Bio-Mediated Improvement of Soil and Soil-Structure Interface Behavior

University Of California-Davis, Davis CA

Investigators

Abstract

In this project we will explore and evaluate the potential of a bio-mediated ground improvement technique to (1) improve the engineering properties (i.e. strength, stiffness) of a finite zone of soil and (2) heal zones of soil damaged by construction methods. The former purpose parallels other conventional grouting techniques (e.g. treatment of large finite zones of soil which are inadequate for construction on constructed performance), while the latter purpose could be used to treat soil in the immediate vicinity of construction elements (such as piling) which has undergone damage (e.g. crushing, decementation) during the installation process. In both cases, the overarching objective is to improve the performance of constructed systems through improving the ?weak link? in the load transfer mechanisms. Within this project our objective is to advance a bio-mediated technique which induces calcite precipitation with granular soils. We will continue the development of an aerobic process whose feasibility has been established in the laboratory by the PIs and others, and explore a parallel anaerobic process with the same precipitated calcite end product. Biological aspects of the treatment process will be investigated, including long-term permanence, treatment optimization, and environmental impact. At the mm-to-cm length scale we will investigate the influence of the bio-treatment on soil and soil-structure interface behavior, examining changes in material state, permeability, response to static and cyclic loading across a range of strain magnitudes, and soil-structure interface shear. Finally, we propose to perform m length scale model testing of the injection feasibility for treatment of a finite zone of soil and for treatment immediately around a pile using a wedge shaped chamber that accurately replicates radial flow and diffusion from a line injection source in situ. This will enable assessment of full scale field injection feasibility at reduced costs and localized measurements of the injection process not possible in the field. This research program is designed to advance the bio-treatment method from proof-of-concept to a maturity that would motivate government agencies and industry to continue its development. The education, outreach, and training activities span K-16+ students, teachers, and research faculty. The research team has linked with a prominent science and engineering education textbook publishing company to develop classroom lecture modules and laboratory exercises. NSF Research Experience for Teachers (RET) and Research Experience for Undergraduate (REU) fellows will be involved in technical research as well as in the K-16+ curriculum development.