Monitoring Drilled Shafts Supporting a Bridge over a Landslide in Northern AL-Video

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Video Summary

After a major landslide near Huntsville in February 2020, Alabama DOT replaced a damaged roadway section with twin bridges supported by large drilled shafts socketed into limestone. The foundations were designed to resist ongoing ground movement rather than stabilize the slide. A remote monitoring system was installed to assess performance, including shape arrays in 24 shafts, free-field inclinometers and shape arrays, piezometers, and a weather station.<br /><br />Over more than two years, the system recorded rainfall-related groundwater changes and movement in nearby slopes. Most shafts moved less than the instruments’ stated accuracy; a few showed measurable movement, reaching about 0.2 inches. Shaft movement generally corresponded with rainfall and free-field movement, occurred in connected pairs, and partly rebounded during drier periods. Although some patterns remain difficult to explain, the small displacements support the design approach and indicate that the bridges are performing satisfactorily. The presentation also notes that installing instruments earlier could have provided valuable baseline data.

Keywords

landslide

Huntsville Alabama

drilled shafts

bridge foundations

remote monitoring

groundwater movement