## 5 Discussion
### Electrolyte Solution Optimization
This experimental result indicates that during the electrochemical modification process of mudstone, the addition of AlCl\({}_{3}\) solution changes the lattice structure and bonding state inside the mudstone, improves the bonding state between the powder crystal structures and results in the peak value and residual shear strength of the modified mudstone being better than that of the 25% CaCl\({}_{2}\) solution modification. The electrochemical modification of mudstones has a long research history and an abundance of results. Studies on the modification of various types of electrolytes have primarily focused on comparing changes in parameters such as tensile strength, water absorption, swelling, and resistivity. Many researchers have investigated the modification of coastal calcareous soils using CaCl\({}_{2}\) as the electrolyte and the modification of illite and kaolinite [33]. CaCl\({}_{2}\) and Al\({}_{2}\)(SO\({}_{4}\))\({}_{3}\)*18H\({}_{2}\)O have been demonstrated to be effective cementing agents [34]. However, comparative studies on the efficacy of modifications with different electrolyte solutions are scarce. AlCl\({}_{3}\) electrolyte was found to be more effective in modifying mudstone than CaCl\({}_{2}\) electrolyte, resulting in a significant increase in shear strength for the selected mudstone specimens. The CaCl\({}_{2}\)-based electrolyte solution was selected for the modification test because the introduction of calcium ions tends to result in the calcification of the cemented state of the mudstone, thereby increasing the mudstone's mechanical strength. As the application scenario of this study is a soft rock slope, the mudstone shear strength and hydraulic properties were utilized as comparison variables. The test results indicated that a CaCl\({}_{2}\) solution with a mass fraction of 25% was the most effective at altering the mudstone samples. This result contradicts the results of [PERSON] et al. [33], who discovered that a 15% CaCl\({}_{2}\) solution was the most effective for the electrochemical modification of offshore calcareous soils. The mudstone specimens chosen for this study had a mineral composition dominated by kaolinite. The calcareous soils studied by [PERSON] et al. (2004) were inherently rich in Ca\({}^{2+}\) and thus required less Ca\({}^{2+}\) to achieve optimal electrochemical modification than in this study. In addition, [PERSON] et al. [33] also found that a 10% solution of Al\({}_{2}\)(SO\({}_{4}\))\({}_{3}\)*18H\({}_{2}\)O was the most effective for the electrochemical modification of offshore calcareous soils, and this study also found that a 10% solution of AlCl\({}_{3}\) was the most effective for mudstone specimen modification. The results of the two studies are similar and it was found that a 10% solution concentration is best for the electrochemical modification of soils or mudstones that do not have Al\({}^{3+}\). This study focuses on the changes in the shear strength of mudstone before and after electrochemical modification. [PERSON] et al. conducted field tests on the electrochemical reinforcement of soft, sensitive clays using the electro-penetration method and discovered a roughly 50% increase in the undrained shear strength of the clay in the electrode region [35]. [PERSON] et al. found an average increase in the undrained shear strength of approximately 195% for soils close to the cathode [36]. [PERSON] et al. observed an average increase of 125%-130% from the anode to the cathode [37]. [PERSON] et al. reported an increase in undrained shear strength of soils by 38% to 138%, with the effective cohesion increasing from 0 to 11 kPa [33]. In this study, electrochemical modification increased the undrained shear strength of the mudstone. The peak shear strength of the mudstone specimens modified with 25% CaCl\({}_{2}\) solution was \(\tau_{4}=93\) kPa, and the peak shear strength of the specimens modified with 10% AlCl\({}_{3}\) solution was \(\tau_{5}=130\) kPa.