Reinforced Soil Design using a two-part Wedge Mechanism: Justification and Evidence

Paul McCombie, Mike Dobie

Research output: Contribution to journalArticle

6 Citations (SciVal)


Design methods for reinforced soil structures are normally divided into: external stability (defines structure dimensions) and
internal stability (determines reinforcement layout). This paper examines a method of calculation which has been developed for the internal
stability check based on a simple two-part wedge mechanism. The wedges are defined by a first plane across the width of the reinforced soil
zone, and a second plane upwards through the retained backfill. Reinforcement intersected by the first wedge contributes to the equilibrium
of forces. A large family of two-part wedges is defined, and sufficient reinforcement must be provided to ensure that all can achieve equilibrium without overloading the reinforcement. Extensive experience of using this technique indicates that the critical two-part wedge in an efficiently designed structure will normally be defined by a line crossing the reinforced soil zone at about 45 degrees, then extending through the backfill at the Coulomb angle. If seismic inertia forces are added, then the angles of both wedges will become less steep. The two-part wedge mechanism is compared with more comprehensive stability analyses, as well as observed behaviour in shaking table tests on small-scale reinforced soil walls.
Original languageEnglish
Pages (from-to)17-22
Number of pages6
JournalGeoResources Journal
Issue number4
Publication statusPublished - 29 Nov 2015


  • Geotechnics; Reinforced soil; Geosynthetics; Calculation; Stability; Design method


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