Journal of Natural Disaster Science

QUANTITATIVE ANALYSIS OF THE RELATION BETWEEN GROUNDWATER MOVEMENT AND SLOPE FAILURE

Takashi OKIMURA
Lecturer, Faculty of Engineering, Kobe University, Kobe

(Received 11 January, 1982 and in revised form 24 June, 1982)

Abstract

Mountainslope failure (very rapid mass movements) often occur during heavy rain, and groundwater is considered to play a role in these failures. Results of a water level simulation study demonstrated that when water level acceleration (changes in the water level movement) peaks appeared in a bore hole many failures took place.

To determine why failures occur when water level acceleration is increased, we designed a confined interflow model that incorporates the results of a soil horizon investigation. The process in which the water level acceleration peaks appear was analyzed in this model. Results showed that water level acceleration increased when the discharge of the interflow into the tank of the model was increased.

Discharge of the interflow is thought to be related to the intensity of rainfall. We found that failures took place when the intensity of the rainfall was suddenly increased. In addition, we found that failures occurred two or three hours after the peak rainfall.

The mechanical stability of the surface soil layer was analyzed from the results of this confined interflow model study. Results showed that failures happened when there was an increase in the rate cf safety factor reduction.

Key words

mountainslope failure, rainfall, simulation, soil horizon, groundwater, confined flow, slope stability