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Calcareous sand is a crucial construction material for island and reef development and reinforcing it using Microbially Induced Calcite Precipitation (MICP) technology is a promising new method. This study employed 3D scanning technology to assess changes in the particle size and morphology of MICP-treated, coated calcareous sand particles. Single-particle crushing tests were conducted to analyze their crushing strength, crushing energy, crushing modes, and fragment fractal dimensions. The results indicated that MICP treatment significantly increased particle size, surface area, and volume, while reducing flatness. At a cementation solution concentration of 1 mol/L, both crushing strength and crushing energy were optimized. The coated particles exhibited three crushing modes: explosive crushing, mixed crushing, and splitting crushing. Thicker coatings led to a tendency for particles to break into larger fragments through the mixed and splitting crushing modes. Fractal analysis revealed that coating thickness directly affects the local crushing characteristics of the particles. [ABSTRACT FROM AUTHOR]

• A discrete element simulation framework considering calcite crystal shape was proposed. • The DEM model can model the generation of calcite grains after bond failure. • The DEM model can capture the macroscopic behavior of bio-cemented sands. • The mechanism of bio-cementation was analyzed from the micro scale. Microbial-induced calcite precipitation (MICP) is an effective way to stabilize soils, but the microscopic mechanism is unclear. Discrete element method (DEM) models of the mechanical behaviors of bio-cemented sands offer a way to understand this process. This paper used DEM simulations considering calcite crystal shape to understand the microscopic behavior of MICP-cemented sands. Simulation results showed that macrocracks caused by biaxial tests are mainly caused by shear failure. Decreasing calcite content increases the number of high-amplitude acoustic emissions events. The magnitude of the contact force becomes more homogenous with increased calcite. Sand particles initially sustain the load, then calcite particles contribute more to the strong contact force chain. The calcite concentration also affects the magnitude and direction of anisotropy. The proposed DEM model demonstrates its potential to analyze the underlying mechanisms of MICP process. [ABSTRACT FROM AUTHOR]