Slope Stability Analysis of Vertical Unsupported Slopes near West Approaches of Al-Alam Bridge

Abstract

There are vertical slopes on the western banks of Tigris near Al-Alam Bridge in Tikrit, Iraq. These slopes are not supported and are located near an important road at Tikrit University. This study aims to find a safety factor (FOS) of the slope to prevent failure, besides its effect on human and financial losses. The study consists of two parts: the first part studied the layers of the slope and found the soil resistance coefficients. The second part analyzed the stability of the natural slope itself under the impact of the water level change of the Tigris River and the external loading. The analysis was done by a program called (PLAXIS 3D), which depends on the finite element method. The finite element method is a numerical approach that searches for approximate solutions and solves problems by dividing the problem into several triangular elements linked to each other by points called (nodes). The results showed that the vertical slope stability at the natural state with no influences indicated was in a semi-stable state with a factor of safety equal to (1.04865). The factor of safety decreased by (0.423%) with rising the river level until it reached (1.04074) at (93 m a.s.l.[1]). As for the applied external loads condition, the factor of safety for imposed (50,150 and 250 kN/m2) decreased by (4.738%), then the soil body failed when the factor of safety was (0.9902). In the critical state, the soil body failure at this stage and the factor of safety became equal to (0.98769) with decreasing by (5.812%).