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Track maintenance requirements are determined by the condition and subsequent performance of a track section. By being able to quantify the condition of a track functionally as well as structurally the performance of a track can be predicted and its maintenance can be planned pro-actively. Generally, maintenance is conducted on a reactive and/or preventative basis without investigating the cause of maintenance requirements. This usually results in the ineffective use of available maintenance resources. The goal of this dissertation is to provide a basis for determining the most cost effective means of track maintenance as influenced by the substructure. To achieve this goal the relationships between the functional condition of track, as represented by the rate of geometry deterioration, and substructure conditions were examined. To achieve the research goals data were obtained from investigations performed at sites in South Africa on the Heavy Haul Coal railway line and at sites in the United States on the Facility for Accelerated Service Testing, High Tonnage Loop in Pueblo, Colorado. This study provides a procedure to identify sections that perform badly and a measuring and interpretation technique to investigate the cause of substructure related problems. The procedures allow the track maintenance engineer to pro-actively evaluate his track substructure condition and maintenance requirements, allowing him to identify the cause of bad performance as well as the appropriate corrective actions. The geometry measurements are analyzed to identify sections of track with different performance characteristics, and continuous track deflection measurements are used to identify the source of the problem and the need for further investigation.

<p> Ground conditions at underground gold mines in Nevada range from good to extremely poor and implementing the most appropriate ground support can be challenging. Existing empirical ground support design methods were developed predominantly from experience in tunneling or more competent ground, making them less applicable to underground gold mining in Nevada. This research presents empirically derived support guidelines from experience at 5 underground gold mines in Nevada, including: discussions with engineers and miners, review of ground control management plans and consulting documents, and roughly 400 ground control case-studies. Support design recommendations are based on the Weak-Rock Mass Rating (W-RMR) which is a modified Rock Mass Rating (RMR) classification incorporating the Unified Soil Classification System (USCS) for very weak rock masses. Ground support recommendations include rock bolt pattern support pressure, rock bolt length category, excavation surface support, and excavation strategy.</p>

The Chiricahua National Monument in southeastern Arizona presents several interesting questions to the process geomorphologist. First, why are columnar landscapes characteristic of the tuffs? Air photo analysis reveals that column geometries in both cross section and plan view are controlled by two locally radiating, vertical joint sets and a third horizontal joint set. Differential compaction of the tuff may also have led to jointing. The resultant joint planes provide avenues for water migration and consequent focusing of chemical weathering. Second, how can we arrive at the rate of formation of such landforms? The total amount of material erosionally removed from the entire Turkey Creek Caldera ash flow facies present in the monument watersheds was calculated using a digital elevation map. An average denudation rate of 0.017 mm/yr was calculated for the watershed based on the eroded volume. Third, the column ages determined by the denudation rate and the prevalence of different erosional processes, each with its own efficiency, during different climatic periods, suggest a two stage erosional history with rapid erosion during glacial periods and slow erosion during interglacial periods. Fourth, how mechanically stable are the "balanced rocks" and "hoodoos"? Strength parameters for the tuffs were measured. Six columns with very different profiles were measured and then modelled by finite element meshes. Despite their fragile appearances, all columns were well within their static mechanical failure limits. Failure by slip along joint surfaces is the most likely block failure mode, but is greatly minimized by erosional necking of columns into hourglass shapes. Necking causes the principal stresses in the column to rotate out of vertical and focus on the neck. The redirected stresses act as a normal confining stress across dipping joints that would, in the absence of the neck, imperil the column. Fifth, what can the preservation of columns tell us about the seismicity of southeastern Arizona? The dynamic loads of an earthquake should induce resonances that would greatly imperil the larger, thinner columns. The upper height limit of the column population indicates the past occurrence of an earthquake that triggered this resonant vibration and consequent failure. It appears, therefore, that the last column-destroying quakes occurred 2.4 My ago. (Abstract shortened by UMI.)

In this study, a set of rules is established, which when implemented in the modeling of dilatant soils, within the framework of associative plasticity, enables very successful shear and dilatancy predictions. The proposed approach is based on a number of principles, the most important of which are: (1) The plasticity model must have a loading surface that hardens kinematically, and a failure surface that is perfectly plastic. (2) Experimental evidence shows that uniformly deformed sand samples dilate with a constant rate when they reach their ultimate strength value, while critical state is only achieved at very large strains. There is a unique point A on the loading surface that corresponds to the experimentally observed dilatation rate. The hardening rule must, therefore, ensure that the stress point approaches A as it approaches the failure surface. These principles are implemented in a plasticity model and compared to numerous published monotonic and cyclic tests, with varied stress paths, performed on a true triaxial apparatus. The agreement between experimental data and theoretical predictions is excellent.

Slope stability problems with non-circular slip surfaces have been characterized as a problem in optimization in which the safety factor expression is the function to be minimized. The Simplex Method of Nelder and Mead (1965), one of the most powerful direct search methods, has been implemented into program STABL5 (Carpenter et al, 1985) to examine the feasibility of using advanced optimization principles in conjunction with the relatively high problem dimension associated with non-circular slip surfaces. Parametric studies were performed on LSLIP1 in order to determine recommended values for the various input parameters. STABL5 and the revised code LSLIP1 were utilized to solve five slope problems representing a wide range of conditions. The revised code with its built-in Simplex search strategy proved to be more accurate, efficient and reliable than the original code with the random grid search.

A new fracture grouting technology has been developed to meet the requirements of high-level nuclear waste isolation. Bentonite fracture grouting tests are performed on a fracture model, made of circular acrylic plates with outer diameter of 30 cm and a central injection hole of 2.5 cm diameter. Suspensions with bentonite concentration of 9% to 31% have been injected into fractures with apertures of 9 to 39 microns under injection pressures less than 0.5 MPa. After grouting, the hydraulic conductivities of the fractures are reduced from the 10-1 to the 10-5 cm/s level. When the suspension is thin enough and the fracture is very small, channeling develops in the grouted fractures. Preliminary results indicate that the permeability of a grouted fracture does not increase with time in 125 days. The flow properties of bentonite suspensions, viscosity, shear stress, yield stress and gelation, are investigated. Water flow through ungrouted fractures and movement of water in bentonite grout are studied.

The scope of these studies encompasses both field site testing and scale modeling. The purpose was to better understand the complexities of electromagnetic diffraction geotomography, or the imaging of ground between boreholes using electromagnetic waves. Two field sites and a scale model tank were investigated. One field site, the San Xavier Mine facility, is located in metamorphosed paleozoic limestone. This site proved a challenge in that the medium was fairly inhomogeneous and resulted in server wave scattering. Inter-borehole transmission allowed only 15 MHz to penetrate for an adequate signal level. Both a parallel scan and geotomography of targets produced inconclusive results. The Apache Leap site contained a homogeneous quartz-latite tuff, allowing penetration of 150 MHz. Parallel scans of a metal pipe target, proved that alterant geotomography, or scans performed before and after tracer injection, was a possibility for future studies. The model tank allowed the use of horizontal dipole antennas, a coil substitute. Target effects produced strong interference patterns.

Various filtering and integration techniques were used to analyze geologic, geophysical and geochemical data from the Twin Peaks area located in the DeLamar mining district in Southwestern Idaho. In particular rank correlation and favorability analysis were employed in this study. The data analysis was used to delineate target areas considered favorable for epithermal gold-silver mineralization. The interpretation of geophysical data was emphasized because of the importance of subsurface geologic features and complications caused by post mineral cover. Field investigation of the target areas provides strong evidence supporting the potential for significant mineralization in four of the twelve target areas selected.

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