###### Abstract
As a result, an increased safety factor reduces the cost of remedial measures. It is extremely important to study the recovery strength under the state of residual shearing. Therefore, it is necessary to study the mechanism of strength recovery and its influencing factors before using it in landslide design and remediation. Several studies have been conducted on the recovery characteristics of the shear strength. [PERSON] [3] showed that the shear surface of colluvial clay soil experiences \"healing\", resulting in the shear strength of the pre-existing failure surface becoming greater than the residual value. [PERSON] [4] found that, before a landslide reactivates, the shear strength of the slide zone recovers during the stable period. [PERSON] et al. [5; 6] studied the strength recovery mechanism of different normally consolidated clays and found that the recovery strength increased with time whether using the direct shear test or the ring shear test. [PERSON] and [PERSON] [7] conducted laboratory ring shear tests of recovery strength on four natural soils, which demonstrated significant strength recovery at low effective vertical stress of 100 kPa or less. In highly plastic soil, with effective vertical stress of 100 kPa or less and liquid limits between 80% and 112%, the recovered strength is closer to the fully softened shear strengths after a long recovery period. This is due to the small difference between the fully softened shear strength and the residual strength \begin{table}
\begin{tabular}{c c c} \hline \hline
**Characteristic** & **Reversal Direct Shear** & **Ring Shear** \\ \hline Shear method & & \\ Mass of sample & Less & More \\ Sample state & Undisturbed sample & Remolded sample \\ Shear displacement & Intermittent & Progression \\ Sliding surface & Continue to change & Remain constant \\ Soil extrusion during shearing & Less & More \\ Orientation of particles at the sliding surface & Straight & Rotary \\ \hline \hline \end{tabular} Note: The instrument applicable sample state refers to the situation defined in favor of sample testing. Both reversal direct shear and ring shear instruments can be applied to undisturbed and remolded samples.  
\end{table} 
Table 1: Comparison of characteristics of reversal direct shear and ring shear instrument. of low-plasticity soil. [PERSON] [8] studied the self-healing in fine-grained soil during infiltration. [PERSON] et al. [9; 10] performed experimental analyses of the strength recovery of slide zone soil of landslide along a reservoir bank and showed that there was a significant strength recovery of the peak strength after a short resting time; however, with changing shear displacement, attenuation occurred at a short displacement. It was thought that this might be the result of the soil particle interactions having an influence on the strength recovery of the slide zone soil. [PERSON] et al. [11; 12] studied the self-healing phenomenon of a red-bed landslide. The relationship between the recovery strength of the shear surface and the healing time was analyzed by a reversal shear test, and the law of the recovery strength under different vertical stress was then analyzed. It was found that the healing time has a significant effect on the recovery strength compared with the vertical stress. The influence of healing time on recovery strength is more significant than that of vertical stress, and the recovery strength increases with the increase in time. [PERSON] et al. [13] studied the self-healing of a landslide using laboratory ring shear tests with different shear rates and grain sizes. They found that the peak strength of the landslide that had undergone accelerated creep damage was greater than the previous peak strength. [PERSON] et al. [14] investigated the strength healing law with different vertical stresses and recovery times via direct shear tests on loess with specialized properties. [PERSON] et al.