Innovative Drilled Shaft Installation Process Through Existing Bridge FoundationsÂ-PPT Presentation

PPT Presentation

Pdf Summary

The project expanded a bridge on the Houston Ship Channel by adding two lanes and four columns. The original expansion design called for each new column to be supported by 12 driven concrete piles, but TxDOT selected a single large-diameter drilled shaft instead. Each shaft was 78 inches in diameter and up to 125 feet long, with strict location tolerances because it would support a column on its own.<br /><br />Installing the shafts presented unusual challenges. Crews worked from a barge in deep water, where tides, currents, and winter storms made it difficult to remain on position. They also had to drill through the existing bridge foundations, which included thick pile caps and old piles.<br /><br />The installation process began by using a large casing rotator to core a 100-inch opening through the 11-foot-thick pile cap and seal slab. A crane-supported drill rig and specialized tools then removed the concrete, reinforcing steel, and other obstructions. Crews installed a permanent 78-inch casing through the upper 72 feet, carefully controlling its alignment. Once the obstructions were cleared, they advanced the shafts using bentonite slurry, placed full-length reinforcing cages from the barge, and poured concrete by tremie.<br /><br />The work required powerful equipment, including a casing rotator capable of 4,000 foot-kips of torque. During construction, the existing foundations were encountered about five feet deeper than expected. The presentation relates the site to historical land subsidence in the Houston–Galveston region, but does not establish a definitive cause for the depth difference.<br /><br />The project demonstrated that large drilled shafts could be installed through existing foundations in a tidal channel by combining a staged coring process, heavy equipment, specialized tooling, and careful alignment control.

Keywords

Houston Ship Channel

bridge expansion

drilled shaft

large-diameter casing

pile cap coring

bentonite slurry

tremie concrete

marine construction

foundation retrofit

TxDOT