New Mississippi River Bridge - Design Challenges

Design Challenges

Subsurface exploration by geotechnical engineering company Modjeski and Masters showed thick deposits of low-density sand below the water table. Such loose sand might liquify during an earthquake. Several ways to reduce the risk were considered, including in-situ densification of the sands, but ultimately the foundations were changed to feature 12-foot-diameter (3.7 m), 120-foot-long (37 m) drilled piers founded in the limestone bedrock to support the bridge superstructure. The bedrock is 120 feet (37 m) below the surface on the Illinois side and between 30 and 60 feet (18 m) on the Missouri side.