## 3 Results and Discussion
### Initial Shear Stress Ratio (\(\alpha\))  
The initial shear load parameter \(\alpha\) obtained by anisotropically consolidating the specimens can differ according to certain soil parameters. Compared to level ground conditions with an initial shear stress ratio of \(\alpha=0\), only a few experimental studies on the monotonic behavior of sands in sloping ground conditions with higher initial shear stress ratios (\(\alpha>0\)) are available, where the shear component is also present during the initial static condition. Therefore, this study (18 tests) includes anisotropically consolidated specimens prepared with initial axial loading in a drained condition. The initial shear stress ratio \(\alpha\) is defined as the ratio of the initial axial stress (\(q_{s}\)) divided by twice the effective confining stress (\(\sigma_{3\mathrm{c}}\)).  
For example, when \(\alpha=0.5\) and \(\sigma_{3\mathrm{c}}=150\) kPa, the load will be 0.29 kN, and for \(\sigma_{3\mathrm{c}}=250\) kPa, the specimens will undergo a 0.49 kN load. Equation (1) indicates that the initial static shear stress level increases with the increase in \(\alpha\) values, and the limiting case of \(\alpha=0\) represents level ground conditions without the initial static shear stress. Depending on the density of soil and the initial effective stress level, the presence of initial static shear stress may have either have an improving or aggravating impact on the resistance to liquefaction:  
\[\alpha=\frac{\tau}{\sigma^{\prime}3\mathrm{c}}=\frac{q_{s}}{2\sigma^{\prime}3 \mathrm{c}}=\frac{\sigma^{\prime}1\mathrm{c}-\sigma^{\prime}3\mathrm{c}}{ \sigma^{\prime}1\mathrm{c}+\sigma^{\prime}3\mathrm{c}} \tag{1}\]  
Figure 9: Effective stress paths at a different effective confining pressure: (a) 159 kPa; (b) 250 kPa; (c) 350 kPa in isotropic and anisotropic stress condition for Dr\({}_{0}=45\%\). Alpha (\(\alpha\)): the initial shear stress ratio.  
The excess pore water pressure (PWP) buildup of three specimens with a relative density of 45%, confining pressure of 150 kPa, and different initial shear stress (\(\alpha\) = 0, 0.3, and 0.5) are shown in Figure 10. All the samples in these three tests exhibit dilative behaviors because of the high relative densities, whereas their PWP intensities differ depending on the initial shear stress ratio. In addition, upon increasing the initial shear stress, the PWP peak declines and subsequently, the intensity of the dilation increases. Due to the reduction in the excess pore pressure, the particle contact friction increases and causes resistance to liquefaction.  
Figure 11 displays different initial shear stress with higher confinement (250 kPa) compared to Figure 10. It can be seen that the initial shear stress not only changes the behavior intensity, but also the entire behavior to dilation in (R-A)\({}_{6}\), liquefaction in (R-B)\({}_{6}\) and limited liquefaction in (R-C)\({}_{6}\), where the initial shear stress ratios are 0, 0.3, and 0.5, respectively. This result is completely different from those observed in the specimens in Figure 10, where the excess PWP buildup is considerably more and has to be preserved up to high strain levels. The increase in PWP reduces the effective stress, which is the particle skeleton strength (reduction in the particle contact friction); therefore, such reduction leads to liquefaction. This may also show the inverse dependency of \(\alpha\) on the effective confining pressure.  
Figure 10: Comparative curvature for (R–A)\({}_{3}\), (R–B)\({}_{3}\) and (R–C)\({}_{3}\) in the u–\(\varepsilon\)% plane. Alpha (\(\alpha\)): the initial shear stress ratio.