Analysis of the breakage of the bio-cementation generated on glass beads during a direct shear test using a DEM model

The improvement of soil behaviour by the bacterial precipitation of calcium carbonate has been extensively studied in geotechnical engineering. However, the evolution of bio-cementation bonds under shear conditions is only partially understood. This research presents a micromechanical approach to gain a deeper insight into the interaction between bio-cemented particles. A series of glass bead samples were treated with Microbial Induced Calcite Precipitation (MICP) and then subjected to direct shear tests. A calibrated model based on the Discrete Element Method was used to reproduce the macro-mechanical paths observed in the experiments, allowing the detailed analysis and description of the bond evolution at the microscopic scale in the treated samples. In general, it was found that a higher rate of bond breakage occurred before the peak shear strength was reached, and this was followed by a relatively constant rate of bond breakage associated with a macroscopic softening trend. Tensile stress was identified as the primary fracture mechanism. Finally, it was determined that the bond breakage mechanism is influenced by several factors, such as bond distribution, particle array, and the mechanical parameters of the bond.