During construction of a 5 mile elevated section of the Leroy Selmon Crosstown Expressway, it was discovered (through no fault of AHB) that the installed drilled shaft foundations had insufficient capacity to carry construction loads. This deficiency was not discovered until approximately half of the segmental bridge was constructed and a failure occurred at the leading edge of construction. A geotechnical investigation determined 27 of the constructed bents needed remediation. 2-48” diameter sister shafts with depths of up to 90’ where installed at each deficient bent.
The sister shafts had to be installed under the existing bridge, with as little as 18’ clearance, and in the 45’ median between the existing grade lanes of the toll road. A. H. Beck’s limited access drilling capabilities were required to complete the remediation foundations. Temporary casings were installed down to limestone, and drilling fluid was used to stabilize the remainder of the excavation. A casing oscillator designed by A. H. Beck was used to advance the casing, and a low clearance drill rig designed and manufactured by A. H. Beck was used to excavate the foundations. After the excavation, the shafts where cleaned and SID tested. The reinforcing cages and CSL tubes had to be spliced over the excavation and set in concrete with a pump, also designed and built by A. H. Beck.
ENGINEER: Ardaman & Associates, Inc.