Case Study: Stability of Two Horizontal to One Vertical Embankment

Approximately 12-m (40-ft) tall compacted clay embankment was constructed at a slope of 2 horizontal (H) to 1 vertical (V) and over time the surface (0.45 to 0.8 m (1.5 to 2.5 ft) deep) of the embankment side slopes experienced extensive sloughing. The sloughing was due to a decrease in soil shear strength primarily caused by an increase in water content. Originally, a solution was proposed to reconstruct the slopes to 3H:1V at great cost. After completing comprehensive engineering, cost and benefit analyses, the engineer and owner worked together to develop an alternate solution that included flattening portions of the slopes to 2.5H:1V, improving surface drainage, and implementing a long-term monitoring and maintenance program at approximately half the original cost. This paper evaluates the causes of the sloughing and demonstrates how the owner and engineer can work together to reach cost-effective solutions.