Performance of hybrid MSE/Soil Nail walls using numerical analysis and limit equilibrium approaches

MSE/Soil Nail hybrid earth retaining walls provide a more economical design for applications in cut/fill situations than the traditionally used full height MSE and drilled shaft retaining walls. MSE/Soil Nail hybrid earth retaining walls use a soil nailed wall in the cut section and an MSE wall in the fill section. The paper demonstrates the results of instrumentation and monitoring an MSE/Soil Nail hybrid retaining wall system. Innovative 2D finite element models were used to simulate the behavior of the hybrid retaining wall system. The paper describes the philosophy of design of hybrid MSE/Soil Nail walls and the outline of circumstances which are favorable for such walls. In order to evaluate the global Factor of Safety (FOS) of the soil nail wall portion using the conventional limit-equilibrium design methods (LEM), two different methodologies to simulate the effect of the upper MSE walls were proposed. The obtained results of numerical and limit equilibrium approaches as a design methodology are presented for such type of walls, in this paper.The design of hybrid MSE/SN walls is complicated as it is a composite of two different reinforcement techniques, traditional limit equilibrium approaches cannot be used alone for design of such walls, it shall be supported by numerical methods for estimation of the global factor of safety and failure surface. The limit equilibrium approaches can be used for the estimation of internal stability and facing connection for both soil nails and mechanically stabilized walls.