## 3 Test Results and Analysis  
### Typical Test Results of Saturated Silt Sample under Cyclic Axial-Torsional Combined Loading  
The typical results of the silt tested under wave loading (\(CSR=0.05\), \(\delta=1\)) are shown in Figure 6; the excess pore pressure \(u\) rises more rapidly at the beginning of loading. Then, the increasing rate gradually decreases to zero. When the number of cycles \(N\) is greater than 1600, \(u\) gradually stabilizes and does not reach the effective confining pressure. Under the circular stress path, the specimen produces shear, axial, radial and other strains in different directions. The shear strain \(\gamma\) changes a little with the increase in \(N\), and the axial strain \(\varepsilon_{\mathrm{z}}\) develops rapidly in the initial stage of loading, and then \(\varepsilon_{\mathrm{z}}\) gradually slows down with the increase in \(N\). This test specifies that the direction of radial strain \(\varepsilon_{\mathrm{r}}\) is consistent with the direction of radial stress \(\sigma_{\mathrm{r}}\).  
During axial-torsional cyclic loading, the silt sample will simultaneously generate shear strain \(\gamma\), axial strain \(\varepsilon_{\mathrm{z}}\), hoop strain \(\varepsilon_{\mathrm{0}}\), and radial strain \(\varepsilon_{\mathrm{r}}\). Therefore, a single strain parameter as described with deformation has a certain one-sidedness. Based on the Mohr circle, the major, intermediate, and minor principal strains, \(\varepsilon_{1}\), \(\varepsilon_{2}\), and \(\varepsilon_{3}\), respectively, corresponding to large, medium, and small principal stresses, \(\sigma_{1}\), \(\sigma_{2}\), and \(\sigma_{3}\), respectively, can be calculated. In order to comprehensively reflect the development of the sample  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Case No.**} & \(\sigma_{\max}\) & \(\tau_{\max}\) & \multirow{2}{*}{\(\Delta\)} & \multirow{2}{*}{\(CSR\)} & \multirow{2}{*}{\(\Delta\)} & \multirow{2}{*}{\(CSR\)} & \multirow{2}{*}{
\begin{tabular}{c} **Stress** \\ **Path** \\ \end{tabular} } & \(\sigma_{\max}\) & \(\tau_{\max}\) & \multirow{2}{*}{\(\delta\)} & \multirow{2}{*}{\(CSR\)} & \multirow{2}{*}{\(\mathbf{Stress Path}\)} \\  & (\(\mathbf{kPa}\)) & (\(\mathbf{kPa}\)) & & & & & & (\(\mathbf{kPa}\)) & (\(\mathbf{kPa}\)) & \\ \hline S1 & 3 & 3 & 1 & 0.03 & Circle & S9 & 5 & 2.5 & 2 & 0.05 & Oval \\ S2 & 3.5 & 3.5 & 1 & 0.035 & Circle & S10 & 6.5 & 3.25 & 2 & 0.065 & Oval \\ S3 & 4 & 4 & 1 & 0.04 & Circle & S11 & 8 & 4 & 2 & 0.08 & Oval \\ S4 & 5 & 5 & 1 & 0.05 & Circle & S12 & 3 & 0.75 & 4 & 0.03 & Oval \\ S5 & 6.5 & 6.5 & 1 & 0.065 & Circle & S13 & 5 & 1.25 & 4 & 0.05 & Oval \\ S6 & 8 & 8 & 1 & 0.08 & Circle & S14 & 6.5 & 1.625 & 4 & 0.065 & Oval \\ S7 & 3 & 1.5 & 2 & 0.03 & Oval & S15 & 8 & 2 & 4 & 0.08 & Oval \\ S8 & 4 & 2 & 2 & 0.04 & Oval & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Undrained cyclic shear tests.  
Figure 5: Stress path for cyclic shear loading.  
deformation, the cumulative generalized shear strain \(\gamma_{\rm g}\) is introduced to describe the deformation of the silt [29]. The formula of \(\gamma_{\rm g}\) is as follows:  
\[\gamma_{\rm g}=\frac{\sqrt{2}}{3}\sqrt{\left(\varepsilon_{1}-\varepsilon_{2} \right)^{2}+\left(\varepsilon_{1}-\varepsilon_{3}\right)^{2}+\left(\varepsilon _{2}-\varepsilon_{3}\right)^{2}} \tag{1}\]