## 6 Influencing Factors of the Strength Recovery
### Relationship between the Healing Time and the Strength Recovery  
[PERSON] et al. [26] showed that the healing time has a significant effect on the recovery of landslides. After a certain healing time, there is an obvious healing phenomenon. The frictional healing and holding time has a log-linear relationship; with longer healing time, the rate of healing tends to stabilize and saturate. That is, the healing phenomenon is not significant at a short healing time, which gives a plausible explanation for the strength recovery phenomenon of the 3 h healing in this paper. A regression analysis was performed on the strength recovery value obtained from shearing for healing time of 6 h, 12 h, 24 h, and 72 h, as shown in Figure 13. With increasing healing time, the strength recovery value at the shear surface of the sample continues to increase. The increase in healing time means that the consolidation and hardening time of the sample increase, showing increases in strength recovery value, indicating the dependence of the strength recovery on healing time. The increase in shear strength given different healing times indicates that the slide zone soil has a certain strength healing characteristic, which is manifested in the significant increase in the strength recovery value with increasing healing time. In addition, the strength recovery value under 200 kPa is significantly higher than those under 50 kPa and 100 kPa, and the strength recovery values under 50 kPa and 100 kPa are relatively close to each other, such that the strength recovery under high vertical stress is better than that under low vertical stress. For low-plasticity soil, the characteristic of a gradual increase in shear strength with healing time is not infinite. The shear strength increases up to a certain extent, until the healing time exceeds 100 days, and then gradually converges to the fully softened strength value [21]. The magnitude of the shear strength is determined by the structure of the soil itself. Both the peak strength and the residual strength show a certain degree of recovery, reflecting the structural recovery of the soil during the healing time. After the sample is sheared to the residual strength, the particles produce cementation under a certain vertical pressure and healing time. In particular, the soil particles at the shear surface will interact with each other, and the shear strength will recover and increase under the action of continuous stress. The amount of shear strength recovery during the healing time is related to the mineral composition and content of the soil itself, and the magnitude of recovery rate varies given the same stress and healing time. A nonlinear fitted regression analysis of the healing time and the recovery rate was performed, as shown in Figure 14. It can be seen that, with the increasing of the healing time, the recovery rate gradually slowed and eventually stabilized. The 6 h healing time  
Figure 13: Relationship between the healing time and the strength recovery value given different vertical stresses. had the highest recovery rate. As the healing time increased, the contact area of the soil particles increased, the pores between the mineral particles filled with fine soil particles, the sample porosity decreased, the occlusion force between the particles increased, the degree of cementation of the samples increased, and the soil gradually densified. However, the reduction of pore ultimately reaches a saturated state. Therefore, in the process of the healing time increasing, the soil particles of the shear surface also reach saturation and the recovery rate at the shear surface gradually decreases. Therefore, the strength recovery rate gradually decreases with increasing healing time and the strength recovery value saturates, eventually stabilizing and stopping recovery. From the above analysis, it can be seen that when the soil reaches the residual strength state, the particles have formed a directional arrangement.