This study presents a procedure for calculating the change of the safety factor for unsaturated slopes of homogenous, residual soils suffering from rainfall infiltration within Khanh Vinh district, Khanh Hòa province. Rainfall is supposed as a main trigger caused failure of the potential sliding slopes. Rainwater into the slope due to infiltration caused an increase in moisture content and negative pore water pressure; a decrease in matric suction and in shear strength on the failure surface. | TAÏP CHÍ PHAÙT TRIEÅN KH&CN, TAÄP 19, SOÁ K1- 2016 The effects of rainfall on the stability of soil slopes in Khanh Vinh district, Khanh Hoa province 1 2 Nguyen Thanh Danh 1 Dau Van Ngo 2 Ta Quoc Dung 2 Mien Trung University of Cilvil Engineering, MUCE Ho Chi Minh city University of Technology, VNU-HCMC (Manuscript Received on August 10th, 2015; Manuscript Revised on October 15th, 2015) ABSTRACT This study presents a procedure for calculating the change of the safety factor for unsaturated slopes of homogenous, residual soils suffering from rainfall infiltration within Khanh Vinh district, Khanh Hòa province. Rainfall is supposed as a main trigger caused failure of the potential sliding slopes. Rainwater into the slope due to infiltration caused an increase in moisture content and negative pore water pressure; a decrease in matric suction and in shear strength on the failure surface. Thus, slopes are reduced stability and can be failed. Soil permeability and rainfall intensity were found to be the primary factors controlling the instability of slopes due to rainfall, while the initial water table location and slope geometry only played a secondary role. A numerical model of analysis coupled seepage-stability used to simulate the seepage and slope stability under conditions of specific environment such as soil permeability, rainfall intensity, water table location and slope geometry in the study area. The relationships between safety factor and rainfall intensity, soil permeability, angle slope, high slope were identified to provide a good indication for the management of landslide hazards under the effects of rainfall. Keywords: slope stability, unsaturated residual soil, matric suction, rainfall intensity. 1. INTRODUCTION The impact of climate change affecting rainfall patterns (intensity and duration of rain) in many parts of the world causing many landslides. Many high terrains with tropical and subtropical climate covered mainly by residual soils .
