## 1 Introduction  
Granite residual soil is formed by a series of physical and chemical weathering of the parent granite rock, which is widely distributed in Southeastern China. This type of soil exhibits loose, rich cracks and easy disintegration [1, 2, 3], resulting in severe soil erosion under rainfall conditions [4, 5, 6]. There are 239,125 sites in Benggang covering an area of 1220.05 km\({}^{2}\)[7, 8], with an average rate of erosion of 590,000 t/(km\({}^{2}\)-y) [9]. Benggang has the characteristics of high erosion intensity and an extensive erosion area [10, 11]. Yudu County, one of the counties with severe soil erosion in Jiangxi Province, China, accounts for 29.17% of the whole county due to Benggang. The traditional slope-protection methods in Benggang areas mainly rely on plant measures and engineering measures, which have disadvantages such as a large engineering quantity, inconvenient construction, high cost, and long time [12, 13, 14]. Therefore, it is of great engineering significance to find a new slope-protection strategy that is energy-saving, environmentally friendly, and easy to construct on granite residual soil. Microbial-induced carbonate precipitation (MICP) is one of the emerging geotechnical engineering technologies in recent years [15, 16]. MICP has three typical substances involved in its process: bacteria, substrate, and calcium source, which precipitates carbonate crystals around the soil particles in a biological reaction, thereby remodeling the soil structure [17, 18]. Basedon a soil-enriched, urease-producing bacteria named _Sporosarcina pasteurii_ (ATCC 11859), it uses urea as a substrate, catalyzes the hydrolysis of urea to generate NH\({}_{4}\)+ and CO\({}_{3}\)\({}^{2-}\) through metabolism, and attracts Ca\({}^{2+}\) through the negative charge generated by macromolecules such as proteins inside the bacteria, thus inducing the precipitation of CaCO\({}_{3}\). No toxic substances are produced during the bonding process, indicating that it is an environmentally friendly bonding material [19; 20]. The MICP also demonstrates strong applicability and water stability, which can effectively improve various types of soil, such as organic soil [21], Ioess [22], sand [23], iron tailing [24], and desert [25]. The improvements MICP has on geotechnical materials also depend on the influencing factors of various mineralization processes, such as the calcium sources [26], the bacterial solution concentration [27], the cementation solution concentration [28], the ratio of cement solution [29], the curing age [30], and the pH value [24]. The formation of calcium carbonate crystals has a significant impact on the physical and mechanical properties of the treated soil. The soil treated with MICP is still suitable for plant growth, and its residual urea can serve as a nutrient [19]. However, there are limited studies on the MICP modification of granite residual soil in the Benggang area to improve its ability to resist rainfall erosion. One important way to ensure soil and water loss prevention in the erosion area is to improve the water stability of the surface soil, thereby improving its erosion resistance. The shallow surface granite residual soil in the Benggang area is generally loose after long-term weathering. The calcium carbonate crystals generated by MICP can fill soil pores, and their cementation enhances the connection strength between soil particles [28]. It is crucial to determine the appropriate parameters of MICP, such as bacterial solution concentration and instrumental solution concentration [23]. Hence, a quantitative analysis is necessary for the practical engineering application of MICP in the prevention and control of soil erosion. Soil disintegration refers to the durability of soil when in contact with still water and can be used to evaluate its water stability [31; 32; 33]. [PERSON] et al. [34] investigated the disintegration behavior of the granite residual soil along a typical weathering profile from Xiamen City in China. [PERSON] et al.