HENG VUTHA

Influence of rainfall history on slope failures induced by rainfall

Supervisor Hirofumi TOYOTA

In recent years, slope failures induced by heavy rainfall has caused serious damage in the infrastructure. The slope failure during the rainfall is considered to be happened when the volume of water in the slope increases. The shear stress acting in the slope increases with an increase in total soil weight including water. Furthermore, the shear strength of soil decreases with a decrease in suction induced by wetting. Model slope failure tests due to rainfall were carried out to protect the infrastructure from this kind of disaster.
1)The rainfall initially infiltrate into the ground from the surface. Afterward, the groundwater level in the slope start to rise. When the rainfall intensity is larger, the slope would be collapsed in earlier time because of rising ground water level.
2)Water was stored in the slope during rainfall history, and finally the groundwater remained in the flat part of the model slope.
3)By the comparison of slope failure tests between with rainfall history and without rainfall history, the collapsed time was almost the same to each other during the main rainfall. However, the groundwater in the slope was rising earlier in the case with rainfall history. This means that the risk of failure had been getting higher in earlier time in the case with rainfall history.  
From the results, the importance of groundwater level on slope failure during rainfall was demonstrated. In the future, a study on the influence of the drained condition in the slope should be suggested to propose an effective countermeasure against slope failure.