An Analytical Study on Trustability of Prescribed Slope Inclinations in Design Criteria

In order to investigate trustability of prescribed slope inclinations in design criteria, slope stability analyses were performed on the assumed two embankment sections. Factors of safety against dry condition for the section of 10m high and slope inclination of 1:2 and for the other section of 5m high and slope inclination of 1:1.5 were 1.93 and 2.24 respectively and those values were greater than the design criterion value of 1.50. Factors of safety which were computed through seepage analyses for steady state condition were 1.59 for the section of 10m high and 1.93 for the other section and those values were greater than design criterion value of 1.30. Non-steady state analyses under the same rainfall intensity for the steady state condition were also performed to compare with steady state analyses and it can be seen that factor of safety for the non-steady state condition was converged to the value for the steady state condition as time elapsed. Stability analyses of using piezometric line which were located on the top line of the sections were performed and computed values of factor of safety were 1.20 for the section of 10m high and 1.59 for the other section respectively and it could be seen that the factor of safety for the section of 10m is less than the criterion value of 1.30. According to the results of this study, it can be seen that the slope inclination of 1:1.5 for the slope heights less than 5m and the slope inclination of 1:2.0 for the slope heights between 5m to 10m were safe enough under dry condition and rainfall condition. Nevertheless it can be concluded that slope stability analysis should be performed for the slope over 10m high and with ground water table near the surface of the slope because the factor of safety for that situation was less than the design criterion value.