift can significantly change the seismic response of slender structures, and frames as well. In literature, different support models for foundations are employed in order to simulate foundation uplift in seismic analysis of structures. One of the most widely used models is the Winkler model which assumes distributed tensionless springs beneath a shallow foundation. In this study, two simple algorithms are developed in order to compute static and dynamic response of foundations on tensionless supports. Any formula given in literature for calculation of foundation impedance coefficients can be easily introduced in these algorithms. Hence, the use of Winkler model is critically evaluated through comparisons with the response of a foundation on elastic halfspace. For that purpose, available impedance formulas given for a shallow rectangular foundation on elastic halfspace are used. It is concluded that, the coupling between vertical displacement and rocking of foundation is very significant during uplift. Therefore, the accuracy of Winkler model in uplift v simulation is limited, since the model cannot simulate vertical and rocking response of a shallow foundation concurrently with a single spring coefficient.

Slope stability is an important aspect of geotechnical engineering. Input parameters for the analysis are the governing factors and they must be determined accurately and precisely. Field investigations, laboratory testing and back analyses are vital instruments for the input parameters. This study presents the results of slope stability analysis for the soil slopes at Elbistan-&Ccedil / &ouml / llolar lignite mine. After executing the drilling programme, samples taken from the drilling work, delivered to soil mechanics laboratory for testing. The basic input parameters, namely cohesion and friction angle determined at soil mechanics laboratory were compared to the parameters obtained from back analysis of a large scale slope failure. Input parameters for the analysis are determined by this way. After determining the input parameters, slope stability analyses were carried out both for the permanent and temporary slopes in AfSin-Elbistan lignite basin, &Ccedil / &ouml / llolar sector. The effect of ground water on the stability of slopes was investigated in detail and maximum safe slope angles were determined for different water levels. For limit equilibrium analysis, Rocscience SLIDE software, for finite difference analysis in 3-D, Itasca FLAC3D was used. In the limit equilibrium analyses both circular and composite failures were considered. Shear strength reduction method is used for the finite difference method. The results between limit equilibrium and 3-D finite difference methods were compared. When the failure surfaces obtained from the finite difference analyses were imposed to limit equilibrium analysis, computations are resulted in lower factor of safety values for limit equilibrium analysis.

ABSTRACT HYDRAULICS OPTIMIZATION OF FOAM DRILLING IN DRILLING OPERATIONS &Ouml / zer, Ceren M. Sc., Department of Petroleum and Natural Gas Engineering Supervisor: Assoc. Prof. Dr. Evren &Ouml / zbayoglu September 2009, 72 pages In drilling, drilling fluid affects every single step of operation. If rig system is thought as the human body, drilling mud can be defined as the blood system of it. Drilling fluid carries the cuttings, cools the bit, it conditions the hole and so on. Some special kinds of drilling fluids are used for special purposes such as underbalanced drilling. Underbalanced drilling is generally used to prevent formation damage, lost circulation and to increase the penetration rate.Since 1980&rsquo / s foam is used as drilling fluid for underbalanced drilling purposes and there are some models for bit hydraulic optimizations. In this study, mathematical model has been derived considering not the volumetric flow rate but the mass flow rate of the foams. Maximum hydraulic horse power at the bit is determined as a function of mass flow rate. Using this concept, optimum volumetric flow rates for liquid and gas phases as well as optimum nozzle size are determined.Using this mathematical model, a computer program is developed for comparing the results with the existing data available in the literature. It accounts for the compressibility of foam and pressure losses inside the drill string, bit and annulus.Hole size, drill-string properties, formation temperature and pressure, maximum inlet pressure are used as input parameters. Program calculates static back pressure,pressure losses in the whole system, bottom hole foam properties such as quality and velocity and optimum liquid and gas flow rates which are the key parameters of foamdrilling optimization. Results show that liquid and gas rates should be increased with increasing hole sizeand formation pressure. Increasing temperature gradient causes a minimal decrease on foam rate properties. In addition, pressure losses due to friction increases with increasing hole size and formation pressure. Decrease in formation temperature also decreases the foam quality. Changes in temperature gradient causes minimal changes on foam rate properties. Comparisons of the proposed model with other models from the literature also gave good match. The optimization criteria and assumptions are differing from the existing models. As a result the comparison does not have to one to one match with the others. The results from this study may be used for optimization of flow rate of foam as drilling fluid based on mass flow.