Citation

DeJong J, Morgenstern NR. Can. Geotech. J. 1973; 10(2): 261-281.

Copyright

(Copyright © 1973, National Research Council of Canada)

DOI

10.1139/t73-023

PMID

unavailable

Abstract

It is not often that there is an opportunity to obtain a detailed and overlapping record of ground displacements; that is, heave during excavation and settlement during and subsequent to building construction. This paper presents such a case record and describes briefly site stratigraphy, the instrumentation used, the data obtained, and its analysis. The structures in question are the 34 storey Alberta Government Telephones building and the adjacent 28 storey Oxford building, together comprising the A.G.T./Oxford Complex, located in downtown Edmonton.Heave points were embedded below the base of the 300 × 300 × 45 ft (91 × 91 × 13.7 m) deep A.G.T. excavation in over-consolidated soil. Their elevations were read several times during the phased 1-year excavation period, each time accompanied by measurement of the excavation dimensions. To January, 1972 2.5 years of settlement have been recorded from readings taken on more than 100 basement column plugs. In addition, visual observations were made, construction loading and piezometric data were obtained and laboratory soil tests were undertaken. Analysis of the data was initiated in an effort to gain a better understanding of the mechanisms governing the response of these over-consolidated soils to both loading and unloading.Heave response within the excavation area was found to be rapid and computable by elastic theory. Much of the heave occurred during excavation. The time dependent portion virtually ceased 2-3 months subsequent to cessation of excavation. The amount occurring at adjacent structures outside the excavation was less than that predicted from elastic theory. Analysis of settlement data indicates that during construction settlements are rapid at footing pressures less than the original overburden pressure and can be predicted using elastic theory. Subsequent settlement at higher footing contact pressures also occurs rapidly, but with a stress dependent modulus of deformation. In general, the moduli derived from laboratory test specimens were found to be unsuitable and unreliable. Several conclusions of importance to construction practice and foundation design are drawn relative to proximity effects and phasing of excavation and building construction.


Il est rare d'avoir la possibilité de réunir des observations détaillées et concurrentes de déformation du sol, en soulèvement durant l'excavation et en tassement pendant et après la construction de l'édifice sur un même site. L'article présente un cas type de ce genre et décrit la stratigraphie du site, l'instrumentation utilisée, les observations faites et leur interprétation. Les structures en question sont l'édifice de 34 étages des Alberta Government Telephones et l'Edifice Oxford adjacent de 28 étages, formant le complexe A.G.T./Oxford dans le centre ville d'Edmonton.Des points de contrôle du soulèvement ont été installés sous le fond de l'excavation de 300 × 300 × 45 pi. (91 × 91 × 13.7 m) de profondeur de l'édifice A.G.T. dans un sol sur-consolidé. Leurs élévations ont été prises à plusieurs époques durant les différentes phases de la période d'excavation qui a duré un an chaque mesure étant accompagnée d'un relevé des dimensions de l'excavation. Ensuite et jusqu'en janvier 1972 des relevés de tas...

Language: en