Theses and Dissertations at Montana State University (MSU)
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Item Determination of elastic constants for geosynthetics using in-air biaxial tension tests(Montana State University - Bozeman, College of Engineering, 2018) Haselton, Henry Nathaniel; Chairperson, Graduate Committee: Steven PerkinsGeosynthetics are polymeric membranes used for structural reinforcement for many geotechnical applications such as reinforced pavement. Geosynthetics have been shown to increase the service life of roadways in a variety of field tests. The knowledge of geosynthetics and design methodologies could be improved with a better understanding of geosynthetic material properties. To better understand how geosynthetics perform in field loading situations, geosynthetic tensile resilient material properties are needed. The properties of geosynthetics of interest for this thesis are the resilient tensile modulus of elasticity and Poisson's Ratio (elastic constants) in both material directions. Modulus of elasticity has been traditionally calculated using wide-width uniaxial tests, which is a poor representation of field loading conditions due to the unrestrained sides of the material. Biaxial tension tests are a better representation of field loading conditions and thus were implemented for determination of elastic constants pertaining to different geosynthetic materials. Biaxial tension tests were performed on cruciform shaped samples using a custom device built by the Western Transportation Institute at Montana State University to test geosynthetic samples. A biaxial testing procedure was created using conclusions from a uniaxial testing program implemented to examine the resilient response of geosynthetics after being subjected to four types of loading (cyclic stress relaxation, monotonic stress relaxation, cyclic creep and monotonic creep) over different durations of time. The conclusions of the uniaxial testing program, the available literature and ASTM D7556 were synthesized to create a biaxial testing procedure. Biaxial tension tests were performed in three modes of loading to simulate loading conditions and loadings where a geosynthetic experiences loading in both directions simultaneously. The biaxial tension tests generated stress and strain data used to calculate the elastic constants of six biaxial geogrids and two woven geotextiles. The elastic constants were calculated using an orthotropic linear elastic constitutive model with a least squares approximation. The elastic constants calculated for each geosynthetic material were shown to represent the resilient behavior of geosynthetics in different field loading situations with more realistic boundary conditions than previous uniaxial tests used to characterize the resilient response of geosynthetics.Item Ureolysis induced mineral precipitation material properties compared to oil and gas well cements(Montana State University - Bozeman, College of Engineering, 2018) Beser, Guneycan Dicle; Chairperson, Graduate Committee: Damon Fick; Adrienne Philips (co-chair)Novel methods are needed to prevent or mitigate subsurface fluid leakage, for example stored carbon dioxide, fuels during unconventional oil and gas resource development or nuclear waste disposal. Ureolysis-induced calcium carbonate precipitation (UICP) has been investigated as a method to plug leakage pathways in the near-wellbore environment and in fractures. The enzyme urease catalyzes the hydrolysis of urea to react with calcium to form solid calcium carbonate (similar to limestone). UICP test specimens were prepared in triplicate by filling 2.5 cm (diameter) x 5 cm (length) and 5 cm x 10 cm cylindrical molds with sand and injecting both microbial and plant-based enzymes with urea and calcium solutions to promote precipitation. Sources of urease included jack bean enzyme and S. pasteurii microbe, resulting in both enzyme and microbe induced calcite precipitation (EICP, MICP) specimens. For comparison, Class H well- and Type I-Portland specimens were made by mixing cement paste (API 10B) with sand (ASTM C305). Fine cement specimens were also included in the comparison and were made both by mixing and also injecting to match the process used to make the biocement specimens. For the 2.5 cm x 5 cm specimens, the addition of nutrient broth to the enzyme specimens (ENICP) resulted in increased compression strengths compared with specimens without nutrient (EICP). The average compression strengths of these ENICP specimens reached 77% and 66% of the compressive strength of the 28-day well cement and Type I cement mortars, respectively and were over two times larger than the 28-day strength of the fine cement specimens. For 5 cm x 10 cm specimens, compression strengths of MICP, ENICP, and EICP specimens reached 42%, 38%, and 16% of the 28-day injected fine cement specimens. The average modulus of elasticity of ENICP was 17,316 + or = 1,430 MPa with 8.3 + or = 1.8% CaCO3 content (g/g sand) and was approximately 30% larger than the average modulus measured for the fine cement specimens. The results of this study indicate that the UICP produced specimens may have adequate strength and stiffness for field applications.Item Numerical analysis for rectangular slabs under hydrostatic pressure(Montana State University - Bozeman, College of Engineering, 1952) Bozzay, JosephItem On the development of a refined finite element free from discretization-dispersion for elastic wave propagation modeling(Montana State University - Bozeman, College of Engineering, 1973) Lakshminarayanan, Venkatachalam