## 3 Results and Analysis
### Stress-Strain Behavior under Different Stress Paths
Different ratios of \(\Delta q\) to \(\Delta p^{\prime}\) cause different relative magnitudes of distortion and compaction of soil fabric. This may explain the differences in the \(\varepsilon_{\rm{v}}\)-\(\varepsilon_{\rm{s}}\) curves under different stress paths. [PERSON] et al. [8] adopted the axial strain where \(90\%\) of the maximum deviator stress was mobilized to characterize the ductility of decomposed granite. Similarly, the shear strains corresponding to \(50\%\) and \(90\%\) of (\(q_{max}\)-\(q_{c}\)) are employed in this research, where \(q_{max}\) and \(q_{c}\) denote the maximum deviator stress and the deviator stress after \(K_{0}\) consolidation, respectively, to investigate the influence of consolidation pressure and stress path on the ductility of the UGRS. These two strains adopted are denoted by \((\varepsilon_{\rm{s}})_{50}\) and \((\varepsilon_{\rm{s}})_{90}\), respectively. The variations of \((\varepsilon_{\rm{s}})_{50}\) and \((\varepsilon_{\rm{s}})_{90}\) with consolidation pressure are presented in Figure 8a,b, respectively. Under the same loading angle, both \((\varepsilon_{\rm{s}})_{50}\) and \((\varepsilon_{\rm{s}})_{90}\) increase with the increase in consolidation pressure, indicating that the britteness of the UGRS is weakened after consolidation. It seems that the effect of consolidation pressure becomes more remarkable as the loading angle decreases. \((\varepsilon_{\rm{s}})_{50}\) and \((\varepsilon_{\rm{s}})_{90}\) change with consolidation pressure dras  
Figure 6: Stress–strain curves and volumetric strain\(-\)shear strain curves of the soil in: (**a**) BL tests; (**b**) AL tests; (**c**) CP tests; (**d**) LU tests; (**e**) AU tests. tically when \(\alpha=56.3^{\circ}\), while for \(\alpha=123.7^{\circ}\) only a minor change is observed. Figure 9a,b show the variations of \((\varepsilon_{s})_{50}\) and \((\varepsilon_{s})_{90}\) with loading angle. For each consolidation pressure, the larger the loading angle, the smaller the shear strains required to mobilize 50% and 90% of \((q_{max}\)-\(q_{c})\). In other words, soil specimens under smaller loading angles show a less brittle response in the shearing stage. This may be explained by the stronger confining effect experienced by soil elements, because stress paths with a smaller loading angle have a higher level of mean effective stress. Figure 7: Stress\(-\)strain curves and volumetric strain\(-\)shear strain curves of the soil under: **(a)**\(\sigma_{3\times}=100\) kPa; **(b)**\(\sigma_{3\times}=200\) kPa; **(c)**\(\sigma_{3\times}=300\) kPa; **(d)**\(\sigma_{3\times}=400\) kPa. To examine the influence of stress path on shearing stiffness, the initial secant shear moduli \(E_{0}\) of the UGRS under different stress paths were calculated and the results are provided in Figure 10. It should be noted that the initial secant shear modulus is defined in this paper as the slope of the straight line passing through the two points where \(\varepsilon_{s}=0\) and 0.1%, respectively, on the \(q\)-\(\varepsilon_{s}\) curve. According to [PERSON] [56], the shear strain 0.1% falls into the scope of small strain. As expected, the initial secant shear modulus increases with the increase in consolidation pressure, indicating the hardening of the soil. It is clear that the shearing stiffness of the UGRS is path-dependent. With the increase in loading angle, the initial secant shear modulus first decreases and then increases. There is a certain value of loading angle lying between 90\({}^{\circ}\) and 123.7\({}^{\circ}\), at which the shearing stiffness of the UGRS is lowest. When the loading angle is close to this certain value, the soil shows poor performance in terms of resisting shear deformation. Moreover, it is worth noting that the initial secant shear modulus in the AE test was much larger than those in compression tests.