# Application of Microbially Induced CaCO\({}_{3}\) on the Reinforcement of Rock Discontinuity
## 1 Introduction
However, the peak shear strength of rock masses is mostly controlled by the shear strength of joints. As such, research on improving the shear strength of rock joints via MICP in a saline-alkaline environment needs to be conducted. This study proposes a new five-gradient artificial domestication scheme for _Sporosarcina pasteurii_ in a saline-alkaline environment. The direct shear test was then conducted to assess the shear strength of sandstone joints repaired by microbially induced calcium carbonate precipitation (MICP). The subsequent applications of the MICP technique provided valuable insights into increasing the shear strength of rock joints in a saline-alkaline environment. Over time, rock masses develop joints and discontinuities, which can significantly weaken their shear strength properties, such as cohesion and friction angle. This damage can lead to various consequences, including the dislocation of upper and lower rock masses, collapses, roof arch failures, cracks, and landslides. According to statistical data from the International Consortium on Landslides (ICL) Association, worldwide devastating landslide accidents are caused by the deformation and failure of rock structural planes. Figure 1 illustrates the global distribution of landslide events prior to 2023, based on data from ICL published over the years. To address the engineering challenges posed by geological accidents induced by rock mass joints, numerous scholars have proposed various techniques to enhance the shear strength of rock joints since the 1950s. Currently, grouting reinforcement methods employing traditional grouting materials, such as lime, epoxy resin, and cement, are widely utilized [39; 40]. However, it has been noted that these traditional cementitious materials can impact the pH of the rock mass, leading to environmental erosion and potential harm to groundwater [41]. Furthermore, chemical grouting materials, like epoxy resin, phenolic resin, and polyurethane, are known to be toxic. The negative environmental impact and high energy consumption associated with traditional grouting reinforcement methods emphasize the crucial need to explore nonpolluting, green, efficient, and cost-effective reinforcement techniques for rock joints. One emerging environmentally friendly geotechnical reinforcement technology is the microbially induced calcium carbonate precipitation (MICP) method. This technique offers several advantages, including low energy consumption, simplicity, and environmental safety [13; 16; 42]. Since the 2000s, numerous researchers have conducted extensive experimental studies to enhance the permeability and uniaxial compressive strength of rock masses while reducing their porosity through the MICP technique, yielding promising results [1; 2; 43; 44; 45]. However, previous studies have yet to explore the application of the MICP technique to increase the shear strength of rock joints in order to mitigate catastrophic landslides in saline-alkaline environments, which are prevalent worldwide. Given that saline-alkaline conditions can diminish the shear strength of rock joints, it is imperative to investigate new reinforcement techniques suitable for such environments in practical engineering. This study introduces a novel approach that involves domesticating _Sporosarcina pasteurii_ in a saline-alkaline environment. Various methods of bacterial domestication were assessed, leading to the identification of the most effective approach to enhance bacterial activity and urease enzyme activity in saline-alkaline environments, which was then implemented to increase the shear strength of rock joints. Table 1 displays the worldwide distribution of saline-alkaline land [46]. In this study, the strains suitable for the saline-alkaline environment were obtained using domestication. The cracks in the saline-alkaline environment were filled by strains to increase the peak shear strength of rocks. Figure 1: Distribution of catastrophic landslide accidents (from ICL).