Reliability-based Environmental Impact Assessment in Geotechnical Engineering
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Date
2023-11-30
Authors
Lee, Mina
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
A sustainable design is achieved by balancing the four aspects, so called the four Es, of sustainability – environment, economy, equity, and engineering. Given that geotechnical constructions involve land transformations through earthworks and construction of large-scale concrete and/or steel structures (e.g., bridge abutments, retaining structures, and tunnels), geotechnical engineering can play a vital role in sustainable development by ensuring that the resources are consumed responsibly with minimal emissions to the environment. In this thesis, methodology frameworks, developed based on (i) environmental impact assessment, (ii) reliability-based design, and (iii) multi-objective optimization, are proposed to facilitate the process of sustainable design in geotechnical engineering. The frameworks are applied to common geotechnical structures such as drilled shaft foundation, pile group, and mechanically stabilized earth (MSE) wall. To quantify the environmental sustainability of geo-structures, life cycle assessment (LCA) is used. LCA utilizes inventory of energy and materials to calculate the emissions from the life cycle stages and characterize the emissions into environmental impacts. In this thesis, the procedures of LCA, which have been tailored to geotechnical applications, are demonstrated meticulously with detailed sample calculations to encourage the use of LCA in standard design practices and to demonstrate the usefulness of information obtained from LCA. In fact, for example, it was found, based on this research study, that the global warming impact and human toxicity of a typical drilled shaft are 39 and 486% of annual world impact per person, respectively. The use of reliability-based design (RBD) methods has been strongly promoted in the last two decades to better tackle the uncertainties involved in design and soil parameters; hence, the connection between important factors in RBD and environmental impacts is investigated in this thesis. A comprehensive analysis is conducted on the relationship between reliability and global warming impact of geotechnical designs (i.e., drilled shaft and MSE wall) considering uncertainties in soil properties, material properties, applied load, model, and design dimension. Parametric and sensitivity studies are systematically conducted using reliability analyses, like first-order reliability method (FORM) and Monte Carlo simulations, and LCA. To balance the multiple aspects of sustainability, a multi-objective optimization framework is proposed using which designers can determine design dimensions that aim for minimizations of cost and global warming impact and maximization of reliability of a geotechnical structure. The framework utilizes several methodologies including LCA, FORM, response surface methodology, and non-dominated sorting genetic algorithm (NSGA-II). To encourage sustainability considerations in geotechnical engineering design, charts are developed which are useful for determining (i) global warming impact of the geo-structures designed with working stress design (WSD) and RBD approaches and (ii) design dimensions optimized with respect to cost, engineering reliability, and environmental impact, without the use of and knowledge in the sophisticated methodologies incorporated in the proposed frameworks.
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Keywords
Sustainability, Geotechnical engineering, Multi-objective optimization, Life cycle assessment