peer reviewedPOOR GROUND CONDITIONS on cavernous limestone created severe difficulties at the sites of four piers of the Remouchamps Viaduct. The discovery, during excavations for foundations, of large open cavities prompted a major re-appraisal of site investigation procedure, and also some redesign of the viaduct structure.La situation défavorable des fondations de quatre des piliers du viaduc autoroutier de Remouchamps posa des problèmes de construction. La présence de cavités karstiques largement ouvertes nécessita le re-dessin de la structure du viaduc