Design and stability analysis of a novel pretensioned soil nailing system in Korea

Abstract

In this study, a newly modified soil nailing technology named as the PSN (Pretension Soil Nailing), is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the analytical procedure and design technique are proposed to evaluate maximum pretension force and stability of the PSN system. Also proposed are techniques to determine the required thickness of a shotcrete facing and to estimate probability of a failure against the punching shear. Based on the proposed procedure and technique, effects of the radius of a influence circle and dilatancy angle on the thickness of a shotcrete facing, bonded length and safety factors are evaluated. In addition, effects of the reduction of deformations expected by pretension of the soil nails are examined in detail throughout an illustrative example and FLAC2D program analysis. Numerical analysis is carried out to determine a postulated failure surface as well as a minimum safety factor of the proposed PSN system using the shear strength reduction technique with the FLAC2D program. Global minimum safety factors and local safety factors at various excavation stages computed in case of the PSN system are analyzed throughout comparisons with the results expected in case of the general soil nailing system. Copyright ASCE 2006.