Theses and Dissertations at Montana State University (MSU)
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Item Physiographic components of trail erosion(Montana State University - Bozeman, College of Letters & Science, 2000) Godwin, Ian Chandler Paterson; Chairperson, Graduate Committee: Andrew MarcusNo previous study has sought to discriminate between soil erosion and soil compaction when explaining the "missing" cross-sectional areas of incised trails, assuming instead that erosion was the dominant process. Separating the two processes of erosion and compaction is critical to understanding the relationship between physiographic variables and the structure of trails. The purposes of this project are to estimate the relative effects of compaction and erosion on trail cross sectional area along the New World Gulch Trail, Montana, and to better understand the relationship between erosion, compaction, local topography, vegetation, soil bulk density, and soil texture. The following hypotheses were addressed: 1) adjusting the incised cross sectional area of a trail, by removing the effects of soil compaction, will increase the amount of variance in erosion explained by collected physiographic variables; and 2) inclusion of soil bulk density and soil texture as physiographic variables will increase the amount of variance in cross-sectional area explained along the trail. The goals of this study required the collection of field data, analysis of soil samples, and statistical analysis of data. Soil samples and other field measurements were collected over several months during the summer and fall of 1994. Some of the topographic information used in the statistical analysis originated in Urie's (1994) study of recreational trails. The determination of trail slope as one of the primary components of trail incision is consistent with previous studies. Soil water content is the second most significant independent variable when the percentage of particle sizes are not considered. Percent vegetative cover is also significant in the stepwise regression, although it is not significantly correlated to cross-sectional area. The most significant variable added to those already studied was soil bulk density. When individual variables were regressed against the measured cross-sectional area, off-trail soil bulk density accounted for the second greatest amount of variance (r2 = 0.12) after trail slope (r2 = 0.35). The ratio of on-trail soil bulk density to off-trail soil bulk density, which could be considered a measure of compaction, accounted for even more variance (r2 = 0.18) than soil bulk density.Item Feasability of using a gyratory compactor to determine compaction characteristics of soil(Montana State University - Bozeman, College of Engineering, 2006) Browne, Michael John; Chairperson, Graduate Committee: Robert MokwaProctor impact compaction tests represent the most commonly used laboratory method to determine the maximum dry unit weight and optimum moisture content of soils in the United States. Soil compaction methods in the field have changed dramatically over the last 50 years, though the Proctor tests have remained relatively unchanged. One shortcoming of the Proctor tests is that it uses impact loads to compact the soil in a stiff non-yielding mold. This technique may not accurately simulate modern field compaction methods, which rely on a combination of kneading, vibration, and increased normal pressures to achieve high dry unit weights. Consequently, a more appropriate method of compacting soils in the laboratory is needed. The research presented herein explores the feasibility of using a Superpave Gyratory Compactor (SGC) to compact soil specimens. The SGC was created in the early 1990s to accurately represent in-place asphalt densities. Gyratory compactors simultaneously use static compression and a shearing/kneading action to compact asphalt mixtures. Variables within gyratory compaction (confinement pressure, number of gyrations, soil type, and moisture content) were explored to determine their effects on soil compaction.