A design method for flexible retaining walls in clay

Abstract

Design of retaining walls in clay is typically based on ultimate limit state calculations to prevent collapse with arbitrary factors of safety used to limit deformations. These factors of safety do not take into account the different rates of strength mobilisation in the wide variety of clays found worldwide. As there is substantial uncertainty in this approach, conventional design tends to lead to excessive conservatism with associated high cost. The novel analysis procedure based on the fraction of the strength of soil mobilised for a given wall displacement developed here allows rapid assessment of wall deformations and stresses via a simple two-parameter constitutive model which can be easily calibrated using conventional triaxial data. The model is validated based on field and model case histories with a variety of different clays and propping conditions and is shown to exhibit good performance in predicting the behaviour of published case histories based on soil parameters extracted from previously published soil test data. This novel analysis provides for the first time a route for practising engineers to carry out fast, efficient design at early stages of the design process by considering many potential wall geometries without the computational overhead of complex finite element or finite difference numerical models. KEYWORDS retaining walls; design; clays text Click here to access/download;Main text;A Design Method for Flexible Retaining Walls in Clay_v9.docx

Sand deformation mechanisms mobilised with active retaining wall movement

“…Analysis of the behaviour of flexible retaining walls in a manner similar to that attempted by Deng et al (2019) and Diakoumi & Powrie (2013) requires a link between the movement of the wall and the strains occurring in the soil. The experiments described here have given full-field measurements of the soil deformations and strains, but in order to calculate equivalent strains for flexible walls by superposition, a mathematical model coupling the soil deformations to the wall movements is necessary.…”

“…The displacement fields compatible with equal but opposite wall rotation about the base and top were superposed with the consequent resultant displacement and maximum shear strain being presented in Figures 15(d The ability to adequately predict the strain distribution behind retaining walls at pre-failure states gives the possibility of performing mobilisable strength design following the methods proposed by Deng et al (2019) for retaining walls in clay. Linking the wall displacements to the soil strains through the analyses presented here and hence to earth pressures by utilising a simplified constitutive law allows a deformed shape in which the earth pressures are in equilibrium with the wall bending moments to be achieved by iteration.…”

“…Diakoumi & Powrie (2013) and Deng et al (2019) described a method for the design of flexible retaining walls in clay which takes into account the pre-failure deformations of wall and soil.…”