To be involved in the construction of a deep dredged caisson for a major bridge
pier is one of the most rewarding and professionally challenging experiences one
can have in the bridge construction business. That experience was doubled in
the construction of the two deep dredged caissons for the Highway 82 Bridge
over the Mississippi River near Greenville, Mississippi. The challenges and the
construction risks associated with constructing these two dredged caisson pier
foundations highlight the construction engineering innovation associated with
major bridge pier construction.
The 1, 378-foot Main Span of the Highway 82 Bridge makes it the longest cable
stayed bridge span over the inland rivers of the United States. The main piers for
this bridge are supported on two dredged caissons measuring 80-feet by 122-
feet in plan, founding 200-feet and 170-feet below the river surface. The
challenges of constructing these caisson structures, sinking them through 70-feet
of water to the river bottom and then excavating and further sinking them to the
founding grade without exceeding the design tolerances, were enormous.
The construction engineering opportunities for innovation included major
breakwater structures to create a friendly environment in 11 ft/sec currents, the
first time use of Articulated Concrete Mattresses for river bottom scour control,
unique air dome design to maximize the buoyancy of the caisson structure while
floating, a caisson guide system to assure positive control and positioning of the
caisson during the initial sinking phases, and a comprehensive sinking plan to
assure maximum control and minimum risk. Many of the innovative solutions to
the construction challenges on this bridge will be incorporated into future caisson
construction projects on the lower Mississippi River.
Author: F. Keith Jacobson, Massman Construction Co.
Publisher: DFI