Settlement of a high embankment and overpass structures in Ottawa

Settlement observations have been conducted over a 5-year period on a 20-ft-high earth embankment and 2 highway overpass structures founded on spread footings over a thick deposit of Leda clay. The applied stresses were considerably less that the overconsolidation pressure of the clay. In the five years since construction, settlements of approximately 12 cm have occurred, of which about 4 cm occurred immediately. The observed settlements are compared with settlement predictions on the basis of various types of laboratory tests. The observations indicate that significant settlements occur on a long-term basis and can be attributed to a slow yielding of the clay structure. Piezometers failed to detect any excess pore water pressure due to slow process of consolidation.Des mesures de tassement ont \ue9t\ue9 r\ue9alis\ue9es pendant une p\ue9 riode de cinq ans sur un remblai de 20 pieds de hauteur et sur deux structures de ponts fond\ue9es sur semelles sur un d\ue9p\uf4 t \ue9pais d'argile Leda. Les contraintes appliqu\ue9es \ue9taient nettement inf\ue9rieures \ue0 la pression de surconsolidation de l' argile. Cinq ans apr\ue8s la fin de la construction, des tassements d'environ 12 cm se sont produits, dont 4 cm imm\ue9 diatement. Les tassements observ\ue9s sont compar\ue9s aux calculs \ue9tablis \ue0 partir de diff\ue9rents types d'essais de laboratoire. Les observations indiquent qu'une part importante du tassement se produit \ue0 long terme et peut \ueatre attribu\ue9e \ue0 un fluage lent de la structure de l'argile. Les pi\ue9zom\ue8tres n'ont indiqu\ue9 aucune pression interstitielle du fait de la lenteur du ph\ue9nom\ue8ne de consolidation.Peer reviewed: NoNRC publication: Ye