## 4 Results and Discussion
### Comparisons between the Present Solution and Previous Solution  
Theoretically, the existing undrained solution based on the MCC model [22] is a special case of the present solution based on the SCC model. This is because the SCC model can evolve to the MCC model by setting the relevant structural parameters as sufficiently small values, i.e., \(\Delta e\)\(\rightarrow\)\(c\), \(c\)\(\rightarrow\)\(0\), \(b\)\(\rightarrow\)\(0\), \(\gamma\)\(\rightarrow\)\(0\), and \(\omega\)\(\rightarrow\)\(0\). In this situation, the initial yield surface of structured soils, as shown in Figure 4, tends to be the same as that of the corresponding reconstituted soils; therefore, the initial structural ratio \(R_{s}\) tends to be 1.  
The present solution was implemented in the case of \(R_{s}\)\(\rightarrow\)\(1\), \(c\)\(\rightarrow\)\(0\), \(b\)\(\rightarrow\)\(0\), \(\gamma\)\(\rightarrow\)\(0\), and \(\omega\)\(\rightarrow\)\(0\), and then compared with the existing undrained solution in reconstituted soils of Chen and Abousleiman [22], as shown in Figure 6. Note that only the initial state parameters of normally consolidated soils (\(R\) = 1) in Table 2 were adopted, and the stresses in Figure 6a were normalized by the undrained shear strength \(s_{u}\) (=54.3 kPa) for convenience of comparison. It can be seen that whether the distributions of the stress components along the radial distance, or the effective stress path for a soil element at the cavity wall, the results of present solution for structured soils are highly consistent with those of Chen and Abousleiman [22] for reconstituted soils. Thus, the solution proposed in this study can be regarded as a unified solution for undrained cavity expansion in structured and reconstituted soils.  
Figure 5: The flowchart for solving the cavity expansion problem using the present solution.  
The present solution was further compared with the undrained solution in structured soils proposed by Li et al. [36] to show the significances of destructuration. For the sake of convenience, the case of \(R=3\) in Table 2, which was calculated in [36], was selected, and all of the stresses were normalized by the undrained shear strength \(s_{u}\) (=115.0 kPa). Note that the same initial values at the elastoplastic boundary were adopted to ensure the soils containing the same initial structure. Figure 7 showed the comparisons of distributions of the mean effective stress \(p^{\prime}\), deviator stress \(q\), and excess pore pressure \(\Delta u\). It can be seen that soil structure has significant influences on the stress distributions around the cavity. Although the influences of the structure were considered in the solution of Li et al. [36], the values of \(p^{\prime}\) and \(q\) tends to be constant with the decrease of radial distance \(r/a\) in the plastic zone. This illustrated that only the initial structure was accounted for in their solution, and that the structure degradation was neglected, which resulted in the inability to capture the softening behavior caused by the destructuration. In contrast, the present solution could reflect the effects of structure degradation and crushing. Therefore, the \(p^{\prime}\) and \(q\) calculated in the present solution could finally reach the corresponding values in reconstituted soils at the cavity wall \(r/a=1\) after experiencing strain softening, indicating that the structure of the soils at the cavity wall was destroyed completely.  
Figure 6: Comparison between the present solution and existing solution in reconstituted soils: (a) distributions of \(\sigma^{\prime}\), \(\sigma^{\prime}\), \(\sigma^{\prime}\), and \(\Delta u\) along \(r/a\); (b) the \(p^{\prime}\)–\(q\) stress path.  
Figure 7: Comparison between the present solution and the previous solutions: distributions of \(p^{\prime}\), \(q\), and \(\Delta u\) along \(r/a\).