Thesis (M.S.)--Montana State University--Bozeman, 2006. / Typescript. Chairperson, Graduate Committee: Robert Mokwa. Includes bibliographical references (leaves 126-128).

Thesis (M.C.E.)--University of Delaware, 2009. / Principal faculty advisor: Christopher L. Meehan, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

No description available.

Thesis (M.S.)--Oregon State University, 1981. / Typescript (photocopy). Includes bibliographical references (leaves 125-132). Also available on the World Wide Web.

Many field, experimental, and theoretical studies have contributed greatly to our understanding of the occurrence and formation of deformation bands in porous granular materials, but questions remain regarding the mechanics of strain localization, and how the orientation, thickness and internal strain (shear relative to volume change) of deformation bands is influenced by loading history and evolving rock properties. Here we report on triaxial rock deformation experiments using a non-traditional sample geometry to investigate band formation across the brittle-ductile transition. Five-cm diameter cylinders of Berea sandstone were machined with a circular (8.77 cm radius) notch to form a dog-bone sample geometry. In triaxial compression, the sample geometry obviates end-effects without creating heterogeneous stress gradients that can influence localization. Samples were instrumented to measure local strains in the neck region and acoustic emissions (AE), and then shortened to failure at confining pressures of 50 to 250 MPa. Deformation bands formed at all conditions, and photo mosaics of the outer sample surface were used to determine the thickness and orientation of the bands. Band thickness increases from several to tens of mm thickness and the angle between the bands with the shortening axis changes from 35 to 80 degrees, as confining pressure increases from 50 to 250 MPa, respectively. Mechanical data, including local strain measurements through yield, were used to test theoretical models for the onset of localization and formation of deformation bands as an instability in the constitutive description of homogeneous deformation. Generally, theoretical predictions compare favorably with the observed onset of localization determined by marked changes in the AE rate, and are consistent with the formation of compacting shear bands at higher mean stress. Predictions of changes in band orientation with mean stress are largely consistent with observed trends, but deviate from the observed orientation by as much as twenty degrees.

Much speculation on extraterrestrial life has focused on finding environments where water is present. Heating of smaller icy bodies may create and sustain a possible liquid layer below the surface. If liquid water was sustained for geologically significant times (> 108 years) within the ubiquitous small bodies in the outer solar system, the opportunities for development of simple life are much greater. The lifetime of the liquid water layer will depend on several factors, including the rate of rock/water reaction, which will depend on the rate at which water can be segregated from a melting ice/rock core. For the liquid water phase to migrate toward the surface, the denser rock phase must compact. The primary question that this thesis will answer is how fast melt water can segregate from the core of an ice-rich planetesimal. To answer this question we treat the core as two phase flow problem: a compacting viscous “solid” (ice/rock mixture) and a segregating liquid (melt water). The model developed here is based on the approach derived to study a different partially molten solid: in the viscously deforming partially molten upper mantle. We model a planetesimal core that initially a uniform equal mixture of solid ice and rock. We assume chondritic levels of radiogenic heating as the only heat source, and numerically solve for the evolution of solid and melt velocities and the distribution of melt fraction (“porosity”) during the first few million years after accretion. From a suite of numerical models, we have determined that the meltwater is segregated out of the core as fast as it is created, except in the case of very fast melting times (0.75 My vs. 0.62 My), and small ore radius (~25 to 150 km, depending on the viscosity of the ice/rock mixture in the solid core). In these latter cases, segregation is slower than migration and a high water fraction develops in the core. Heat released by water-rock reactions (not included in this model) will tend to drive up melting rates in all cases, which may favor this latter endmember.

