## 3 Results and Discussion
### Isotropically and \(K_{0}\) Consolidated Samples Test Results  
On Figure 2 the undrained cyclic triaxial test results for sample 1.1 are presented. The isotropic confining pressure was equal to 45 kPa. The soil sample was loaded with the deviator stress \(q\), which their components were as follows \(q_{m}\) = 39.5 kPa and \(q_{a}\) = 4.1 kPa. The soil response to such a loading program could be divided into three stages. The first one is the first loading cycle. In this stage, the soil is accumulating a high amount of permanent strain, which is accompanied by a high generation of excess pore water pressure. The stress path (Figure 2e) rises to planned deviator stress level and mean effective stress \(p^{\prime}\) starts to move towards the deviator stress axis, which indicates a decrease of radial stress due to the mobilization of excess pore water pressure. \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Stress Component** & **1.1** & **1.2** & **1.3** & **2.1** & **2.2** & **2.3** & **2.4** & **2.5** \\ \hline Maximal deviator stress, \(q_{max}\) (MPa) & 43.6 & 46.0 & 43.2 & 117.3 & 100.9 & 101.5 & 169.9 & 79.6 \\ Minimal deviator stress, \(q_{min}\) (MPa) & 35.4 & 37.0 & 35.2 & 96.0 & 74.0 & 80.7 & 138.3 & 53.1 \\ Deviator stress median, \(q_{m}\) (kPa) & 39.5 & 41.5 & 39.2 & 106.7 & 87.5 & 91.1 & 154.1 & 66.4 \\ Deviator stress amplitude, \(q_{b}\) (kPa) & 4.1 & 4.5 & 4.0 & 10.7 & 13.5 & 10.4 & 15.8 & 13.3 \\ Effective confining pressure, \(\sigma^{\prime}_{3}\) (kPa) & 45.0 & 90.0 & 135.0 & 65.0 & 125.0 & 139.7 & 94.2 & 44.9 \\ Cyclic stress ratio, \(CSR\) (\(-\)) & 0.484 & 0.256 & 0.160 & 0.902 & 0.403 & 0.363 & 0.901 & 0.886 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The cyclic triaxial test program. After the first cycle, the second type of soil response began. The pore pressure rose to a local maximal value equal to around 17 kPa in the 4 th cycle (Figure 1a) and then dropped to 15 kPa in the 11 th cycle. After this circumstance, the pore pressure rose with decreasing increment. During this phase, the permanent strains were also accumulated. This phase ended around the 350 th cycle. In the first cycle phase and in the second one, most of the permanent strains occurred. The excess pore pressure reached most of its value in these two stages. The second phase characterized with decreasing strain and excess pore water pressure value increment. Nevertheless, permanent strain accumulation and the pore pressure build-up process dependence are more complex and needs to be investigated further. This can be easily noticed by the Figure 2b,c analysis. Strain accumulation lasted longer than the pore pressure build up or the pore pressure increment slowed down faster than permanent strain accumulation. On Figure 2a after the local minimum, stabilization of the pore pressure increase was observed to a certain point. When axial  
Figure 2: Results of the cyclic triaxial test for sandy silty clay under a confining pressure of 45 kPa and under the isotropic consolidation, initial void ratio \(e_{0}=0.414\)—sample 1.1: (**a**) Excess pore water pressure versus vertical strain characteristic, (**b**) excess pore water pressure characteristic versus number of cycles, (**c**) vertical strain characteristic versus number of cycles, (**d**) deviator stress–vertical strain relationship, and (**e**) the deviator stress–mean effective stress relationship (red color—last 10 cycles; arrow color—violet: Saturation phase, green: Consolidation phase, orange: First cycle of cyclic loading, blue: Cyclic loading program). strain reached a value of approximately 0.5% (about the 350 th cycle), the pore pressure increment had a constant value when related to the axial strain. The last phase was the long term loading phase. In this stage, the pore pressure, as well as the permanent strain, rose with constant increment. The soil reached a stable response to cyclic loading. In this study, 20,000 cycles were applied. The excess pore water pressure was rising slightly between cycle 350 and the last cycle.