A 70-foot-tall, reinforced soil slope that supported a runway extension at Rocky Mountain Municipal Airport began showing signs of movement shortly after its reconstruction. Bryant was engaged to determine the cause of these movements and evaluate any instability risks.

To perform its investigation, Bryant obtained soil samples and performed a variety of laboratory tests on the samples; installed and monitored piezometers; evaluated the effects of the previous failures on the slope’s stability; performed 3D EVS groundwater modeling and evaluated the
drainage, water seepage, and water table; and used Slope/W to analyze the factor of safety and stability of the slope.

Bryant found that while the drainage in the slope was adequate, the strength of the soils comprising the slope was overestimated during the design, and this led to the slope’s instability.