This dissertation focuses on the development of a mechanics based soil-roller interaction model intended to determine the degree of compaction of the top soil layer. The model was calibrated with, and compared to, soils data obtained from field and laboratory tests. The model contained 2 soil layers, but can be expanded to include additional layers. This study concludes that the developed soil-roller interaction model is capable of accurately determining the degree of compaction of the upper soil layer through back calculation of the soil modulus values. The model was able to reach convergence between the calculated and measured values of roller drum deflection through a regression analysis of soil stiffness and damping characteristics. The final values of the stiffness and damping characteristics needed to achieve a 1 percent difference between the calculated and measured values of roller drum deflection fell within expected ranges for the type of material tested. Part of this study included a sensitivity analysis of the input characteristics. The results of the sensitivity analysis revealed that the output of the model was highly sensitive to the mass of the second soil layer and to the elastic and plastic stiffness characteristics within both soil layers, but relatively insensitive to the mass of the first soil layer. The lack of sensitivity to the mass of the first soil layer means that large changes in the layer mass, and by extension the density, will have little effect on the output of the model. This characteristic is a drawback for conventional, density based specifications. However, specifications based on installing fill to the designed values of stiffness or modulus could benefit from the model. Much of the initial difference between calculated and measured roller drum deflection was probably caused by the difficulty in determining accurate starting values for the soil stiffness, damping and mass model characteristics. Future research should focus on ways to determine accurate values of the required input characteristics.

Many field, experimental, and theoretical studies have contributed greatly to our understanding of the occurrence and formation of deformation bands in porous granular materials, but questions remain regarding the mechanics of strain localization, and how the orientation, thickness and internal strain (shear relative to volume change) of deformation bands is influenced by loading history and evolving rock properties. Here we report on triaxial rock deformation experiments using a non-traditional sample geometry to investigate band formation across the brittle-ductile transition. Five-cm diameter cylinders of Berea sandstone were machined with a circular (8.77 cm radius) notch to form a dog-bone sample geometry. In triaxial compression, the sample geometry obviates end-effects without creating heterogeneous stress gradients that can influence localization. Samples were instrumented to measure local strains in the neck region and acoustic emissions (AE), and then shortened to failure at confining pressures of 50 to 250 MPa. Deformation bands formed at all conditions, and photo mosaics of the outer sample surface were used to determine the thickness and orientation of the bands. Band thickness increases from several to tens of mm thickness and the angle between the bands with the shortening axis changes from 35 to 80 degrees, as confining pressure increases from 50 to 250 MPa, respectively. Mechanical data, including local strain measurements through yield, were used to test theoretical models for the onset of localization and formation of deformation bands as an instability in the constitutive description of homogeneous deformation. Generally, theoretical predictions compare favorably with the observed onset of localization determined by marked changes in the AE rate, and are consistent with the formation of compacting shear bands at higher mean stress. Predictions of changes in band orientation with mean stress are largely consistent with observed trends, but deviate from the observed orientation by as much as twenty degrees.

The successful production of high-strength concrete which meets the desired strength and durability is dependent on optimising its rheological (or flow) properties and reducing its loss of workability during the transportation, placing and compaction stages. The research presented in this thesis aimed to: 1. Determine whether mix stability and compactability can be adequately described by the two Bingham parameters of yield value and plastic viscosity. 2. Reduce the uncertainties in material selection with regards to the performance of superplasticizers and cement replacement materials. 3. Examine how the two Bingham parameters vary at different degrees of compaction by vibration. 4. Determine how these influence the strength development characteristics in the hardened state. 5. An additional aim was to carry out any modifications to the test apparatus and methods which experience makes necessary. Measurements with Tattersall's MH two-point workability test apparatus indicated that mix stability correlates more closely with the yield value than with plastic viscosity, whilst the opposite is true with respect to compactability under self-weight. The performance of conventional and new-generation superplasticizers (based on SMF, SNF, MLS, Vinyl and Acrylate polymers) was evaluated with different dosages, mixing procedures and cements. The SNF superplasticizer produced slightly lower initial workabilities than the Acrylate superplasticizer, but the longest workability retentions of the superplasticizers tested. Partial cement replacements by CSF in binary blends produced lower superplasticizer dosage demands, higher initial workabilities and longer workability retentions than those due to PFA and GGBS. When used in ternary blended cements, CSF enhanced the performance of mixes containing PFA or GGBS at w/b ratios of 0.30-0.22. A novel method developed to assess the vibration response of fresh concretes has, for the first time, demonstrated that both the yield value and plastic viscosity decrease during compaction. The method has also demonstrated that the maximum compressive strengths and densities of concretes compacted for different vibration durations/amplitudes coincide with the attainment of zero yield value. Continuous reductions in plastic viscosity during vibration mainly reduced the homogeneity of concrete compacted in short columns.

Th. doct.--Géologie--Paris--Ec. natl. supér. mines, 1989. / Résumé en anglais. Bibliogr. p. 169-183.