UC Davis

Recently, bio-mediated and bio-inspired solutions in the field of geotechnical engineering havebeen proposed as sustainable alternatives to traditional, cement-intensive business-as-usual technologies for infrastructure resiliency through geologic hazard mitigation. As these biogeotechnologies develop, it is imperative that quantitative sustainability assessment, such as life cycle sustainability assessment (LCSA), is employed to assess and guide their sustainable development. This can ensure that they produce both technological and sustainability advantages compared to traditional technologies considering social, environmental, and economic impacts. This dissertation addresses these needs for improved environmental assessment across biogeotechnologies by presenting a framework to evaluate the environmental impacts and cost across the whole life cycle of a geologic hazard mitigation project.

Chapter 1 introduces bio-mediated and bio-inspired geologic hazard mitigation techniques aspotentially sustainable alternatives to existing technologies and life cycle sustainability assessment (LCSA) as a method to evaluate them. Chapter 2 then presents a systematic literature review of emerging bio-mediated and bio-inspired ground improvement LCSA studies, including those focused on enzyme induced carbonate precipitation (EICP), microbially induced carbonate precipitation (MICP) and microbially induced desaturation and precipitation (MIDP). The review demonstrates that environmental impacts such as global warming and eutrophication are the most assessed and that inconsistencies in methodology limit the application of the reviewed assessments.

Chapter 3 of this dissertation presents a framework for the evaluation of the environmentalimpacts and costs incurred across the whole life cycle of geotechnical earthquake mitigation projects. This chapter also provides clear guidance for completion of a whole life cycle assessment following the ISO 14040 and 14044 life cycle assessment standards. Permeation grouting is evaluated as a liquefaction mitigation technique to provide an example implementation of the proposed framework and guidance. This case study shows that the construction stage of the permeation grouting project, specifically raw material supply for the microfine cement grout, contributes greatly to the whole life cycle impacts. Site investigation activities account for less than 1% of whole life cycle impacts suggesting that an increased scope site investigation program could provide a better understanding of the subsurface, reducing design uncertainties, without significantly impacting project sustainability.

Finally, a life cycle assessment of EICP columns for ground improvement is completed inChapter 4 to determine the environmental sustainability of EICP columns as compared to permeation grouting. The study finds that EICP columns impacts are primarily due to calcium chloride and urea production and transportation, with EICP biogeochemical process emissions (i.e., ammonium production) accounting for the high eutrophication potential of EICP columns. Other than when considering eutrophication potential, EICP columns present as a more environmentally sustainable alternative to cement-based ground improvement.