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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Stochastic three dimensional joint geometry: Modeling and verification.

Wathugala, Deepa Nelumkanthi. January 1991 (has links)
Eight 3D (three dimensional) rock joint geometry modeling schemes which investigate statistical homogeneity, and incorporate corrections for sampling biases and applications of stereology are presented. A procedure for verification of the developed models also is presented. In this study, shape of the joints was assumed as circular. The models provide the number of joint sets, and for each joint set, the intensity, orientation, spacing, location and diameter distributions. Miller's method (1983) with new interpretations (Kulatilake et al., 1990b) and equal area polar plots were used together to identify the largest statistically homogenous region around the ventilation drift, Stripa mine, data of which were used for both modeling and verification. Four joint sets were found in this region. A general vector approach to correct sampling bias on joint orientation is presented. Corrected data as well as raw data were subjected to chi-square goodness-of-fit tests to check the suitability of hemispherical normal and Bingham distributions in representing orientation of joint sets. Only raw data of joint set 4 followed Bingham distribution. Therefore, joint set orientations were best represented as empirical distributions. Two methods are presented for the modeling of joint spacing, linear intensity and location. In each method, spacing distributions of joint sets were best represented by exponential distributions. Then, joint intensity and location distributions are represented by Poisson and uniform distributions respectively. Correction of sampling bias on joint spacing also is presented. Joint size modeling was carried out using two methods: area sampling survey method and scanline sampling survey method. In these two methods, corrections of sampling biases associated with joint size modeling are presented. 3D joint sizes were inferred from 2D trace length measurements using geometrical probability and conditional probability concepts. In both methods diameter distributions are represented by gamma distributions. For verification, joints were generated in a volume according to the statistical models, using Monte-Carlo simulation. This volume was intersected by planes to obtain joint traces on exposures of size and shape similar to the ones used to obtain field data. Characteristics of these predicted joint traces were compared with the field data in a statistical sense. For the rock mass under this study, the modeling scheme 3 was found to be the most suitable scheme.
2

Multivariate and geostatistical analyses of Phase I Eastern Lake Survey data.

Rhodes, Hannah Rasmussen. January 1993 (has links)
Many difficulties are encountered when analyzing large spatial data sets. The following research focuses on how various univariate, multivariate, geostatistical, and geographic information systems techniques can aid in the examination of spatial data sets containing large numbers of samples, as well as variables. The analyses are applied to data from Phase I of the Eastern Lake Survey which deals with the effects of acidic deposition on aquatic ecosystems. Relationships among chemical analytes are explored, and outlying or atypical lake samples and chemical analytes are identified using statistical techniques including univariate statistics, correlation analysis, normality testing, multivariate outlier testing, correspondence analysis, and ordinary kriging. The primary objective of the correspondence analysis was to obtain a reduction in the number of chemical analytes in order to make subsequent data analyses and interpretations easier. The main reason for performing a geostatistical analysis of the ELS-I data was to obtain maps of interpolated values for unsampled lake locations. Geographic information systems technology was used to examine the influence of lake size on the kriging analysis. This research should provide useful for future efforts to detect and ameliorate the effects of acidic deposition on aquatic ecosystems.
3

Geomorphology of welded tuffs, Chiricahua National Monument, southeastern Arizona.

Hall, Douglas Benjamin. January 1993 (has links)
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.)
4

Assessment of ground contamination using Kriging techniques

Largueche, Fatima-Zohra January 1996 (has links)
No description available.
5

Seismic behavior of tiedback retaining walls.

Neelakantan, G. January 1991 (has links)
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.
6

Fundamental studies of the deformability and strength of jointed rock masses at three dimensional level.

Wang, Shuxin. January 1992 (has links)
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.
7

Experimental assessment of borehole plug stability.

Cetintas, Arif. January 1994 (has links)
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.
8

A quantitative spatial thoroughness methodology for environmental site characterization

Tsai, Yi-Chang 08 1900 (has links)
No description available.
9

Influence of surface topography on interface strength and counterface soil structure

Yi, Sŏk-wŏn 12 1900 (has links)
No description available.
10

Particle-geomembrane interface strength behavior as influenced by surface topography

Dove, Joseph Edwin 12 1900 (has links)
No description available.

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