## 1 Introduction  
To ensure high-quality economic development, it is crucial for highway construction to prioritize safety and green development. This includes paying close attention to the fully weathered rock-cutting slope of mountainous highways exposed to strong physical weathering [1, 2]. Meanwhile, heavy rainfall may induce landslides, making it imperative to take preventive measures. In Southeast China, there are thick residual layers of granite that have weathered over time [3]. The original rock was composed of feldspar, mica, quartz, and amphibole, with a hard texture, uniform nature, and high strength [4, 5]. However, due to weathering, a significant amount of feldspar has undergone hydrolysis and carbonation, forming kaolinite. Kaolinite possesses a compact structure yet exhibits a high water absorption capacity. Upon exposure to water, it tends to swell and soften [3, 4, 6, 7]. As a result, in regions of southeastern China where rainfall is consistently high, slopes composed of granite residual soil are susceptible to erosion and potential collapse. Traditional methods of slope protection, such as mortar rubble slope protection and sprayed cement mortar, have been found to have certain drawbacks. These include poor landscape aesthetics and high energy consumption leading to environmental pollution [8; 9]. However, the combination of concrete lattice beam and vegetation protection partially fulfills the requirements of ecological protection, but it has complex construction technology and management workload issues [10; 11]. Moreover, granite residual soil is unsuitable for plant growth [12], resulting in high input costs and little protection effect. Therefore, it is crucial to research soil reinforcement techniques that are both environmentally sustainable, cost-effective, and high-performing. In recent years, researchers have explored microbial-induced calcite precipitation (MICP) technology for soil reinforcement. This technology utilizes high-yield urease bacteria to decompose urea and produce carbonate particles. In an alkaline environment, these particles combine with calcium ions to form calcium carbonate crystals, which cement loose soil particles together and significantly enhance soil strength [13; 14]. Dr. [PERSON], from Murdoch University in Australia, was the first to utilize MICP technology to solidify loose sand. As a result, the physical and mechanical indexes, including stiffness and unconfined compression strength (UCS), were significantly improved after solidification [15; 16]. Additionally, the study revealed that the degree of cementation, or strength distribution, varied significantly across different sections of the sand column [17]. Subsequently, other researchers investigated the uniform distribution of calcium carbonate in the sand. They found that the solidification effect of the soil was influenced by various factors, including colony distribution, initial concentration of the bacterial solution, and standing time [18; 19; 20; 21]. Moreover, they expanded the application of MICP technology to silty sand [22], expansive soil [23], dredger fill [24], and other types of soil solidification. Further research indicates that soil properties are closely linked to the crystal type and calcium carbonate content, which directly impacts the soil's reinforcement effect. In the application of granite residual soil reinforcement, [PERSON] et al. discovered that bio-cementation forms a surface coating on granite residual soils, which leads to the hydraulic conductivity by 90.9% from the initial value, and the erosion rate can be reduced by 95.2% [25]. [PERSON] et al. 's research found that the internal friction angle of MICP-treated granite residual soil increased by 10% under a moisture content of 30%, while its cohesion increased by 218% [26]. Moreover, [PERSON] et al. conducted a study on the effectiveness of adding calcium lignocellulosic to improve the microbial growth environment and pore structure of granite residual soil. The results showed a 41.2% increase in compressive strength [27].