## 3 Results and Analysis
### Bearing Strength Characteristics and Effect of Freeze-Thaw Cycles  
Figure 14 shows the CBR test results for Jiamusi expansive soil. To facilitate the analysis, the maximum CBR value under a certain compaction energy was defined as CBR==, and the moisture content at the CBR== was defined as \(w_{\text{CBR}}\). The CBR== and \(w_{\text{CBR}}\) under different compaction energies are listed in Table 6. It was observed that the \(w_{\text{CBR}}\) could be divided into two parts according to the compaction energy: 1 when the compaction energy was large (\(N\) = 98), \(w_{\text{CBR}}\) was 5% higher than the optimal content; 2 when the compaction energy was smaller (\(N\) = 59, 45, 36, 27), \(w_{\text{CBR}}\) was 3% higher than the optimal moisture content. The CBR values were related to the moisture content in an obvious manner. When \(w<w_{\text{opt}}\), the CBR values of the Jiamusi expansive soil were less than 3%. At the given moisture content of \(w_{\text{opt}}\leq w~{}<~{}w_{\text{opt}}+2.6\%\), the CBR values ranged from 3% to 5.2% with the variation of compaction energy; when \(w=w_{\text{opt}}+2.6\%\), the CBR values were greater than 5.3%, which could be 6.8% under large compaction energy; when \(w_{\text{opt}}+2.6\%~{}<~{}w\leq w_{\text{opt}}+5.3\%\), the CBR value was at least 5%, and the CBR values even reached 6.4% under a compaction energy \(N\) of 98. Figure 13: The relationship between the void ratio and number of cycles \(N_{\text{FT}}\). Figure 15 plots the curve of the CBR values and compaction degrees \(K\). For the samples with lower than optimal and optimal moisture content, there was a wide range of compaction, depending on the compaction energy. It is interesting to note that the more than optimal and optimal moisture content samples had higher CBR values at the same degree of compaction than the samples with lower moisture content. Since the moisture contents were less than, equal to, and greater than the optimal moisture content, three different straight lines could be fitted. A regression analysis of the three moisture content categories yielded the following equation with a high degree of correlation:  
\[\text{CBR}=24.77K\text{-}16.85\ R^{2}=0.83\ 19\%\underline{\leq}w\underline{ \leq}26.4\%\]  
\[\text{CBR}=8.50K\text{-}4.94\ R^{2}=0.84\ w=w\ \text{opt}=16.4\%\]  
\[\text{CBR}=9.45K\text{-}6.83\ R^{2}=0.97\ 10.5\%\underline{\leq}w\underline{ \leq}14\%\] \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Compaction** & \(w_{\text{opt}}\)/\% & \(\mathbf{q_{\text{dmax}}}\)/(\(\mathbf{g}\):\(\mathbf{cm}^{-3}\)) & \(\mathbf{CBR_{\text{max}}}\)/\% & \(w_{\text{CBR}}\)/\% & **Compaction** \\
**Energies/Hit** & & & & & **Degree/\%** \\ \hline
98 & 16.4 & 1.84 & 6.44 & 21.7 & 100.00 \\
59 & 16.4 & 1.79 & 6.18 & 19.0 & 97.28 \\
45 & 16.4 & 1.76 & 6.76 & 19.0 & 95.65 \\
36 & 19.0 & 1.73 & 6.28 & 19.0 & 94.02 \\
27 & 19.0 & 1.69 & 5.31 & 19.0 & 91.85 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Peak CBR values CBRf and corresponding moisture contents under different compaction energies. Figure 14: Curve of CBR values and moisture contents under different compaction energies. Based on engineering use and exploratory research, the CBRs of the samples with optimal moisture contents and contents corresponding to the maximum CBR values under different freeze-thaw cycles were studied. The samples with K = 100% and K = 90% were used in this part; the moisture contents of the samples with K = 100% and K = 90% were 16.4% and 19%. The results revealed that the CBR value decreased with an increasing number of freeze-thaw cycles, as shown in Figure 16. It is interesting that the CBR value of the sample with a compaction degree of 90% was greater than that of the sample with a compaction degree of 100%. This could be attributed to the larger expansion strain of the latter, as explained in the following Section. For the sample with the optimal moisture contents, the CBR value decreased from 3.65 to 3.06.