# Compression Behavior of Rubber-Bentonite Mixture under Different Salinities
## 2 Results and Discussions
### Modulus of Compression Change of MX80 Bentonite/Rubber Mixture
#### 2.2.3 Effect of Salt Solution Concentration on Compression Modulus under Different Vertical Loads  
Figure 8 displays the variations in compression modulus for the B6T4 and B4T6 samples under differing salt solution concentrations and vertical loads. In Figure 8a, a similar trend can be observed at vertical loads of 100 kPa and 200 kPa. As the salt solution concentration increased from 0 mol/L to 0.1 mol/L, a significant decrease in compression modulus was observed. However, as the salt solution concentration continued to increase, the compression modulus stabilized. These findings suggest that the B6T4 sample was sensitive to salt solution concentration in the external environment but only when the vertical load did not exceed 200 kPa. As the vertical load increased, the influence of salt solution ion concentration on the B6T4 sample showed no significant changes. Specifically, when the vertical load pressure escalated from 300 kPa to 400 kPa, the compression modulus displayed an increasing trend as compressibility decreased. In Figure 8b, the compression modulus of the B4T6 sample consistently decreases with increasing salt solution concentration under vertical loads of 100 kPa, 200 kPa, and 300 kPa. Moreover, the compression modulus only increases in correspondence with the vertical load increase. These results indicate that the B4T6 sample was more susceptible to the influence of the salt solution ion concentration, and the influence intensified as the vertical load reached 300 kPa, leading to increased internal compaction of the B4T6 sample. Additionally, the compression modulus maintained stability within a certain numerical range under a vertical load of 400 kPa.  
Figure 9 illustrates the compression modulus variation in the B10 specimens under differing vertical loads and salt solution concentrations. The figure shows that the compression modulus of the B10 specimens increased with an increase in vertical load. The most significant change occurred between 200 kPa and 300 kPa, while the change from 300 kPa to 400 kPa occurred gradually. This observation indicated that under a vertical load of 300 kPa, the compactness of the B10 specimens improved significantly. The reduction in the pores between the internal montmorillonite particles led to a denser and compacted specimen structure. Additionally, regardless of the vertical load, the compression modulus of B10 specimens increased while the compressibility decreased with an increase in salt solution concentration. This finding suggested that elevated salt solution concentration had a positive impact on the compression modulus of B10 specimens. The slope of the compression modulus exhibited the most significant change for the B10 specimens under a  
vertical load of 300 kPa when the salt solution concentration increased from 0.1 mol/L to 0.5 mol/L NaCl. With the continuous augmentation of chloride solution ion concentration and increasing vertical load, the compactness within the specimens improved continually. This improvement can be attributed to the rise in solute ions within the pores of the specimens due to the increased salt solution concentration. As the vertical load increased further, the spacing between pores underwent further compression. Consequently, the contact between montmorillonite particles intensified, enhancing the internal compactness and structural integrity of the B10 specimens. Under the combined influence of the chemical and stress fields, the compression modulus increase while compressibility decreased in the B10 specimens.