Browsing by Author "Maurer, Brett"

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    Development of an Improved and Internally-Consistent Framework for Evaluating Liquefaction Damage Potential
    Upadhyaya, Sneha (Virginia Tech, 2019-12-04)
    Soil liquefaction continues to be one of the leading causes of ground failure during earthquakes, resulting in significant damage to infrastructure around the world. The study presented herein aims to develop improved methodologies for predicting liquefaction triggering and the consequent damage potential such that the impacts of liquefaction on natural and built environment can be minimized. Towards this end, several research tasks are undertaken, with the primary focus being the development of a framework that consistently and sufficiently accounts for the mechanics of liquefaction triggering and surface manifestation. The four main contributions of this study include: (1) development of a framework for selecting an optimal factor of safety (FS) threshold for decision making based on project-specific costs of mispredicting liquefaction triggering, wherein the existing stress-based "simplified" model is used to predict liquefaction triggering; (2) rigorous investigation of manifestation severity index (MSI) thresholds for distinguishing cases with and without manifestation as a function of the average inferred soil-type within a soil profile, which may be employed to more accurately estimate liquefaction damage potential at sites having high fines-content, high plasticity soils; (3) development of a new manifestation model, termed Ishihara-inspired Liquefaction Severity Number (LSNish), that more fully accounts for the effects of non-liquefiable crust thickness and the effects of contractive/dilative tendencies of soil on the occurrence and severity of manifestation; and (4) development of a framework for deriving a "true" liquefaction triggering curve that is consistent with a defined manifestation model such that factors influential to triggering and manifestation are handled more rationally and consistently. While this study represents significant conceptual advance in how risk due to liquefaction is evaluated, additional work will be needed to further improve and validate the methodologies presented herein.
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    Moving Towards an Improved Liquefaction Hazard Framework: Lessons Resulting From the 2010-2011 Canterbury, New Zealand, Earthquake Sequence
    Maurer, Brett (Virginia Tech, 2016-10-24)
    The 2010-2011 Canterbury, New Zealand, Earthquake Sequence (CES) resulted in a liquefaction dataset of unprecedented size and quality, presenting a truly unique opportunity to assess and improve the efficacy of liquefaction-analytics in the field. Towards this end, the study presented herein develops and analyzes a database of 10,000 high-quality liquefaction case histories resulting from the CES. The objectives of these analyses are varied, but underlying each is the desire to more accurately assess liquefaction hazard for civil infrastructure (i.e., to predict both the occurrence and damage-potential of soil liquefaction). Major contributions from this work include, but are not limited to: (1) the Liquefaction Potential Index (LPI), the state-of-practice framework for assessing liquefaction hazard, is shown to produce erroneous predictions for a significant percentage of the assessed case histories; (2) the cause of poor predictions is rigorously investigated and specific shortcomings of the LPI framework are identified; (3) based on the limitations identified, and using insights from historical data, a revised liquefaction hazard framework is developed; and (4) the revised framework is shown to assess liquefaction hazard more efficiently relative to both LPI and a competing alternative framework newly proposed in the literature. Ultimately, significant room for improvement remains with respect to accurate assessment of liquefaction hazard. The findings presented in this dissertation thus form the basis for future development of a further-improved framework. Moreover, a methodology is proposed by which improvements can be measured in a standardized and objective manner.