# Experimental Study of Erosion Prevention Model by Bio-Cement Sand
## 1 Introduction  
The stability of bank slopes has been paid much attention, and the stability of bank slope erosion and seepage is also directly related to the sediment start-up process. Whether the sediment particles start up on the bank slope determines whether the bank slope erosion occurs and the stability of seepage. In nature, although the flow rate of riverbanks and riverbanks is much smaller than that of rivers, it has a great impact on sediment starting, sediment transport, and the stability of riverbeds and bank slopes [1]. Since the 1990s, [PERSON]. [2], [PERSON]. [3], [PERSON]. [4], and [PERSON] [5] have taken the lead in continuous research and exploration, and have accumulated rich experience in microbial culture, grouting technology design, and mineralization mechanism. MICP technology, known for its environmentally friendly approach to soil reinforcement, has gained widespread application in recent years for the protection of soil surfaces. It has been observed that by applying a combination of microbial slurry and cementing fluid onto the soil surface, a calcium-solidified layer with excellent water stability can be formed, effectively enhancing the erosion resistance of soil slopes and reducing erosion rates [6]. The inadequate cohesive force among soil particles and the limited capacity to withstand hydraulic shear stress are significant factors contributing to soil erosion and loss. Hence, enhancing interparticle bonding strength represents a crucial approach for improving soil erosion resistance. For instance, incorporating polymers into the soil matrix caneffectively mitigate surface runoff and reduce soil loss [7; 8]. Microbial solidification of loose soil is a new technology developed in recent years [9]. The fundamental principle involves the introduction of urease-producing microorganisms and a mixture of CaCl\({}_{2}\) and urea into loose soil, utilizing the urease microorganisms to facilitate urea hydrolysis for CO\({}_{2}^{3}\) production. In an environment characterized by high carbonate concentration and alkaline conditions, Ca\({}^{2+}\) will serve as nucleation sites within cells [10; 11], leading to precipitation and formation of CaCO\({}_{3}\) crystals. This process aims to consolidate loose soil particles [12; 13]. Compared with current chemical curing agent technologies, it offers advantages such as reduced environmental pollution, lower energy consumption, and decreased emissions [14; 15]. The strength and stability of the protective layer are crucial factors in determining its effectiveness as a protective barrier [16; 17]. [PERSON] [18] conducted flume tests on Ottawa graded sand treated with the polymer-modified MICP method to investigate its efficacy in controlling bridge scour. [PERSON] [19] observed erosion patterns over time, measured soil loss weight and rate, and analyzed outflow characteristics to enhance surface erosion resistance. [PERSON] [20] combined geopipe technology with MICP for on-site implementation of coastal erosion protection. [PERSON] [21] demonstrated the performance of surface treatment using flume erosion tests and utilized the erosion function device for more precise assessment of erodibility in treated sand. Microbially induced carbonate precipitation (MICP) can significantly strengthen sand by improving cohesion between particles, thereby enhancing microbial soil's resistance to erosion. Therefore, establishing the relationship between cohesion and calcium carbonate content, and studying the mechanism behind improved soil erosion resistance through cohesion are key aspects in understanding microbial cemented soil's ability to resist erosive forces. The protective layer formed by microbial mortar typically has a shell-like structure, making it challenging to create standardized specimens for compressive strength testing [22].