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Willacy County Post-Grouted Drilled Shafts 

Description: The FM 597 North floodway pilot channel bridge had excessive settlements occurring at bent 2. To stabilize the bridge, bent 2 was retrofit with 2 new post grouted drilled shafts. This retrofit consisted of the installation and grouting of 2 - 30” diameter post grouted shafts 46 feet in length utilizing Beck’s patented process, “Post Stress Pier” US Patent No. 6,371,698. The shafts were instrumented with strain gauges placed 2 feet above the base, telltales, and a post grouting plate. Due to the high water table and weak soils at the top of the ground permanent casings where install and the shafts where excavated using Bentonite slurry. After the shaft installation and the shaft concrete reached design strength the shafts where grouted. During the grouting operation a reference beam was set up over the shafts and the upward shaft displacement was measured with LVDT’s. All of the instrumentation was monitored with a data acquisition system throughout the grouting process. While base grouting, the downward acting grout pressure is resisted by the skin friction of the shaft thusly preloading the soils at the base, resulting in a quantifiable increase in shaft capacity.

Structures Sub-Contractor: McAllen Construction, Inc. Howard Pebley, Owner

Owner: Texas Department of Transportation

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