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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 Performance and design of steel pipe pile to concrete cap connections subject to seismic or high transverse loading(Montana State University - Bozeman, College of Engineering, 2016) Kappes, Lenci Robert; Chairperson, Graduate Committee: Michael Berry; Michael Berry, Jerry Stephens and Ladean McKittrick were co-authors of the article, 'Concrete filled steel tube piles to concrete pile-cap connections' in the journal 'Structures Congress 2012' which is contained within this thesis.; Michael Berry, Flynn Murray, Jerry Stephens and Kent Barnes were co-authors of the article, 'Seismic performance of concrete-filled steel tube to concrete pile-cap connections' in the journal 'ASCE Journal of Bridge Engineering' which is contained within this thesis.; Michael Berry and Jerry Stephens were co-authors of the article, 'Analysis methodology for concrete-filled steel pipe piles to concrete cap connections' which is contained within this thesis.This research investigated the seismic behavior of the connection between concrete-filled steel tube (CFT) piles and concrete pile caps. This connection is an important component of an accelerated bridge construction technique, which involves driving steel piles to a finished elevation just below the design deck level, forming a pile cap around the ends of the driven piles, reinforcing this cap, and then filling the piles and the cap formwork with concrete. This cap then serves as the support for the superstructure of the bridge. Conventional configurations of the CFT to pile cap connection often involve congested and complex reinforcing schemes, which can limit the use of this bridge support system. The research discussed herein evaluated the performance of a new detailing scheme that significantly reduces congestion and construction issues, and developed a mechanics-based analysis tool to predict load carrying capacity of this type of connection. This new reinforcing scheme uses U-shaped reinforcing bars to encircle the tip of the embedded CFT pile within the cap, which act to confine the concrete immediately around the pile and transfer the loads throughout the cap. In this research, six connection specimens with various details were tested under lateral loads until failure while monitoring applied loads and lateral displacements. As intended, five specimens experienced failure in the concrete cap, with the remaining specimen failing through plastic hinging in the CFT at the face of the cap. The focus of this test program was on characterizing the failure behavior of the concrete cap; typically, this behavior was observed to consist of crushing of the concrete adjacent to the pile near the face of the cap and at the tip of embedment, followed by yielding of the longitudinal reinforcement, and concluding with yielding of the transverse reinforcement and the formation of diagonal cracks extending from the embedded pile to the edge of the cap. Based on the results of this and a previous investigation, an analysis methodology (similar to moment-curvature analysis) was developed and evaluated. This methodology proved to be an effective means for predicting the ultimate capacity of CFT to concrete pile cap connections.Item A dilatancy approach to estimating the bearing capacity of shallow foundations on sand(Montana State University - Bozeman, College of Engineering, 1996) Madson, Craig RobertItem Bearing capacity of shallow foundations on simulated lunar soil(Montana State University - Bozeman, College of Engineering, 1995) Gui, DanmeiItem The mechanical properties of biofilm populated sand(Montana State University - Bozeman, College of Engineering, 1998) Gyr, PhilipItem Interaction of superstructure, foundation, and soil(Montana State University - Bozeman, College of Engineering, 1981) Hightower, John JosephItem Axial capacity of piles supported on intermediate geomaterials(Montana State University - Bozeman, College of Engineering, 2008) Brooks, Heather Margaret; Chairperson, Graduate Committee: Robert L. MokwaPile foundations used to support bridges and other structures are designed and installed to sustain axial and lateral loads without failing in bearing capacity and without undergoing excessive movements. The axial load-carrying capacity of a driven pile is derived from friction or adhesion along the pile shaft and by compressive resistance at the pile tip. There are well established analytical methods for evaluating pile capacity and for predicting pile driving characteristics for cohesive soil, cohesionless soil, and rock. However, past experience indicates these methods may not be reliable for piles driven into intermediate geomaterials (IGMs), which often exhibit a wide array of properties with characteristics ranging from stiff or hard soil to soft weathered rock. Methods to determine the axial capacity, driving resistance, and long-term resistance of piles driven into intermediate geomaterials are not well established. Nine projects, in which piles were driven into IGMs, from the Montana Department of Transportation were analyzed. Each project contained information from CAPWAP dynamic analyses, construction records, and design reports. The purpose of any analyses, of the nine projects, was to better predict the behavior of piles in IGMs. IGMs were divided into two broad types, cohesive and cohesionless. The computer program DRIVEN is often used to predict the axial capacities of piles; however, in IGMs the design method is unreliable. Attempts were made to determine trends within the available data. Normalized resistances for shaft and toe capacities did yield slight correlations of shaft resistance to pile length in IGMs. Iterative solutions using DRIVEN to match the CAPWAP ultimate capacity did not provide meaningful trends or correlations. Slight modification of MDT's original DRIVEN inputs was required in most cases to match the CAPWAP ultimate capacity. Because no meaningful trends were found from analysis, other capacity calculation methods were used to determine other methods that accurately predict pile capacity within IGMs. The Washington Department of Transportation Gates formula is the most accurate method of those attempted. More research is required for further analysis of piles in IGMs.