Compression Set-Induced Seal Failure in Demountable Flood Barriers: Diagnosis and Mitigation Through Void-Engineered Gasket Geometry

Generic gaskets used in demountable property flood resilience (PFR) barriers may degrade under repeated compression and hydrostatic loading. This study examines compression set in closed-cell EPDM foam and compares five profiles with 0, 10, 15 and 20% internal void fractions, including a 15% void profile with a curved flood-facing surface. After one deployment, the solid control recovered to 14.3 mm from 16.5 mm. With a nominal compressed thickness of 11.5 mm under 5 mm installation compression, this corresponds to a residual loss of 2.2 mm, 13.3% of the original thickness and a deployment-based apparent compression set of 44%. All five profiles were compared using linear elastic finite element analysis. Full-scale testing evaluated Profile 5 under BS 851188-1:2019+A1:2021 and Profile 1 under matched 1 h hydrostatic tests at 600 mm across three deployments. One full-length specimen was tested for each of Profiles 1 and 5; the leakage results are therefore descriptive repeated observations rather than independent replicates. Profile 5 produced no measurable leakage at any assessed stage, whereas Profile 1 recorded 335, 1323 and 1481 mL during the matched hydrostatic cycles. Under a comparative 1 mm displacement, the simulations showed geometry-dependent differences in compliance and instantaneous stress redistribution. Because the linear elastic model used a smaller displacement than the 5 mm experimental compression, it is interpreted only as comparative geometry screening and does not simulate compression set, viscoelastic relaxation, cyclic degradation or unloading recovery. Profile 5 therefore warrants further investigation, but conclusions are restricted to the tested assemblies and conditions.