Consolidation Behaviour of Colluvium Derived from Overconsolidated Glaciolacustrine Deposits Under Highway Embankment Fills

ABSTRACT: Upgrading the Alaska Highway 97 at South Taylor Hill, BC, across a slow-moving landslide complex, required placing fills, as well as constructing stabilizing toe berms. One of the challenges faced in the project was determining the rate of pore-pressure dissipation in colluvium, derived from overconsolidated interbedded glaciolacustrine silts, sands and clays, underlying the fills. The colluvium was expected to retain some of the overconsolidated behavior, but still have a greater rate of pore pressure dissipation due to the disturbance and presence of higher permeability sands. Oedometer consolidation and cone penetration dissipation tests provided a wide range of consolidation coefficients. Pore pressures in the colluvium were monitored throughout, allowing comparison of observed pore pressure dissipation with laboratory and CPT based estimates. Understanding the variability will give greater confidence in determining the consolidation behavior of colluvium derived from overconsolidated materials and allow for this behavior to be accounted for in the geotechnical design.