Adapting Diaphragm Wall Design for Post-Disaster Structures on Soft Ground: Challenges Under the 6th Generation Seismic Code-Paper

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The paper presents the design of a seismically resilient foundation system for an 11-storey post-disaster hospital in British Columbia. The project faced highly sensitive soft clay extending to about 16 m, variable-permeability glacial till, pressurized groundwater, restricted urban space, and increased seismic demands under Canada’s sixth-generation seismic hazard model.<br /><br />Conventional foundation options were judged inefficient: meeting the required axial and lateral capacities with standard piles would have required more than 900 piles. Instead, the design combined diaphragm walls, barrettes, a reinforced raft, steel piles, and prestressed tie-down anchors. The diaphragm wall served as excavation support and part of the permanent system; barrettes transferred major axial and lateral loads into dense till. The raft and anchors also helped resist groundwater uplift.<br /><br />The team used site-specific 1D and 2D seismic response analyses and an iterative, performance-based modelling workflow across PLAXIS 2D and 3D, ETABS, and SAFE. Soil–structure interaction, nonlinear soil behaviour, and barrette group effects were assessed, with model parameters calibrated against field testing, including static load, O-cell, and anchor pullout tests.<br /><br />The study reports that this integrated approach met the hospital’s life-safety, operational-continuity, and seismic-resilience objectives while addressing construction constraints. It demonstrates how calibrated numerical analysis, tailored foundation elements, and coordinated structural–geotechnical design can support critical infrastructure on challenging ground. The authors recommend considering similar systems for urban projects where soft soils, groundwater, and high seismic demands make conventional foundations impractical.

Keywords

seismically resilient foundation

post-disaster hospital

diaphragm walls

barrettes

soft clay

groundwater uplift

soil-structure interaction

performance-based design

PLAXIS modeling

seismic response analysis