# An Experimental Study for Swelling Effect on Repairing of Cracks in Fine-Grained Clayey Soils
## 3 Results and Discussion
### Swelling and Swell-Ability  
Swelling is one of the fine-grained clayey soil features that can have both positive and negative effects on geotechnical projects. The swelling potential directly depends on clay particles. Of course, the type of clay mineral affects the degree of swelling but is generally reduced by increasing the coarse particles. For example, Bentonite is much more swellable than Kaolin. In this regard, the Bentonite additive content in clayey soil was used to obtain the swelling potential and activity number. The swelling evaluation is illustrated in Table 2 and Figure 4.  
Regarding this figure, the 12.5% Bentonite admixture to clay causes about a 6-fold increase in the soil's swelling potential and 1.2-fold increase in activity. Using the consolidation test [31], the rate of swelling variation for the studied soil is evaluated. The consolidation test used [PERSON]'s one-dimensional consolidation theory to estimate the consolidation characteristics of soils, swelling potential, and swelling pressure of the clayey soils. A simple one-dimensional consolidation model consists of a rectilinear element of soil subject to vertical changes in loading and through which vertical (only) seepage flow is taking place. Whereas fully swollen sample is compressed back under vertical compressive stress, the vertical swelling pressure (\(\sigma_{\text{vs}}\)) is determined from the e-log \(\sigma_{\text{v}}\) curve as the pressure corresponding to the initial void ratio (e\({}_{0}\)). Figure 5 provides the results of the free swelling and swelling pressure for pure and additive Kaolin and Bentonite samples. According to this figure, the free swelling of Kaolin and Bentonite is 0.5  
Figure 3: Effect of the Bentonite additive on the compaction behavior in clayey soil.  
and 6.42 (mm), respectively, and their swelling pressures are about 0.1 and 6.5 (kg/cm\({}^{2}\)), respectively. Figure 6 provides the consolidation coefficient and swelling coefficient due to the increase in Bentonite percentage, which indicates that Bentonite values increase the coefficients. In addition, a swelling pressure index was obtained for all specimens with various amounts of Bentonite, as illustrated in Figure 7. As indicated by the results in this figure, it can be mentioned that the Bentonite additive increased the swelling pressure. On the other hand, Kaolin has an insignificant effect on clayey soil; therefore, the Kaolin additive is discarded to estimate the swelling pressure index. However, in clayey soil, the Bentonite additive plays a significant role in the swelling pressure. Based on these findings, it appears that Bentonite has a higher swelling degree than Kaolin. The reasons for this occurrence were related to the nature and high affinities of water, which distribute themselves evenly throughout water, swell when wet and reverse when dry, and have electrically active surfaces and high specific charges (charge/mass). Bentonite expands up to 10-12 times its dry size and has excellent swell characteristics. Kaolin has a low rate of activity.  
Figure 4: Effect of the Bentonite additive on swelling and activity variation in clayey soil.  
Figure 5: Diagram of the swelling and consolidation status for different samples.  
Figure 6: Effect of the Bentonite percentage on consolidation and swelling coefficients.