# Response of Corroded Steel Pipeline Without and with CFRP Reinforcement to Reverse Fault Movement
## 4 Results and Analyses
### Mechanical Response of Corroded Pipeline Crossing Reverse Fault
#### 4.3.2 Failure Modes of Pipeline with Corrosion at Football  
Figure 11 shows the peak strain of the hanging and footwall pipelines with different corrosion extents at the footwall at a distance L = 3.2 m from the fault plane. Figure 11 indicates that the corrosion at the footwall has a minor influence on the strain of the hanging wall pipeline. Although the top compression and bottom tensile strain fluctuate to a certain extent, this does not affect its main failure mode. Figure 11 reveals that as the fault displacement increases, the compressive strain of the pipe's top with different corrosion extents varies significantly. As the corrosion extent increases, the critical fault displacement of local buckling decreases gradually. If the residual wall thickness is only 0.6 t, local buckling failure occurs at the pipe's top when the fault displacement is only 0.33 m.  
Figure 12 shows the variation trend of pipeline peak ellipticity under different fault displacements. From Figure 12, it is noted that the ellipticity increases with the increase in fault displacement. However, when the fault displacement exceeds 0.4 m, the influence of corrosion extent becomes evident. When the fault displacement exceeds 0.9 m, the pipeline with different corrosion extents gradually exhibits an elliptic deformation failure.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Failure Mode**} & \multicolumn{5}{c}{**Remaining Wall Thickness**} \\ \cline{2-6}  & **0.6 t** & **0.7 t** & **0.8 t** & **0.9 t** & **t** \\ \hline Local buckling & 0.51 & 0.51 & 0.51 & 0.51 & 0.6 \\ Tensile fracture & 0.52 & 0.62 & 0.8 & 1.1 & 1.21 \\ Elliptic deformation & 0.78 & 0.79 & 0.79 & 0.92 & 0.99 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Critical fault displacement of the pipeline with corrosion at the hanging wall (m).  
Figure 10: Peak ellipticity of the pipeline with corrosion at the hanging wall.  
Table 6 shows a critical fault displacement of the pipeline with corrosion at the footwall. It is evident from Table 6 that as the corrosion extends, the critical fault displacement of local buckling and elliptic deformation of the pipeline continues to decrease, especially the local buckling, which decreases sharply, while the tensile fracture is the largest and unaffected by corrosion. When the fault displacement exceeds 0.87 m but does not reach 1.15 m, a double failure mode of local buckling and elliptic deformation occurs at the footwall pipeline section. When the fault displacement exceeds 1.15 m, there are multiple failure modes of local buckling, tensile fracture, and elliptic deformation at the footwall pipeline section. The results indicate that when corrosion occurs at the footwall, an increasing corrosion extent will weaken the resistance of the pipeline to local buckling and elliptic deformation. With the increase of fault displacement and corrosion extent, the failure mode of the footwall pipeline will change from single one to multiple forms.