## 3 Test Results and Microscopic Observation Analysis
### Influence of Rock Block Proportion on Microbial-Solidified Soil-Rock Mixture  
Under the condition that the concentration of bacteria liquid, the concentration of cementation reagent, and the ratio of solution remain unchanged when the rock particle size is 0.2-0.4 cm, the stress-strain values of the soil-rock mixture under different rock block proportions are shown in Figure 3. It can be analyzed from Figure 3 that the peak value of the soil-rock column with a rock block proportion of 50% is the highest, and the bearing capacity reaches the maximum at this time. The stress-strain values of the soil-rock mixture with the rock particle size of 0.4-0.6 cm under different rock block proportions are shown in Figure 4, and the peak value is also at 50% of the rock block proportion. The stress-strain curves of the soil-rock mixture with the rock particle size of 0.6-0.9 cm under different rock block proportions are shown in Figure 5, and the peak value is at 60% of the rock block proportion. The results show the following:  
1. The bearing capacity of the soil-rock mixed column cemented is related to the size of the pores between the soil and rock. Due to the small particle size of the silt, it is in close contact with the rock when it is mixed, which increases the rock content and increases the pore space in the sample. _Sporosarcina pasteurii_ are aerobic bacteria that increase pore space. It is conducive to the combination of bacteria and calcium ions in the cementing solution and the formation of calcium carbonate crystals on the bacterial surface film, which consolidates the surrounding soil and rocks and increases the strength of the sample. Figure 2: Results of unconfined compression test of soil–rock mixture (See Table 2 for the sample corresponding to each letter). 2. The bearing strength of the soil-rock mixture is related to the amount of rock block proportion, and the strength and deformation mechanism during shearing are also different with different rock block proportions [74]. For the samples with rock content of 20% and 30%, the content of boulders is low, and the content of silt is high. During the loading process, the silt and the boulder are stressed together, the arrangement of the particles is tight due to the adjustment of the position between the particles, and the macroscopic performance is the shrinkage of the sample volume. As the small particles cohesively break down and move, the sample reaches its peak and completes the test. For the samples with rock block proportions of 50% and 60%, the content of boulder particles is high. The main reason is that large pores will appear in the sample of the block rock particles. In the initial stage of loading, the block rock is first subjected to pressure, and the silt is temporarily \"protected\" in the pores under the \"cover\" of the block rock particles. As you continue to load and increase the stress, the bonding between particles is destroyed, the pores are reduced, the particles are dislocated, and the sample volume is visually compressed. 3. In the soil-rock mixture, the silt particles are small. Under the action of loading stress, after the pores are destroyed, the bound water increases due to the shrinkage of the pores, and the bond strength between particles is reduced. As the stress increases, the volume shrinks, and the large particles re-contact to increase the bond strength again so that the sample reaches the peak value quickly, and the axial strain of the sample reaches the peak value is small. 4. During the stress loading process at a constant rate, the soil-rock mixture is not a uniform carrier of the medium, and the edges and corners of the blocks are first subjected to pressure during the loading process. The stress on the surface of the sample is uneven. With the increase in the stress load, the stress-strain curve shows a jagged upward trend and peak value. 5.