## 4 Discussion  
The results of the vacuum preloading test demonstrate that flocculation treatment accelerates the development rate of the slurry's clogging zone and reduces its horizontal strain value, indicating that flocculation treatment effectively mitigates slurry clogging. Among the tested flocculants, lime exhibited the most significant effect in mitigating slurry clogging. This is because lime-flocculated slurry undergoes property modifications through ion exchange and pozzolanic reactions (Equations (5)-(7)). Through ion exchange, lime replaces low-valence cations, such as K\({}^{+}\) and Na\({}^{+}\), on the surfaces of slurry particles with high-valence cations like Ca\({}^{2+}\), which compresses the electric double layer and reduces interparticle spacing. Additionally, the cementitious materials generated by the pozzolanic reaction adhere to the surfaces of slurry particles, resulting in a more stable soil structure. These flocculation effects enhance the permeability and reduce the compressibility of lime-flocculated slurry [43], which minimizes vacuum pressure loss during transmission and alleviates non-uniform consolidation. As a result, lime-flocculated slurry exhibits the fastest clogging zone development, the lowest horizontal strain, and the most effective mitigation of clogging.  
\[2\mathrm{Na}^{+}+\mathrm{Ca}(\mathrm{OH})_{2}=\mathrm{Ca}^{2+}+\mathrm{Na}( \mathrm{OH})_{2} \tag{5}\]  
\[\mathrm{Ca}^{2+}+\mathrm{OH}^{-}+\mathrm{SiO}_{2}\rightarrow\mathrm{C}- \mathrm{S}-\mathrm{H} \tag{6}\]  
\[\mathrm{Ca}^{2+}+\mathrm{OH}^{-}+\mathrm{Al}_{2}\mathrm{O}_{3}\rightarrow \mathrm{C}-\mathrm{A}-\mathrm{H} \tag{7}\]  
For organic polymer flocculants, the dual-use PAC and APAM treatment is more effective in mitigating clogging in high-water-content slurry compared to the single-dose APAM treatment. This is because the flocculation mechanism of APAM primarily relies on the adsorption of polymer chains onto the surfaces of clay particles [47]. This adsorption occurs through hydrogen bonding between the amide groups of the PAM chain and the hydroxyl groups on the clay particles, reducing interparticle spacing and facilitating the expulsion of trapped water. As a result, APAM flocculation treatment enhances the filtration performance of the slurry (Figure 5), leading to a faster water discharge rate in the early stages of the vacuum preloading test. However, APAM-flocculated slurry tends to form large and loose flocs that trap significant amounts of water, which are difficult to expel under vacuum pressure [48]. These water-retaining flocs accumulate near the PVD, significantly reducing the permeability of the slurry (Figure 13) and hindering the transmission of vacuum pressure. This explains why APAM alone has a relatively limited effect in mitigating slurry clogging.  
In contrast, PAC reduces the zeta potential of the slurry through charge neutralization, thereby disrupting the stability of the colloidal structure and promoting the aggregation of slurry particles into micro-flocs [49]. This process enhances the flocculation efficiency of APAM, ultimately improving the dewatering performance of the dual use of PAC and APAM-flocculated slurry. Additionally, PAC acts as a skeleton builder, forming a more porous and less compressible slurry structure [50]. As a result, the dual use of PAC and APAM-flocculated slurry exhibits better permeability, a larger clogging zone width, and more effective mitigation of slurry clogging compared to APAM alone.