Hydraulic characteristics and water immersion damage energy evolution mechanism of fractured rock repaired by microbial-induced calcite precipitation (MICP).

Based on microbial-induced calcium carbonate precipitation (MICP) technology, this paper systematically studies the influence of cementing fluid concentration and microorganism-to-cementing fluid ratio on the compressive properties of MICP-repaired fractured rocks through laboratory experiments and microscopic tests. The research examines the strength attenuation and energy dissipation characteristics under different immersion times using stress-strain curves and an energy damage model at the optimal ratio. Key results demonstrate: (1) At 1 mol/L cementing liquid concentration and 1:1 bacterial-to-cementing liquid ratio, the repaired samples achieve 15.47 MPa unconfined compressive strength and 2.5 × 10-5 cm/s saturation permeability coefficient; (2) Calcium carbonate deposition exhibits "denser at top, sparser at bottom" vertical differentiation, homogenizing over time. ImageJ binarization shows 34.4% greater coverage at 28 days versus 3 days, evolving from discrete particles to continuous cementitious phase; (3) As the number of dry-wet cycles increases from 0 to 15, the peak total energy linearly attenuates from 64.8 to 23.4 kJ/m3, a decrease of 63.9%. The proportion of dissipated energy increases from 83.1 to 88.7% and the energy storage efficiency decreases by 83.7%; (4) Cycling elevates initial damage to 0.38, reduces damage threshold by 31% and accelerates energy dissipation across compaction-elasticity-plasticity-failure stages. Post 10 immersions, stabilized energy loss accompanies 38.3% strength reduction and 5.6% lower dissipation rate. These findings establish design thresholds and life assessment criteria for MICP-reinforced fractured rock in reservoir drawdown zones.