3.4.4. Variation Rules of Shear Strength Parameters

Figure 18 shows the relationship curves of water content, cohesion *c*, and internal friction angle *φ* of silt. Table 3 summarizes the parameters of the direct shear strength tests before and after silt treatment during the wetting process. Table 3 and Figure 18 show that at low water content (2–4%), the *c* values of XG-silt increased by more than a factor of 2.3, and *φ* increased by more than a factor of 1.5. However, when the water content was lower than 8%, the sample strength was enhanced both before and after treatment, whereas *c* and *φ* only slightly increased. At high water contents (16% and 22%), *c* increased by factors of 1.4 and 1.8 times, respectively, and *φ* increased by factors of 1.4 and 1.9. The experimental results are consistent with those of Soldo et al. [35,36] and Chang et al. [55]. Additionally, the test results showed that the addition of XG can greatly improve the strength and stability of silt during the wetting process.

**Figure 17.** Wetting strength of the silt specimens with different water contents under a vertical stress of 100 kPa: (**a**) *mbp*/*ms* = 0%; (**b**) *mbp*/*ms* = 2%.

**Figure 18.** Comparison of shear strength parameters before and after treatment: (**a**) *w-c* relation curve; (**b**) *w-φ* relation curve.
