## 4 Conclusions  
In this study, a dam slope in Hainan Province was taken as the geological background. Focusing on the theoretical problem of stability monitoring of the slope weathering transition zones under cyclonic rainfall, the evolution law of anchor bolt axial force and pore water pressure was studied by means of a physical model test and numerical simulation. The conclusions are as follows:  
1. Physical model test results showed that pore water pressure in the weathering transition zone during the rainfall infiltration stage was positively correlated with rainfall intensity, and pore water pressure increased significantly during the hydraulic fluctuation stage. The increase of permeability caused by hydraulic fluctuation and the expansion of the rock fracture network are the main causes for the increase of lateral deformation of the slope. The numerical simulation results showed that rainfall infiltration increased the pore water pressure in the shallow layer, the hydraulic effect of the structural plane increased the deep pore water pressure, and the strain softening caused by the decrease of effective stress is the main reason for the increase of slope displacement. 2. The physical model test results showed that during the rainfall infiltration stage, splash erosion and runoff led to rapid loss of anchor bolt preload in the middle and lower parts of the strongly weathering zone. With the increase of self-weight stress, tension cracks occurred at the top of the slope, and the axial force of the anchor bolt near the top of the slope increased. During the stage of hydraulic fluctuation, anchor bolt axial force decreased first, then increased, and finally tended to stabilize. ITS unloading response was observed at some monitoring points. In the numerical simulation, the axial force of the bolt increased continuously with the lateral displacement of the slope. 3. Based on the results of the physical model test and numerical simulation, the evolution laws of bolt axial force and pore water pressure in the weathering transition zone were analyzed, and a stability monitoring criterion of the slope weathering transition zone based on the Logistic function was established. In view of the long-term monitoring of bolt axial force as a common technique for slope disaster prevention,  
Figure 18: Fitting results: (**a**) Fitting curve of axial force at monitoring point F-1 and pore water pressure at monitoring point P-3; (**b**) Fitting curve of axial force at monitoring point F-2 and pore water pressure at monitoring point P-3. the monitoring criterion proposed in this study provides a useful reference for slope disaster prevention under cyclonic rainfall. * In this study, the physical model test was carried out under 1-g condition, making it very difficult to simulate the effective stress field distribution of the prototype slope. Therefore, the obtained slope failure mode is different from the real situation. Centrifuge model tests should be carried out in the future to obtain more accurate slope failure modes and weathering transition zone stability monitoring criteria. Conceptualization, H.S. ; methodology, H.S. and Q.F. ; software, Q.F. and Z.M. ; validation, Z.M. and Y.W. ; investigation, Q.F., Z.M. and Y.W; resources, H.S. and Q.F. ; data curation, Q.F. ; writing--original draft preparation, Q.F. ; writing--review and editing, H.S. ; visualization, H.S. and Q.F. ; supervision, H.S. and Y.W. project administration, H.S. ; funding acquisition, H.S. All authors have read and agreed to the published version of the manuscript. This research is supported by the National Natural Science Foundation of China (Grant No. 52109120), the Hainan Province Science and Technology Special Fund (Grant Nos. ZDYF2024 SHFZ060 and ZDYF2024 GXJS307), and the Open Research Fund Program of the State Key Laboratory of Hydroscience and Engineering (Grant No. sklhse-2024-D-01). Not applicable. The data presented in this study are available on reasonable request from the corresponding author.