Slope Stability Analysis after Decline of Water Level at the River Meander Considering Strain and Monte-Carlo Probabilistic Method

While investigating the stability of slopes at the rivers, uncertainty of soil shear strength parameters and their spatial variations affect the accuracy of results. Nowadays, probabilistic analyses are adopted to understand the probability of slope stability as the complementary methods. Throughout the current research on the meanders in Shalmanrood river of Guilan, the probabilistic analysis using Monte-Carlo method was carried out after field and laboratory studies on the soil. Accordingly, the pore pressure and strain under unsteady condition were modeled using finite element method. Then the slope stability was evaluated combining Monte-Carlo and limit equilibrium methods and compared with other researches’ results. The results showed that at meandering section 2 (the highest curvature), pore water pressure was dissipated in low rate after decline of the water level at the river. Additionally, results of strain analysis demonstrated that at the water elevations lower than normal level, swelling and compression occurred in meanders with slight and high curvatures, respectively. The probabilistic analysis with Monte-Carlo method applying Ordinary Slice method approximated the probability of slope failure within a bigger time span, as compared to Morgenstern-Price method. Meanwhile by decrease of the water level in river, the probability density function (PDF) of the safety factor showed a descending trend within 9.6 hours. In meander with the maximum curvature (section 2), a bigger temporal variations were observed in the position of PDF of safety factor, as compared to the minimum curvature (section 4).