Parametric Study of Different Soil Nails on Slope Stability Based on Finite Element Method

Due to the development in the field of infrastructure and transportation, the available land for construction has become scarce. Hence, the urge to utilize weak and unstable ground is inevitable. The stability of steep cuts and slopes is one such problem that needs to be addressed. Soil nailing is a widely accepted method for slope stabilization, road widening projects, and constructing deep foundations, which is a technique to facilitate the stabilization of slope by driving reinforcement into the soil. The paper presents an investigation for understanding the soil nailing mechanism in slopes with different types of soil nails against the conventional soil nails that are widely being used. It is observed that the new and improved screwed soil nail offers an alternative to conventional soil nail. Available literature indicated a gap in the dynamic response studies on different model nails in c–Φ soils. The present study covers the use of finite element analysis (using PLAXIS 2D) for comparing the stability of different profiles of soil nails in c–Φ soil. The factor of safety was estimated for slopes stabilized using the smooth and screw soil nails. The soil slopes were modelled at three different slope angles of 45°, 60° and a vertical cut of 90° with horizontal. Each type of soil nail is used to reinforce the slope at different nail inclinations from 0° to 40° with the horizontal at 5° intervals till the factor of safety starts decreasing. The study incorporates three different nail spacings (1, 1.5, and 2 m) and six different lengths (4, 5, 6, 7, 8, and 9 m). The optimum inclination of the soil nail to the corresponding slope angle is determined. The variation in soil nailing mechanism with change in nail type from conventional smooth nail to screw nail is also analyzed. This enabled to understand the behavior of soil slopes to the change in nail geometry and the nail type. Seismic load is applied from the bottom of slope using the earthquake data of El Centro North South data to study deformation of soil-nailed slopes in comparison with unreinforced soil slopes for all slope angles. Generalized finite element analysis is used with the strength reduction method to determine factor of safety and slip surfaces. A comparative study is also carried out between results obtained from numerical modeling of different soil-nailed slopes.