Estimating pre-load induced settlement from laboratory test data and field monitoring records: A Case Study at Temple View Eastern Redevelopment Project, Hamilton

Predicting consolidation settlements in soft soils based on laboratory test data is commonly undertaken by geotechnical engineers, whereas the use of full scale trial embankments to compare these predictions is not always possible at the design phase. At Temple View both laboratory and trial embankment settlement data was used to predict fill induced consolidation settlements and to design surcharge embankments over compressible peat deposits to mitigate post construction creep settlements. Laboratory data used for the settlement analysis comprised oedometer tests that were undertaken on representative peat samples from across the site. The laboratory data was used to compute primary and secondary settlements under various surcharge heights. In comparison, settlement monitoring data from the trial embankment was used to back calculate both time rate (C_v) and settlement magnitude (C_c) parameters using the Asaoka graphical method. The parameters back calculated from the trial embankment data resulted in surcharge embankment design heights of between 0.5m and 1.5m lower than those designed from the laboratory parameters. The comparison has shown that laboratory values can be far higher than what full scale field data suggests and that reliance on 1D laboratory consolidation testing alone may be over conservative.