## 5 Discussion
### Electrolyte Solution Optimization  
According to the research plan designed in Figure 1, the electrochemical medium selection process is conducted in steps. First, the best modification effect is selected from the two electrolyte solutions, CaCl\({}_{2}\) and AlCl\({}_{3}\), and the optimal solution concentration is determined. Based on this, the mudstone was modified with the optimal electrolyte solution and electrodes made of graphite, aluminum, and iron. The optimal electrode material was then selected based on the shear strength of the modified mudstone. From the above research results, a set of optimal electrode materials, electrolyte solutions, and concentrations was selected. Multiple concentrations were established for each solution, with mass fractions of 15%, 20%, 25%, 30%, and 35% for the CaCl\({}_{2}\) solution and 5%, 10%, 15%, 20%, and 25% for the AlCl\({}_{3}\) solution. The specimens were modified with the two electrolyte solutions of different concentrations. The modified samples were subjected to a direct shear test, and the shear strength of the modified specimens under 200 kPa vertical pressure was obtained, as shown in Figure 8.  
According to the shear strength test results, the electrolyte modification and its solution concentration were ranked in terms of their effectiveness. CaCl\({}_{2}\) solutions with a mass fraction of 25% and AlCl\({}_{3}\) solutions with a mass fraction of 10% modify the reinforcement more effectively. The enhancement effect of the AlCl\({}_{3}\) solution on the shear strength of the specimens is greater than that of the CaCl\({}_{2}\) solution; consequently, the 10% AlCl\({}_{3}\) solution is the most effective in modifying the reinforcement. During the shear process, specimens modified with CaCl\({}_{2}\) solution exhibited significant soft plasticity. The peak shear strength and residual shear strength were essentially the same, and there was no significant decrease in the post-peak strength. The specimens modified with 5%, 10%, and 15% mass fractions of AlCl\({}_{3}\) solution exhibited brittle damage during shear, with obvious strain softening characteristics; the 5% AlCl\({}_{3}\) solution-modified specimens also exhibited a continuous decrease in residual strength as shear progressed, whereas the specimens modified with  
Figure 8: Shear strength of mudstone corresponds to different mass fraction electrolyte solutions (\(\sigma\) = 200 kPa). (**a**) CaCl\({}_{2}\); (**b**) AlCl\({}_{3}\). 20% and 25% mass fractions exhibited no brittle damage during shear and continued to exhibit soft plasticity. From Figure 8a, it can be seen that the mudstone samples modified with 15% to 35% CaCl\({}_{2}\) solution still maintain the soft plastic characteristics of the clay rock and there is a gradual change from peak strength to residual strength. The residual shear strength of the modified mudstone samples is significantly improved compared to the original mudstone samples or those subjected only to electro-osmotic drainage. The residual shear strength of the mudstone sample with a 25% moisture content after electro-osmotic drainage is 70 kPa. After modification with a 25% CaCl\({}_{2}\) solution, the residual shear strength of the mudstone sample with the same moisture content reaches 93 kPa, indicating an increase of more than 20 kPa. The electrochemical modification effect is significant. After the mudstone sample modification by AlCl\({}_{3}\) solution, its structure changes from cohesion soil to sandy soil, as shown in the shear strength chart in Figure 8b. The shear process exhibits brittle failure, where the peak strength suddenly decreases to the residual strength without a gradual decrease.