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/m 3 , 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.