Effect of Extreme Rainfall Intensity on Matric Suction and Ground Movement

Increased intensity of rainfall events due to extreme climate change has led to the substantial increase in the occurrence of disasters, especially in a tropical-climate country such as Malaysia. Rainfall-induced landslide has become one of the most common types of disasters, and its triggering factors are still uncertain and impossible to predict. In this study, the effect of extreme rainfall intensity on groundwater behaviour is addressed through laboratory-scale testing. The adopted rainfall intensity is 60 mm/h, which was the heaviest hourly rainfall intensity recorded in Sarawak on 3rd January 2016 and 80 mm/h, which was the corresponding value recorded in Penang on 10th October 2016. The simulation is conducted on four cases. The simulated rainfall exhibits a duration of 6 h. In addition, the overall trend of the matric suction measurement and soil moisture in all cases is discussed on the basis of the results obtained from laboratory studies. After the rain simulator stopped, the matric suction decreases, and it remains stagnant, followed by a significant drop in the reading. For all cases, failure occurs, albeit at different times with different volumes of mass wasting.