Numerical Load Testing of a Geosynthetic Reinforced Soil

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2016-12
Authors
Kaya, Landon
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[Honolulu] : [University of Hawaii at Manoa], [December 2016]
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Geosynthetic reinforced soil (GRS) abutments have been increasingly used due to several advantages over traditional concrete abutment walls. Two notable advantages include: (1) Fast and cost-efficient method of construction due to the elimination of cast-in-place reinforced concrete abutments; and (2) Reduced carbon footprint due to less use of cement since cement production produces an enormous amount of carbon dioxide. GRS abutments have to be designed for settlement and bearing capacity. Available design procedures are often based on large scale load tests on GRS columns which is expensive and not routinely performed. Therefore, using a numerical model to simulate these load or performance tests would offer a more economical alternative. The FEMtij program was used for analyzing GRS load tests in 2-D and 3-D. In 2-D , the ideal constitutive models for the soil, CMU blocks, geotextile, and footing were the subloading tij, Drucker-Prager, linear elastic with post-yield softening, and linear elastic, respectively. Three factors that greatly affect the GRS capacity were investigated by performing a sensitivity analysis. These factors were the effects of soil-footing friction angle, the constitutive model of the CMU (Drucker Prager vs linear elastic), and the constitutive model of the geotextile (linear elastic with post-yield softening vs linear elastic). The 3D analyses were less successful, details of which can be found in the thesis. From the calculated 2D load-settlement and lateral displacement curves, and heat maps of shear strain, the following observations and conclusions were made: (1) The capacity of the GRS increased with increasing soil-footing friction angle. (2) Using a Drucker-Prager model for the CMUs caused the GRS to have a smaller capacity than if they were linear elastic. (3) Modelling CMU blocks with an elasto-plastic model is important due to some of the CMUs crushing during the performance tests. (4) By allowing the geotextiles to soften after exceeding its tensile strength, the GRS capacity was less than if the geotextiles were linear elastic. (5) It is important to model a softening geotextile because of the observed ripping of the geotextiles during the performance tests. (6) Shear bands were observed in the GRS columns. They are inclined at 45° and 50° to the horizontal for GRS columns without and with CMU blocks, respectively.
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M.S. University of Hawaii at Manoa 2016.
Includes bibliographical references.
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Theses for the degree of Master of Science (University of Hawaii at Manoa). Civil & Environmental Engineering
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