Strengthening of Slope by Soil Nailing Using Finite Difference and Limit Equilibrium Methods

The instability of slope has always been a major problem in the construction industry as it can cause various economic and social loss. In the present study, some typical slopes generally encountered in Indian Railways are analyzed numerically to determine its stability in terms of factor of safety (FOS) under static and seismic conditions using Finite difference method (FDM) and limit equilibrium method (LEM). For simulating seismic conditions, pseudostatic force analysis is carried out with horizontal seismic coefficient of 0.18 corresponding to zone IV of Indian seismic zoning system. Minimum FOS for stable slope is taken as 1.5 and 1.1 for static and seismic conditions, respectively. Soil nailing is used for stabilising unstable slope. For designing soil nail system, initially parametric study is conducted by varying the nail length and inclination using Finite difference code FLAC 2D for obtaining the optimum nail parameters required for slope stabilisation. The optimum length and inclination of soil nail from parametric study comes out to be 0.83 H and 15°, respectively. Stabilisation of unstable slope is carried out using the results obtained from parametric study. It is found that the nail inclination and nail length have a considerable effect on the FOS, nail axial force and shear force. It is also found that results by both the approaches are comparable, though, FOS obtained by LEM is slightly higher than FDM.