## 3 Landslide Deformation Zoning Characteristics
### Deep Deformation Characteristics of the Landslide  
Inclinometer readings were carried out in the three landslide areas, divided according to surface crack characteristics and sliding depth. Deep deformation trends and zoning accuracy of the landslide areas were investigated while verifying the depth of the landslide zone. The data obtained from deep displacement monitoring were the cumulative horizontal displacement along the main slide direction of the borehole; 0 displacement was taken as the initial monitoring time and weathered shale was taken as the non-sliding surface at the bottom of the borehole.  
Deep deformation monitoring data of the BK17 borehole in Zone I are shown in Figure 7. Sliding phenomenon exists at depths of 7-11 m and 27-31 m. The shallow sliding zone is 7 m deep, which is the broken sandy mudstone of the slope toe group. The cumulative horizontal displacement reached 350 mm on 19 April 2022, when the relative displacement with the sliding bed was 200 m. It can be seen from the on-site working records that the drainage treatment of the landslide in Zone I was completed in April 2022, and the landslide in Area I stopped deforming after May 2022. Therefore, groundwater is the main factor influencing the deformation of the landslide. With the distribution of surface cracks and field investigation, it can be seen that there are tension cracks on the rear side of the BK17 borehole. The front edge has good air-conditioning due to construction and water guide pipes provided in the water barrier, so shallow sliding has formed in this area.  
The deep sliding zone at 27 m depth is strongly weathered black shale with low strength and susceptibility to creep sliding, combined with drilling core data. The sliding belt is a deep sliding belt in Zone III, with a cumulative displacement of 70 mm from 22 September 2021, to 19 April 2022, and a relatively slow deformation rate compared with Zone I. After drainage treatment in Area I was completed, the accumulated displacement of the landslide was 50 mm from 3 May 2022, to 7 July 2022, and the deformation rate decreased. The landslide in Zone II has remained stable, and the inclinometer readings were aimed mainly at the landslide in Zone I and Zone III.  
Deep deformation monitoring data of the BK24 borehole in Zone II are shown in Figure 8. The shallow sliding zone in this area is relatively stable. Only historical landslide marks exist at the rear edge, and the leading edge shear outlet is not exposed. Thus, the landslide does not form a good airtight condition. Deep sliding begins at a depth of 30 m,  
Figure 7: Monitoring data of borehole BK17.  
where the bottom is of strongly weathered shale, and the upper part of the sliding zone is 16 m deep, which is the bottom of the sandy mudstone of the Pojiao group and the top of the strongly weathered shale. There are no fresh cracks and slip marks near the site borehole. Monitoring data show that the maximum cumulative displacement of the landslide is 130 mm, and the overall landslide deformation shows a non-linear trend. Before 12 December 2021, the cumulative displacement rate was 1.077 mm/day. After that, the deformation rate was 0.231 mm/day, which indicates that the deformation state of the landslide is a non-linear deceleration deformation.