A CONSIDERATION FOR EVALUATING OF SLOPE HEALTH MONITORING DURING RAINFALL FOCUSING ON VOLUMETRIC WATER CONTENT

Abstract

 Rainfall-induced shallow landslides have become more frequent owing to recent occurrences of extreme weather in Japan. The authors obtained research finding from previous studies that slope deformation due to rainfall-induced shallow landslide starts to increase after reaching the initial quasi-saturated volumetric water content (IQS). On the other hand, it was pointed out as problems to confirm the behavior of volumetric water content in the depth direction with respect to slope deformation and verify the consistency between the model test result and the filed measurement result. In this research, we summarized the results of a model experiment and a field measurement to solve these problems. By grasping the temporal change of volumetric water content in the depth direction, it is possible to understand the process from detection of IQS to formation of saturated zone, rise of water level and occurrence of displacement. When the measurement result on the actual slope were considered based on the result of the model slope experiment, it was confirmed that the result on the actual slope agree well with the result of the model slope experiment. In addition, when the IQS index was created as an index for judging whether the slope reached the IQS during rainfall and applied to the measured data on the actual slope, it was shown that the time when the volumetric water content reached IQS could be detected in real time.