This paper focuses on the influencing factors of MICP solidification of soil–rock mixture. After selecting the best soil–rock ratio through screening, the MICP process is tested from two aspects of rock content and particle size. The results show that the soil–rock mixture is not a uniform carrier of the medium, and the force on the surface of the sample is not uniform. With the increase in stress load, the stress–strain curve shows a sawtooth upward trend and peak value. The microbial cemented soil–rock mixture had a particle size of 0.2–0.4 cm and 0.4–0.6 cm under the rock block proportion of 50%. The unconfined compressive strength of the microbial cemented soil–rock mixture with a rock particle size of 0.6–0.9 cm reaches the highest at 60% rock block proportion. When the rock content is 20–50%, the unconfined compressive strength decreases with the increase in particle size. When the rock content is 60%, the value of unconfined compressive strength first decreases and then increases with the increase in particle size; both SEM and XRD test results proved that Sporosarcina pasteurii could effectively induce the formation of calcium carbonate and crystallizes at the pores of the particles to improve the mechanical properties of the soil.

In this paper, we focus on the application of mechanical properties in a soil–rock mixture modified by microbial mineralization under the influence of different factors, including pH value, cementing solution concentration, and cementing time. Cementing fluids and samples with different pH values, calcium ion concentrations, and mineralization cementation were prepared. The process of urea hydrolysis MICP under different factors was studied. A solidified soil–rock mixture sample under triaxial compression was measured. Then, combined with scanning test methods, such as SEM and XRD, the influence of different factors on the mechanical strength and failure mode of the soil–rock mixture structure was analyzed from a microscopic point of view. The results show that a low concentration of cementing solution with a high concentration of bacteria liquid generated the highest calcium carbonate content and the strongest cementing ability. When the pH value of the cementation solution is six, the cementation effect between the pores is the best, and the deviatoric stress is stronger. When wet-curing samples, short or long curing time will adversely affect the strength of soil–rock mixture samples, the strongest curing and cementing ability is 5 days. The microscopic results show that the microbial mineralization technology fills the pores between the particles, and the interaction force between particles is enhanced to enhance the strength of the soil–rock mixture.