Diaphragm wall retaining system – a simplified model for design loads

ABSTRACT Diaphragm walls are the ideal solutions for constructive utilisation of underground space to surmount the space constraints causing hindrance to infrastructural developments in urban areas. Accurate analysis methods to determine the wall forces and deformations are vital for the safe and cost-effective implementation of diaphragm wall projects. This paper describes a simplified method formulated for the analysis of diaphragm walls to process design values. The developed methodology is a combination of the net pressure method, the apparent pressure method and the limit equilibrium concept, with modifications to mitigate the demerits of each method towards the applicability for diaphragm walls. The design values for each excavation stage of a diaphragm wall supported excavation acted upon by any loading condition and ground water level can be computed with the methodology. Formulations for determining vertical axial forces are developed from the basic concepts of pile foundations by modifying the expressions to integrate the specific requirements of diaphragm walls. The developed formulations are validated against numerical analysis with Plaxis by comparing wall internal forces and axial strut forces. Around 90% of the results were found to have a percentage variation of less than 10% compared to Plaxis results, indicating the suitability of the method for application to diaphragm walls.