Ground characterisation and performance of a sinking motorway, waterview connection project, New Zealand

The paper presents the results and interpretations of an extensive data collected during the procurement phase of SH16 motorway upgrade. The strength and consolidation characteristics are investigated for two prevalent soil units (AH and ATcl). The AH soil is identified to manifest a response which is typical of a sensitive structured soft soil, whereas the ATcl soil is noticed to manifest an over-consolidated behaviour. The estimates based on either CSSM and SHANSEP have limitations to predict undrained shear strength profiles for the sensitive AH soil, but predicting rather well the shear strength of ATcl soil. The undrained shear ratio su/’v at OCR = 1 for AH soil appears to be a consistent indicator of shear strength development with depth. The non-linear one-dimensional compression displayed by the AH soil is proposed to model using a unique relationship between liquidity index and vertical effective stress. The predictive capability of this relationship is demonstrated by numerical simulations of settlement monitored during the construction and post-construction phase of the original SH16 motorway embankment.