This paper will describe the large caisson pier foundations for four of the bridges
crossing the Mississippi River in the New Orleans area; and will discuss some of
the unusual problems encountered during their sinking. Certain settlement
phenomena experienced during their service life will also be related:
The four bridges in order of their construction:
The Huey P. Long Bridge, River Mile 106.1, completed in 1935
The Greater New Orleans Bridge No. 1, River Mile 96.0, completed in 1958
The Hale Boggs Bridge, River Mile 121.6, completed in 1983
The Greater New Orleans Bridge No. 2, River Mile 96.1, completed in 1988
Each of these bridges employed large open-dredged concrete caissons as
foundations for one or more of the river piers, with the smallest being the 65ft by
102ft caissons for Piers I and II of the Huey P. Long Bridge and the largest being
the 99ft by 214ft caisson for Pier II of the Greater New Orleans Bridge No. 2.
The Huey P. Long caissons are founded in a dense fine sand at -170 while all of
the other bridge caissons are founded in hard preconsolidated clay at elevations
varying from -150 to -185.
The Huey P. Long Bridge is currently being widened without increasing the
caisson foundations under any of the river piers; and the design reasoning that
led to this decision is presented.
Author: William B. Conway, Modjeski and Masters, Inc.
Publisher: DFI