# Application of Microbially Induced CaCO\({}_{3}\) on the Reinforcement of Rock Discontinuity
## 4 Conclusions  
In this research, we utilized laboratory-extracted _Sporosarcina pasteurii_ to enhance the shear strength of rock joints. We conducted direct shear tests on the rock samples before and after applying MICP to assess the impact of _Sporosarcina pasteurii_ reinforcement on the shear performance of rock joints. This study's significance lies in the use of environmentally friendly methods to reinforce rock joints and enhance their shear strength. Our research technique presents a novel approach for employing the MICP technique to improve the shear strength of jointed and fractured rocks under specific environmental conditions. The primary conclusions are as follows:  
* The maximum cell concentration of the five-gradient acclimated strains in the saline-alkaline environment was more than 97% of that of the undomesticated strains in the neutral environment. Additionally, the carbonate yield was significantly higher than that of the directly domesticated strains after interaction with the cement fluid.
* The domesticated _Sporosarcina pasteurii_ has not only good adaptability to the saline-alkaline environment but also has good temperature adaptability at temperatures from 10 to 30 \({}^{\circ}\)C.
* In the saline-alkaline environment, using _Sporosarcina pasteurii_ obtained from multi-gradient domestication leads to a higher carbonate yield and shear strength of sandstone joints strengthened by MICP. Compared to other domestication methods, the five-gradient domestication strain shows better MICP performance, increasing the peak shear strength by 14.19% to 28.56%. The shear strength parameter \"c\" and internal friction angle \"_p_ \" of the joint surface can be increased by 72.56% and 3.75%, respectively.
* The peak shear strength of MICP-cemented rock joint specimens increases as the curing time is extended. However, the strength develops most rapidly in the early stage of curing, with the rate of strength improvement gradually slowing down in the later stage of curing.  
This paper uses artificial two-dimensional parallel cracks, while the actual engineering situation mostly involves three-dimensional non-parallel cracks. In future studies, we plan to use rocks collected from the field to investigate natural three-dimensional fractures. We will also consider variations in the opening of natural fissures by constructing non-parallel fissures.  
All the authors contributed to this research, [PERSON] conducted the tests and analyzed the experimental data. [PERSON] wrote the paper, [PERSON], [PERSON] and [PERSON] revised the paper. All authors have read and agreed to the published version of the manuscript.  
Figure 15: Typical shear failure characteristics of three kinds of artificial rock joint specimens.  
**Funding:** This research was funded by [National Natural Science Foundation of China] grant number [51474050 and U1602232] and [Program for Liaoning Excellent Talents in University] grant number [LN2014006].  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data used to support this study are included within the article.  
**Conflicts of Interest:** The authors declare no conflicts of interest.