## 5 Discussion
### Electrode Material Optimization
Their investigation revealed that electro-osmosis relies on the ions in the original soil rather than those produced by the electrode reaction. [PERSON] et al. [16] screened iron as the optimal electrode material by comparing the electro-osmosis effect and ionic strength, which is the primary reason for the discrepancy with the results of this study. In contrast, this study used the shear strength of the mudstone as a screening criterion and found graphite electrodes to be the most effective. Our findings differ from those of [PERSON] et al. [16] due to disparities in target orientation and application scenarios. In their study of the effects of the electrode material and current interval on the electro-osmotic permeability coefficient and voltage loss at the soil-electrode interface, [PERSON] et al. discovered that the voltage loss was related to the anode material, with metal anodes exhibiting less loss than carbon anodes [33]. These studies ranked electrode materials according to different objectives, resulting in varying conclusions. Figure 11: Shear strength of specimens at 3 electrode conditions (10% AlCl\({}_{3}\)). In a study conducted by [PERSON] et al. on the electro-osmotic consolidation of clay soils in Bangkok using copper and carbon electrodes along with prefabricated vertical drains, it was discovered that electro-osmotic drainage consolidation was superior with carbon electrodes, resulting in 9% greater electro-osmotic drainage than copper electrodes and a 144% increase in the shear strength of clay soils [38]. In contrast, [PERSON] et al. investigated the effect of electrode type on the electro-osmosis of Malaysian soils and found that different types of electrodes produced the same cumulative drainage. However, the effect on shear strength was dependent on the electrode type [39]. Considering that more types of electrodes are compared in this study, including graphite, iron and aluminum, the results still indicate that graphite electrodes are the best material. [PERSON] et al. [38] increased the shear strength of clay by 144% without the addition of any electrolyte solution. In the present study, the shear strength increased from \(\tau_{0}\) = 59 kPa to \(\tau_{1}\) = 70 kPa, an increase of 118%, when only electro-osmotic drainage was applied. [PERSON] et al. [38] used a maximum voltage difference of 120 V/m, while in the present study, the maximum voltage difference was only 60 V, which is the primary reason for the difference in the shear strength increment. As shown in Table 4, the shear-damaged specimens modified with graphite, iron, and aluminum electrodes were dried to determine the moisture content of each specimen. The graphite electrode group exhibited the best drainage effect and the highest degree of specimen hardening. The relatively poor drainage effect of the two metal electrode groups is attributed to the formation of a large number of metal oxides at the anode after oxidation due to energization. These oxides, being insulating, cause the passivation of the metal electrodes, thereby reducing the potential difference between the cathode and anode, affecting the efficiency of the energized modified drainage. The oxides formed by the iron electrode primarily penetrate the soil, whereas those formed by the aluminum electrode are mostly adsorbed on the surface of the electrode, significantly impacting the energizing efficiency of the modification experiment. Consequently, the iron electrode is superior to the aluminum electrode in terms of the drainage effect. On the other hand, non-metallic electrodes, such as graphite, do not oxidize when energized, resulting in the most effective drainage consolidation effect. Figure 12 depicts the results of straight shear experiments on graphite electrode-modified specimens.