## 3 Results and Discussion
### The Effect of Consolidation on the Soil Response to Cyclic Loading  
For the purpose of establishing the difference between the soil response to cyclic loading for samples consolidated in isotropic and \(K_{0}\) conditions, the plots of distinct cycles are presented in Figure 10. Figure 10 presents the cycles 1000 and 20,000 where the \(\Delta\)_nt-\(\varepsilon\)_ characteristic for one cycle of isotropically consolidated sample is presented. The plot shows, that the hysteresis curve had the same shape. The 1000 cycle was characterized by a hysteresis curve in which the area of the hysteresis and its inclination changed. The pattern of hysteresis curve evolution was similar for tests 1.1 and 1.3. Figure 9: Results of the cyclic triaxial test for sandy silty clay under a confining pressure of 44.9 kPa and under the \(K_{0}\) consolidation, initial void ratio \(\epsilon_{0}=0.400\), \(K_{0}=1.00\)—sample 2.5: (**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, blue: Cyclic loading program). The inclination and the area of the hysteresis curve rose in both cases. The different responses could be observed in the case of sample 1.2 wherein cycle 20,000 the inclination, as well as the area, was smaller. The unloading process in this test showed that sample tended to decrease excess pore water pressure much faster than the recovering of strain. This difference of the response to cyclic loading was caused by the initial void ratio difference since there was no distinct difference in deviator stress conditions. The impact of the initial void ratio could be seen in terms of the generated excess pore water pressure in one cycle. The excess pore water pressure in the case of tests 1.1 and 1.3 had risen up to 1.8 and 1.7 kPa. In the case of sample 1.2, the excess pore water pressure built up to 1.1 kPa, which was less when comparing the amount of generated pore pressure. On the other hand, the axial strain in one cycle caused by cyclic loading seemed to be independent of the initial void ratio. The axial strain in one cycle was equal to 0.0216%, 0.0177%, and 0.0146% respectively for the initial consolidation pressure \(\sigma^{\prime}\)3,0 equal to 45 kPa, 90 kPa, and 135 kPa and seemed that the \(\sigma^{\prime}\)3,0 was the governing factor in this phenomena. The excess pore water pressure in the case of \(K_{0}\) consolidated samples had different characteristics. The \(\Delta u\) in one cycle was greater for test 2.2 where the deviator stress parameters were smaller in terms of the stress median and greater in terms of deviator stress amplitude. Test 2.2 was characterized by the excess pore water pressure equal to 4.5 kPa after 10,000 cycles. The same excess pore water pressure value was observed in the case of sample 2.5. The value of \(\Delta u/q_{a}\) ratio was equal to 0.257, 0.333, 0.240, 0.190, and 0.338 respectively. The difference between the ratios was caused by different initial void ratios and different median levels of deviator stress. The impact of \(e_{0}\) shows that the bigger the initial void ratio value was the greater value of the \(\Delta u/q_{a}\) ratio in one cycle would be. Although the deviator stress amplitude was greater in the case of sample 2.2, while the \(q_{m}\) value was otherwise. Another  
Figure 10: Pore pressure versus the axial strain for selected cycles from the triaxial tests: (**a**) Isotropically consolidated samples, and (**b**) K\({}_{0}\)-consolidated samples. way of loading, in the case of sample 2.2 results in different characteristics of the excess pore water pressure generation. The excess pore water pressure in cycle 1000 had different characteristics than the cycle observed in cycle 20,000 or 10,000.