## 3 Test Result Analysis
### Effect of Dry-Wet Cycling and Temperature on Shear-Strength Parameters  
To further explore the effects of dry-wet cycling and temperature on the shear strength parameters, we plotted the curves of the cohesion and friction angle values obtained from all tests for the C-M-S specimens in Figures 7 and 8. From Figure 7 we noted that the C-M-S cohesion after dry-wet cycling was less than that of the intact CMS. The C-M-S cohesion decreased with increasing in the \(N\) and stabilizes after a certain \(N\). At 35 \({}^{\circ}\)C, the soil cohesion decreased from 34.7 to 9.4 kPa as the \(N\) increased from 0 to 5, corresponding to a 61.94% decline in cohesion over 5 cycles. This result revealed that the C-M-S cohesion was strongly affected in the first three cycles. As can be observed in Figure 7, the cohesion decreased with increasing temperature. The cohesion after the third cycle decreased from 12.6 to 11.0 kPa as the temperature was raised from 0 to 70 \({}^{\circ}\)C. It was also noteworthy that the cohesion decreased by a greater degree at higher temperatures after the second cycle. This was because each dry-wet cycle destroyed the soil structure, the temperature limited stress drop, and the cohesion reduced faster [35]. The observed linear-reduction trend in the cohesion could be expressed by the following formula:  
\[c_{\mathrm{T}}=c_{0}+a_{1}(T-T_{0}) \tag{3}\]  
where \(T\) and \(T_{0}\) denote the temperature and initial temperature, respectively, \(c_{T}\) and \(c_{0}\) denote the cohesion for temperature \(T\) and initial cohesion, respectively; \(a_{1}\) the fitting coefficient. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{\(T\)} & \multirow{2}{*}{\(N\)} & \multicolumn{3}{c}{**Peak Deviator Stress/kPa**} & \multirow{2}{*}{\(c\)} & \multirow{2}{*}{\(\phi^{{}^{\prime}}\)/\(\rho^{{}^{\prime}}\)} & \multirow{2}{*}{\(D_{\rho}\)} & \multirow{2}{*}{\(H_{\mathrm{m}}\)} \\ \cline{3-4} \cline{6-9}  & & **100 kPa** & & & & & \\ \hline \multirow{6}{*}{0 \({}^{\circ}\)C} & 0 & 150.79 & 234.94 & 277.10 & 36.50 & 14.00 & 1.324 & 0.299 \\  & 1 & 131.01 & 190.77 & 255.16 & 26.80 & 13.71 & 1.330 & 0.275 \\  & 2 & 101.67 & 168.07 & 225.20 & 16.30 & 13.65 & 1.336 & 0.242 \\  & 3 & 87.62 & 150.85 & 203.04 & 12.60 & 12.94 &The cohesion of unsaturated soil \(c_{1}\) could be expressed as  
\[c=c_{\rm T}+(u_{\rm a}-u_{\rm w})\tan\phi^{b} \tag{4}\]  
where \(c\) is the cohesion of unsaturated soil, \(u_{a}\) is the pore air pressure, \(u_{\rm w}\) is the pore water pressure, \(\phi^{b}\) is the friction angle. Under the assumption that \(\tan\phi^{b}\) was independent of the temperature [36], the C-M-S cohesion \(c\) was be expressed as  
\[c=c_{0}+a_{1}(T-T_{0})+(u_{\rm a}-u_{\rm w})\tan\phi^{b} \tag{5}\]  
Shear strength \(\tau_{Tf}\) of the CMS subjected to a given temperature could be expressed as  
\[\tau_{Tf}=c_{0}+a_{1}(T-T_{0})+(u_{\rm a}-u_{\rm w})\tan\phi^{b}+(\sigma-u_{\rm a })\tan\phi^{\prime} \tag{6}\]  
where \((\sigma-u_{a})\) denotes the normal net stress, \(\tau_{Tf}\) denote shear strength for temperature \(T\) of the CMS, \(\phi^{\prime}\) is the net friction angle. From Figure 8, we noted that the friction angles for all specimens almost unchanged with the values fluctuating between \(14.00^{\circ}\) and \(10.60^{\circ}\). This was probably because the grain composition of the CMS did not vary under the application of dry-wet cycling and temperature. The saturated sample was used in the triaxial test to make the grain gap smaller, leading to a small change in the friction angle. Comparing Figures 7 and 8, the effect of dry-wet cycling on the cohesion was greater than that on the friction angle. The degradation of cohesion was more significant than the friction-angle variation. To further understand how the shear-strength deterioration of the CMS changed with dry-wet cycling and temperature, we next obtained the cohesion degra  
Figure 8: Variation in the friction angle values with dry–wet cycling and temperature.