Development of Design Criteria for Prevention of Slope Failures

摘要

A total of 242 embankments were examined along a 122-mile transect of 1-10 AND 1-20 highways in Louisiana. A total of 99 slope failures had occurred 8-15 years after construction (mean volume = 15,105 cubic feet). Most of the failures occurred on slopes greater than 16 degrees. Over 70% of the failures were found in modern alluvium parent material as compared to loess, sandy alluvium and Priairie Terrace alluvium. It is believed that the high amount of smectite in these soils created most of failures when the slope moisture content rose. A predictive model for the first 15 years after construction was developed. A high-rise slope has an 85-90% chance of failure and is constructed of soil with: 47% clay content, a plasticity index (Pl) 29%, a liquid limit (LL) 54%, and net smectite 33%. Low-risk slopes have a chance of less that 5% of failure and are constructed of soils with: 32% clay, 16% Pl, 36% LL, and net smectite 18%. Determination of the risk category can be done easily in the laboratory using Atterberg limits. Control of slops stability depends upon control of expansive clays in the high-and intermediate-risk slope soils. It is recommended to lime stabilize these soils or use a new slope design. A map of the distribution of these soils in Louisiana is included. Four different design nomographs based on a