Parametric Analysis of Factors that Affects the Rainfall Induced Slope Stability

Slope failures are one of the most vital problems in geotechnical engineering applications which may cause damage both in human life and financial. Slope failures are frequently observed especially in regions where rainfall is high. The most important factor affecting slope stabilities is rainfall infiltration. It is known that infilled soils are generally unsaturated soil. Therefore, the analysis of infill slopes should be performed within the scope of unsaturated soil mechanics. Rainfall infiltration causes the groundwater level to rise, which reduces the shear strength of the soil causing slope instability. In this study, the effect of rainfall intensity, rainfall duration, soil permeability, groundwater level, cohesion of soil, internal friction angle of the soil, and slope angle of the slope on the slope stability were analyzed parametrically by using GEOSTUDIO software. The infiltration analyses were performed using Seep/w module and factor of safety number of unsaturated soil slope were determined using Morgenstern method of Slope/w module of GEOSTUDIO software. Furthermore, different factor of safety numbers was found for each analysis along with the interpretation of the parameters effecting the slope stability. The results obtained in the present investigation showed that the rainfall intensity affects the stability of the slope. It was determined that there existed a non-linear relationship between rainfall intensity and safety number. As the rainfall intensity increases, the negative pore water pressure in the soil decreases nonlinearly, and the factor of safety number of the slope similarly decreases by 10% relative to the initial condition. When the rainfall duration change was taken into account, it was found that short time-heavy rainfalls affected the slope stability more than long time-low density rainfalls. Moreover, slope angle significantly influenced slope stability. It was observed that when the slope angle increased from 40° to 50°, factor of safety number decreased by 18.34%.