Particle Morphology of Calcareous Sand and MICP-Treated Efficiency

Microbial-induced calcium carbonate precipitation (MICP) is a promising approach to improve the geotechnical engineering properties of granular soils. MICP has advantages of environment friendliness, low disturbance, low cost, etc. Calcareous sand is a special type of granular soil, and its particles are highly irregular and angular. In this paper. a series of experimental tests were undertaken to investigate the influence of soil particle morphology on the efficiency of the MICP process in calcareous sand. Effects of the concentration of bacteria solution and grouting method were quantified and compared in terms of calcium carbonate (CaCO₃) content and unconfined compressive strength (UCS). The results show that fractal dimension of the calcareous sand particle ranges from 1.08 to 1.21. Period of 10–35 h after activation is the logarithmic growth stage of the bacteria. Single-phase grouting is better than two-phase grouting method. The UCS of the MICP-treated calcareous sand specimens is about 300–700 kPa and it has an exponential distribution with the CaCO₃ content.