## 1 Introduction  
A vertical curtain is often used to cut off confined aquifers to control drawdown during deep excavation. However, the vertical curtain cannot cut off deep and thick confined aquifers. When a partially penetrating waterproof curtain cannot control the drawdown inside and outside of the pit, recharging and horizontal curtains are often possible measures. Normally, forming a waterproof horizontal curtain is too expensive. In the current study, a microbial induced carbonate precipitation (MICP) horizontal seepage reducing body (HSRB) was developed to solve the problem.  
MICP belongs to a class of new, environmentally friendly engineering technologies used in rock and soil reinforcement, concrete crack repair, ancient building reinforcement, and contaminated soil treatment [1; 2; 3; 4; 5]. This bioreinforcement method has simple response, a controllable process, is green, is environmentally protective, and has broad application. MICP technology is widely used in various types of bad soils [6; 7; 8; 9]. The MICP technology utilizes some bacterial strains in nature to precipitate calcium carbonate, which can fill and repair cracks in stone and concrete materials, strengthen soil, improve soil strength,prevent building leakage, avoid sand liquefaction, and prevent slope damage and other disasters [10; 11; 12; 13; 14]. In addition, MICP technology can also reduce soil permeability [15]. Compared with traditional chemical grouting, the bacterial and cementing solutions used in this method have lower viscosity and can easily penetrate into geotechnical materials [16; 17; 18], which make it suitable for handling deeper and thicker geological materials [19]. Therefore, it is feasible to utilize MICP technology to form a horizontal seepage reducing body (HSRB) in a deep confined aquifer. 3D simulation of solute migration in porous media has been widely used [20]. A solute is different from an ordinary solute when it is transformed into living organisms, such as microorganisms. Living substances move themselves and react with the surrounding environment when they migrate in underground water. At present, most mathematical models of microbial migration are based on the convection dispersion equation. [PERSON] and [PERSON] et al. proposed colloidal filtration theory on the basis of the convection dispersion equation [21; 22]. However, a large number of soil column tests have shown that filtration and desorption, especially filtration, have an important effect on microbial migration and retention [23; 24]. Desorption, death, and inactivation of microorganisms have a definite effect on migration [25; 26]. Therefore, [PERSON] established a microbial migration model based on the convection dispersion equation and comprehensively and accurately described the migration process of microorganisms [26]. The previous research results of pollutants and microbial migration provide theoretical support for the numerical simulation of microbial and cementation fluid used in MICP technology. Seepage blockage problem-solving methods are also developed based on numerical analysis [27; 28; 29; 30; 31; 32], analytical solutions [33; 34], experimental work, field investigations [35; 36; 37; 38; 39], and experimental investigation [40].  
In this study, the foundation pit of the No. 4 working shaft of the Guanyuan project in the Pudong New Area of Shanghai was taken as the engineering background. The MICP HSRB formation method was developed and verified through numerical simulation. On the basis of laboratory experiments regarding the formation mechanism of MICP HSRB [41], _S. pastevii_ and cementation solutions were selected as the MICP injecting into the fine sand of layer \(\circledR\) with a recharging well. The solute migration of each solution was numerically simulated to study the formation a process of MICP HSRB. The optimal scheme using MICP grouting technology to form HSRB was established through the analysis of the main influencing factors of solute migration, which can provide guidance for MICP HSRB application.