Professor Stuart Haigh has given the Géotechnique Lecture 2021 on a topic of ‘Performance-Based Design of Propped Retaining Walls’ at Institution of Civil Engineers on 16th November 2021. The Géotechnique lecture is a biennial top lecture in geotechnical engineering, nominated by the editorial panel of the top journal Géotechnique.
As geotechnical design is typically governed by allowable displacements rather than collapse, techniques which can predict wall and soil displacements prior to ultimate collapse can allow more efficient performance-based design to be carried out. Professor Stuart Haigh
‘Retaining wall systems are typically designed using Limit State Design assuming that active and passive earth pressures are developed to achieve stability, however the mobilisation of these earth pressures may well require substantial wall displacements,’ Professor Haigh said, ‘As geotechnical design is typically governed by allowable displacements rather than collapse, techniques which can predict wall and soil displacements prior to ultimate collapse can allow more efficient performance-based design to be carried out.'
In the lecture Professor Haigh introduced the development of a performance-based design methodology for propped and cantilever retaining walls in both clay and sand. This design method has been proposed at Cambridge during the PhD research of Dr Chuhan Deng under the supervision of Professor Haigh. Centrifuge model testing was used to investigate the mobilisation of strain and earth pressure within the soil surrounding the wall with displacement of rigid wall sections, with the relationships developed from these centrifuge tests being then superposed to predict the equilibrium deflections of flexible retaining walls both with and without props.
An original software, Prowd (Program of Retaining Wall Design), developed by Dr Deng, Professor Haigh, and Dr Zhang from University of Luxembourg, was also introduced in the lecture.Prowd provides an innovative method for rapidly calculating the bending moments and deflections of propped and cantilever retaining walls in clay soils. Soil strains are calculated using analytically and experimentally derived mechanisms and are linked to earth pressures utilising mobilisable strength design through a simple constitutive law. Prowd is available as a free download from https://www.prowd.org/and has already been downloaded by Engineers from over 20 companies including Arup, Mott MacDonald, Ramboll and GCG.
‘Prowd is a work in progress and we are extending it to retaining wall design in sand,’ Dr Deng said, ‘The soil settlement induced by staged excavations is also calculable using the performance-based design method and we will add this function into Prowd soon.’