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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 Aggregate piers: stress transfer mechanism and construction effect(Montana State University - Bozeman, College of Engineering, 2022) Gamboa, William; Chairperson, Graduate Committee: Mohammad KhosraviThis thesis is a compilation of two different papers based on the behavior of aggregate piers which is a soil improvement method used to increase the bearing capacity and reduce the expected settlements of soils in which different types of structures are supported. The first paper describes the results of two modulus load tests and a dimensional finite difference analysis (FDA) conducted to evaluate the load-displacement response of isolated aggregate piers. Load test aggregate piers were constructed with two different materials: the first one with 38 mm base coarse and the second one with 75 mm subbase coarse materials. The numerical analyses provided reasonable predictions of the load-displacement response of the isolated aggregate piers. Parametric analyses using the validated numerical model illustrate that the lateral stress increment on the soil around the pier during the installation process of the pier should be considered in the numerical analysis, otherwise the settlement can be overestimated. The second paper is based on two full-scale load tests that were conducted to examine the load transfer mechanisms of end-bearing single and group aggregate piers. The first included a load test on a 0.76 m diameter isolated aggregate pier. The length of the aggregate pier was 4.3 m. The second test included a 2.1 m square reinforced concrete footing supported by four 0.76 m diameter aggregate piers of 4.3 m long. The soil consists of soft to medium stiff layers of sandy and clayey silt overlain by a 2-m-thick, softer silty clay layer. At the bottom, weathered rock was found. The load transfer mechanism within the length of the piers was examined using a series of load cells and tell-tale reference plates installed at different depths of the aggregate piers. Additionally, the installation effect was investigated using Cone Penetration Tests (CPT) conducted prior and after construction of the aggregate piers and inclinometers installed at multiple locations around the aggregate piers. The results of the experiments were compared with those in the literature to provide insights on the performance of aggregate piers with different configurations (single vs. group) and depths (floating vs end-bearing) in different soil profiles.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 Effect of variation of member stiffness on behavior to timber bridge floor systems(Montana State University - Bozeman, College of Engineering, 1985) Riple, Arne BengtThis paper investigates the effects incurred in a bridge floor system resulting from variation in member stiffnesses. If the stiffness in one stringer is reduced, without reducing the stiffness in the other members, a higher load must be carried by the nonreduced members. The increased loading condition results in reduced capacity for the floor system. The study is accomplished using a computer simulation to analyze the member reactions in the floor system. Using a structural grid as a model for the bridge floor, a matrix solution based on the stiffness method is solved by computer. Figures are presented to show the effects on member reactions resulting from variation in stiffness and loading conditions. Results show the effects occurring in both exterior and interior stringers as well as in the floor planks. The governing effects from these members are combined to show the effects in the floor system. Reducing the stiffness in an exterior stringer results in a greater reduce tion in capacity of the floor system, compared to reduction in capacity due to reduction in an interior stringer.