Mechanism of shallow landslide due to heavy rainfall using large-scale model test of unsaturated soil

Rainfall-induced shallow landslides causes serious damages with urban development. The characteristics of these damages are with local area and unexpected occurance. Therefore it is no time to escape from home. But, it is difficult to predict the time of occurance with rainfall-induced shallow landslide. If We can see the warning sign of slope before failure without dagerous, the damage is less. therefore, we need to find the warning sign into slope during heavy rainfall. Ordinaly, slope instability with heavy rainfall is caused by rain water penetration. Then we focus on the slope deformation with rainwater penetration. We conducted the large-scale model test of slope failure due to rainfall. The shape of soil slope model is 5m hight, 4m wide and 1m depth with weathered granite. Also two types of slope angle are 30 and 40 degrees. We measured the moisture content, graundwater height and surface displacement in model slope with several measuring points. We conclude the results of these experiments: 1.Slope deformation is accelerated with rainwater penetration and groundwater table. 2.In steep slope, slope deformed with rainfall under unsaturated state of soil layer. This may provide a useful and reasonable warning information of rainwater penetration of slope monitoring to mitigate the damages.