Author(s): Yingzheng Zhou; Dawei Guan; Liang Cheng
Linked Author(s):
Keywords: Enzyme-induced carbonate precipitation; Bio-cemented sand; Marine erosion resistance; Seawater mineralization
Abstract: Enzyme-induced carbonate precipitation (EICP), which precipitates calcium carbonate within the soil matrix to cement the granular grains, presents a promising bio-mediated approach for scour countermeasures. To encourage the application of EICP in mitigating erosion of non-cohesive soil in marine environments, this study explores the erosion performance of bio-cemented sand and optimizes its treatment process. In the erosion experiments, various parameters such as curing duration, cementation degrees, and urease activities are examined to understand their influence on erosion behaviors of bio-cemented sand soil. The results suggest the critical role of the interaction between calcium carbonate content and crystal features in determining the effectiveness of erodibility reduction. As the precipitated amount increases, the cemented soil exhibits enhanced hydraulic erosion resistance, with the erosion mode shifting from particle erosion and aggregated detachment to chunk fracture. Furthermore, the research modifies the EICP grouting formulation by leveraging calcium from seawater to stimulate carbonate precipitation, in contrast to conventional practices using lab-graded calcium reagents. The results indicate that enzyme activity is slightly inhibited in marine conditions, and the efficacy of urea hydrolysis is influenced by the injected rate of seawater and the ambient temperature. Through continuously injecting a cementation solution based on seawater, the sand columns are consolidated and their unconfined compressive strength is significantly enhanced, reaching a maximum value of 2.8 MPa. This notable enhancement can be attributable to the strong interparticle cementation facilitated by the substantial precipitates of aragonite, calcite magnesium and magnesium carbonate. Collectively, these findings are anticipated to serve as valuable theoretical foundations for future engineering applications.
Year: 2024