Optimum Design Analysis of a Nailed Slope Based on Limit Equilibrium Methods: Case Study - Cluj-Napoca Landslide

摘要

Slope instability in the form of landslides is a major concern among geotechnical problems due to subsidence of the top soil material. An optimum design of gabion mesh wire with nails fixed into the withholding material is one of the prime solutions to this problem. Therefore, the present study applied this reinforcing solution to a landslide prone site located on the Northern side of Hoia hill in Cluj-Napoca, center of Romania which previously has been deciphered by means of drainage technique solution. The study scope was steered at investigating the optimum length, angle of inclination and profile of nail arrangement on a slope under saturated and unsaturated ground conditions by comparing the output results of Bishop, Janbu, Spencer and Morgenstein Price (GLE) analysis principles in GEO-SLOPE through their factor of safety (FOS) and shear strength. Among these four major methods of analysis, no major differences were found in the location of the slip failure surface but some minor differences were found in their FOS's & the constituting material's contributing strengths like frictional strength. After installation of slope nails, it was found that the maximum FOS is obtained when length of all the nails exceeds the depth of the slip circle and the required length for anchorage section is reached. In setting the nail's angle of inclination as the parametric study item, the best angle that satisfies LEM was found to be between 20°-40° degrees. But the optimum angle of inclination for LEM was found to be 30° for saturated ground and 40° for unsaturated state. The optimum layout of the soil nail was found to be longer at the top and bottom and shorter in the middle or longer at the bottom and shorter at the top, which is contrary to some researcher's guidelines for soil nail design during top-down construction.