About the Event
Mn/DOT's response to regulations suggesting that retaining walls be designed for at-rest rather than active conditions was to measure the earth pressure behind a wall. Factored loads and resulting moments would increase significantly with the addition of specifications that require at-rest pressures. Mn/DOT walls have performed well and they traditionally have been designed for active loading.
Earth pressure cells, tiltmeters, strain gages, inclinometer casings, extensometers, and survey reflectors were installed in fall 2002 during construction of a reinforced concrete cantilever retaining wall located along I-494. A data acquisition system with remote access monitored some 60 sensors on an almost continuous basis.
Analyses of the data indicated the development of active earth pressure. Movement of the 26-ft (7.9-m) high wall at the end of backfilling consisted of translation away from the backfill (+12 mm), rigid body rotation into the backfill (-4 mm at the top of the stem), and deflection of the structure away from the backfill (+4 mm at the top of the stem). Back-calculation of loading on the wall from deflection readings also indicated the development of active earth pressure.
The presentation will also explore the relationship between wall translation, lateral loading, and the effectiveness of the shear key.