Settlement studies on the Mt. Sinai Hospital, Toronto

Construction of large structures on soil without the benefit of piles or caissons to transfer the building loads down to bedrock or other solid strata is sometimes done with much apprehension. There are savings to be gained so settlement studies were carried out on the Mt. Sinai Hospital in Toronto which is resting on a steel-reinforced concrete mat foundation. Total settlement under the center of the main wing of the building is about 0.6 inches, much less than the predicted 5 inches from laboratory consolidation tests. The best laboratory value for modulus of elasticity in the stress range applied by the building loads is about 600 TSF. Laboratory and field values of modulus agree reasonably well if Poisson's ratio is between 0.3 and 0.4 but is poor if a modulus of 0.5 is assumed. It is concluded that a mat foundation on a subsoil typical of the downtown Toronto area is completely satisfactory; the laboratory consolidation test overestimates the settlement of the structure on glacial till; compression of the soil under these loading conditions is mainly elastic; triaxial shear tests with cycled axial stress is a more accurate method of determining modulus of elasticity; improvements in modulus determination can result from larger specimens; 0.5 is questioned as a value for Poisson's ratio; and at the time of construction the mat foundation for this building was the most economical under the stated design conditions.La construction de gros ouvrages reposant directement sur le sol sans l'utilisation de pieux ou de caissons pour transf\ue9 rer les charges au socle ou \ue0 d'autres strates solides est parfois r\ue9alis\ue9e avec beaucoup d'appr\ue9hension. Comme cette facon de proc\ue9der permettrait de r\ue9aliser des \ue9conomies, des \ue9tudes sur le tassement ont port\ue9 sur le Mt. Sinai Hospital \ue0 Toronto qui repose sur une fondation sur semelles en b\ue9ton arm\ue9. Le tassement total sous le centre de l'aile principale de l'immeuble est d'environ 0.6 pouce, ce qui est de beaucoup inf\ue9rieur aux 5 pouces pr\ue9vus \ue0 partir des essais de consolidation r\ue9alis\ue9s en laboratoire.Peer reviewed: NoNRC publication: Ye