## 3 Results and Discussion
### Effect of Ion Concentration on the Permeability of Soil Mixtures  
Experimental results show the permeability coefficients of the bentonite-stone chip mixture at a degree of compactness of 100% and at different bentonite contents when in contact with DIW. The permeability coefficient of the soil mixture decreased as the bentonite content increased. The soil mixture had permeability coefficients of 7.99 \(\times\) 10\({}^{-5}\), 3.03 \(\times\) 10\({}^{-5}\), 9.80 \(\times\) 10\({}^{-7}\), 3.74 \(\times\) 10\({}^{-7}\), and 2.50 \(\times\) 10\({}^{-7}\) cm/s for bentonite contents of 5, 7, 9, 11, and 13%, respectively. When the bentonite content increased to 9%, the permeability coefficient decreased to 10\({}^{-7}\) cm/s, which is the level required for anti-seepage applications. Figure 6 shows the permeability coefficients of the zeolite-bentonite-stone chip mixture for a bentonite content of 11% and different zeolite contents and ZnCl\({}_{2}\) concentrations. The pure bentonite-stone chip mixture had a permeability coefficient of 3.74 \(\times\) 10\({}^{-7}\) cm/s when in contact with DIW. Adding 12.50% zeolite reduced the permeability coefficient to 6.55 \(\times\) 10\({}^{-8}\) cm/s. As the zeolite content increased to 25 and 50%, the permeability coefficient decreased to 4.65 \(\times\) 10\({}^{-8}\) and 5.1 \(\times\) 10\({}^{-8}\) cm/s, respectively. This finding indicates that adding zeolite improves the anti-seepage performance of the soil mixture when in contact with pure water. At a ZnCl\({}_{2}\) concentration of 0.01 mol/L, the bentonite-stone chip mixture (0% zeolite content) had a permeability coefficient of 5.73 \(\times\) 10\({}^{-7}\) cm/s. Adding 12.50, 25, and 50% zeolite increased the permeability coefficient to 5.98 \(\times\) 10\({}^{-8}\), 5.80 \(\times\) 10\({}^{-8}\), and 5.70 \(\times\) 10\({}^{-8}\) cm/s, respectively. For zeolite contents of 0, 12.50, 25, and 50%, the soil mixture had permeability coefficients of 9.30 \(\times\) 10\({}^{-6}\), 4.43 \(\times\) 10\({}^{-6}\), 6.59 \(\times\) 10\({}^{-6}\), and 2.60 \(\times\) 10\({}^{-6}\) cm/s, respectively, for 0.03 mol/L ZnCl\({}_{2}\), and 1.40 \(\times\) 10\({}^{-5}\), 7.9 \(\times\) 10\({}^{-6}\), 3.27 \(\times\) 10\({}^{-6}\), and 1.28 \(\times\) 10\({}^{-6}\) cm/s at 0.10 mol/L ZnCl\({}_{2}\). The permeability coefficients exceeded 1.0 \(\times\) 10\({}^{-7}\) cm/s, which is required for anti-seepage liners. For a bentonite content of 25%, the zeolite-bentonite-stone chip mixture had permeability coefficients of 6.60 \(\times\) 10\({}^{-7}\), 7.13 \(\times\) 10\({}^{-8}\), 5.80 \(\times\) 10\({}^{-8}\), and 6.10 \(\times\) 10\({}^{-8}\) cm/s at the zeolite contents of 0, 12.50, 25, and 50% when in contact with the 0.03 mol/L ZnCl\({}_{2}\) solution and 7.60 \(\times\) 10\({}^{-7}\), 8.40 \(\times\) 10\({}^{-8}\), 6.70 \(\times\) 10\({}^{-8}\), and 6.30 \(\times\) 10\({}^{-8}\) cm/s when in contact with the 0.10 mol/L ZnCl\({}_{2}\) solutions, respectively. Overall, the addition of zeolite reduced the permeability coefficient of the soil mixture to the 1 \(\times\) 10\({}^{-8}\) cm/s level, causing an average decrease of one order of magnitude. These results indicate that when in contact with a ZnCl\({}_{2}\) solution with a concentration greater than 0.03 mol/L, the bentonite content of the soil mixture must be increased to 25% to satisfy the requirements for anti-seepage applications. It can be seen that the addition of zeolite can effectively reduce the permeability coefficient of the mixture. The addition of zeolite in DIW can fill the voids between the particles of the mixture, thus increasing the water seepage path and enhancing the impermeability of the mixed soil. In different concentrations of an ionic solution, the competitive adsorption of metal ions by zeolite shares the contraction pressure of the double bentonite layer, maintains the original pore structure, does not appear to have a significant seepage channel, and improves the chemical compatibility of the mixed soil.