## 3 Clay Content on Freeze-Thaw Characteristics of Solidified Soils
### Strength Loss Rate  
The peak stress was taken as the unconfined compressive strength of the specimens, and the cement-solidified soil under the same condition of maintenance was used as the control specimen. The relationship between the unconfined compressive strength and the number of freeze-thaw cycles of the SSGM-solidified soil and cement-solidified soil is shown in Figure 7.  
As shown in Figure 7, the unconfined compressive strength of the SSGM-solidified soil gradually decreases with an increasing number of freeze-th  
Figure 6: Stress–strain curves of solidified soil with different soil types: (**a**) CSS011; (**b**) CSS122; (**c**) CSS111; (**d**) CSS100. Figure 7: Unconfined compressive strength vs. number of cycles: (**a**) SSGM-solidified soils; (**b**) cement-solidified soils. the rate of strength reduction diminishes as the clay content decreases, resulting in flatter curves. The unconfined compressive strength of the SSGM-solidified soil decreases from 7041.8 kPa to 6978.6 kPa, 5680.0 kPa to 5450.1 kPa, 5052.1 kPa to 4853.8 kPa, and 1205.7 kPa to 1052.8 kPa, respectively. From Figure 7b, the unconfined compressive strength of cement-solidified soil decreased from 6224.6 kPa to 6115 kPa, 5747.3 kPa to 5609.7 kPa, 5435.0 kPa to 4969.7 kPa, and 3494.5 kPa to 957.7 kPa, respectively. The strength of the SSGM-solidified soil after undergoing freeze-thaw cycles was not lower than the strength of the cement-solidified soil under the same conditions. The process of freeze-thaw cycles caused a significant pore water migration redistribution effect in clay particles due to their high water absorption and strong adhesion; the high-clay-content soil, in the process of freezing and thawing, has a larger ice crystal expansion and contraction amplitude. The extrusion of soil particles leads to the destruction of the internal pore structure of the soil body, showing a more pronounced reduction in strength. By fitting the relationship between unconfined compressive strength of SSGM-solidified soil and the number of cycles, the following equation is obtained:  
\[q_{un}=q_{u0}+a*b^{n} \tag{2}\]  
where \(q_{un}\) is the unconfined compressive strength of the specimen after \(n\) times of freeze-thaw cycles, kPa; \(q_{u0}\) is the unconfined compressive strength of the specimen before freeze-thaw cycles, kPa; \(a\), \(b\) are the fitting parameters. The fitted parameters are shown in Table 4, from which it can be seen that the fitted coefficients R\({}^{2}\) are all greater than 0.95, and the correlation of the fitted relational equation is good. The rate of loss of strength of the specimen is calculated according to Equation (3):  
\[K_{q}=\frac{q_{u0}-q_{un}}{q_{u0}}\times 100\% \tag{3}\]  
where \(K_{q}\) is the strength loss rate, %; \(q_{u0}\) is the strength of the specimen before cycling, kPa; \(q_{un}\) is the strength of the specimen after the \(n\) cycles, kPa. A smaller strength loss rate \(K_{q}\) indicates stronger freeze-thaw resistance of the solidified soil. The relationship between the strength loss rate and the number of cycles is shown in Figure 8.  
The rate of strength loss versus the number of cycles for SSGM-solidified and cement-solidified soils is shown in Figure 8. As can be seen in Figure 8, after 10 freeze-thaw cycles, the strength loss rates of SSGM-solidified soil specimens CSS011, CSS122, CSS111, and CSS100 were 18.37%, 22.70%, 23.49%, and 29.09%, respectively. The strength loss rates of cement-solidified soil specimens CSS011, CSS122, CSS111, and CSS100 were 20.59%, 22.64%, 25.69%, and 78.01%, respectively. Experimental results demonstrate that a lower clay content corresponds to reduced strength loss rates and enhanced freeze-thaw resistance in solidified soils. SSGM-solidified soil exhibits comparable freeze-thaw durability to