The Effect of Rainfall Variability on Slope Stability in Canada Hill, Miri

Abstract

Canada hill is about 200 m high and located in Miri, Sarawak. Landslide is found commonly happens in Canada Hill areas and it has become a threat to the nearby villagers. This study investigates the rainfall intensity to the stability of slope failures. To achieve this objective, a slope located in Canada Hill was selected for numerical modelling. The numerical software SEEP/W was adopted for seepage analysis while SLOPE/W for stability of the slope. The parameters such as shear strength, permeability, soil water characteristic curve etc. were based on literature. The modelling of rainfall intensity was referred to historical data. The minimum, maximum and average rainfall intensity from historical data is chosen to model the infiltration of rainfall. The numerical results showed that with the continuous min. rainfall intensity of 1.509 mm/hr, the slope will not be saturated after 1 day. With the continuous rainfall intensity of 19.241 mm/hr for 24 hours, the residual soil and clay layer will be saturated at 24 hours. This is due to the infiltration of seepage flow and the increase of pore water pressure. The losing of soil suction in residual soil is significant when rainfall intensity is 36.974 mm/hr. The pore water pressure tends to weaken the soil in terms of reducing in the shear strength and matric suction of the soil. The stability of the slope will be affected. The results show that higher rainfall intensity, the lower the safety factor of the slope. This research provides a good understanding of the influence of rainfall intensity in Miri area to the stability of slope.