Abstract:

 Biomineralization of soil solidification methods is currently diversified, and different mineralization methods have their own limitations. The enzyme-induced carbonate precipitation (EICP) lacks nucleation sites, while the targeted activation of urease-producing microorganisms induced mineralization (biostimulation) has a longer solidification cycle and lower strength. Aiming at these problems, a mineralization method of biostimulation combined with EICP to reinforce soil is developed. In this paper,  reclaimed sea sand from Xiamen Xiang'an International Airport was investigated. Unconfined compressive strength tests (UCS), calcium carbonate production measurements, scanning electron microscope (SEM), X-ray diffraction (XRD), and microbial diversity testing were used to evaluate and analyze the solidification effect of the combined method. Some findings were observed.          1) Biostimulation combined with EICP mineralization can get a higher UCS, up to 2 300 kPa, which was greater than the sum of the UCS of the two separate mineralizations. 2) Biostimulation combined with EICP can promote the formation of calcium carbonate precipitation while improving its distribution uniformity, and optimize the crystal structure of calcium carbonate. 3) Microbial community analysis shows that biostimulation can highly stimulate urease-producing bacteria. EICP has a slight stimulating effect on some species. The species richness and uniformity of biostimulation combined with EICP are between those of EICP and biostimulation.

Key words: targeted activation, enzyme-induced carbonate precipitation (EICP), land reclamation sea sand, solidification, microbial community