Observations and analyses of the 1994 submarine landslide at Skagway, Alaska

摘要

A massive subaenal submarine landslide at Skagway, Alaska on November 3, 1994 destroyed 900 feet (275 m) of dock during a reconstruction project. The author visited the site within a few days of the failure and became extensively involved as a technical expert on causation. Three lawsuits ($36 million in claims) were resolved by year 2000. The failure and subsequent flow slide occurred at extreme low tide and scoured soft marine silts in the foundation to depths of up to 80 feet (24 m). The initiation of failure is attributed to the weight of a fill and riprap stockpile constructed three weeks earlier, combined with the extreme low tide. Four construction workers observed the failure at close range. Their observations provide valuable insight into the onset of a marine flow slide failure. Stability analyses were performed in both total and effective stresses and showed that the factors of safety were around 1.0 at the time of failure. The effective stress analysis is of particular interest because it had to take account of partly consolidated marine silts, wood piles of the existing dock, and artesian pressures in the talus below the silt.