Biochemical,Strength and Erosional Characteristics of Coral Sand Treated by Bio-Stimulated Microbial Induced Calcite Precipitation

Microbial induced calcite precipitation (MICP), a bio-cementation process, can be adopted to improve the engineering properties of granular soils. Bio-stimulation, via directly enriching indigenous ureolytic bacteria, is a sustainable and economical approach to achieve MICP. In this study, batch solution experiment was firstly conducted to investigate the biochemical aspects of the bio-stimulated MICP process in coral sands. Three different enrichment media were compared. The statistical analysis was performed to reveal statistically significant factors that influence ureolytic activity, pH value, and viable cell number. Then, the unconfined compression and rainfall-induced erosion tests were conducted to investigate the strength and erosion-resistance of bio-stimulated MICP treated coral sands. The experimental results demonstrate that the enrichment duration, initial urea concentration, and enrichment type are major influencing factors of the ureolytic activity. It is found in this study that yeast-extract-based enrichment media with 170 mM initial urea concentration and enriched for 72 h could achieve the best bio-stimulated MICP treatment efficiency. In addition, higher initial urea concentration in the enrichment medium could yield higher ureolytic activity, which could consequently result in higher cementation content and thus larger UCS and better resistance to rainfall-induced erosion.