Lateral Deformation in Strut-Braced Excavations vs. Other Retaining Systems
In excavations stabilized using conventional retaining walls, lateral wall movement and rotation create an active earth pressure condition behind the wall. This pressure can be calculated using classic theories such as Rankine or Coulomb.
However, retaining walls in strut-braced excavation systems behave differently in terms of lateral deformation.
Unlike cantilever retaining walls that allow top displacement and satisfy the conditions for Rankine or Coulomb analysis—where the failure wedge has room to form—cross-lot bracing prevents such movement.
In these systems, the wall tends to rotate around a point near the top, close to the ground surface, rather than sliding as a rigid body. Due to the restraining effect of the horizontal struts or tiebacks, no failure wedge develops, and typical active pressure conditions do not occur.
In the upper zones of the wall, where displacement is minimal, the lateral earth pressure often remains close to the at-rest condition. In contrast, the lower portions of the wall may even experience sub-active pressures due to constrained deformation.
The location of struts and their stiffness influence the stress distribution along the wall, resulting in a nonlinear pressure profile.
This structural behavior deviates from typical cantilever walls, where rotation and displacement lead to classic pressure distributions. In strut-braced walls, the top portion acts as a pivot, significantly altering how soil pressure is exerted and transferred.
Therefore, Rankine and Coulomb theories cannot accurately describe the real pressure distribution in strut-braced systems.
As shown in Figure 2, laboratory studies by Sherif and Fang illustrate the lateral earth pressure distribution behind a dry granular backfill wall rotating about its top. Their results clearly indicate a non-hydrostatic pressure pattern specific to this wall movement mode.
