Vein of Groundwater Flow Behavior in a Land-Slide by Continuous Monitoring of Ground Temperature

To examine the dynamics of groundwater flow within landslide mass, we installed 29 thermocouples at the depth of one meter along three survey lines crossing the main body of Nishi-ikawa landslide in Tokushima, Japan, and continuously monitored the ground temperature since 30 April 2010. Through comparing the variation of these 1-m deep ground temperatures, we estimated the location of groundwater flow vein and found that: (1) characteristic of annual change in the 1-m deep ground temperature on Nishi-ikawa landslide was lower than the value estimated by Takeuchi’s equation, (2) some measurement points on Nishi-ikawa landslide read decreasing values, showing approximately the same tendency as the constant-temperature zone during heavy rain in summer season. We than inferred that these decrease in 1-m deep ground temperature resulted from the flow of groundwater from deeper layer such as the constant-temperature zone to the shallow layer through vein-like passes in the landslide mass during infiltration of heavy rain.