## 3 Materials and Methods
### Parameter Selection
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Layer**} & \multirow{2}{*}{**Soil**} & \multicolumn{2}{c}{**Experimental Value (cm/s)**} & \multicolumn{2}{c}{**Recommended Value**} & \multirow{2}{*}{\(S_{s}\) (L/m)**} \\ \cline{3-3} \cline{5-6}  & & \(K_{g}\) & \(K_{h}\) & (cm/s) & \\ \hline / & Shallow clay layer & \(2.21\times 10^{-7}\) & \(3.69\times 10^{-7}\) & \(5.0\times 10^{-5}\) & \(8.0\times 10^{-4}\) \\ \(\oplus_{2}\) & Clayey slit with silly clay & \(1.25\times 10^{-4}\) & \(1.97\times 10^{-4}\) & \(3.0\times 10^{-4}\) & \(4.5\times 10^{-4}\) \\ \(\oplus_{3}\) & Silty clay & \(7.07\times 10^{-5}\) & \(8.97\times 10^{-5}\) & \(8.0\times 10^{-5}\) & \(8.0\times 10^{-3}\) \\ \(\oplus_{4}\) & Silty clay & \(3.46\times 10^{-7}\) & \(4.17\times 10^{-7}\) & \(4.0\times 10^{-5}\) & \(8.0\times 10^{-3}\) \\ \(\oplus_{1}\) & Sandy salt & \(1.04\times 10^{-7}\) & \(1.70\times 10^{-7}\) & \(1.48\times 10^{-3}\) & \(4.5\times 10^{-4}\) \\ \(\oplus_{2}\) & Silit & \(4.21\times 10^{-4}\) & \(5.84\times 10^{-4}\) & \(1.40\times 10^{-3}\) & \(5.0\times 10^{-4}\) \\ \(\oplus_{21}\) & Interlayer of silty clay and Silit & \(4.6\times 10^{-5}\) & \(5.8\times 10^{-4}\) & \(6.0\times 10^{-5}\) & \(4.5\times 10^{-4}\) \\ \(\oplus_{22}\) & Silty sand with silty clay & \(1.0\times 10^{-3}\) & \(6.4\times 10^{-3}\) & \(6.4\times 10^{-3}\) & \(5.0\times 10^{-4}\) \\ \(\oplus\) & Silit & \(1.0\times 10^{-2}\) & \(9.0\times 10^{-2}\) & \(5.0\times 10^{-2}\) & \(2.0\times 10^{-5}\) \\ (11) & Silit & \(5.0\times 10^{-3}\) & \(4.9\times 10^{-2}\) & \(1.0\times 10^{-2}\) & \(3.0\times 10^{-5}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Hydraulic conductivity of the soil layers. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Aperture(mm)**} & **Pipe Diameter** & **Wall Thickness** & **Top Buried Depth** & **Buried Depth of Filter** & **Length of Filter** \\  & **(mm)** & **(mm)** & **of Filter Pipe (m)** & **Pipe Bottom (m)** & **Tube (m)** \\ \hline
850 & 400 & 8 & 82 & 86 & 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Structure information of injection well. this problem, [PERSON] and [PERSON] classified the field data reliability of different scale flow paths into three categories: high, medium, and low [47]. The empirical formula of longitudinal dispersion was obtained through regression analysis of field data, which was not limited by the size of the flow path. \[a_{l}=0.83(\log L_{s})^{2.414} \tag{9}\]  
In the range of the No. 4 well foundation pit, the solute flow path did not exceed 20 m, and the longitudinal dispersion was calculated as 1.56 and 1.38 m by using empirical Equations (8) and (9) considering the scale effect. In the aspect of the indoor scale test, the results of the vertical dispersion of the sand column test by some scholars were approximately 0.2-1.0 cm. In accordance with the results of the sand column test conducted by the author, the dispersion of fine sand in the layer of Shanghai was 11.5 cm. Therefore, the longitudinal dispersion of MICP bacteria and cementation fluid in the layer of silty fine sand ranged from 0.2 cm to 1000 cm. The solute migrated with the flow of water, and its migration speed mainly depended on the flow velocity. When the bacteria solution was driven by the seepage field formed by the recharging well, the water flow velocity in the seepage field formed by the recharging well was large due to the large amount of water injected by the reinjection well. The influence of convection was greater than that of other effects. At this time, only convection occurred in the sand, and the proportion of dispersion was extremely small. Therefore, determining the influence of longitudinal dispersion in the range of 0.2-1000 cm on solute migration under field conditions was necessary. Thus, numerical simulations were performed for the sensitivity analysis of longitudinal dispersion. Set longitudinal dispersion \(a_{l}\) was 0.2 cm, 12 cm, 50 cm, 100 cm, 200 cm, and 1000 cm.