## 4 Test Scheme  
To analyze and discuss the recovery strength, the ring shear tests of the slide zone soil under the initial state and after a healing time were compared. The test was performed in accordance with a \"shear-pause-shear-pause-shear\" cycle. First, the slide zone soil was consolidated and sheared to the residual strength state after consolidation was completed. Then, under the condition in which the vertical stress and the shear stress remained unchanged, a pause state was maintained. After reaching the specified healing time, the sample was again sheared to the residual strength. Then, the process was repeated. The shear strength and residual strength of the first shearing and the shearing following different healing times were recorded during the test.  
Using an undisturbed sample, a ring shear test was conducted to simulate the possible strength recovery of the Huaipa landslide under large-displacement shear conditions. Because of the long duration of the test, effective measures were taken to prevent water evaporation. The specific test plan was as follows.  
1. After the consolidation of the slide zone soil was stable, shearing was applied at a rate of 0.2 mm/min. When the sample reached the residual strength for the first time, the vertical stress and shear stress were maintained, such that the undisturbed stress conditions during the reactivation of the Huaipa landslide could be reproduced. The sample was paused for 3 h and then was sheared to a new stable residual strength state. Then, the sample was paused for 6 h and sheared to the next residual state. Subsequently, it was paused for 12 h, sheared to the next residual state, paused for 24 h, sheared to the next residual state, paused for 72 h, and sheared to the final residual state.
2. The above shear cycle state was completed at three different vertical stresses: 50 kPa, 100 kPa, and 200 kPa.  
The primary shearing is performed to obtain the residual shear state of the sample. The residual state is confirmed when the shear value is minimum and the data observed by the computer are basically stable. Then, the strength recovery test is carried out. When the shearing reaches the residual state, the shearing stopped, the sample is kept static in the ring shear instrument, and the vertical stress is constantly applied during the process. Because the sliding mass of the field is still affected by the shear stress after movement, the shear strength remains constant throughout the pausing time during the strength recovery test to simulate the field conditions. During the period, the change in shear strength is observed by the computer to prevent any reduction of shear strength. Whether it is consolidation process, shear process, or pausing process, data changes can be observed through the computer so as to visually observe the strength recovery.  
The strength recovery value and recovery rate are defined in this study. The strength recovery value is the difference between the peak shear strength obtained by resehearing and the residual strength of the previous shearing. The recovery rate is the ratio of the strength recovery value to the healing time.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Relative Clay Mineral Contents/\%**} & \multicolumn{3}{c}{**Interstratified Ratio/\%**} \\ \hline
**I/S** & **Illite** & **Kaolinite** & **Chlorite** & **S\({}_{\text{I/S}}\)** & **S\({}_{\text{C/S}}\)** \\ \hline
28 & 43 & 11 & 18 & 50 & / \\ \hline \hline \end{tabular}
\end{table}
Table 4: Mineralogical composition of sample.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Type and Content of Minerals/\%**} & \multirow{3}{*}{**Clay Mineral/\%**} \\ \hline
**Quartz** & **Potassium Feldspar** & **Plagioclase** & **Calcite** & **Dolomite** & \\ \hline
57.3 & 1.6 & 6.5 & 10.1 & 0.9 & 23.6 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Rock composition of sample.