## 2 Testing Program
### Experiment Process  
The experiments were conducted in a constant temperature environment (28 \({}^{\circ}\)C), with the device shown in Figure 2. The testing system consisted of two constant pressure and constant speed pumps (constant pressure accuracy, \(\pm\)0.1%; resolution, 0.001 mL), two intermediate vessels, one core holder (working pressure, 50 MPa), one ring pressure pump, and related valve groups and pipelines. Pump A was used to inject simulated groundwater and pump B to inject repair reagents. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multirow{2}{*}{\begin{tabular}{c} **Simulated** \\ **Groundwater** \\ **(Na\({}_{2}\)CO\({}_{3}\)** \\ **Solution**) \\ \end{tabular} } & \multicolumn{6}{c}{**Repair Reagent**} \\ \cline{3-10}  & & \begin{tabular}{c} **Scheme 1** \\ **(Na\({}_{2}\)CO\({}_{3}\)** \\ **Solution** \\ \end{tabular} & \begin{tabular}{c} **Scheme 2** \\ **Single CaCl\({}_{2}\)** \\ **Solution** \\ \end{tabular} & \begin{tabular}{c} **Scheme 2** \\ **FeCl\({}_{2}\) + CaCl\({}_{2}\)** \\ **Solution** \\ \end{tabular} & \
\begin{tabular}{c} **Scheme 3** \\ **Scheme 4** \\ **Solution** \\ \end{tabular} &
\begin{tabular}{c} **Scheme 5** \\ **FeCl\({}_{2}\) + CaCl\({}_{2}\)** \\ **Solution** \\ \end{tabular} \\ \hline Ion concentration & CO\({}_{3}\)\({}^{2-}\) & Ca\({}^{2+}\) & Fe\({}^{2+}\) & Ca\({}^{2+}\) & Fe\({}^{2+}\) & Ca\({}^{2+}\) & Fe\({}^{2+}\) & Ca\({}^{2+}\) & Fe\({}^{2+}\) \\ (mg/L) & 500 & 333.3 & 93.4 & 266.4 & 163.5 & 216.5 & 233.3 & 166.5 & 466.6 \\ \hline \multicolumn{10}{l}{Molar ratio of Fe to Ca} & \multicolumn{6}{c}{M = 1:4} & \multicolumn{6}{c}{M = 1:1.9} & \multicolumn{6}{c}{M = 1:1} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Preparation of aqueous solutions for different experimental schemes. Figure 1: Single fractured rock specimen. To begin, we fully saturated the fractured rock specimen with water and loaded it into the core holder with a confining pressure of 5 MPa. We then turned on pump A to inject simulated groundwater into the fractured rock sample at a constant flow rate of 2 mL/min. When the pressure at the inlet and outlet ends of the core no longer obviously fluctuated, the seepage was deemed stable. Based on the monitored water pressure value, the initial permeability was calculated. No pressure was applied to the outlet end of the core holder in this test, so the water injection pressure at the inlet end was equivalent to the pressure difference between the inlet and outlet ends. Then, we reduced the injection flow rate of pump A to 1 mL/min and turned on pump B to inject repair reagent at a constant flow rate of 1 mL/min (keeping the total injection flow rate at 2 mL/min) to explore the permeability change law of the fractured rock sample under precipitate generation conditions. During the experiment, the water pressure changes at the injection end of the core holder were monitored in real time to reflect the effect of chemical precipitates on fracture plugging and repair. Finally, when the water injection pressure reached 5 MPa (equal to the confining pressure), the fracture repair was regarded as complete; pumps A and B were then turned off. The experiment was stopped and the rock specimen was taken out. After the rock specimen naturally dried, three consolidated sediment samples were collected from the fracture surface using a spatula or tweezers under a stereomicroscope. Then, the microscopic distribution of the sediment samples was observed using a scanning electron microscope (SEM) to investigate the adsorption-consolidation characteristics of precipitates in the fracture and to provide a basis for explaining the PR mechanisms of the fractured rock specimen after repair. Notably, the same fractured rock specimen was used to ensure the comparability of the experiment results of each scheme. Therefore, every time a scheme was tested, a weak acid solution was used to dissolve and remove the precipitate on the fracture surface. This operation was carried out under a stereomicroscope.