Mobilisable strength design for flexible embedded retaining walls

Soil–structure interaction may have an important influence on the behaviour of embedded retainingwalls, affecting both wall bending moments and ground movements. However, it can be difficult andtime consuming to capture in design, especially in a way that gives a physical insight into the keybehavioural mechanisms involved. A calculation procedure has been developed for retaining wallspropped near the crest that takes into account both the non-linearity of the stress–strain behaviour ofthe soil and the flexibility of the wall. Results for different pore water pressure conditions, soilstrengths and soil and wall stiffnesses are presented in the form of look-up charts, and are comparedwith those derived from factored limit equilibrium analyses. A dimensionless parameter is introducedto represent the relative soil–wall stiffness, and its importance is demonstrated. A critical flexibilityratio is identified at which the bending moments start to reduce below those given by a conventionallimit equilibrium calculation. This ratio is linked to the wall deflection, and is used to distinguish astiff from a flexible system in soils of different strengths and pore water pressure conditions. Theapproach is discussed in relation to previous studies

Mobilisable strength design for flexible embedded retaining walls

The discusser read with interest the paper by Diakoumi & Powrie (2013) proposing an interesting method for the analysis of propped flexible retaining walls based on the mobilisation of active and passive pressures on the wall due to movement of wall segments. An assumed deformation mechanism within the soil is used to estimate the strain associated with rotation of a particular wall segment. This mechanism is then superposed for each wall segment, the resulting earth pressures are calculated; the equality between the wall bending moments implied by equilibrium and those required to achieve the appropriate bending of the wall is used to calculate the rotation of each segment. Although the method of analysis provides insight into the conservatism of conventional design calculations for different wall flexibilities, there are two aspects of the paper which provoke further discussion