Cb. Crawford et Ki. Morrison, CASE-HISTORIES ILLUSTRATE THE IMPORTANCE OF SECONDARY-TYPE CONSOLIDATION SETTLEMENTS IN THE FRASER-RIVER DELTA, Canadian geotechnical journal, 33(6), 1996, pp. 866-878
The technique of preloading the deep, compressible soils in the Fraser
River delta has been used for more than 40 years to prevent excessive
settlement of major structures. This paper documents 22 years of sett
lement under preloading and after construction of the facilities for a
major waste water treatment plant in the delta. These results are sim
ilar to observations for as long as 28 years at five additional sires
in the delta. it was found that as much as one half of the measured su
rface settlement occurred during or within a few weeks of the full app
lication of the preload and that subsequent settlements have the chara
cteristics of secondary consolidation. This could not have been predic
ted from laboratory tests, and it raises questions concerning the true
nature of consolidation in situ. For practical purposes the observati
ons provide guidance for the prediction of long-term settlements in th
e region.