A case study on the slope displacement criterion at the critical accelerated stage triggered by rainfall and long-term creep behavior

This study describes the application of a multipoint shape accel array to investigate the relationships between the slope displacement, precipitation, and groundwater level. Considering the displacement tangent angle ( α ) of the displacement–time curve for slopes, we examined the correlation between the slope displacement stages and precipitation. In addition, the threshold values of the slope displacement derived from previous studies were compared and transformed to improve the values of α . The average velocity of creeping in the slope was used as the displacement velocity in the uniform-velocity displacement stage. The results are as follows: (1) The driving displacement threshold value of the cumulative precipitation was approximately 300 mm before the construction of the catch pits, and increased to 500 mm thereafter. (2) A displacement velocity ratio of 8 can be used as an early warning index. (3) When the improved displacement tangent angle was larger than 70°, the slope displacement was in the attention stage; when the angle was larger than 85°, the slope displacement was in the alert stage, and when the angle was greater than 87°, the slope displacement was in the action stage. (4) The displacement velocity ratio is an arctangent function of the improved tangent angle. The displacement velocity ratio amplifies the difference between the stages when the accelerated displacement of the slope approaches the latter part of the critical stage.