A STUDY ON THE EFFECT OF FLOODING DEPTHS AND DURATION ON SOIL SUBGRADE PERFORMANCE AND STABILITY

In the event of flooding, the road infrastructure especially the subgrade will be affected in terms of its capacity to support the pavement. It is well known that subgrade deterioration will eventually cause pavement failure. However, little is known on how the subgrade reacts to different flooding conditions especially in terms of the depth and duration of the floods. The aims of this study are to evaluate the moisture content variation and strength of the subgrade using the flood simulation model. The pavement loading characteristics are referred to the Manual on Flexible Pavement Design published by the Malaysian Public Works Department (ATJ 5/85 Rev. 2013). The flood parameters used for this experimental model are based on actual data of flooding events from 1991 to 2014. It includes the parameters of flood water level, flood duration and repeated flooding. The samples were exposed to flooding for a duration of 3, 24 and 48 hours for unrepeated flooding and 2, 5, and 24 hours for repeated flooding. Flood water levels were set to 0.3 m, 0.6 m and 1 m. This study shows that there is a strong relationship between moisture content and subgrade strength The increase in the duration of the flooding affected the performance of the subgrade due to the increasing moisture content. The study also revealed that the rate of deterioration in subgrade strength for second flooding events is 15% more than for first flooding events. The result of this experiment will be used to develop the basis for including flooding characteristics in the modified California Bearing Ratio test for soils in flood prone areas.