## 3 Test Result Analysis
### Effect of Dry-Wet Cycling and Temperature on Shear-Strength Parameters
Figure 7: Cohesion curves of soil specimens under dry–wet cycling and temperature. dation degree \(D\). The parameter \(D\) had been applied to measure changes in the material strength owing to environmental conditions [37], and it could be expressed as follows:  
\[D=\left(1-\frac{S_{N}}{S_{O}}\right)\times 100\% \tag{7}\]  
where \(D\) is the degradation degree of cohesion, \(N\) indicate the number of cycles, \(S_{N}\) is the C-M-S cohesion after dry-wet cycling, and \(S_{\text{o}}\) is the C-M-S cohesion not subjected to dry-wet cycling. From Table 2 and Equation (7), we could infer that the cohesion decreased with increasing in \(N\). For cycles 1, 2, 3, 4, and 5, the average degradation degrees of cohesion were 29.04%, 52.47%, 65.34%, 69.61%, and 71.30%, respectively. The result suggested that the cohesion significantly degraded at first, and then gradually degraded with the increase of dry-wet number. It was obvious that after the third cycle, the particles of the CMS tended to be evenly arranged, and the surface friction tended to be stable. To quantitatively study the degradation of cohesion during dry-wet cycling, an exponential-function-fitting analysis was conducted on the cohesion degradation degree. The fitting results are presented in Figure 9 and Table 3. The fitting function could be expressed as follows:  
\[D(\text{N})=a-b\cdot\exp\left(-\frac{N}{d}\right) \tag{8}\]  
where \(a\) is the final degradation degree, \(b\) is the parameter that controls the deterioration rate (a larger \(b\) corresponds to faster cohesion degradation), and \(d\) is the fitting parameter. From Table 4, we noted that the correlation index \(R^{2}\) fitted by Equation (8) were mostly greater than 0.9; thus, it was clear that Equation (8) suitably fitted the relationship between the deterioration degree and the \(N\). Under the assumption that \(\tan\phi^{b}\) was independent of \(N\), we could rewrite cohesion \(c_{N}\) as  
\[c_{N}=\left[1-a+b\cdot\exp\left(-\frac{N}{d}\right)\right]\left[c_{0}+\left(u_ {\text{a}}-u_{\text{w}}\right)\tan\phi^{b}\right] \tag{9}\] \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **0**\({}^{\circ}\)**C** & **35**\({}^{\circ}\)**C** & **70**\({}^{\circ}\)**C** \\ \hline \(a\) & 84.18 & 73.47 & 72.74 \\ \(b\) & 84.45 & 74.60 & 73.80 \\ \(d\) & 1.97 & 1.43 & 1.50 \\ \(R^{2}\) & 0.99 & 0.98 & 0.98 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Fitting parameters of cohesion degradation. Figure 9: Degradation of cohesion under dry–wet cycling. where \(c_{N}\) and \(c_{0}\) denote the cohesion for \(N\) and initial cohesion, respectively \(a_{1}\) the fitting coefficient; \((u_{a}-u_{w})\) is the suction, which is obtained by the pressure plate device method. The change in shear strength \(\tau_{Nf}\) of the CMS with \(N\) can be expressed as  
\[\tau_{Nf}=\left[1-a+b\cdot\exp\left(-\frac{N}{d}\right)\right]\left[c_{0}+(u_{ \mathrm{a}}-u_{\mathrm{w}})\tan\phi^{b}\right]+(\sigma-u_{a})\tan\phi^{\prime} \tag{10}\]  
where \((\sigma-u_{\mathrm{a}})\) denotes the normal net stress, \(\tau_{Nf}\) denote C-MS shear strength with \(N\), \(\phi^{\prime}\) is the net friction angle.