1998 – Safety of Meadowbank Dam Against Sliding Parameter Uncertainty

Richard I Herweynen

For concrete gravity dams, when the foundation’s value of cohesion is low, it is very difficult to meet the sliding criteria proposed by ANCOLD. Low cohesion is generally associated with serious foundation defects. This was the case for Meadowbank Dam, with a foundation having persistent horizontal seams containing material of a clayey silt size classification. By adopting the ANCOLD strength reduction factors, it was found that a large number of ground anchors would be required to meet the ANCOLD sliding criteria. During original design, extensive laboratory and insitu testing was performed on the seam material. This paper proposes a methodology for arriving at less severe strength reduction factors based upon a statistical analysis of the strength parameters measured in the Meadowbank Dam foundation.

Additionally, a probabilistic approach using a Monte Carlo simulation is used to give further weight to this argument. This paper concludes that the probability of Meadowbank Dam failing due to sliding is very low and within acceptable limits.