Effect of Nails Orientation and Length on Soil-Nailed Retaining Structures Stability-Article

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The study used FLAC3D finite-difference modelling to assess how nail length, orientation and position affect the stability and wall-top displacement of soil-nailed slopes of different heights, with and without a 100 kPa surcharge. Nail lengths ranged from 0.5 to 1.5 times the slope height, and orientations from 0° to 30°.<br /><br />In general, nails oriented between 0° and 10° provided the best combination of safety and displacement control. Longer nails usually increased the factor of safety and reduced wall-top movement, although the benefit to displacement diminished beyond a “reduction point.” This point depended on slope height and surcharge: it occurred at greater nail lengths for taller slopes and at shorter lengths under surcharge. Orientations above 10° were generally less effective.<br /><br />The slope’s lower third had the greatest influence on the factor of safety, while its upper third had the greatest influence on wall-top displacement; the middle third had an intermediate effect. The influence of surcharge on both measures decreased as slope height increased.<br /><br />The results suggest that nail layout should be tailored to slope height, loading and the performance objective. In particular, longer or differently oriented nails may be appropriate in different slope segments. The analysis did not account for groundwater effects, and its findings are based on numerical modelling.

Keywords

FLAC3D

finite-difference modeling

soil-nailed slopes

slope stability

nail length

nail orientation

wall-top displacement

surcharge loading

factor of safety

numerical simulation