Limit equilibrium methods of analysis are typically used to determine the global stability of the SRW. The factor of safety against sliding is defined as the ratio of the maximum shear possessed by the soil on the trial failure surface plus contributions from the soil reinforcement (τ available) to the shear resistance developed along the potential failure surface (τ mobilized), i.e.:įS= τ available/τ mobilized or resistance/driving. Limit equilibrium requirements are applied to the slices comprising the soil structure. It models a group of slices and the forces acting on each slice as shown in Figure 2. The Bishop’s method is the most commonly used. Several methods of analysis (such as Janbu, Spencer and Bishop) have been developed to analyze the global stability in a soil mass. A special case of the compound failure is the Internal Compound Stability (ICS) failure surface that exits at the SRW face above the foundation soil (Fig. A deep-seated failure is characterized by a failure surface that starts in front of an SRW, passes below the base of the wall and extends beyond the tail of the geosynthetic reinforcement (see Figure 1, surface F).Ĭompound failures are typically described by a failure surface that passes either through the SRW face or in front of the wall, through the reinforced soil zone and continues into the unreinforced/retained soil (Fig. There are two primary modes of global stability failure: deep-seated and compound. The designer should also review local code requirements applicable to designing soil retention structures.

when the geotechnical subsurface exploration finds soft soils, organic soils, peat, high plasticity clay, swelling or shrinking soils or fill soil.for excessive surcharges above the wall top,.a 3H:1V or steeper slope at the toe or top of the SRW,.groundwater table is above or within the wall height of the SRW,.Global stability analysis is an important component of SRW design, particularly under the following conditions: The general mass movement of a segmental retaining wall (SRW) structure and the adjacent soil is called global stability failure.

Slope stability surcharge top