Abstract: Model-scale solidification tests were conducted on granular strongly weathered granite using microbially induced
calcite precipitation (MICP) grouting technology. The physical-mechanical properties and microstructural characteristics of the solidified specimens were systematically investigated. The results demonstrate that MICP successfully consolidated the modelscale granular strongly weathered granite (Φ25×50 cm) into a stiff coherent structure. Physical-mechanical analyses revealed spatial heterogeneity of cementation performance: optimal in the middle section, moderate in the lower section, and poorest in the upper section. The solidified specimens exhibited an average calcium carbonate content of 12.42% and a dry density of 1.85 g/cm3. The permeability coefficient decreased by an average of 76.1% compared to untreated material. The maximum unconfined compressive strength reached 5.01 MPa, with an average value of 3.42 MPa. The mean ultrasonic velocity was 2.919 km/s along the diameter direction (13.5% higher than untreated specimens at 2.571 km/s) and 2.957 km/s along the axial direction. Microscopic analyses indicate that MICP grouting mainly produces calcite cement with columnar, acicular-clusters, and platy morphologies, alongside minor spherical vaterite and rhombohedral magnesium-calcite. Cementation within the mid-lower sections shows relatively uniform distribution and dense packing, forming a compact network, whereas the upper section is relatively loose. This study provides theoretical basis and experimental data support for MICP-mediated solidification of granular strongly weathered granite. 

Key words: MICP, model-scale, solidification, granular strongly weathered granite, microscopic test