Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Effect of spatial variability of soil and soil-cement ground reinforcement on behavior of soil and overlying structures under static and dynamic loadings(Montana State University - Bozeman, College of Engineering, 2022) Zaregarizi, Shahabeddin; Chairperson, Graduate Committee: Mohammad Khosravi; This is a manuscript style paper that includes co-authored chapters.This study presents the results of spatial variability effect of soil and soil-cement (SC) ground reinforcement on behavior of soil and overlying structures under static and dynamic loadings. The objective is to evaluate the improvement/merit of employing stochastic modeling approaches, such as spatially correlated random fields, relative to deterministic analysis with uniform properties for the soil and SC walls. The results of studies are used to provide a representative SC shear strength for use in practical applications to account for spatial variability in soil-cement strength properties.Item Effect of bio-cementation on thermal properties of silty sand(Montana State University - Bozeman, College of Engineering, 2022) Gunyol, Pinar; Chairperson, Graduate Committee: Mohammad KhosraviIn recent years, there has been an increasing interest in the use of biological technologies in geotechnical engineering to improve thermal properties of geomaterials. Urea hydrolysis is a chemical reaction which can generate favorable conditions that result in the precipitation of calcium carbonate. Certain microbes or plant sources produce the urease enzyme which catalyzes the hydrolysis of urea to form carbonate (CaCO 3) to bond soil particles. Cementation located between the grain particles acts as a highly conductive heat transfer path by increasing the contact area between the sand particles. In this thesis, the applicability of bio-cementation via microbially induced calcite precipitation (MICP) on silty sand specimens with different fines contents of 0%, 5%, and 15% were investigated. MICP promoting fluids were injected into sand-filled columns and the resulting calcium conversion was measured. At the end of the injections, the MICP treated specimens were tested for cementation uniformity. The amount of precipitated CaCO 3 gradually decreased as the distance from the injection ports increases. The observed bio-cementation distribution could be attributed to the filtration of bacterial cells through the soil particles. The resulting effect of filtration on CaCO 3 distribution was observed to be more prominent for silty sands, presumably due to the presence of fine grains. Thermal conductivity measurements were assessed after each pulse during the MICP treatment using a TR-3 sensor. Under the saturated and untreated conditions, thermal conductivity increased with increasing fines content. In addition, MICP treatment can increase the thermal conductivity of saturated silty sands with the increasing number of treatment pulses. An increase of about 18% in thermal conductivity of the soil was achieved at an average CaCO 3 content of 10.7% presumably due to the formation of calcium carbonate bridges binding the soil grains together. The results presented herein suggests that MICP treatment can be a viable option to increase the thermal conductivity of soils in the range of fines content studied here (less than 15%). The findings of this research could be used to improve the efficiency of geothermal boreholes and other energy geo-structures using MICP by improving thermal conductivity of dry and partially saturated soil.Item In-plane shear behavior of geosynthetics from bias biaxial tests using digital image correlation(Montana State University - Bozeman, College of Engineering, 2019) Schultz, Emily Christine; Chairperson, Graduate Committee: Steven PerkinsGeosynthetics are polymeric membranes used for structural reinforcement of soils in a variety of roadway and foundation applications, many of which create biaxial loading on the geosynthetic. Orthotropic linear elastic models have been used to represent geosynthetic behavior at working load levels for engineering design purposes. Typically, the models rely on index parameters obtained from test methods that do not represent the biaxial field loading conditions. Proper calibration of these models requires load-strain data obtained from tests that have controlled stress and strain boundaries such as biaxial tension tests. Previously at Montana State University, Haselton (2018) successfully used a custom biaxial device to perform biaxial tension tests on cruciform shaped geosynthetic specimens, producing a partial set of resilient elastic constants for two woven geotextiles and six biaxial geogrids. To complete the set of elastic constants by determination of the in-plane shear modulus, another mode of loading was necessary. Literature from biaxial shear tests of architectural membranes suggested cutting the cruciform shaped samples with the principal material directions on a 45-degree bias, which causes the sample to shear when the cruciform axes are unequally loaded. This test mode was successfully implemented with the existing biaxial device to determine the resilient in-plane shear modulus using an orthotropic linear elastic model. Full-field strain measurements were captured using digital imaging correlation (DIC) software available at Montana State University. DIC was shown to produce equivalent strain measurements to the mechanical instrumentation (LVDTs) used by Haselton, enabling a combined dataset. The full-field DIC strain measurements were then used to validate Haselton's assumption regarding the region of uniform strain and to identify the region of uniform strain for data collection in this thesis. DIC also showed reasonably pure biaxial tension in the cruciform samples, validating the elastic constant derivations for both Haselton and this thesis.Item Experimental investigation of the thermal effects of frost susceptible soils(Montana State University - Bozeman, College of Engineering, 2005) Newell, Zachary Allen; Chairperson, Graduate Committee: Robert Mokwa.Damages to engineering structures attributed to frost action of subgrade soils amounts to millions of dollars annually. Theoretical research has been conducted to examine the details of the frost action phenomenon since the 1940's. However, a reliable and practical approach for evaluating the frost susceptibility of soils is nonetheless a goal that has eluded engineers and scientists alike. The research presented herein focuses on the procedures necessary to obtain a numerical model capable of predicting the thermal response of frost susceptible soils. A field facility was designed and constructed with the purpose of measuring and comparing in-situ frost heave characteristics with laboratory-scale test results. A laboratory-testing device was also designed, constructed, and instrumented in order to measure the thermal response of various soil types in a controlled freezing environment. Geotechnical index testing was conducted on the soil types used in the freezing experiments to fully characterize the soils and examine potential correlations between common soil index properties and frost action behavior. The results of the first season of experimentation provided the framework for a testing protocol necessary for the development of a predictive numerical model. The data obtained from the laboratory tests was used to calculate a new engineering parameter called the segregation potential (SP), which was used as an input into the numerical model developed throughout this research. The model simulated the freezing and thawing characteristics of the soil type found at the field facility. The simulated results were then compared to the in-situ frost action behavior observed at the facility. An improved testing protocol is necessary to obtain more accurate and consistent results. As this research progresses and laboratory testing proceeds, a more extensive database will be acquired and used to build empirical correlations between the thermal and geotechnical index properties of frost susceptible soils. Furthermore, continued research will allow for the advancement of a predictive numerical model that design engineers could use to simulate and predict the freezing and thawing effects of frost susceptible soils incorporated into common engineering structures.